Submitted to: Journal of Animal Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/1/2002
Publication Date: 10/14/2002
Citation: Guzik, A.C., Southern, L.L., Bidner, T.D., Kerr, B.J. 2002. The tryptophan requirement of phase i, ii, and iii nursery pigs. Journal of Animal Science. 80:2646-2655. Interpretive Summary: Tryptophan is an essential dietary amino acid that is equally second or third limiting in typical diets for pigs. In diets consisting primarily of corn, it is the first limiting amino acid because of the low tryptophan content and availability in corn. The tryptophan content in the diet is important for optimal growth performance, and reliable requirement estimates are imperative when formulating diets based on the ideal protein concept. Recent research has estimated digestible tryptophan requirements, since this estimation may be more accurate because of the variation in digestibility of protein-bound tryptophan in feedstuffs. Although there have been no experimental estimates of the digestible tryptophan requirement of nursery pigs that segregate pigs into weight ranges of 12 to 15, 15 to 35 and 35 to 65 pounds, which is typical of current feeding systems, the National Research Council Subcommittee on Swine Nutrition, 1998 provided recommendations for the requirement for tryptophan based on a collaboration of work from various scientists. Results from these experiments show that the digestible tryptophan requirement is 0.21, 0.20, and 0.18% for pigs weighing 12 to 15, 15 to 35 and 35 to 65 pounds, respectively. Research results described in this report provides nutritionists at swine production facilities and feed companies vital data on protein sources and dietary lysine levels necessary to optimize growth performance and to minimize nitrogen excretion in young pigs.
Technical Abstract: Five Exp. were conducted to determine the digestible Trp (dTrp) requirement of nursery pigs. Treatments were replicated with four or five pens of five or six pigs each. Pigs were weaned at 21 (Exp. 1, 2, and 5) or 19 d (Exp. 3 and 4), and diets were fed for 8 (Exp. 1), 13 (Exp. 2 and 3), or 14 d (Exp. 4 and 5). Experiment 1 (160 pigs, initial and final BW of 8.4 and 11.4 kg) evaluated six protein sources low in Trp relative to a positive control diet. The results indicated that a diet with Canadian field peas (CFP) supplemented with Trp, resulted in ADG, ADFI, and gain:feed (GF) equal to (P > 0.10) the positive control diet. In Exp. 2 (75 pigs, initial and final BW of 13.2 and 19.2 kg) were fed: 1) Trp-deficient diet (0.13% dTrp) with CFP, 2) Diet 1 with added Trp (0.23% dTrp), 3) positive control diet (0.22% dTrp). Daily gain, ADFI and GF were decreased 0.01) in pigs fed Diet 1 compared with pigs fed Diets 2 and 3, but ADG, ADFI, and were equal (P > 0.10) in pigs fed Diets 2 and 3. in pigs fed Diet 1 compared with pigs fed Diets 2 and 3, but ADG, ADFI, and Experiments 3 (180 pigs, initial and final BW of 5.2 and 7.3 kg, 4 (120 pigs, initial and final VE of 10.3 and 15.7 kg) were conducted to estimate the dTrp requirement of Phase I, II, and III nursery pigs, using CFP as the primary protein source. Response variables were ADG, ADFI, GF, and plasma urea N concentrations. In Exp. 3 (Phase I) the average dTrp requirement was to be 0.018% (0.22% total Trp). In summary, the dTrp requirement is 0.21, 0.20, and 0.18% for Phase I, II, and III nursery pigs, respectively.