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Three pen trials were conducted to determine the main effect of alum addition to litter on form of poultry litter P using a 2 x 2 factorial structure of the subunit treatments: diets including high available phosphorus/low phytate corn (HAPC) and phytase (PHYT). Male broilers (1,760 per flock) were grown to 42 d having starter diets with 0.45% available P and grower diets with 0.35% available P. In the first trial, total litter P (tP) was greatest for the yellow dent corn (YDC) diet (12 g/kg) and least for the HAPC and PHYT combination (H&P) diet (6.9 g/kg) with the individual PHYT and HAPC diets falling in between at 9.1 g/kg and 9.4 g/kg tP. Also in the first trial, the litter water-soluble P (wP) was highest for PHYT (2.8 g/kg), least for the HAPC and H&P diets (1.5 g/kg) with the YDC diet falling between (2.2 g/kg). Alum was added to the litter after the first experiment. In the second and third experiments, alum inclusion significantly reduced the wP when compared with the treatments with no alum. In the third trial, the least wP was present in the alum-HAPC treatment. Phytase, YDC, and HAPC diets with no alum litter treatment generated the most wP. Since these diets appear to have little or no difference with respect to quantity of wP, this work suggests that form of litter P generated by alternative diets should be considered as criteria when attempting to reduce P in broiler litter applied to land.

High available phosphorus corn (HAP) developed using the low phytic acid 1-1 (lpal-1) allele of the corn LPA1 gene containing 0.27% P, with 0.17% nonphytate P (NPP), was compared to near isogenic normal corn (LPA1), which contained 0.23% P and 0.05% NPP. Five levels of NPP from either HAPC or normal corn (0.40, 0.35, 0.30, 0.25 and 0.20% + 300 phytase units (FTU)/kg microbial phytase) were combined in a 2 x 5 factorial experiment for a total of 10 dietary treatments. Each dietary treatment was fed to eight replicate cages with five Hy-Line W-36 hens per replicate cage from 20 to 40 wk of age. Feed consumption and egg production were not significantly affected by dietary NPP level or corn type. Feed conversion ratio (g feed:g egg mass) was improved at the 0.35% NPP level (1.856) compared to the other levels of NPP--0.40, 0.30, 0.25, and 0.20% + phytase having feed conversion ratios of 1.872, 1.905, 1.930, and 1.898, respectively. Egg weight and egg mass decreased significantly as dietary NPP decreased; diets with 0.20% NPP plus phytase had equal egg mass to the 0.35 and 0.40% NPP diets. A significant corn type x NPP interaction effect was observed for egg weight, such that within the HAP corn diets, egg weight decreased more markedly at the 0.25% NPP levels compared to the normal corn 0.25% NPP diets. Specific gravity was not affected by dietary treatment, but percent dry shell was improved at the lower AP levels and with phytase treatment. Dietary NPP level and corn type had no significant effect on bone ash. Excreta levels of total phosphorus decreased significantly as dietary NPP decreased and were lower in the HAP corn excreta compared to normal corn excreta. Total P, Ca, Zn, Cu, and Mn retention were significantly affected by NPP level and corn type. HAP corn reduced Ca, Zn, Cu, and Mn retention compared to normal corn; this negative effect was alleviated by phytase supplementation to HAP corn diets. HAP corn allowed less dicalcium phosphate supplementation in layer diets compared to normal corn while supporting equal egg production. Phytase supplementation of low NPP diets had no significant positive effects on egg production parameters in either corn type diets.

A study was conducted to evaluate the ability of the young (0 to 3 wk) broiler chicken to utilize the P provided by a high available P corn [HAPC; 0.27% total P and 0.17% nonphytate P] in comparison with yellow dent corn (YDC; 0.23% total P and 0.03% nonphytate P), and to determine the extent to which supplementation with exogenous phytase enzyme could reduce the demands for dietary P and subsequently reduce P excretion. Diets prepared using the two types of corn differed in the amount of phytate-bound P, with the HAPC diets containing approximately 50% less phytate-bound P. Treatment diets were prepared by varying the amount of dicalcium phosphate, and ranged from 0.10 to 0.50% nonphytate P for YDC diets, and from 0.18 to 0.50% nonphytate P for HAPC diets. Sublots of each diet were supplemented with 800 units/kg phytase. Each diet was fed to six pens of five male chicks of a commercial broiler strain from 1 to 21 d of age. Regression analysis was used to estimate nonphytate P requirements for each corn type with and without phytase supplementation. The greatest need for nonphytate P was for maximum tibia ash, with requirements of 0.39, 0.29, 0.37, and 0.32% in diets with YDC, YDC plus phytase, HAPC, and HAPC plus phytase, respectively. Addition of phytase liberated approximately 50% of the phytate-bound P from each diet. These levels were sufficient to support body weight, feed conversion, and livability. Fecal P content of broilers fed diets with YDC at the NRC (1994) recommended level of 0.45% nonphytate P was 1.21%, whereas at the respective requirement points indicated above, the P content was 1.09, 0.87, 0.78, and 0.64% in feces from broilers fed diets with YDC, YDC plus phytase, HAPC, and HAPC plus phytase, respectively. Thus, fecal P output could be reduced while maintaining optimum performance by the use of reduced dietary nonphytate P, introduction of HAPC, and phytase supplementation. One of the greatest benefits of phytase supplementation appeared to be maintaining livability at lower dietary levels of nonphytate P.

A study was conducted to determine the extent fecal P levels could be reduced while maintaining performance. Various strategies were employed including the use of a high available phosphorus hybrid of corn (HAPC), supplementation with phytase enzyme, and reduced dietary P levels. The use of HAPC resulted in a 50% reduction in phytate-bound dietary P as compared with a normal yellow dent corn (YDC) diet. Dietary nonphytate P was maintained at either NRC (1994) recommendations for appropriate age periods or reduced by 0.075 or 0.15%. Portions of the diets were supplemented with 1,000 units of phytase/kg. Male chicks of a commercial strain were grown to 56 d on the test diets. Broilers fed diets with HAPC had BW, feed conversion, livability, and tibia ash that were equal to or superior to those fed diets with YDC with considerably reduced fecal P content at any dietary level of nonphytate P. Phytase supplementation enabled birds to maintain live performance at lower levels of nonphytate P, further reducing the fecal P output. One of the greatest contributions of phytase was a reduction in mortality at the lower levels of nonphytate P. Dietary P levels could be reduced by 0.075% under NRC (1994) recommendations without adversely affecting live performance; a reduction of 0.15% in conjunction with phytase supplementation maintained BW, feed conversion, and livability but reduced tibia ash. The extent to which dietary P levels can be reduced over the entire feeding program is subject to further research.

Broiler males were examined for their response to feeds containing CP 1 to 2% below levels advocated by NRC (1994) and when supplemented with L-glutamic acid. Crude protein and glutamic acid treatments were imposed in starting, growing, and finishing feeds over 7 wk with K at high and low levels likely to occur in practice (0.80 vs 0.65 to 0.55%). All feeds were formulated to be isocaloric (3.20 kcal ME/g) and satisfy NRC (1994) essential amino acid (EAA) minimum requirements. Improved live weight gain occurred during the first 6 wk with supplementation of glutamic acid to the low CP feed but not when intact protein per se was used to increase CP. A similar advantage in growth was obtained from glutamic acid in response to its addition at equivalence of 1 to 2% CP as well as when dietary adjustments maintained low CP. Response to altered K could not be interpreted because of concurrent differences in glutamic acid and AMEn intakes. High glutamic acid levels did not decrease abdominal fat unless CP increased concurrently, whereas carcass back bruising and drumstick deformations were relieved by supplemental glutamic acid independent of CP. Increased weight gain from glutamic acid was only evident with drumsticks and debris that included the back when carcasses were cone-deboned. Supplemental glutamic acid is believed to improve the rate of connective tissue formation during rapid growth.

Broilers were grown to 42 days of age on diets supplemented with salinomycin (60 mg/kg), monensin (99 mg/kg), or halofuginone (3 mg/kg) and continued on unmedicated diets to 49 days of age. There were no significant (P greater than .05) differences among anticoccidials in final body weight, feed conversion, or mortality rates. Samples of birds were processed for dressing percentage and parts yield. Both males and females fed salinomycin had significantly higher breast meat yield as a percentage of postchill weight than those fed halofuginone but not those fed monensin; differences were not significant for breast meat yield of males or females fed monensin or halofuginone. Males fed halofuginone had significantly heavier leg quarters than those fed salinomycin but not those fed monensin. Females fed salinomycin had significantly higher water uptake during chill than those fed monensin or halofuginone. Results of the present study indicate that the anticoccidial used in growing broilers may influence some carcass yield parameters.

Broilers were grown to 49 days of age on diets supplemented with bambermycins (BAM, 2.2 ppm), bacitracin methylene disalicylate (BMD, 27.5 ppm), virginiamycin (VM, 11 ppm), or an unmedicated control. Samples of birds were processed for dressing percentage and parts yield. There were no significant (P greater than .05) effects of antibiotics on final body weight, feed conversion, or mortality. In male broilers, BMD and VM significantly (P less than or equal to .05) increased dressing percentage and percentage yield and reduced the skeletal rack as a percentage of postchill weight compared to those fed the nonmedicated control. All antibiotics significantly increased breast skin weight and breast skin as a percentage of postchill weight of as compared with those fed the unmedicated control. In female broilers, BAM and BMD significantly increased dressing percentage and percentage yield and increased breast weight and breast as percentage of postchill weight as compared with those fed the unmedicated control diet. Females fed BMD also had significantly heavier leg quarters and breast skin than those fed the unmediated control. Females fed VM had increased breast skin weight and breast skin as a percentage of postchill weight than those fed the unmedicated control. The results of the present study indicate that antibiotics may influence dressing percentage and parts yield in the absence of improvements in body weight gain or feed utilization.

Male broiler chicks were grown to 21 days of age under normal conditions, then placed in environmental chambers maintained under constant (24 C) or cyclic (24 to 35 C) heat conditions. Chicks were acclimated for 1 wk on a standard grower basal diet. Standard grower basal diets were fortified with 0, 125, 250, 500, or 1,000 ppm coated ascorbic acid (AA) or 0, 125, 250, or 500 ppm acetylsalicylic acid (ASA). Test diets were fed for 14 days in two separate studies. Cyclic heat conditions reduced feed intake and significantly reduced weight gains in both trials. Feed efficiency was not significantly affected by heat stress. Neither AA or ASA had beneficial effects on broiler growth or feed efficiency.