Date Full Report Received10/12/2006
Date Abstract Report Received01/01/2006
National Pork Board Website: Environmental Research Reports, Report #04-101
Excessive production of nitrogen from livestock production systems has place a strain on the environment. Methods to reduce nitrogen losses from farm animals will become necessary to ensure a sustainable animal production and maintain an environmentally conscious industry. The long-term objective of this project was to determine the feasibility of the use of crystalline amino acids in diets to reduce nitrogen generated by farm animals. The specific objective of this study was to determine if protein synthesis in the gut decreases in pigs fed diets containing low crude protein concentration with crystalline amino acids. This study was part of an overall programmatic research question aiming at determining if amino acid utilization by the gut is lower in pigs receiving low crude protein diet with crystalline amino acid supplementation compared to that in pigs receiving diet containing intact proteins only (feed ingredients). Maintaining the integrity of the intestine is crucial in order to ensure health and well-being of animals.
Ten barrows (Yorkshire X Landrace), with an average BW of 14.6 kg ± 0.37 were used. Pigs were housed individually in pens in a controlled temperature room set at 22º C and offered feed twice daily at 0800 and 1600 of either a Control diet containing conventional feed ingredients (17.37% CP, analyzed) or a low crude protein diet (14.07% CP, analyzed) containing crystalline amino acids (Low CP + CAA) L-lysine•HCl, DL-methionine, L-threonine, L-tryptophan.and L-cystine. The amount of feed offered was calculated to provide five times the metabolizable energy required for maintenance (106 kcal/ kg x BW0.75). Barrows were weighed at the beginning of the study (d 0), d7, d14, and prior to euthanasia on day 21. Feed intake was recorded daily. Pigs were surgically fitted with indwelling jugular catheters to administer a dose of labeled tracer (L-[2H3-ring]-phenylalanine) to measure protein synthesis in the intestine. Blood samples were collected 5 min prior to infusion and every 5 min for 15 min and then every 10 min for a total of 35 min. Samples were centrifuged at 4º C and 3000 x g for 10 min. Plasma was removed and frozen at -20º C until analysis. Pigs were first sedated with an i.m. injection (1 mL/ 34 kg BW) of 250 mg zolazapam, 250 tiletamine diluted in 2.5 mL ketamine and 2.5 mL xylazine-100. Following sedation, pigs were euthanized with an intravenous administration of pentobarbital (86.27 mg/kg of BW). The entire small intestine was quickly removed and freed from the mesentery. Intestinal tissue samples (whole tissue and mucosa) were obtained from the duodenum, jejunum and ileum. Phenylalanine enrichment in plasma and tissue samples was determined by gas chromatography mass spectrometry (GCMS) and fractional protein synthesis rate was estimated using protein-bound phenylalanine enrichment in mucosa and whole intestinal tissue and the precursor enrichment in the respective tissue free pool. Fractional synthesis rate of protein in the mucosa did not change across intestinal segments but in whole tissue, FSR was lower (P ≤ 0.1) in the ileum compared to that of other segments in both treatments. Overall, mucosa FSR was higher than that of whole tissue for both treatments, i.e., Control (P ≤ 0.1) and Low CP + CAA (P < 0.05). Our results demonstrate that reducing dietary CP by 3.3 % with crystalline amino acid supplementation does not affect intestinal protein synthesis, neither in the mucosa nor in the whole tissue. Therefore, reducing dietary CP by 3.3% does not negatively impact intestinal protein accretion, and may maintain intestinal health integrity.