Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/24/2005
Publication Date: 5/16/2005
Citation: Guzk, A.C., Shelton, J.L., Southern, L.L., Kerr, B.J., Bidner, T.D. 2005. The tryptophan requirement of growing and finishing barrows. Journal of Animal Science. 83:1303-1311. Interpretive Summary: Optimum amino acid intake is important to maximize growth, feed efficiency, and carcass lean deposition in pigs. Although there has been numerous research conducted on the lysine requirement in growing-finishing pigs, there has been limited research conducted on the total or true tryptophan requirement. Providing optimal tryptophan concentrations in growing-finishing diets will not only optimize animal performance, but because environmental issues with nitrogen losses from swine operations has become more pressing and several crystalline amino acids are economically available, understanding tryptophan limitations in low crude protein diets is paramount. Based on data obtained in these experiments and a summary of published literature, the total and true ileal digestible tryptophan requirement is 0.21 and 0.18% for 30-kg pigs; 0.17 and 0.14% for 50-kg pigs; 0.13 and 0.11% for 70-kg pigs; and 0.13 and 0.11% for 90-kg pigs. Research results described in this report provides nutritionists at universities, feed companies, allied industries, and swine production facilities data on how to define the tryptophan needs of growing-finishing pigs to formulate diets necessary to optimize growth performance and subsequently minimize nitrogen losses into the environment.
Technical Abstract: Five experiments were conducted to determine the true ileal digestible Trp (tidTrp) requirement of growing and finishing pigs fed diets containing 0.87% (Exp. 3), 0.70% (Exp. 4), 0.61% (Exp. 5), and 0.52% (Exp. 1 and 2) tidLys during the early-grower, late-grower, early-finisher, and late-finisher periods, respectively. Treatments were replicated with three or four replications with three or four pigs per replicate pen. Treatment differences were considered significant at P = 0.10. Experiment 1 was conducted with 27 pigs (initial and final BW of 78.3 and 109.8 kg) to validate whether a corn-feather meal (FM) Trp-deficient (0.07%) diet, when supplemented with 0.07% crystalline L-Trp, would result in growth performance and carcass traits similar to a conventional corn-soybean meal (C-SBM) diet. Pigs fed the corn-FM diet without Trp supplementation had decreased growth performance and carcass traits, and increased plasma urea N (PUN) concentration. Supplementing the corn-FM diet with Trp resulted in greater ADG and G:F than pigs fed the positive control C-SBM diet. Pigs fed the corn-FM diet had similar carcass traits as pigs fed the C-CBM diet, but loin muscle area was decreased and fat thickness was increased. In Exp. 2, 60 pigs (initial and final BW of 74.6 and 104.5 kg) were used to estimate the tidTrp requirement of finishing pigs. The levels of tidTrp used in Exp. 2 were 0.06, 0.08, 0.10, 0.12, or 0.14%. Response variables were growth performance, PUN concentrations, and carcass traits and quality. For Exp. 2, the average of the estimates calculated by broken-line-regression was 0.104% tidTrp. In Exp. 3, 4, and 5, barrows (n = 60, 60, or 80, respectively) were allotted to five dietary treatments supplemented with crystalline L-Trp at increments of 0.02%. The basal diets contained 0.13, 0.09, and 0.07% tidTrp in Exp, 3, 4, and 5, and initial BW of the pigs in these experiments was 30.9, 51.3, or 69.4 kg. The response variable was PUN, and the basal diet used in Exp. 3 and 4 contained corn, SBM, and Canadian field peas. The tidTrp requirements were estimated to be 0.167% for pigs weighing 30.9 kg, 0.134% for pigs weighing 51.3 kg, and 0.096% for pigs weighing 69.4 kg. Based on our data and a summary of the cited literature, we suggest the following total Trp and tidTrp requirement estimates: 30-kg pigs, 0.21 and 0.18%; 50-kg pigs, 0.17 and 0.14%; 70-kg pigs, 0.13 and 0.11%; and in 90-kg pigs, 0.13 and 0.11%.