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Current feed evaluation systems often assume that fermented starch (i.e. resistant starch (RS)) yields less energy than digested starch. However, growth rates of pigs fed low and high RS diets are often the same when feed is available ad libitum. This may be explained by its effect on digestive processes changing feeding behavior, and consequently energy utilization. This study aims to investigate the effect of RS on nutrient digestion and digesta passage rate in pigs, in combination with its effect on feeding behavior and growth performance under ad libitum conditions. In experiment 1, 20 male pigs (40 ± 2.82 kg) were fed diets containing either 50% waxy maize starch (low in RS (LRS)) or high-amylose maize starch (high in RS (HRS)), and soluble and insoluble indigestible markers. After 14 days of adaptation to the diets, pigs were fed hourly to reach steady state (6 h), dissected, and digesta were collected from eight segments. From the collected samples, nutrient digestion and passage rate of the solid and liquid digesta fraction were determined. In experiment 2, 288 pigs (80 ± 0.48 kg; sex ratio per pen 1 : 1; boar : gilt) were housed in groups of 6. Pigs were ad libitum-fed one of the experimental diets, and slaughtered at approximately 115 kg. Feed intake, growth and carcass parameters were measured. Ileal starch digestibility was greater for LRS-fed than for HRS-fed pigs (98.0% v. 74.0%; P < 0.001), where the additional undigested starch in HRS-fed pigs was fermented in the large intestine. No effects of RS on digesta passage rate of the solid or liquid digesta fraction and on feeding behavior were observed. Growth rate and feed intake did not differ between diets, whereas feed efficiency of HRS-fed pigs was 1%-unit higher than that of LRS-fed pigs (P = 0.041). The efficiency of feed used for carcass gain did not differ between diets indicating that the difference in feed efficiency was determined by the non-carcass fraction. Despite a 30% greater RS intake (of total starch) with HRS than with LRS, carcass gain and feed efficiency used for carcass gain were unaffected. RS did not affect digesta passage rate nor feeding behavior suggesting that the difference in energy intake between fermented and digested starch is compensated for post-absorptively. Our results indicate that the net energy value of fermented starch currently used in pig feed evaluation systems is underestimated and should be reconsidered.

To overcome negative energy balance during the peripartal period of sows, an ad libitum feeding strategy (ADLIB) as alternative for commonly used restricted feeding (STANDARD, on average 3kg feed/day) was evaluated. Plasma metabolites and thyroid hormones, change of back fat thickness (BF), reproductive traits, and piglet performance were monitored. Voluntary feed intake of ADLIB sows declined at farrowing but was still more than twice the amount of what was offered to STANDARD sows. Consequently, ADLIB sows lost less BF than STANDARD sows (P=0.041). Additionally, BF change was affected by body condition. LEAN sows (BF<18mm on d 105 of gestation) lost less BF than MODERATE sows (18mm≤BF≤22mm) which lost less BF than FAT sows (BF>22mm) (P<0.001). Except for a decreased percentage of stillborn piglets for MODERATE sows (P=0.044), reproduction results were not affected. Piglet weaning weight of ADLIB-FAT and STANDARD-MODERATE sows was reduced in comparison with that of ADLIB-LEAN sows (P=0.005). Regardless of body condition, all metabolites and thyroid hormones measured showed a time dependent profile (P<0.001). On d 112 of gestation increased concentrations of creatinine (P=0.004), non-esterified fatty acids (P=0.039), and serum crosslaps (P=0.016) for STANDARD sows were observed. Triglycerides were increased for FAT sows (P<0.001), and decreased faster over time for ADLIB (P=0.013) and for FAT (P=0.012). Although ad libitum feeding during the peripartal period only resulted in less mobilization of muscle, fat, and bone reserves on d 112 of gestation, results of BF change and piglet weaning weight indicated that ad libitum feeding is beneficial for sow performance provided that BF is below 22mm., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Traditionally in swine nutrition, analyses of starch and fiber have focused on assessing quantity; however, both have a wide range of functional properties making them underappreciated nutrients. Starch ranging from low to high amylose changes from rapidly digestible in the upper gut to poorly digestible but fermentable in the lower gut thereby changing from a source of glucose to VFA source. Likewise, fibers ranging from low to high viscosity affect digesta flow and from slowly to rapidly fermentable alter production of VFA serving as energy for the gut or whole body. Our hypothesis is that total extent, kinetics, and site of digestion or fermentation of starch and fiber are important for whole body nutrient use and intestinal health. To elucidate their effects, we developed in vitro, lab-based methodologies to describe kinetics of digestion and fermentation and linked these with in vivo models including i) ileum cannulation to collect digesta, ii) portal-vein catheterization to sequentially sample blood, iii) slaughter method to collect site-specific intestinal tissue and digesta, and iv) indirect calorimetry. Using these methods, kinetics of nutrient absorption was associated with pancreatic and intestinal hormones released into the portal vein, intestinal microbiota, and gene expression in intestinal tissue and microbiota. These studies confirmed that slowly digestible starch is partially degraded in the distal small and large intestine and fermented into VFA including butyrate (10-fold increase in net portal appearance), which reduces insulin responses by 60% and whole body energy use. Starch entering the distal intestine altered mRNA abundance of nutrient transporters and was bifidogenic. Extremely viscous purified fiber dampened glycemic responses and reduced digesta passage rate by 50% thereby increasing ileal digestion of dietary nutrients whereas increased fiber in feed grains reduced nutrient digestibility. Fermentable fiber increased butyrate and insulin production. These methods will therefore support elucidation of mechanisms that link starch and fiber properties to whole body nutrient use and intestinal health.

As environmental constraints become more important issues for the animal industry, selecting feed ingredients that yield good animal performance but also minimize environmental impact of animal production becomes critical. The objective of this research was to identify which compositional features would be desirable for soybean meal to maximize nutritional value and minimize animal waste. Eight soybean samples were selected from a database of 72, such that maximal variability for CP, NDF, and ADF content was obtained. Samples were subsequently processed into meal using standardized procedures. In Experiment 1, 8 cannulated pigs were used to determine ileal digestibility following a Latin square design. In Experiment 2, 5 of the samples were used in complete feeds and 10 pigs were used in a crossover Latin square design to determine the total tract digestibility, odorants in fresh and 5-d-old manure, and ammonia emission from manure. Differences up to 6% in ileal DM digestibility and 8% in ileal CP digestibility were observed. This difference was reduced to 1.1% for total tract DM digestibility and 4% for total tract CP digestibility. Differences in odorant concentration were 3-fold and for in vitro ammonia emission were 42%. The only compositional variable with a significant effect on digestibility was stachyose, which negatively affected ileal digestibility of DM (r = -0.80, P = 0.02) and energy (r = -0.73, P = 0.04). None of the compositional variables measured affected ileal CP digestibility. Ileal CP digestibility, however, was correlated with estimated CP fermentation in the large intestine (r = -0.86, P = 0.06) and with in vitro ammonia emission after 48 h (r = -0.81, P = 0.09). In conclusion, nutritionally relevant variability exists in soy varieties. Low stachyose content is important for maximizing ileal energy digestibility of soybean meal. Although no compositional variable was identified that explained differences in ileal CP digestibility, maximizing ileal CP digestibility is of interest for maximizing the nutritional value of soybean meal and possibly for reducing ammonia and odor emissions.

The objective of this study was to compare three infrared spectroscopy techniques for routine evaluation of AA in animal meals. Animal meals (n = 54) with known AA contents were scanned with a near (NIRS), mid (FTIR), and Raman infrared spectrometer. For NIRS and Raman, samples were scanned "as is", whereas for FTIR, samples had to be finely ground before scanning to obtain reasonable spectra. Both FTIR and Raman data suffered from noise; for Raman, this prevented the development of calibrations. Using derivatized spectral data and a standardized outlier removal procedure, calibrations for nutritionally relevant AA could be developed that were equivalent for both NIRS and FTIR. The variation across AA tested explained (r2) by these calibrations was 70% for NIRS and 68 + 3% for FTIR. Removing spectral data between 4,000 and 2,000 cm(-1) from the FTIR data improved calibrations (P = 0.09) and explained an average of 77% of the variation with prediction errors lower than obtained with NIRS (P < 0.01). However, FTIR calibrations based on the entire or the shortened spectrum contained fewer samples than did NIRS calibrations (41 and 39 vs. 48, respectively; P < 0.01) because more samples were removed as outliers. In conclusion, Raman did not yield acceptable spectra for animal meals. For FTIR, sample preparation was more time-consuming because the samples required grinding before analysis. Using the entire mid-infrared range, FTIR calibrations were comparable to NIRS calibrations. Calibrations for FTIR were improved by eliminating wave numbers that exhibited more noise, resulting in prediction errors better than those for NIRS. Thus, FTIR has the potential to yield better calibrations for AA in animal meals than NIRS, but it requires greater care in sample preparation and scanning.

Typically, in vitro methods used for estimating the amount of ileal digestible AA do not exhaustively digest samples, and arbitrary methods for separating digestible from indigestible protein are used. This may lead to over- or underestimation of digestibility coefficients. A method that exhaustively digests proteins using pepsin and pancreatin was developed, and the first objective of this research was to confirm that exhaustive digestion was indeed appropriate and to determine the fractionation method for separating digestible from indigestible proteins. For this, three homoarginine-labeled animal proteins were prepared. Samples were subsequently digested in vivo and in vitro to determine which fraction should be considered indigestible, and in vitro followed by in vivo to determine whether the extent of digestion in vivo was improved by predigestion. In vivo, soluble but unabsorbed peptides were smaller than 1 kDa, suggesting that the size of soluble peptides is not what prevents their absorption. Thus, all in vitro-soluble proteins should be considered digestible. In vitro, 88 +/- 3% of the soluble peptides were smaller than 1 kDa, with the remainder between 1 and 5 kDa, suggesting that in vitro digestion is less complete. Predigested samples were digested in vivo to the same size distribution as the nonpredigested samples. The second objective was to test whether in vitro digestibility assays based on these principles equaled in vivo digestibility. For this, digestibility data for 25 animal proteins were compared. Results showed a lack of correlation between lysine digestibility coefficients; however, across samples, the extent of digestion did not differ for lysine (P = 0.71), threonine (P = 0.26), methionine (P = 0.18), or valine (P = 0.66), whereas in vitro digestibility coefficients were lower for (the less water-soluble) histidine (P = 0.05), isoleucine (P < 0.01), leucine (P < 0.01), and phenylalanine (P = 0.05). In conclusion, in vitro digestibility assays should exhaustively digest proteins to mimic in vivo digestibility. All in vitro-soluble peptides could be considered digestible, because in vivo, no large soluble peptides were observed whose size prevented them from being absorbed. However, an in vitro assay based on these principles lacked precision for highly water-soluble AA, and underestimated digestibility for other AA. Better solubilization of the digesta and more replicates may improve the in vitro assay further.

An educational program was developed for extension agents, faculty, and graduate students to illustrate the effect of diet composition on odor from swine manure. Participants in this program first received a 2-h detailed review on odorous compounds in manure and the effect of diet on odor. For the second portion of the training, nine manure samples were used from pigs fed diets formulated with feed ingredients predicted to have different effects on odor emission or a nutritionally adequate corn-soybean meal diet. Participants were instructed to rate the odor from these samples for pleasantness, irritation, and intensity on a scale of 0 (best) to 8 (worst), using manure from the corn-soybean meal fed pig as the reference with a score defined as 4 for each variable. Results obtained were summarized and discussed before concluding the program. Participants were Cooperative Extension Agents (n = 13) with swine responsibilities and graduate students and faculty (n = 8). The manure from the diet with the worst odor scores (1% garlic) was rated at 70% more odorous across the three odor variables (P < 0.05) than the diet with the least odorous manure (purified diet). Even though a reference sample was used, individual participants differed in their perception of irritation across samples (P < 0.05), ranging in average score across diets from 2.4 (moderately better than reference) to 5.0 (slightly worse than reference). With extension agents, a 1 to 7 scale (very interesting to not at all interesting) was used for evaluation of the training session. Participants found the material to be interesting (mean = 1.7, SD = 0.7) and the training exercise to be well organized and coherent in its presentation (mean = 1.8, SD = 0.7). Participants enjoyed this training and learned that differences in odor are achievable through altering diet composition, and that the response to swine odor depends on individual odor perception.

To assess differences in soybean meal quality related to region of production, researchers in Illinois, Kansas, North Carolina, The Netherlands, and Ohio collected four soybean meal samples processed locally at least 15 d apart. These samples were assayed for ileal amino acid digestibility by pigs using a common soybean meal and a soy protein concentrate as references, and a low-protein casein diet for determination of endogenous amino acid losses. Digestibility was determined at each university using seven barrows surgically fitted with ileal cannulas in a 7 x 7 Latin square design. The experimental diets contained 17% CP from the test material except for the low-protein casein diet. Animals were fed twice daily, 12 h apart, at a level of 45 g x kg(-0.75) BW for each meal. Following a 5-d adaptation period, ileal digesta were collected for two 12-h periods for 2 d to be used for determination of ileal digestibility. Variation in amino acid digestibility was very small among and within sites and was much smaller than variation in the concentration of amino acids. Among sites, samples from The Netherlands had less total and thus digestible lysine and methionine than the U.S. samples (P < 0.05). The soybean meals tested in this experiment were approximately 4% higher in amino acids than that reported in the NRC (1998). True (standardized) digestibilities, however, were very similar to NRC values except for cysteine and threonine, which were 5 and 3 percentage points lower in this experiment, respectively. In conclusion, soybeans grown in the United States and locally processed into soybean meal were very similar in nutritional composition. Soybean meals produced in The Netherlands were lower in lysine and methionine (P < 0.05) but had a digestibility similar to that produced in the United States.