The Dynamic Conversion of Dietary Protein and Amino Acids into Chicken-Meat Protein

This review considers the conversion of dietary protein and amino acids into chicken-meat protein and seeks to identify strategies whereby this transition may be enhanced. Viable alternatives to soybean meal would be advantageous but the increasing availability of non-bound amino acids is providing the opportunity to develop reduced-crude protein (CP) diets, to promote the sustainability of the chicken-meat industry and is the focus of this review. Digestion of protein and intestinal uptakes of amino acids is critical to broiler growth performance. However, the transition of amino acids across enterocytes of the gut mucosa is complicated by their entry into either anabolic or catabolic pathways, which reduces their post-enteral availability. Both amino acids and glucose are catabolised in enterocytes to meet the energy needs of the gut. Therefore, starch and protein digestive dynamics and the possible manipulation of this ‘catabolic ratio’ assume importance. Finally, net deposition of protein in skeletal muscle is governed by the synchronised availability of amino acids and glucose at sites of protein deposition. There is a real need for more fundamental and applied research targeting areas where our knowledge is lacking relative to other animal species to enhance the conversion of dietary protein and amino acids into chicken-meat protein.

264 Effects of Low Dietary Crude Protein Diets Containing Coarse Wheat Bran as an Alternative to Zinc Oxide in Nursery Pig Diets

An experiment was conducted to determine the effect of reduced crude protein (CP) in diets containing coarse wheat bran (CWB) without pharmacological levels of Zn (ZnO) on growth performance and fecal dry matter (DM) of nursery pigs. A total of 650 pigs (DNA 241′600; initially 6.6 kg), were used with 5 pigs/pen and 26 replicate pens/treatment. Pens were assigned to 1 of 5 treatments in a RCB design based on BW. Treatments were fed for 13-d, contained 4% CWB, and consisted of: 1) diet with pharmacological ZnO (2,000 mg/kg Zn) and 21% CP formulated to 1.35% standardized ileal digestible (SID) Lys; 2) a diet with 110 ppm added Zn and 21% CP (1.35% SID Lys); 3) a diet with 110 ppm added Zn formulated to 18% CP (1.20% SID Lys); 4) an 18% CP diet with 110 ppm added Zn formulated to 1.35% SID Lys by the addition of increased levels of feed grade amino acids; and 5) diet 4 with addition of non-essential amino acids (NEAA; glycine and glutamic acid). Data were analyzed using the lmer function in R. Overall, pigs fed 21% CP with ZnO had increased (P < 0.05) ADG compared to those fed 18% CP (1.35% SID Lys) with high levels of feed grade amino acids or those fed the reduced SID Lys (1.2%) diet. Gain-to-feed ratio was increased (P < 0.05) for pigs fed 21% CP diets and those fed the 18% CP diet with NEAA compared to pigs fed 1.2% SID Lys and pigs fed high levels of feed grade amino acids. Fecal DM was increased (P < 0.05) for pigs fed reduced SID Lys diet. In conclusion, reducing CP (subsequently SID Lys) in diets without ZnO decreased growth performance but increased fecal DM.

Progress towards reduced-crude protein diets for broiler chickens and sustainable chicken-meat production

The prime purpose of this review is to explore the pathways whereby progress towards reduced-crude protein (CP) diets and sustainable chicken-meat production may be best achieved. Reduced-CP broiler diets have the potential to attenuate environmental pollution from nitrogen and ammonia emissions; moreover, they have the capacity to diminish the global chicken-meat industry’s dependence on soybean meal to tangible extents. The variable impacts of reduced-CP broiler diets on apparent amino acid digestibility coefficients are addressed. The more accurate identification of amino acid requirements for broiler chickens offered reduced-CP diets is essential as this would diminish amino acid imbalances and the deamination of surplus amino acids. Deamination of amino acids increases the synthesis and excretion of uric acid for which there is a requirement for glycine, this emphasises the value of so-called “non-essential” amino acids. Starch digestive dynamics and their possible impact of glucose on pancreatic secretions of insulin are discussed, although the functions of insulin in avian species require clarification. Maize is probably a superior feed grain to wheat as the basis of reduced-CP diets; if so, the identification of the underlying reasons for this difference should be instructive. Moderating increases in starch concentrations and condensing dietary starch:protein ratios in reduced-CP diets may prove to be advantageous as expanding ratios appear to be aligned to inferior broiler performance. Threonine is specifically examined because elevated free threonine plasma concentrations in birds offered reduced-CP diets may be indicative of compromised performance. If progress in these directions can be realised, then the prospects of reduced-CP diets contributing to sustainable chicken-meat production are promising.

Preliminary Observations On The Use Of Dry Urea Treatment And Toasting For Improving The Nutritive Value Of Jackbean

Raw unprocessed jackbean contains 28 - 30% crude protein but also contains toxic elements that limit its use as feed ingredient for monogastric animals. A 21-day feeding trial was conducted to determine the effect of dry urea treatment prior to toasting on its nutritive value for young broiler chicks. One of two batches of raw jackbean was mixed with 2.5% of its weight of crushed urea and allowed to stand for 10 days and then toasted. The other batch was toasted without urea application. The two treated jackbean meals were used to compound broiler starter diets at 10 and 20% dietary levels, respectively, and along with control diet fed to groups of 40 young broiler chicks for 21 days. Hydrolysis of urea by the urease of the jackbean was completed in six days. Urea treatment/toasting slightly reduced crude protein content of jackbean, but diets containing it at both 10% and 20% compared favourably with the control. Raw toasted jackbean significantly (P<0.05) depressed performance of the young broiler chicks at 20% dietary level.

Effect of incorporating forage pea (Pisum sativum L.) hay into cereal hay on ruminal fermentation and apparent digestibility when fed to beef heifers

The objective of this study was to evaluate the inclusion rate of pea hay in barley or oat hay diets for beef cattle. Six ruminally cannulated heifers (407 ± 38 kg) were used in a 6 × 6 Latin square (25 d periods) with a 2 × 3 factorial design. Treatments included whole-crop barley or oat hay with pea hay blended in to achieve inclusion rates of 0%, 15%, or 30% (dry matter basis) of the forage. Pea hay inclusion increased dry matter intake (DMI; P = 0.03) by 0.75 kg d−1 relative to diets without pea hay, but the response was not linear or quadratic. Inclusion of pea hay linearly increased mean ruminal pH (P = 0.039), the concentration of butyrate in ruminal fluid (P = 0.013), plasma urea nitrogen (N) concentration (P = 0.001), and quadratically increased ruminal ammonia concentration (P < 0.001). Pea hay inclusion reduced crude protein (CP) digestibility by 2.87% relative to cereal-only treatments (P = 0.025), but did not affect N intake, microbial N, or N excretion. Overall, pea hay inclusion increased DMI, increased ruminal butyrate concentration, but reduced CP digestibility without affecting N balance.