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Title: Development of a precision-fed ileal amino acid digestibility assay using 3-week-old broiler chicks

Author
item Kim, Elizabeth
item UTTERBACK, P - University Of Illinois
item PARSONS, C - University Of Illinois

Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/20/2011
Publication Date: 3/15/2011
Citation: Kim, E.J., Utterback, P.L., Parsons, C.M. 2011. Development of a precision-fed ileal amino acid digestibility assay using 3-week-old broiler chicks. Poultry Science. 90:396-401.

Interpretive Summary: Formulation of diets on a digestible amino acid basis can allow for better predictions on animal growth, a return on feed investment, and decrease harmful environmental effects. Current methods of determining amino acid digestibility in poultry are costly, expensive, and time consuming. The objectives of this study were to develop a new quick, less expensive, and time consuming method for determining amino acid digestibility that would complement current techniques. In order to run such an assay, the amount of time needed to empty the gastrointestinal tract, how much feed to precision-fed, and what collection time is optimal to maximize the amount of ileal digesta collected are important. Broilers at 21 days old were fasted and excreta were collected every 2 hours for 14 hours. The results indicated that 8 hours was sufficient to empty the gastrointestinal tract. A second study was conducted to determine how much feed was needed to yield maximal ileal digesta. The amount of ileal digesta is important because an optimal amount of sample is required for chemical analyses. Feeding 10 g of feed was observed to yield the most ileal digesta. Based on the findings of the previous experiments, the amino acid digestibility of a standard corn-soybean meal diet were fed and then ileal digesta were collected at different times to determine if there were differences in amino acid digestibility. Amino acid digestibility was observed to be significantly lower at 2 hours post-feeding. Based on the findings of this study, a less time consuming and less expensive amino acid digestibility chick assay can be used.

Technical Abstract: The objective of these studies was to develop a precision-fed ileal digestibility assay, primarily for amino acids (AA), using 3-wk-old broiler chicks. For all experiments, day-old Ross × Ross 708 broiler chicks were fed a standard corn-soybean meal starter diet until 21 d of age. In experiment 1, feed was removed and excreta were collected at 2, 4, 6, 8, 10, 12, and 14 h after feed withdrawal. Results indicated that 8 h of feed withdrawal was sufficient to empty the ileum of feed residues. In a subsequent experiment, chicks were fasted overnight for 10 h and then tube-fed various amounts (from 6 to 15 g) of a corn-soybean meal mixture (60:40). Ileal digesta from Meckel’s diverticulum to the ileo-cecal junction were then collected at various collection times between 3 and 7 h postfeeding. Results indicated that the amount of digesta in the distal ileum was generally maximized by 4 h postfeeding and by feed intakes of 9 g or greater. Based on the results of the previous study, apparent and standardized ileal digestibility values of AA in a corn-soybean meal chick starter diet were then determined at 2, 3, and 4 h postfeeding. Digestibility values were similar for the 3- and 4-h collection times, but were numerically or significantly (P = 0.05) lower at the 2-h collection time. The results of this study indicate that ileal AA digestibility can easily be determined in 3-wk-old broiler chicks when using a precision-fed assay. For such an assay, it is recommended that the chicks be fasted for at least 8 h before tube-feeding, that they be precision-fed approximately 10 g of feed, and that the ileal contents be collected at approximately 4 h postfeeding.