Crystalline lysine and threonine supplementation of soft red winter wheat or triticale, low-protein diets for growing-finishing swine.

Five trials, with five treatments each, involving a total of 240 pigs were conducted to evaluate the effectiveness of supplementation of soft red winter wheat- or triticale-based diets with crystalline lysine and threonine for growing and finishing pigs (25 to 110 kg). Within each trial, wheat- or triticale-based diets were supplemented with soybean meal to meet the requirement of the first- (lysine) or third- (isoleucine/methionine + cystine) limiting amino acid. Diets formulated to the third-limiting amino acid also were supplemented with feed grade L-lysine. HCl and L-threonine to meet the requirements of the first- and second-limiting amino acids. A cornsoybean meal diet was included in each trial as a positive control treatment resulting in the five dietary treatments. Three different crop years of soft red winter wheat and triticale were utilized. Three of the trials, conducted in successive years with each using a different crop year of grain, were done at Marianna, and the other two, conducted in successive years using yr 1 and 2 crops, respectively, were done at Gainesville. In all trials, growing diets (.82% lysine) were fed from 29 (Marianna) or 25 kg (Gainesville) to 55 kg average BW and finishing diets (.64% lysine) to 110 or 100 kg. Over the three crop years, the wheat and triticale averaged 11.3 and 11.0% crude protein, .36 and .38% lysine, and .36 and .37% threonine, respectively. Overall, at either location, growth rate and carcass lean content were not affected by grain source (P > .10). At Marianna, gain:feed was 2 to 3% lower for pigs fed the triticale diets than for pigs fed wheat (P = .15) or corn (P < .10); gain:feed was not affected by grain source at Gainesville (P > .10). At both locations, substantial replacement of soybean meal protein with crystalline lysine and threonine did not affect pig growth or carcass lean content (P > .10), even when the diet contained very little or no soybean meal as occurred for finishing pigs (55 to 110 kg) fed diets containing triticale.