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A 20-day trial was conducted to determine the impact of aflatoxin B1 (AFB1) and dietary protein concentration on performance, nutrient digestibility, and gut health in broiler chicks. The 6 dietary treatments were arranged in a 2 × 3 factorial with 3 crude protein (CP) concentrations (16, 22, and 26%) with or without 1.5 mg/kg AFB1 Each diet was fed to 6 replicate cages (6 chicks per cage) from zero to 20 d of age. Endogenous N and amino acid loss were estimated from birds fed a N-free diet with or without 1.5 mg/kg AFB1 A significant interaction between AFB1 and CP concentration was observed for growth performance, where reduction of BW gain, feed intake, gain:feed ratio, and breast muscle weight by AFB1 were most profound in birds fed the 16%-CP diet, and were completely eliminated when birds were fed the 26%-CP diet (AFB1 by CP interaction; P ≤ 0.023). Similarly, AFB1 reduced serum albumin, total protein, and globulin concentrations in birds fed 16 and 22% CP diets, but not in those fed the 26%-CP (AFB1 by CP interaction; P ≤ 0.071). Gut permeability was increased in birds fed AFB1-contamiated diets as measured by serum lactulose/rhamnose ratio (main effect; P = 0.04). Additionally, AFB1 tended to increase endogenous N loss (P = 0.09), and significantly reduced apparent ileal digestible energy and standardized ileal N and amino acid digestibility in birds fed the 16%-CP diet, while birds fed higher dietary CP were not affected (AFB1 by CP interaction; P ≤ 0.01). Further, AFB1 increased the translation initiation factor 4E-binding protein (4EBP1), claudin1, and multiple jejunal amino acid transporters expression (main effect; P ≤ 0.04). Results from this study indicate that a 1.5 mg AFB1/kg diet significantly impairs growth, major serum biochemistry measures, gut barrier, endogenous loss, and energy and amino acid digestibility. Aflatoxicosis can be augmented by low dietary CP, while higher dietary CP completely eliminated the impairment of performance, serum proteins, and nutrient digestibility from aflatoxicosis in zero to 20 d broiler chicks., (© 2016 Poultry Science Association Inc.)

A study with a 2 × 3 × 2 factorial arrangement was conducted to determine the effects of 2 dietary protein levels (high = CPh and low = CPl) during rearing, 3 dietary energy levels (3,000, MEh1; 2,800, MEs1; and 2,600, MEl1, kcal/kg AMEn, respectively) during the first phase of lay, and 2 dietary energy levels (2,800, MEs2; and 3,000, MEh2, kcal/kg AMEn, respectively) during the second phase of lay on body composition and reproduction in broiler breeders. No meaningful interactions for energy and protein treatments within the different phases of the study were found and, therefore, this paper focusses on the main effects. Pullets fed the CPl diet had a 12.8% higher feed intake, 14% lower breast muscle, and 97% higher abdominal fat pad portion at 22 wk age. The increased abdominal fat pad and decreased breast muscle of the CPl compared to the CPh birds increased hatchability during the first phase of lay, due to a decreased embryonic mortality between d 10 to 21 of incubation, and increased egg production during the second phase of lay. Feeding birds the MEh1 and MEl1 diets slightly decreased egg production compared to the MEs1 birds. Birds fed the MEh1 diet showed a higher mortality compared to the birds fed the MEs1 and MEl1 diets. Feeding birds the MEh2 diet did not affect egg production, increased hatchability of fertile eggs, decreased embryonic mortality between d 3 to 21 of incubation, and increased the number of first-grade chicks. It was concluded that a low-protein diet during rearing changed body composition with positive effects on incubation traits during the first phase of lay and improved egg production during the second phase of lay in broiler breeders. A high-energy or low-energy diet compared to a standard diet during the first phase of lay slightly decreased total and settable egg numbers while a high-energy diet during the second phase of lay increased hatchability and number of saleable chicks., (© 2015 Poultry Science Association Inc.)

A study was conducted to determine the influence of dietary energy and protein concentrations on growth performance and carcass traits of Pekin ducks from 15 to 35 d of age. In experiment 1, 14-d-old ducks were randomly assigned to 3 dietary metabolizable energy (11.8, 12.8, and 13.8 MJ/kg) and 3 crude protein concentrations (15, 17, and 19%) in a 3×3 factorial arrangement (6 replicate pens; 66 ducks/pen). Carcass characteristics were evaluated on d 28, 32, and 35. In Experiment 2, 15-d-old ducks (6 replicate cages; 6 ducks/cage) were randomly allotted to the 9 diets that were remixed with 0.5% chromic oxide. Excreta were collected from d 17 to 19, and ileal digesta was collected on d 19 to determine AMEn and amino acid digestibility. In Experiment 1, there were interactions (P<0.05) between dietary metabolizable energy and crude protein (CP) on body weight (BW) gain and feed intake, wherein BW gain increased more to increasing dietary CP as dietary metabolizable energy increased. However, feed intake was only influenced by dietary crude protein at 11.8 MJ ME/kg and not 12.8 or 13.8 MJ/kg. As dietary CP increased from 15 to 19%, breast meat yield increased by 10.8% on d 35 (P<0.01). Conversely, increasing metabolizable energy from 11.8 to 13.8 MJ/kg increased dressing percentage, breast skin, and subcutaneous fat, but decreased breast meat yield (% but not weight) on d 35 (P<0.01). In Experiment 2, the determined AMEn for diets formulated to contain 11.8, 12.8, or 13.8 MJ ME/kg were 11.66, 12.68, and 13.75 MJ/kg, respectively; determined standardized ileal digestible Lys was 0.95, 1.00, and 1.21% for diets formulated to contain 15, 17, or 19% crude protein, respectively. The best body weight gain and feed conversion ratio was obtained when ducks were fed a high dietary AMEn (13.75 MJ/kg) and high CP (19%, 1.21% SID Lys). These results provide a framework for subsequent modeling of amino acid and energy inputs and the corresponding outputs of growth performance and carcass components., (© The Author 2015. Published by Oxford University Press on behalf of Poultry Science Association.)

In a companion study, high amino acid (AA) or apparent metabolizable energy (AME) densities in the diets of broilers from 8 to 21 d of age were found to improve feed conversion. A total of 1,120 male Ross×Ross 708 chicks were randomly allocated to 80 pens (8 treatments, 10 replications per treatment, 14 chicks per pen). A 2×2×2 factorial arrangement of treatments was used to investigate the interaction among the protein source (high distillers dried grains with solubles diet [hDDGS] or high meat and bone meal diet [hMBM]), AA density (moderate or high), and AME density (2,998 or 3,100 kcal/kg) of diets on small intestine morphology. Duodenum, jejunum, and ileum samples from 2 chicks per pen were collected and measured individually at 21 d. Jejunum sections were processed for histological analysis. Chicks fed hDDGS diets exhibited longer small intestines than did chicks fed hMBM diets. Particularly, when chicks were fed high AA density diets, jejuna were longer in groups fed hDDGS diets than groups fed hMBM diets. Dietary treatments did not affect jejunum villus height, width, area, crypt depth, villus to crypt ratio, goblet cell size, or cell density. In birds fed diets containing a moderate AA and a high AME density, jejunum muscle layers of chicks fed hDDGS diets were thicker than those fed hMBM diets. Chicks exhibited a lower feed conversion ratio (FCR) and a higher BW gain when their crypts were shorter. In conclusion, an hDDGS diet may facilitate small intestine longitudinal growth in broilers, which may subsequently improve dietary nutrient absorption. In addition, broiler chicks with shallow intestinal crypts exhibited better growth performance., (© 2014 Poultry Science Association Inc.)

An experiment with 210 male (Ross 308) 1-d-old broilers was conducted to test the hypothesis that a coarse diet improves performance of broilers fed a poorly digestible protein source. A highly digestible diet based on soybean meal was gradually replaced by a low digestible diet based on rapeseed meal (RSM) in 5 steps (RSM-0%, RSM-25%, RSM-50%, RSM-75%, and RSM-100%). Two diet structures (fine and coarse) were used as an additional factor. These 2 factors and their interactions were tested at different ages in a factorial arrangement with 10 dietary treatments. An increase in indigestible dietary protein negatively affected feed intake (P = 0.003), BW gain (P = 0.008), and feed conversion ratio (P = 0.034). This increase in dietary indigestible protein contents resulted in a decrease (P = 0.001) in total cecal volatile fatty acid concentration from 209.1 to 125.9 mmol/kg of DM digesta in broilers with increasing RSM in diets. Increase in the indigestible protein level, from RSM-0% to RSM-100%, resulted in a decrease (P = 0.042) in villus heights (1,782 vs. 1,574 µm), whereas crypt depths increased (P = 0.021; 237 vs. 274 µm). A coarse diet improved feed intake (P = 0.006), BW gain (P = 0.014), and feed conversion ratio (P = 0.009). Broilers fed coarse diets had approximately 11, 24, and 10% lower relative empty weights of the crop, proventriculus, and jejunum, respectively, whereas a 15% heavier gizzard was found compared with those fed the fine diets. Dietary coarseness resulted in approximately 16% lower gizzard pH, 21% greater villus heights, 27% lower crypt depths, 24% reduced branched-chain fatty acids, and 12% lower biogenic amines in the cecal digesta compared with broilers fed fine diets. In conclusion, feeding coarse particles improved broiler performance irrespective of digestibility of the diet. Hindgut protein fermentation can be reduced by coarse grinding of the diet., (©2014 Poultry Science Association Inc.)

The combined effects of growth pattern (GP) and dietary CP level during rearing (2 to 22 wk of age) on body composition and performance were investigated in broiler breeder females from 0 to 40 wk of age. One-day-old pullets (n = 768) were randomly allotted to 48 pens according to 2 growth patterns (standard = SGP and high = HGP) and fed using 1 of 3 dietary CP levels (high = CPh, medium = CPm, and low = CPl). From 19 to 22 wk of age, feeding level was gradually adjusted to obtain a similar target BW for all birds, and then until 40 wk of age, all birds received similar amounts of a standard breeder diet. During the rearing period, the HGP pullets were fed a higher feed intake level (6.5%) than SGP pullets. To meet BW targets at 22 wk of age, feed intake from d 14 onward had to be increased for the CPm (4.6%) and CPl (10.0%) treatments. Breast muscle percentages of HGP and SGP pullets were similar at any age, although abdominal fat pad at 20 wk was 0.18% higher for HGP pullets. Pullets fed the CPl diet had a lower breast muscle percentage compared with pullets fed the CPm and CPh diets (0.46 and 0.85% at wk 10, 0.81 and 1.45% at wk 20, respectively). Abdominal fat pads in CPl pullets were 0.18 and 0.22% (wk 10), and 0.24 and 0.42% (wk 20) higher compared with CPm and CPh pullets, respectively. At 40 wk of age, no effects on breast muscle and abdominal fat pad were found among all treatments. Egg production, sexual maturation, and egg weight were not affected by GP and CP levels during rearing. It was concluded that a low CP diet during rearing decreased breast muscle and increased abdominal fat pad, whereas a high GP only increased abdominal fat pad, at the end of the rearing period. Decreasing dietary CP level seems to be more effective in increasing abdominal fat pad than increasing GP.

A 12-wk experiment was conducted to study the effects of feeding regimen, inclusion of a fiber source, and CP content of the diet on performance of broiler breeder hens. In total, 360 hens and 60 males, 43 wk of age, were assigned to 60 floor pens (6 hens and 1 male each). There were 12 treatments arranged factorially with 2 feeding regimens [restricted (R) and liberal feeding (close to ad libitum consumption; LIB)], 3 sources of fiber (0, 3% inulin, and 3% cellulose), and 2 levels of CP (14.5 and 17.4%). No interactions among main effects were observed for any of the traits studied, and therefore, only main effects are presented. Body weight, liver weight, and abdominal fat weight were higher (P < 0.001) for the LIB than for the R-fed hens. However, egg production (P < 0.001), fertility index (P < 0.05), and percentage of hatch (P < 0.01) were lower for LIB than for R hens. The weights of ovaries (P < 0.05) and the size of the first preovulatory follicle (P < 0.05) were higher for the LIB than for the R hens. Also, egg yolk, egg weight, and BW of the hatching chicks were higher (P < 0.001) for the LIB hens. The inclusion of a fiber source in the diet decreased (P < 0.05) feed intake, BW gain, absolute liver and abdominal fat weight, and egg yolk weight, with effects being more pronounced (P < 0.05) with cellulose than with inulin. Hens fed additional fiber produced more (P < 0.05) eggs that were more fertile (P < 0.05) than control hens. Crude protein content of the diet did not affect hen performance but reduced (P < 0.01) the relative weight of the liver, ovary, and abdominal fat. It is concluded that the inclusion of inulin or cellulose in the diet improved hen performance and that an increase in dietary CP reduced obesity in broiler breeder hens.

Dietary zinc was used to induce molt in 200 White Leghorn birds in caged housing at the age of 70 wk. The birds were equally and randomly allocated to 4 groups each of 50 birds as G1 (control; CP 16%, no supplement), G2 (CP 18%, no other supplement), G3 (CP 16%, symbiotic Perfectin: 85 mg•L(-1) in drinking water daily), and G4 (CP 16%, probiotic Protexin: 85 mg•L(-1) in drinking water daily) after the completion of molt. The sampling was conducted 3 times at 5% production, peak production, and end of production with 15 birds being killed at each sampling from each group to collect the blood for harvesting of serum. Serum health markers including total oxidant status, total antioxidant capacity, homocysteine concentration, and paraoxonase, arylesterase, and ceruloplasmin activity were determined by the prescribed assays. The overall total antioxidant capacity was increased, whereas total oxidant status and homocysteine concentrations were reduced significantly (P ≤ 0.01) in all the supplemented groups compared with the control. The paraoxonase and ceruloplasmin activity were enhanced (P ≤ 0.01) in the supplemented groups compared with the control, and arylesterase activity was increased (P ≤ 0.01) in only G2 compared with the other groups. Although protein supplementation significantly reduced the oxidative stress, supplementation with symbiotic and probiotic also improved the health status by decreasing the oxidative stress in the birds.

This experiment was carried out to investigate effects of maternal ME and CP levels on growth performance, carcass traits, and meat quality of broiler offspring. A total of 1,134 thirty-week-old Chinese Yellow broiler breeders was randomly assigned to 3 dietary ME levels (11.09, 11.51, and 11.92 MJ/kg) and 3 CP levels (15.5, 16.5, and 17.5%) in a 3×3 factorial arrangement. Each dietary treatment had 6 replicates with 21 hens per replicate. At 39 wk of age, 30 settable eggs per replicate were selected for hatching. All broiler offspring were fed the same diets. There were significant ME×CP interactions in egg CP and ether extract (EE) contents, BW at d 1, 22 to 42 d ADG, ADFI during 1 to 21 d and 43 to 63 d, shear force, plasma albumin, cholesterol, and triglycerides contents of broiler offspring. Dietary ME at 11.92 MJ/kg increased average egg weight, egg EE content, and broiler 1-d-old BW compared with 11.09 MJ/kg group at 16.5%, 15.5%, and 17.5% CP levels, respectively (P<0.05). Maternal 11.51 and 11.92 MJ/kg of ME increased 1 to 21-d ADFI, and 11.51 MJ/kg of ME decreased lightness (L*) value of broiler offspring compared with 11.09 MJ/kg group at 17.5 and 16.5% CP levels, respectively (P<0.05). Broiler breeder dietary CP at 17.5% decreased egg EE content, increased average egg weight, egg CP content, BW at d 1, and 1 to 21-d ADFI of broiler offspring compared with 15.5% CP group at 11.92 MJ/kg of ME level (P<0.05). Maternal dietary 15.5% CP increased dressing percentage and decreased yellowness (b*) value of broiler offspring compared with 16.5% and 17.5% CP groups at 11.51 MJ/kg of ME level, respectively (P<0.05). Collectively, the results indicate that maternal diets composed of 11.51 to 11.92 MJ/kg of ME and 17.5% CP at 39 wk of age increased growth performance during 1 to 21 d in Chinese Yellow broiler, whereas 11.51 MJ/kg of ME and 15.5% CP improved carcass dressing percentage and meat color of their offspring.

An experiment was conducted to investigate the effects of dietary protein source on the digestive enzymes and electrolyte composition of digesta fluid in the duodenum, jejunum, and ileum of chickens. A 2 × 3 factorial and completely randomized design that used 2 types of diets that differed only in their protein source [a corn-soybean meal-miscellaneous meal diet (CSMD) and a corn-miscellaneous meal diet (CMD)] and 3 types of cannulated roosters (duodenal, jejunal, and ileal cannulations) was adopted. The experiments included 5 replicates for each of the 6 treatments, and each replicate involved 3 cannulated chickens. The digesta samples were collected for 1 h every 4 h between 09:30 and 18:30 h on d 31, 33, and 35 of the experiment. The amylase, lipase, trypsin, and chymotrypsin activities and the electrolyte composition in the duodenal, jejunal, and ileal fluid were determined. In general, no significant differences between the 2 dietary groups were observed for the mean of duodenal, jejuna, and ileal amylase, trypsin, chymotrypsin, and lipase, respectively. However, the duodenal amylase activity was lower in the CMD group than the CSMD group (P < 0.05), which was probably related to the lower duodenal pH value that was observed in this group (P < 0.01). A higher jejunal Mg(2+) concentration was observed in chickens that were fed the CMD (P < 0.05), whereas the differences in the Na(+), K(+), Cl(-), and Ca(2+) concentrations in the small intestine were not significant between the 2 diets (P > 0.05). In conclusion, the digestive enzymes and electrolytes in the small intestinal fluid of chickens adapted to the protein source of the diet, and each segment of the small intestine displayed different modifications.

A study was conducted to examine the reproductive parameters of Cobb 500 broiler breeder hens fed 2 different types of diets varying in digestible lysine concentration. In total, 240 Cobb 500 broiler breeder pullets were placed in individual cages and given experimental diets from 35 to 45 wk of age. Treatments 1 and 2 were diets formulated using only commercially available feed ingredients and consisted of digestible lysine intakes of 1,200 (IDL) and 1,010 mg/hen per day (ID). Treatments 3 and 4 consisted of semipurified diets with the inclusion of l-glutamic acid to maintain isonitrogenous conditions with digestible lysine intakes of 1,010 (SPL) and 600 mg/hen per day (SP). Hens fed the SPL and SP diets had lower hen-day egg production than hens fed the ID diet, with hens receiving the IDL diet yielding intermediate values. Hens fed the SP diet had the lowest (P < 0.05) egg weight, but no differences were observed among dietary treatments for egg specific gravity. Fertility and hatchability of eggs set were lowest (P < 0.05) for hens fed the SPL dietary treatment. No differences were observed for early and middle embryonic mortality, contaminated, or pipped eggs. Late embryonic mortality was observed to be higher (P < 0.05) in hens fed the SP diet. A decrease in the daily intake of digestible lysine appeared to improve broiler breeder reproductive performance when hens were fed a semipurified diet. In contrast, the same effect was not observed when hens were fed a standard industry-type diet that contained less lysine.

An experiment was conducted to determine the effects of period on the performance, immunity, and some stress indicators of broilers fed 2 levels of protein and stocked at a normal or high stocking density. Experimental treatments consisted of a 2 × 2 × 2 factorial arrangement with 2 levels of prebiotic (with or without prebiotic), 2 levels of dietary CP [NRC-recommended or low CP level (85% of NRC-recommended level)], and 2 levels of stocking density (10 birds/m(2) as the normal density or 16 birds/m(2) as the high density), for a total of 8 treatments. Each treatment had 5 replicates (cages). Birds were reared in 3-tiered battery cages with wire floors in an open-sided housing system under natural tropical conditions. Housing and general management practices were similar for all treatment groups. Starter and finisher diets in mash form were fed from 1 to 21 d and 22 to 42 d of age, respectively. Supplementation with a prebiotic had no significant effect on performance, immunity, and stress indicators (blood glucose, cholesterol, corticosterone, and heterophil:lymphocyte ratio). Protein level significantly influenced broiler performance but did not affect immunity or stress indicators (except for cholesterol level). The normal stocking density resulted in better FCR and also higher antibody titer against Newcastle disease compared with the high stocking density. However, density had no significant effect on blood levels of glucose, cholesterol, corticosterone, and the heterophil:lymphocyte ratio. Significant interactions between protein level and stocking density were observed for BW gain and final BW. The results indicated that, under the conditions of this experiment, dietary addition of a prebiotic had no significant effect on the performance, immunity, and stress indicators of broilers.

This paper, the second from a comprehensive study, describes the effects of varying growth rate by feeding at different planes of nutrition with a constant ME:CP ratio on muscle characteristics and meat quality in 2 distinct broiler breeds of male chickens (Arbor Acres, a commercial line; and Beijing-You, a Chinese nonimproved line). Experimental diets, differing on average by 2% CP, were formulated with high-, medium-, or low-nutrient densities for 3 growing phases. Male hatchlings (216 of each breed) were randomly assigned to 6 pens of 12 birds in each treatment. Altered histological characteristics of muscle fibers, early postmortem muscle metabolism, and meat quality were investigated in the pectoralis major and biceps femoris. At their market age, Arbor Acres broilers had significantly higher concentrations of plasma protein and lipid metabolites, ratios of white to red and intermediate fibers, pH, L* and b* values, and lower concentrations of plasma glucose metabolites, muscle-fiber diameter, muscle contents of energy stores, a* value, drip loss, and shear force than the values found for the Beijing-You chickens (P < 0.01). Higher nutrient density increased the size of the muscle fibers, decreased glycogen reserve, and reduced the rate and extent of acidification in the Arbor Acres chickens, while accelerating transformation of red and intermediate-to-white fibers, enhancing energy stores, and hastening the decrease in pH postmortem in the Beijing-You chickens (P < 0.05). In each breed, most meat quality variables (e.g., shear force, drip loss, and color) were consistent with the histological and biochemical changes caused by the feeding strategy. Together, dietary nutrient density can influence meat quality as a result of altered histological and initial energy and metabolic characteristics of the muscle. Many of the responses to diet are breed and tissue dependent in broiler chickens.

To evaluate the effect of decreasing dietary protein on growth performance, carcass traits, and intestinal mucosal morphometry, 180 female Hubbard strain broiler chickens were divided into 3 groups and fed 3 isoenergetic diets ad libitum from 14 d of age until slaughter age (49 d). The treatments varied according to 3 protein levels: high-protein diet (HiP, 22.5% CP, DM basis), medium-protein diet (MedP, 20.5% CP), and low-protein diet (LowP, 18.5%). Diets were obtained by replacing wheat middlings with soybean meal and were formulated to meet or exceed broiler amino acid requirements of the NRC. Morphometric indices of duodenum, jejunum, and ileum were measured at the end of the feeding period and included villus height, crypt depth, villus-to-crypt ratio, and apparent villus surface area. The dietary protein level had a significant effect on final BW of birds, whereas ADG, ADFI, and feed efficiency remained unaffected by dietary treatment. The muscle (breast and drumstick) yields were significantly higher in birds fed the HiP diet compared with those of the MedP and LowP diets. Meat quality traits were not affected by the protein level. The villus surface area of all intestinal segments did not change among groups. Instead, reducing the dietary protein level to 20.5% resulted in a higher villus height and villus height to crypt depth ratio in the duodenum and ileum. On the basis of our findings, even if the high-protein diet promoted meat yield, a medium-protein diet could positively support broiler growth performance, as confirmed by favorable morphometric features of the intestine.

A series of experiments were conducted to investigate the effect of starter diet protein levels on the performance of broilers vaccinated with a commercially available live oocyst coccidiosis vaccine before subsequent challenge with a mixed-species Eimeria challenge. Data indicated that an increasing protein concentration in the starter diet improved broiler performance during coccidiosis vaccination. Prechallenge performance data indicated that vaccination could decrease BW and increase feed conversion ratio. The time period most important for the observed effects appeared to be between 13 and 17 d of age. This reduction in performance parameters of vaccinated broilers compared with nonvaccinated broilers was eliminated by the conclusion of the experiments (27 d) in the diet groups with higher protein. Vaccination was effective at generating protective immunity against Eimeria challenge, as evidenced by increased (P < 0.05) BW gain, improved feed conversion, reduced postchallenge mortality, and reduced lesion development in vaccinated broilers compared with nonvaccinated broilers. These observations support numerous other reports that confirm live oocyst vaccination can be used effectively as a preventive against avian coccidiosis in commercially reared broilers. More important, these findings suggest that reduced protein concentration of starter diets can lead to significant losses in broiler performance when using a vaccination program to prevent coccidiosis.

Central composite design (CCD; 5 levels and 4 factors), response surface methodology (RSM), and artificial neural network-genetic algorithm (ANN-GA) were used to evaluate the response of broiler chicks [ADG and feed conversion ratio (FCR)] to dietary standardized ileal digestible protein (dP), lysine (dLys), total sulfur amino acids (dTSAA), and threonine (dThr). A total of 84 battery brooder units of 5 birds each were assigned to 28 diets of CCD containing 5 levels of dP (18-22%), dLys (1.06-1.30%), dTSAA (0.81-1.01%), and dThr (0.66-0.86%) from 11 to 17 d of age. The experimental results of CCD were fitted with the quadratic and artificial neural network models. A ridge analysis (for RSM models) and a genetic algorithm (for ANN-GA models) were used to compute the optimal response for ADG and FCR. For both ADG and FCR, the goodness of fit in terms of R(2) and MS error corresponding to ANN-GA and RSM models showed a substantially higher accuracy of prediction for ANN models (ADG model: R(2) = 0.99; FCR model: R(2) = 0.97) compared with RSM models (ADG model: R(2) = 0.70; FCR model: R(2) = 0.71). The ridge maximum analysis on ADG and minimum analysis on FCR models revealed that the maximum ADG may be obtained with 18.5, 1.10, 0.89, and 0.73% dP, dLys, dTSAA, and dThr, respectively, in diet, and minimum FCR may be obtained with 19.44, 1.18, 0.90, and 0.75% of dP, dLys, dTSAA, and dThr, respectively, in diet. The optimization results of ANN-GA models showed the maximum ADG may be achieved with 19.93, 1.06, 0.90, and 0.76% of dP, dLys, dTSAA, and dThr, respectively, in diet, and minimum FCR may be achieved with 18.63, 1.26, 0.84, and 0.69% of dP, dLys, dTSAA, and dThr, respectively, in diet. The results of this study revealed that the platform of CCD (for conducting growth trials with minimum treatments), RSM model, and ANN-GA (for experimental data modeling and optimization) may be used to describe the relationship between dietary nutrient concentrations and broiler performance to achieve the optimal target.

A study was conducted to evaluate the effects of dietary protein level and protein digestibility on the growth performance and carcass characteristics of broilers from 1 to 35 d of age. Broiler chickens (n = 320) were fed 4 different ideal protein-balanced, isocaloric diets in a 2 × 2 factorial design with 2 levels of protein [high protein (HiPro; 20 and 18% or 200 and 180 g/kg) and low protein (LoPro; 18 and 16% or 180 and 160 g/kg) on d 1 to 14 and d 15 to 35, respectively] and 2 levels of protein digestibility [high digestibility (HiDig) and low digestibility (LoDig); approximately 85% and 80% CP digestibility, respectively]. The HiDig diets were formulated using soybean meal and fishmeal, whereas the LoDig diets used wheat distillers dried grains with solubles and meat and bone meal as the primary protein sources. The standardized ileal digestibility (SID) values of the wheat distillers dried grains with solubles and meat and bone meal (56.5 and 72.0% SID for lysine, respectively) were measured before the experiment to improve the accuracy of the diet formulations. During the starter phase, the interaction was significant for ADG; birds fed the LoPro-LoDig diet grew slower than birds fed the other 3 diets (P < 0.05). During the grower phase, the interaction was significant for ADFI; birds fed the LoPro-LoDig diet had the lowest ADFI compared with those fed the other 3 diets. The interaction between protein level and digestibility was significant for the SID of most of the AA and was significantly higher for birds fed the HiPro-HiDig diet compared with those fed the other 3 diets. Total breast meat yield was significantly higher in birds fed the HiPro diets than in those fed the LoPro diets, whereas birds fed the HiDig diets had significantly more abdominal fat than those fed the LoDig diets. The results suggest that low-protein diets can support growth performance equal to high-protein diets when highly digestible ingredients are used. However, maximum breast meat yield requires a high-protein diet and is not affected by ingredient digestibility.

Because dietary nitrogen intake affects nitrogen content in manure, diet management has been recognized as a means to reduce ammonia emissions from poultry operations. The objectives of the present research were 1) to determine the extent to which the CP content of laying diets can be reduced, based on performance criteria, and 2) to determine how ash:nitrogen ratios of manure, eggs, and hens are affected by dietary protein changes. Egg-type hens were fed equal daily amounts of essential amino acids in diets that provided 13, 15, or 17 g of protein/d. Each diet was fed to 20 hens, with 2 hens/cage. The planned digestible lysine intake was 0.71 g/hen per day. Ratios of other digestible amino acids to lysine were methionine plus cysteine, 0.83; threonine, 0.68; and isoleucine, 0.94. The experiment began when hens were 29 wk old and continued until they were 57 wk old. Egg production averaged approximately 90%, and daily protein intake caused no effects on egg production or grams of egg per hen per day. Feed intake was higher for hens fed 13 g of protein than for hens in the other 2 treatments (P < 0.01). Average feed intake for the experiment was approximately 95 g/d. Composition of the eggs was not affected by protein intake. Average values were DM, 30.5%; ash, 31.0% of DM; and nitrogen, 6.31% of DM. The average manure DM production was 25.9 g/hen per day, with an ash content of 25.5% of DM. Manure nitrogen content ranged from 3.98% of DM for hens fed 13 g of protein to 5.68% for those fed 17 g of protein (P < 0.01). A method is outlined that uses the analysis of fresh manure and manure leaving the poultry operation to estimate the loss of nitrogen as ammonia.

An experiment was performed to investigate the effect of animal vs. vegetable protein sources in the diet of laying hens on the development of hen performance. A diet containing protein sources of only vegetable origin was compared with 4 diets, each containing 1 of 4 processed animal proteins (PAP). Two PAP (Daka-58 and Sonac-60) were classified as meat meals, and the remaining 2 (Daka-40 and Sonac-50) were classified as meat and bone meals. First, fecal digestibility of nutrients in the PAP was determined in Lohmann Brown layers. Hens (n = 132) were housed in 22 cages (6 hens/cage) and allotted to 5 dietary treatments. In the PAP diets (4 replicates/treatment), 100 g/kg of CP of animal origin was added, replacing soybean meal and corn (Zea mays) in the basal diet (6 replicates/treatment). The PAP sources differed largely in chemical composition and digestibility coefficients. Energy content (AME(n)) varied from 1,817 (Daka-40) to 3,107 kcal/kg (Sonac-60), and digestible lysine varied from 15.4 (Daka-40) to 28.3 g/kg (Sonac-50). Subsequently, the effect of a control diet (without PAP) vs. 4 PAP diets (50 g/kg of CP of animal origin from the same batches as used in the digestibility study) on performance was determined. All diets were isocaloric (AME(n) = 2,825 kcal/kg) and isonitrogenous (digestible lysine = 6.8 g/kg). Hens were housed in 40 floor pens (12 hens/pen, 8 pens/treatment) from 20 to 40 wk of age. Feed intake levels of the hens fed the meat and bone meal diets were reduced compared with those of hens fed the meat meal diets, whereas the feed intake level of hens fed the control diet was intermediate. Laying hen performance differed between treatments, being was most favorable for the Sonac-50 treatment and most adverse for the Daka-40 treatment. Differences in laying hen performance seemed to be related partly to differences in feed intake and corresponding amino acid intake.

We studied the effects of feed restriction and different energy and protein contents of the diet on BW, abdominal adipose tissue percentage, and adiponectin gene expression in abdominal adipose tissue in broiler chickens. Two experiments were conducted to determine whether feed restriction and dietary energy and protein levels alter adiponectin mRNA abundance in broiler chicks. Body weight and abdominal adipose tissue percentage were recorded and abdominal adipose tissue samples were collected at sampling days. Adiponectin mRNA expression in abdominal adipose tissue was quantitated using real-time quantitative PCR. We found that BW, abdominal adipose tissue percentage, and adiponectin gene expression were decreased in restricted chicks compared with those fed ad libitum at 32 d of age, but feed restriction had no effect on abdominal adipose tissue percentage and adiponectin gene expression at 49 d of age (experiment 1). Body weight was increased significantly in broilers fed on low-energy diets compared with those fed high-energy diets in experiment 1. Also, increasing levels of dietary protein increased BW in broiler chicks in experiment 2. A positive response in adiponectin gene expression and abdominal adipose tissue percentage was achieved by decreasing protein level in the diet of chicks at 32 d of age, but dietary protein had no effect on adiponectin gene expression at 49 d of age (experiment 1). Also, in experiment 2, abdominal adipose tissue percentage increased as dietary protein with fixed level of energy decreased in broiler chickens at 42 and 56 d of age. In experiment 1, increasing dietary energy levels increased adiponectin gene expression and abdominal adipose tissue percentage in chicks at 32 d of age. Also, we showed that dietary energy had an effect on abdominal adipose tissue percentage at 49 d of age. In experiment 2, a high-energy diet with a fixed level of protein increased abdominal adipose tissue percentage in chicks at 42 and 56 d of age. Dietary energy and protein levels had no significant effect on adiponectin gene expression in abdominal adipose tissue in broilers.

Different types (light to heavy) of laying hens are used in practice. There are questions about the optimum level of balanced protein (BP) supply in feed for different types of hens. Therefore, a broad range of amino acids intake levels [550 to 800 mg of true fecal digestible (TFD) Lys/hen per d] was tested on heavy (Lohmann Brown Classic) and light (Lohmann LSL Classic) laying hens from 24 to 60 wk of age. The other indispensable amino acids were fed in fixed ratios to TFD Lys in all treatments. A total of 282 Lohmann Brown Classic and 282 Lohmann LSL Classic hens (24 wk of age) were divided into 12 experimental groups (individually housed) based on daily egg mass production and BW. Replicates of the heavy strain started with a similar average daily egg mass production (51.1 g/hen per d), laying percentage (95.9%), and hen weight (1,860 g). Replicates of the light strain started with a similar average daily egg mass production (52.0 g/hen per d), laying percentage (97.3%), and hen weight (1,478 g). Diets were fed restrictively with an aimed feed intake of 110 g/hen per day [308 kcal/hen per d of AME(n (layers))] and 100 g/hen per day [280 kcal/hen per d of AME(n (layers))] for heavy and light hens, respectively, to achieve the required BP intake levels. For light hens, a BP intake with 600 mg of TFD Lys was sufficient for optimal laying percentage, whereas maximum laying percentage was not achieved with the highest TFD Lys in heavy hens. For egg weight, daily egg mass production as well as feed conversion regression analysis revealed that asymptotes were not achieved with the highest amino acid levels in both layer strains.

A radial basis function neural network (RBFN) approach was used to develop a multi-input, multi-output model for the effect of diets varying in the percentage of ME provided by protein (% ME(P)), fat (% ME(F)), and carbohydrate (% ME(C)) on live weight gain, protein gain, and fat gain in growing chickens. Thirty-three data lines representing response of the White Leghorn male chickens during 23 to 33 d of age to the diets varying in the % ME(P), % ME(F), and % ME(C) were obtained from literature and used to train the RBFN model. The prediction values of the RBFN model were compared with those obtained by multiple regression models to assess the fitness of these 2 methods. The fitness of the models was tested using R2, MS error, mean absolute deviation, residual SD, and bias. The developed RBFN model was used to evaluate the relative importance of each input parameter on chicken growth using a sensitivity analysis method. The calculated statistical values corresponding to the RBFN model showed a higher accuracy of prediction than multiple regression models. The sensitivity analysis on the model indicated that dietary % ME(P) is the most important variable in the growth of chickens, followed by dietary % ME(F) and % ME(C). It was found that the RBFN model is an appropriate tool to recognize the patterns of input-output data or to predict chicken growth in terms of live weight gain, protein gain, and fat gain given the proportion of dietary percentage of ME intake supplied through protein, fat, or carbohydrates.

This study was conducted to assess the influence of dietary CP and ME on growth parameters of the French guinea fowl, a meat-type variety. In a 2 x 3 x 3 factorial arrangement, 297 one-day-old French guinea keets (162 females and 135 males) were randomly assigned to experimental diets comprising 3,050, 3,100, and 3,150 kcal of ME/kg, each containing 21, 23, and 25% CP from hatch to 4 wk of age (WOA), and 3,100, 3150, and 3,200 kcal of ME/kg, each containing 19, 21, and 23% CP at 5 to 8 WOA. Using BW and G:F data from hatch to 8 WOA, the Gompertz-Laird growth model was employed to estimate growth patterns of the French guinea fowl. Mean differences in exponential growth rate, age of maximum growth, and asymptotic BW among dietary CP and ME levels were not significant. However, instantaneous growth rate and weight at inflection point were significantly higher (P < 0.05) in birds on the 25% CP diet than those on the 21% CP diet at hatch to 4 WOA (1.12 kg/wk and 0.79 kg vs. 1.04 kg/wk and 0.74 kg, respectively). The exponential growth rate was also higher (P < 0.05) in birds fed the 3,050 kcal of ME/kg diet with either 23 or 25% CP than those fed diets containing 3,050 kcal of ME/kg and 21% CP. Mean G:F was higher (P < 0.05) in birds fed diets containing 3,050 kcal of ME/kg and either 21 or 23% CP than those in other dietary treatments. Therefore, based on the Gompertz-Laird growth model estimates, feeding 21 and 23% CP and 3,100 kcal of ME/kg at hatch to 4 WOA and 19 and 21% CP with 3,150 kcal of ME/kg at 5 to 8 WOA can be recommended as adequate for growth for the French guinea fowl broilers.

An experiment was conducted to quantify the effects of 3 nutritionally complete (similar protein and energy) corn-based diets that contained different dietary protein concentrates (potato-CP 76%, fish-CP 66%, or a mixture of soy proteins, soybean meal-CP 48%, and full-fat soy-CP 36%) on the incidence of spontaneously occurring subclinical necrotic enteritis (NE) in broiler chickens. A total of 1,260 birds were placed into 18 solid floor pens (70 birds per pen) and fed 1 of the 3 experimental diets from 15 to 31 d of age. The weight gains and feed intakes of the birds fed the potato- and fish-based diets were lower (P < 0.001) than those of the birds fed the soy-based diets. Weight gain:feed intake ratio and mortality rate were not affected (P > 0.05) by dietary treatment The birds fed the potato-based diets had a higher incidence of necrotic lesions in the duodenum (P < 0.001) and proximal jejunum (P < 0.01) than those fed the soy-based diets. The chickens fed the potato-based diet had a higher (P < 0.001) proportion of moderate to severe duodenal and distal ileal hemorrhages and liver lesions than the birds fed the soy-based diet. There was also a higher (P < 0.05) level of serum antibodies for Clostridium perfringens alpha toxin in birds fed the potato-based diet compared with the other 2 diets. The birds fed the fish-based diet had a similar (P > 0.05) incidence of subclinical NE in comparison to the birds fed the soy-based diet, although there was a higher incidence of intestinal hemorrhagic lesions. The differences in incidence of subclinical NE were not consistent with the relatively small differences in amino acid content between the diets or in the contents of nonstarch polysaccharides. However, the potato protein-based diet had higher trypsin inhibitor activity and a lower lipid content that could have contributed to the increased incidence of subclinical NE.

The study presented here aimed to investigate the effect of dietary protein content on Arg needs and immunological responses of broiler chicks during the starter period. A total of 715 one-day-old male Ross broiler chicks were randomly assigned to 5 replicate pens for each of 11 experimental diets during a 21-d feeding trial. The dietary treatments included a corn-soybean meal control diet or experimental diets (corn-soybean meal-corn gluten meal) containing 5 dietary Arg levels of 80, 90, 100, 110, or 120% of NRC recommendations and 2 dietary protein levels of 19 and 22.35% of diet. Increasing dietary CP content significantly (P<0.001) increased daily feed consumption and weight gain. Also, feeding diets deficient in Arg to the chicks led to a noticeable decline in feed intake, and dietary Arg supplementation overcame decreased feed consumption and weight gain observed in Arg-deficient chicks. Feed efficiency was affected only by dietary Arg concentration so that chicks on Arg-deficient diets markedly (P<0.001) increased feed conversion ratio. Contrast comparisons showed that the highly variable responses of chicks to dietary Arg level were mainly attributed to dietary protein concentration: more dietary protein content and higher Arg demands. Among lymphoid organs, thymus (P<0.001) and spleen (P<0.05) were affected by dietary Arg deficiency, whereas diets low in CP content decreased (P<0.001) relative weights of thymus and bursa of Fabricius. Increase in dietary CP level from 19 to 22.35% caused an increase (P<0.001) in the proportion of lymphocytes and consequently lower (P<0.05) heterophil-to-lymphocyte ratio. Broiler chicks on Arg-deficient diets decreased the proportion of heterophils in peripheral blood. Furthermore, skin reaction to phytohemagglutinin P was impaired when the diets were low in CP and Arg contents. Similarly, a decrease in dietary CP and Arg levels diminished the antibody production response to Newcastle disease virus. The broken-line analysis indicate that the Arg requirements of starting broiler chicks for optimal immune functions (107% of NRC values) are higher than those for maximum growth performance (101%) or feed efficiency (103%) and are dependent on dietary protein concentration.

A study was conducted in a completely randomized design to evaluate the performance, excreta characteristics, and some blood nitrogen metabolite concentrations of 28-d-old male broilers fed 4 experimental diets in which CP was decreased in a stepwise manner from 23 to 17%. The other 4 diets were formulated to have 19 and 17% CP, in which 2 of them contained an additional 10% of particular essential amino acids (EAA) and 2 were supplemented with Gly and Glu. Ileal digestible quantities of all EAA were almost equal in the diets, and total amount of each EAA was maintained at or above NRC requirements. Decreasing dietary CP below 19% depressed performance and appetite and increased fat deposition in the whole body and abdominal cavity significantly. Adding the Gly and Glu mixtures to low-CP diets improved performance and decreased fat deposition. Uric acid, moisture, and acidity of excreta were decreased by reduction of dietary CP; excretory ammonia level was increased in 17% CP diets. Blood ammonia level was increased and plasma uric acid was decreased with reduction of CP to 17%. Supplementing Gly and Glu increased plasma and excretory uric acid level in spite of decreasing blood ammonia concentration. The aminostatic hypothesis cannot explain the sharp reduction in appetite in this experiment, because alteration of dietary CP had no significant influence on most plasma free amino acid levels. Therefore, reduction of CP to 19% not only does not impair performance but also decrease nitrogen, ammonia, and pH of excreta that may improve upon litter and air quality. Adding large amounts of crystalline EAA to diets with low intact CP increased blood and excretory ammonia concentration, which due to its negative effects on tissue metabolism may be the main cause of retarded growth and appetite in decreased CP diets below 19%.

Two studies evaluated effects of metabolizable energy (ME), digestible Lys (dLys), and amino acid (AA) balance on broiler performance. In experiment 1 diets contained 3 levels of ME (3,000, 3,100, and 3,200 kcal/kg) in combination with 4 levels of dLys (1.05, 1.13, 1.21, and 1.29%). A fixed proportion of dLys relative to CP and key indispensable AA was maintained in graded increments of CP from 21.9 to 26.9%. There was no interaction of ME and dLys for 21 d BW gain or adjusted feed conversion ratio, which improved linearly with dietary dLys. Increasing the dLys or ME had no effect on feed intake, and the linear improvement in performance was attributed to a step-wise increase in dLys when diets contained a balance of AA and CP. Experiment 2 evaluated broiler response to 20 d of age when diets contained graded increments in dLys while maintaining a fixed proportion of dLys relative to CP and indispensable AA (balanced CP), or when dLys was increased in diets by supplementing synthetic l-Lys to 1 of 2 basal diets with 22.0% CP (low CP) or 27.0% CP (high CP) without adjusting concentrations of other AA or CP. The BW gain of broilers fed the low CP diet series followed a quadratic response, and the dLys requirement was estimated to be 1.19 +/- 0.03% (1.30% total Lys). By contrast, BW gain on both the high CP and balanced CP diet series increased linearly. The higher BW gain and continued response to dLys above 1.19% when CP and AA concentrations were increased confirmed that the dLys requirement of broilers was dependent on the dietary CP. When a fixed ratio of dLys to CP was applied and indispensable and dispensable AA were not limiting, broiler BW gain and adjusted feed conversion ratio responded positively to incremental dLys up to at least 1.32% (27.2% CP) and was independent of the dietary ME over a range from 3,000 to 3,200 kcal/kg.

The response of digestive enzymes activities in the jejunal fluid of Peking ducks to dietary ME and CP content was investigated. In experiment 1, jejunal digesta from 24 cannulated male white Peking ducks of 18 wk of age were collected for 1 h out of every 4 h beginning at 0930 h on d 16, 18, and 20 of the experiment. The activities of amylase, trypsin, and chymotrypsin in jejunal fluid were determined. In experiment 2, 72 male cannulated ducks were randomly sorted into 4 groups. Four treatments consisted of combinations of 3,050 and 2,800 kcal/kg of ME, and 17.50 and 14.40% CP content were available ad libitum. Jejunal digesta samples were collected for 1 h every 4 h from 0930 to 1830 h on d 31, 33, and 35 of the experiment according to the results of experiment 1. The activities of amylase, trypsin, chymotrypsin, lipase, sucrase, and maltase in jejunal fluid were determined. In experiment 1, significant differences were found in the average activities of amylase and chymotrypsin among days. The collection time significantly affected the 3 enzyme activities, and average enzyme activities during the day were higher and more stable than during the night. In experiment 2, the effect of dietary ME content on the 6 digestive enzymes activities was not significant. But the dietary protein content significantly changed amylase, trypsin, and chymotrypsin activities.

Ammonia (NH(3)) emission is a major concern for the poultry industry. The objective of this research was to determine whether inclusion of dietary fiber and a reduced dietary CP content would decrease NH(3) emission from laying-hen manure. A total of 256 Hy-Line W-36 hens were fed diets with 2 levels of CP (normal and reduced) and 4 fiber treatments in a 2 x 4 factorial arrangement. The fiber treatments included a corn and soybean meal-based control diet and diets formulated with either 10.0% corn dried distillers grains with solubles (DDGS), 7.3% wheat middlings (WM), or 4.8% soybean hulls (SH) to contribute equal amounts of additional neutral detergent fiber. The CP contents of the reduced-CP diets were approximately 1 percentage unit lower than those of the normal-CP diets. All diets were formulated on the basis of digestible amino acid content and were formulated to be isoenergetic. Fresh manure was collected such that pH, uric acid, and Kjeldahl N contents could be measured. The NH(3) emission from manure was measured over 7 d by placing pooled 24-h manure samples in NH(3) emission vessels. Data were analyzed by ANOVA with Dunnett's multiple-comparisons procedure to compare results from the fiber treatments with the control, whereas the main effect of protein was used to compare the normal- and reduced-CP treatments. Dietary corn DDGS, WM, or SH lowered (P

Ammonia emission is a major concern for the poultry industry and can be lowered by dietary inclusion of fibrous ingredients and by lowering the dietary CP content. The objectives of this research were to determine the effects of dietary fiber and reduced-CP diets, which may lower NH(3) emission, on egg production and N balance in laying hens. A total of 256 Hy-Line W-36 hens were fed diets with 2 contents of CP (normal and reduced) and 4 fiber treatments in a 2 x 4 factorial arrangement from 23 to 58 wk of age. The fiber treatments included a corn and soybean meal-based control diet and diets formulated with either 10.0% corn dried distillers grains with solubles (DDGS), 7.3% wheat middlings (WM), or 4.8% soybean hulls (SH) added to contribute equal amounts of neutral detergent fiber. The CP contents of the reduced-CP diets were approximately 1 percentage unit lower than that of the normal-CP diets. All diets were formulated on a digestible amino acid basis to be isoenergetic. There were no effects (P > 0.05) of including corn DDGS, WM, or SH in the diet on egg production, egg weight, egg mass, yolk color, feed consumption, feed utilization, or BW gain. Although the corn DDGS and WM diets resulted in an increase (P < 0.001) in N consumption, N excretion was not affected (P > 0.10) compared with hens fed the control diet. The reduced-CP diets did not affect egg weight, feed consumption, or BW gain (P > 0.05); however, egg production, egg mass, feed utilization, N consumption, and N excretion were lower than that from the hens fed the normal-CP diets (P < 0.05). The results of this study show that the diets containing 10% corn DDGS, 7% WM, or 5% SH did not affect egg production or N excretion. However, the 1% lower CP diets caused a lower egg production and lower N excretion.

This study was conducted to evaluate optimum dietary concentrations of ME and CP for egg production performance of the Pearl Gray guinea fowl laying hens. In a 2 x 3 factorial arrangement, 360 Pearl Gray guinea fowl replacement pullets (22 wk of age) were randomly assigned to experimental diets with 2,800 and 2,900 kcal of ME/kg of diet, each containing 14, 16, and 18% CP, respectively. Each dietary treatment was replicated 4 times, and feed and water were provided ad libitum. Experimental birds were raised in laying cages and received 16 h of light throughout the study period. The birds were observed for feed consumption, hen-day egg production (HDEP), egg weight (EW), egg mass (EM), feed conversion ratio, internal egg quality, shell thickness (ST), and BW at the end of each 28-d lay period at 26 to 50 wk of age and at 62 to 86 wk of age. Mortality was recorded as it occurred. Mean HDEP, EW, EM, and ST were higher (P < 0.05) in hens receiving diets with 2,800 kcal of ME/kg of feed than those fed diets containing 2,900 kcal of ME/kg of diet. Hens on 14% CP diets also exhibited higher (P < 0.05) HDEP, EM, and ST than those fed diets containing 16 and 18% CP diets. Mean feed conversion ratio of birds on 2,800 kcal of ME/kg of diet and 14% CP diets were significantly lower than those of hens on other dietary treatments. Differences in feed consumption, EW, internal egg quality, BW, and mortality among dietary ME and CP concentrations were not significant (P > 0.05). Overall, diets composed of 2,800 kcal of ME/kg of diet and 14% CP were utilized more efficiently by the Pearl Gray guinea fowl laying hens at 26 to 50 and 62 to 86 wk of age.

The objectives of the study were to evaluate the effectiveness of a reduced-emission (RE) diet containing 6.9% of a CaSO(4)-zeolite mixture and slightly reduced CP to 21-, 38-, and 59-wk-old Hy-Line W-36 hens (trials 1, 2, and 3, respectively) on egg production and emissions of NH(3), H(2)S, NO, NO(2), CO(2), CH(4), and non-CH(4) total hydrocarbons as compared with feeding a commercial (CM) diet. At each age, 640 hens were allocated, randomly to 8 environmental chambers for a 3-wk period. On an analyzed basis, the CM diet contained 18.0, 17.0, and 16.2% CP and 0.25, 0.18, and 0.20% S in trials 1, 2, and 3, and the RE diet contained 17.0, 15.5, and 15.6% CP and 0.99, 1.20, and 1.10% S in trials 1, 2, and 3. Diets were formulated to contain similar Ca and P contents. Average daily egg weight (56.3 g), average daily egg production (81%), average daily feed intake (92.4 g), and BW change (23.5 g), across ages, were unaffected by diet (P > 0.05) over the study period. Age effects were observed for all performance variables and NH(3) emissions (P < 0.05). In trials 1, 2, and 3, daily NH(3) emissions from hens fed the RE diets (185.5, 312.2, and 333.5 mg/bird) were less than emissions from hens fed the CM diet (255.1, 560.6, and 616.3 mg/bird; P < 0.01). Daily emissions of H(2)S across trials from hens fed the RE diet were 4.08 mg/bird compared with 1.32 mg/bird from hens fed the CM diet (P < 0.01). Diet (P < 0.05) and age (P < 0.05) affected emissions of CO(2) and CH(4). A diet effect (P < 0.01) on NO emissions was observed. No diet or age effects (P > 0.05) were observed for NO(2) or non-CH(4) total hydrocarbons. Results demonstrated that diet and layer age influence air emissions from poultry operations.

A 2 x 2 factorial experiment was conducted to compare the effects of 2 male broiler breeder feed allocation programs (Concave or Sigmoid) during the rearing period to 26 wk of age and the interaction with dietary CP (12 or 17%) on BW and fertility. From 0 to 2 wk, all birds received a starter diet, after which, pens were randomly assigned to the 4 treatment combinations that ended at 26 wk of age. All males were weighed individually at 4, 8, 12, 16, 22, 26, 28, 32, 36, 40, 48, 52, 56, and 64 wk of age, and fertility was determined weekly from 27 to 32 wk of age and then every 2 wk to 64 wk of age. At 49 wk of age, the male feed allocation for all treatments was increased by 5 g/d. Even when fed the same as Sigmoid program males during the production period, males reared on the Concave feeding program lost BW from 32 to 40 wk of age and exhibited lower BW from 40 to 48 wk of age, which corresponded to a more rapid decrease in fertility. The 17% CP diet increased BW from 8 to 32 wk of age, but no significant differences were subsequently observed. The 12% CP rearing diet improved both weekly and cumulative fertility. A significant interaction between rearing feeding program and dietary CP during the third quartile period showed that the Concave program-17% CP diet combination was most negatively affected. The increase in male feed allocation at 49 wk restored fertility and caused differences among treatments to diminish. These data suggested that BW during the early rearing period did not affect fertility, but an increased BW due to either providing fast feed increments toward the end of the rearing period (Concave) or feeding a 17% CP diet produced males that were unable to sustain fertility after 40 wk of age without an appropriate allocation of feed.

A 3 x 3 treatment arrangement varying in dietary protein and TSAA:Lys was used to evaluate the effect of low-protein diets fed to Hy-Line W-98 laying hens. Phase I was 20 to 43 wk of age with 18.9, 17.0, and 14.4 g of protein/hen per day and 0.97, 0.85, and 0.82 TSAA:Lys, whereas phase II was 44 to 63 wk of age with 16.3, 14.6, and 13.8 g of protein/hen per day and 0.92, 0.82, and 0.72 TSAA:Lys. Egg production and feed consumption decreased from 83.7 to 82.2% and 98.8 to 95.6 g, respectively. Feed efficiency improved from 1.680 to 1.645 g of feed/g of egg mass with decreasing dietary protein. Body weight gain was similar for hens fed high or medium protein diets. In phase II, hens consuming 13.8 g of protein/day had significantly reduced egg weight compared with hens consuming 14.6 or 16.3 g of protein/day. Wet and dry albumen percentage, albumen solids, and albumen and yolk protein percentages were significantly decreased with feeding low-protein diets. Yolk protein percentage was increased from 14.85 to 15.11% when decreasing the ratio from 0.97 to 0.82. Hens consuming a low-protein diet produced eggs with the lowest specific gravity. An interaction was observed for protein retention during phase I, feeding 14.4 g of protein/day or a ratio of 0.97 improved protein retention by 9 and 16%, respectively. Overall, hens consuming 16.3 or 14.6 g of protein/hen per day performed similar to hens consuming 18.9 and 17.0 g of protein/hen per day during P1 and P2, respectively. Also, hens consuming diets containing 0.97 and 0.92 TSAA:Lys produced eggs with improved shell quality as compared with other ratios during P1 and P2, respectively.

This study was undertaken to assess dietary ME and CP concentrations for optimum growth performance of Pearl Gray guinea fowl pullets. In a 3 x 3 factorial arrangement, 540 one-day-old Pearl Gray guinea keets were randomly assigned to experimental diets with 2,900, 3,000, and 3,100 kcal of ME/kg of diet, each containing 20, 22, and 24% CP, respectively, from 0 to 8 wk of age (WOA). From 9 to 16 WOA, these diets were adjusted to contain 3,000, 3,100, and 3,200 kcal of ME/ kg, and each had 17, 19, and 21% CP, respectively. Each dietary treatment was replicated 4 times, and feed and water were provided ad libitum. Body weight and feed consumption were measured weekly. Mortality was recorded as it occurred. Overall, feed consumption was higher in birds on 2,900 and 3,000 kcal of ME/kg of feed and the 24 and 21% CP diets than other dietary treatments at 0 to 8 and 9 to 16 WOA, respectively. When compared with other dietary treatments, cumulative BW gains were higher (P < 0.05) in birds fed 3,000, 3,000 and 3,100, and 3,100 and 3,200 kcal of ME/kg of diet at 2 to 5, 6 to 8, and 9 to 16 WOA, respectively. Pullets receiving 24 and 21% CP diets also exhibited higher BW gains than other dietary treatments at 0 to 8 and 9 to 16 WOA, respectively. Feed conversion ratios were lower (P < 0.05) in birds fed 3,000, 3,100, and both 3,100 and 3,200 kcal of ME/kg of diet at 1 to 5, 6 to 8, and 9 to 16 WOA, respectively, than other dietary treatments. Pullets fed 24% CP diets and either 17 or 19% CP diets exhibited lower (P < 0.05) feed conversion ratios than other dietary treatments at 1 to 8 and 9 to 16 WOA, respectively. Thus, diets comprising 3,000 and 3,100 kcal of ME/kg were utilized more efficiently by the Pearl Gray guinea fowl pullets at 0 to 5 and 5 to 16 WOA, respectively. Also, these birds more efficiently utilized diets containing 24 and 17% CP at 0 to 8 and 9 to 16 WOA, respectively.

Increased dietary protein intake rapidly (3 h) decreases hepatic malic enzyme and increases hepatic histidase mRNA expression in broiler chicks. A series of experiments was conducted to determine the role that glucagon or a specific mixture of dietary amino acids might have in regulating the rapid changes in mRNA expression of these enzymes, when dietary protein intake is increased. Three hours after the injection of glucagon (240 microg/kg of BW) into the brachial vein of broiler chicks, hepatic malic enzyme mRNA expression was significantly lower and hepatic histidase mRNA expression was significantly greater than the level detected in saline-injected chicks. In addition, broiler chicks fed a high (40 g/ 100 g of diet) protein diet had significantly higher plasma glucagon levels at 1 and 3 h after initial access to this diet than broiler chicks fed a basal (22 g/100 g of diet) protein diet. The plasma glucagon concentration, however, was not different between the chicks fed the 2 dietary protein levels at 2 h after the initial access to the 2 diets. When a mixture of indispensable or dispensable amino acids was added to the basal diet to equal the concentrations of the individual indispensable or dispensable amino acids in the high protein diet, hepatic mRNA expression of malic enzyme and histidase were intermediate to the expression found in chicks fed the basal and high protein diet. The results indicate that glucagon may mediate the changes in the mRNA expression of malic enzyme and histidase in response to dietary protein intake and that total amino acid intake rather than the ingestion of specific amino acids regulates the mRNA expression of malic enzyme and histidase in chicks.

Two experiments with 14- to 35-d-old male broilers were performed to investigate the interactions between increasing levels of balanced protein (BP; 9.7, 10.7, 11.7, and 12.7 g of digestible Lys/kg of feed) and physical feed form. In Experiment 1 diets were offered as coarse mash and pellets of either good or poor quality. Good pellet quality was characterized by high durability. In Experiment 2 diets were offered as good quality pellets or coarse mash. However, for the latter particle size, distribution either was kept constant with increasing BP or changed with increasing proportion of soybean meal. Feed intake generally decreased with increasing BP; however, feed intake was highest in good pellets fed to broilers and lowest in mash fed to birds. Although there was only a small response on weight gain in mash-fed birds, feed conversion improved substantially for all feed forms with increasing BP. Particle size distribution did not affect this effect. Highest weight gain was achieved with good pellets; to achieve similar performance with poor pellet quality, higher levels of BP were needed. Carcass evaluation suggested increasing breast meat yield and particularly decreasing fat accretion with increasing BP. Results of both experiments indicate that optimum dietary amino acid levels for growing broilers may vary among different physical feed forms.

Four completely randomized designed experiments (EXP) were conducted to determine the effect of energy, amino acid (AA) levels, and bulk density of diets on growth performance of chicks fed diets containing corn (C) or cornstarch:dextrose (CD) as energy sources and soybean meal (SBM) or soy protein isolate (SPI) as protein sources. The chicks were fed C-SBM diets 6 to 8 d posthatching before allotment to treatment, and the assay periods ranged from 7 to 14 d. Initial weights were 86, 93, 94, and 71 g in EXP 1 to 4, respectively. Treatments were replicated 6 to 8 times with 4, 5, or 6 chicks per replicate. In EXP 1, the treatments were 1) C-SBM (1.26% Lys and 3,200 kcal of ME/kg); 2) CD-SPI (1.26% Lys and 3,460 kcal of ME/kg); 3) CD-SPI (1.36% Lys and 3,460 kcal of ME/kg); and 4) CD-SPI (1.26% Lys and 3,200 kcal of ME/kg). The AA in all diets were increased in proportion to Lys. In EXP 2, chicks were fed C or CD as the energy source and SBM or SPI as the protein source in a 2 x 2 factorial arrangement. In EXP 3, the treatments were 1) C-SBM (1.26% Lys and 3,200 kcal of ME/kg); 2) CD-SPI (1.26% Lys and 3,200 kcal of ME/kg); 3) Diet 1 limit-fed to chicks consuming 90% of Diet 2; 4) Diet 2 limit-fed to chicks consuming 90% of Diet 2. In EXP 4, Diets 1 and 2 were the same as Diets 1 and 2 in EXP 3, but fed in mash or pelleted form. In all EXP, chicks with access ad libitum to diets with SPI had decreased (P < 0.02) average daily gain (ADG) and feed intake (ADFI) compared with those with access ad libitum to diets with SBM. In EXP 2, feeding C- or CD-dextrose as the energy source had no effect (P > 0.05) on ADG, ADFI, or gain:feed. In EXP 3, ADG was decreased in chicks fed the diets with SPI relative to those fed diets with SBM, but the decrease was much greater in chicks that had access ad libitum to feed (protein source x feed intake, P < 0.01) than in those limit-fed to the same feed intake. In EXP 4, ADG, ADFI, and gain:feed were decreased (P < 0.01) in chicks fed diets with SPI as the protein source. Pelleting increased (P < 0.01) ADG, ADFI, and gain:feed regardless of protein source, but the increase was much greater in chicks fed the diets with SPI (protein source x feed form, P < 0.01). Results from these EXP indicate that diets with SPI compared with SBM do not result in maximum growth performance in commercial broilers, and the problem may be due somewhat to nutrient deficiency but more to the physical form of the diet.

Two experiments were conducted to determine broiler response to dietary protein during short (1 wk) or prolonged (>3 wk) heat stress (HS). In experiment 1, 21-d-old birds were kept at 20.3 degrees C (thermoneutral; TN), 27.3 degrees C (medium temperature; MT), or 31.4 degrees C (high temperature; HT) and fed diets with 18, 20, 23, or 26% CP for 21 d. Each treatment consisted of 2 blocks of 3 replicates of 15 birds. In experiment 2, broilers were fed diets with 18 or 26% CP or fed ad libitum 2 diets with 10 or 30% CP. Birds were kept at TN (23.5 degrees C) or slowly introduced to HS from 7 to 14 d of age and kept at HT thereafter (chronic; CHS; 29.4 degrees C), and a third group was moved to HT at 21 d (acute HS; AHS; 29.4 degrees C). There were 16 replicates of 4 chickens per treatment distributed in 2 blocks. Performance, body composition, and protein deposition were ascertained from 21 to 28 d and from 28 to 42 d (short and prolonged exposures, respectively). Feeding high protein diets in experiment 1 resulted in linear improvements in body weight gain and feed:gain (P < 0.001) for MT and HT birds, whereas TN birds exhibited a linear (P < 0.001) response to protein. Feed intake declined as CP increased for HT birds during the third week of the study (P < 0.05). In trial 2, better performance was always observed in TN birds. HS depressed performance, although feeding high CP partially ameliorated this effect under AHS and CHS. Regardless of temperature, choice-fed birds selected high protein diets (mean 25.6% CP) and performed similarly to those fed 26% CP. CHS birds showed similar performance to those under AHS. Efficiency of protein deposition was unaffected (P > 0.05). Level of HS and duration of hyperthermia may determine the response of birds to dietary protein. Discrepancies between the 2 studies in response of birds to protein found after prolonged exposure to HS are discussed in view of the differences in levels of certain amino acids used within each experiment.

The objective of this study was to investigate the effect of dietary macronutrient ratio on energy, protein, and lipid metabolism and on the involvement of diet-induced thermogenesis in feed intake regulation of broiler chickens. Male broilers were reared from 1 to 7 wk on isoenergetic diets with substitutions between fat and protein and similar carbohydrate content [low protein (LP): 126 vs. 242 g of protein/kg; low fat (LF): 43 vs. 106 g of fat/kg]. Every week from 21 d onward, 3 chickens per group were placed in open-circuit respiratory cells to measure energy and protein metabolism in fasting, short-term refeeding (5 h) and ad libitum conditions. As LP chickens had a significantly lower BW from 2 wk onward, all parameters were expressed per kilograms of metabolic BW. Feed intake, gross energy intake, and apparent metabolizable energy intake were significantly higher in LP than LF birds. The excessive energy relative to protein intake resulted in significantly increased heat production and energy retention as fat. The latter effect and a significantly increased respiratory quotient indicated higher de novo lipogenesis in the LP chickens. Furthermore, the efficiency of protein retention was significantly better in LP broilers. Neither diet-induced thermogenesis nor feed intake during a 5-h refeeding period was affected by diet composition. Our results indicate that isoenergetic substitution of fat for protein has a strong effect on growth and on energy and protein balance in broilers. The theory linking diet-induced thermogenesis to feed intake could not be corroborated or countered, and further research is warranted.

Several experiments in which the dietary ideal protein (IP) levels were increased indicate that with current IP recommendations the maximum performance of broilers will not be achieved. However, available data of this IP-increment approach is scarce and, for the starter phase, entirely lacking. The objective of the present study, therefore, was to generate data regarding the effects in the starter phase and to test the impact of adequate vs. high IP levels in preceding phases on the response to IP increment in the phase under study. To evaluate this, an IP dose response in the starter phase and factorial arrangements combining adequate or high IP levels in starter and grower diets with low, adequate, or high IP levels in finisher diets were carried out with male and female broilers. Enhanced dietary IP levels in the starter diet increased BW gain in the starter phase and in the consecutive grower phase. Moreover, it was shown that a delay in BW gain due to suboptimal IP levels in the starter diet could only be partly compensated for in later phases of life. These results demonstrate the need for a reevaluation of IP levels used in practical starter diets. Feed conversion efficiency and BW gain responses to increased IP levels in the grower and finisher diets were less pronounced when high compared with adequate IP levels were fed in the preceding phase. This difference in response could not be detected statistically but was consistent between experiments and phases. Therefore, this phenomenon should not simply be neglected.

A series of four experiments was conducted to determine whether-shell quality during the late stages of egg production can be improved by using diets that are effective in reducing egg size. The experiments involved dietary manipulation of protein, methionine, choline, folic acid, and vitamin B12. In experiment 1, reducing dietary protein in combination of reducing the dietary methionine and choline or this diet without supplemental folic acid and vitamin B12 resulted in reduced egg weight and improved shell quality. However, egg production also was drastically reduced. In experiment 2, reducing the dietary level of methionine, without adding supplemental choline, folic acid, and vitamin B12 reduced egg size and improved shell quality, but egg production was reduced as well. In this experiment reducing the dietary methionine without supplemental folic acid and vitamin B12 reduced egg size and improved shell quality with no adverse effect on egg production. In experiment 3, reducing the dietary level of methionine and choline or reducing the dietary level of choline, folic acid, and vitamin B12 reduced egg size and improved shell quality without adverse effects on egg production. On the other hand, reducing dietary methionine, folic acid, vitamin B12, and supplemental choline reduced egg weight and improved shell quality but lowered egg production. In experiment 4, reducing dietary methionine together with reducing choline and vitamin B12 reduced egg size and improved shell quality with no adverse effect on egg production. The results of this series of experiments generally indicate that certain manipulations of the combination of methionine, choline, folic acid, and vitamin B12 have the potential to reduce egg weight and improve shell quality without affecting egg production during the latter stages of the egg production cycle.

An experiment was carried out to determine the effect of dietary protein level on the specific activity of hepatic L-threonine dehydrogenase in young growing chicks. Six replicate pens of seven Leghorn chicks were fed semipurified diets containing 23, 27, or 32% CP with identical relative proportions of amino acids in each protein group. Body weights and feed consumption were measured for 3 d, and hepatic mitochondria were isolated for assay of threonine dehydrogenase (TDH) activity. Weight gains and feed efficiency increased at each level of protein supplementation, but feed consumption was not affected by protein level. The specific activity of threonine dehydrogenase in isolated liver mitochondria was significantly (P < 0.05) higher in the 32% CP group than in the 23% CP group, and the activity in the 27% CP group was intermediate. We conclude that moderate increases in dietary protein level result in elevated hepatic threonine dehydrogenase activity in growing chicks.

The purpose of the present study was to test the suitability of the solids of nejayote (a waste product from the tortilla industry) in diets for broilers. The nejayote was obtained from two different tortilla-making factories and the solids were obtained by centrifuge then dried in a hot-air drier. Diets were formulated to be isocaloric and isonitrogenous according to the NRC dietary requirements (1994). Nejayote solids were supplemented at 2, 4, and 6% of the diet. Results show that the content of protein and calcium in the dried solids of nejayote were 5 and 13%, respectively. The performance of broilers fed diets supplemented with dried nejayote did not differ from that of those fed the control diet. Therefore, it is concluded that nejayote solids are suitable for broiler feed and do not affect growth performance. Utilization of nejayote solids at higher levels is a possibility provided that no adverse effects on body weight, feed utilization, and feed:gain ratios are observed.

This study evaluated three spent hen meals (SHM) that were produced in commercial rendering plants. The levels (percentage) of selected nutrients (mean and range) in the meals were: CP, 64 (56 to 71); ash, 16 (12 to 18); lysine, 4.0 (3.6 to 4.3); methionine, 1.3 (1.2 to 1.4); cystine, 1.1 (0.8 to 1.5). Protein efficiency ratios (PER; weight gain per unit of protein intake) were determined in chicks fed 10% CP diets containing a SHM as the only source of dietary protein. The PER values for the SHM averaged 1.6 but varied from 1.1 to 2.2. An experiment was conducted using New Hampshire x Columbian chicks during the 7 to 20 d age period to determine the effect of substitution with either 7.5 or 15% of a SHM to a 21.5% CP corn-soybean meal diet. When substituted at 7.5%, growth performance was not affected by two of the SHM but was depressed by the other one. Growth performance was decreased by all SHM when substituted at 15% of the diet. True amino acid digestibility and TMEn of the SHM were determined using the precision-fed cecectomized rooster assay in which four roosters were crop-intubated with 30 g of a SHM and excreta were collected for 48 h. True amino acid digestibility varied among SHM (P < or = 0.05) and digestibility of cystine was substantially lower than digestibility of the other amino acids. Mean TMEn (kilocalories per gram of DM) of the SHM was 3.003 but varied by 44% among samples. The results of this study indicated that SHM has substantial nutritional value for poultry but the nutritional quality may vary greatly among samples.

This experiment evaluates the effect of decreasing dietary CP, in addition to the effects of dietary supplements of L-Thr to low CP diets, in Large White Nicholas toms from 0 to 18 wk of age. Toms were fed dietary treatments consisting of four levels of dietary CP as a percentage of NRC (1994) recommendations (100, 92, 84, and 76% of NRC recommendations). Additional treatments consisted of supplements of L-Thr (0.1 and 0.2% of diet) added to the 92 and 84% NRC CP treatments. All eight dietary treatments were formulated to meet a minimum of 105% of NRC (1994) recommendations for Met, TSAA, Lys, Thr, and Trp. Body weight, feed conversion, mortality, and carcass composition responses were measured. Decreasing CP to 84% of NRC resulted in 18-wk BW lower than that (P < or = 0.001) of toms fed diets containing 100 or 92% of NRC CP; however, toms fed 84% of NRC CP diet supplemented with 0.1% L-Thr had 18-wk BW equal to (P < or = 0.001) that of the 100 and 92% NRC CP treatments. Toms fed diets containing 76% of NRC CP had depressed BW and feed:gain in comparison to all other treatments. No adverse effects in cumulative feed:gain (0 to 18 wk) were noted by decreasing CP from 100 to 84% of the NRC recommendations. Mortality did not differ among treatments. Treatments had no effect on carcass fat expressed as a percentage of hot carcass weight. Breast meat yield (deboned Pectoralis major and Pectoralis minor) was highest (P < or = 0.001) in toms fed the 100 and 92% NRC CP treatments. The 84 and 76% NRC CP treatments resulted in decreased breast meat yield regardless of L-Thr supplements. These results indicate that diets containing Met, TSAA, Lys, Thr, and Trp at a minimum of 105% NRC recommendations may support favorable breast meat yield when CP is decreased to 92% of the NRC (1994) recommendation. If growth and feed conversion are the desirable traits, rather than breast meat yield, CP levels below 92% of the NRC (1994) recommendation may support favorable responses.

Chickens from three genetic stocks known to differ in growth potential consumed ad libitum either a single (control) diet or a choice of two diets that differed in protein and energy. Formulation of the choice diets was such that when mixed in specific proportions they provided single diets that decreased in protein and increased in energy over the experimental period. When comparisons of feeding regimens were made at a common age, body weights and feed efficiencies for all stocks were enhanced in chicks fed a single diet. When comparisons were made at a common body weight for controls, chickens fed the single diet were about 15% heavier than those given a dietary choice. For feed efficiency, however, the pattern remained for the faster growing stock whereas there was no difference between feeding regimens for the slower growing stock. Chicks provided a choice of diets had heavier abdominal fat pads and lighter breasts relative to body weight than those fed a single diet. With choice feeding, there were stock by diet interactions for dietary preferences through the first 9 d after hatch. Early on, the interactions resulted from the faster growing stocks exhibiting a greater preference for the diet higher in protein and lower in energy than the slower growing stock. By Day 5, however, the interaction occurred because stocks exhibited either no dietary preference or preferred the diet that was lower in protein and higher in energy. Regardless of genetic stock, at 9 d of age and thereafter there was a clear preference for the diet lower in protein and higher in energy than the diet higher in protein and lower in energy. These data for feed intake were consistent with behavioral observations that showed a preponderance of chicks eating from the feeder containing the diet lower in protein and higher in energy. Compared to a single diet, under choice feeding, energy utilization was negatively influenced more in the faster than slower growing stocks. Protein and sulfur amino acid utilization was not affected by feeding regimen in faster growing stocks, but was enhanced under choice feeding in the slower growing stock. Although lysine utilization was enhanced by choice feeding in all stocks, the effect was greater in the slower than in the faster growing ones. These data demonstrate that although broiler diets are formulated to enhance growth and overall feed efficiency, chicks that are provided a dietary choice of protein and energy do not eat to maximize growth or feed efficiency.

An experiment was conducted to determine the effect of feeding method (constant vs variable) and method of formulation (lysine vs protein) on the performance and profits of first cycle, phase 2 DeKalb Delta hens from 40 to 52 wk of age as influenced by egg and feed prices. Treatments 1 to 5 were formulated based on lysine to contain 0.65 to 0.81% TSAA and fed continuously regardless of feed consumption (constant feeding). Treatments 6 to 10 and 11 to 15 were formulated based on lysine to supply 570 to 650 mg TSAA and protein to supply 580 to 660 mg TSAA per hen per d, respectively, and fed based on feed intake. Dietary TSAA level had no overall significant effect on feed consumption, egg production, egg weight, mortality, or body weight. Hens fed diets using the constant method of feeding had significantly higher egg production, egg weight, egg specific gravity, and body weight than hens fed diets formulated based on lysine or protein using the variable method of feeding. When the treatments in the two variable feeding methods were compared, feed consumption was significantly higher for hens fed diets formulated based on protein whereas egg production, egg weight, egg specific gravity, and body weight were not different. It was concluded that method of formulation (lysine vs protein) and TSAA levels required for maximum profits can vary from at least 570 to 821 mg per hen per d depending upon energy and protein cost.

Three experiments were conducted with cage-reared broilers to 21 d following nutrient restriction from 6 to 12 d age. In Experiment 1, birds were full-fed from 6 to 11 or given 50% of ad libitum intake on a daily basis, or 100% of ad libitum intake on a daily basis when the diet was diluted 50% with oat hulls. Birds were not able to fully recover body weight depression by 21 d, although birds previously restricted, by whatever method, were more efficient (P < 0.01) in overall energy intake:body weight gain. Prior feed restriction had no effect on ability to metabolize diet energy (P > 0.05), although these birds did exhibit increased nitrogen retention compared to birds full-fed from 6 to 11 d. In a second experiment, birds were fed diets with 1.25, 1.38, 1.51, 1.63, 1.76, or 1.88% lysine in the realimentation diet from 12 to 21 d. Lysine level had no effect on growth rate or feed efficiency (P > 0.05) for full-fed birds; however there was a linear (P < 0.05) decline in growth rate from 12 to 21 d in response to extra dietary lysine for the birds previously feed restricted from 6 to 12 d. In a third experiment, birds were fed diets varying in energy (3,000 to 3,300 kcal/kg) or protein (22 to 29% CP) from 12 to 21 d following ad libitum vs 50% feed restriction from 6 to 11 d age. Protein level of the diet had little effect on performance traits to 21 d, although there was an indication of improved growth in response to the higher energy concentration. Birds full-fed from 6 to 11 d showed increased liver size at 21 d when fed more protein, although the converse was true for the restricted birds (P < 0.05). The growth response to diet energy was associated with increased carcass fatness. In general, there does not seem to be any advantage to manipulating diet formulation during realimentation of birds previously nutrient-restricted.

An experiment was conducted to quantify the relationships between broiler carcass specific gravity and chemical composition (percentage moisture, percentage lipid, percentage protein). Carcasses of widely varying compositions were produced by feeding several dietary protein and energy combinations (52 to 64% moisture, 0.6 to 2.5% ash, 1.6 to 11.7% lipid, and 4.9 to 8.0% nitrogen). Very strong relationships were found between percentage moisture and percentage lipid (r = -0.969) and percentage moisture and percentage N (r = 0.968). Strong relationships were found between specific gravity and percentage lipid (r = -0.872) and specific gravity and percentage N (r = 0.857). Specific gravity is recommended as a means to estimate carcass fat in broiler chickens.