Threonine supplementation of low-protein, lysine-supplemented, sorghum-soybean meal diets for growing-finishing pigs

Abstract

An investigation was conducted to determine whether low-protein (LP), lysine-supplemented, sorghum-soybean meal (S-SBM) diets are deficient in threonine (Thr) for pigs fed ad libitum. Treatments were replicated eight times with four or five pigs each. Average initial and final weights were 32.9 and 103.4 in experiment 1 and 30.1 and 100.6 kg in experiment 2. The crude protein contents of the basal grower and finisher diets were 13.7 and 15.0% respectively. Experiment 1 consisted of the following treatments: (1) S-SBM; (2) S-SBM+0.1% L-Thr; (3) LP, S-SBM+0.10% L-lysine (Lys); (4) LP, S-SBM+0.1% Lys+0.1% Thr. Gain: feed ratio was lower ( P<0.10) in pigs fed diet 3 compared with pigs fed diets 1, 2 and 4. Plasma urea nitrogen (PUN) was lower ( P< 0.01) in pigs fed diets 3 and 4 compared with pigs fed diets 1 and 2. Experiment 2 was similar to experiment 1 except Lys from sorghum and SBM was reduced by 0.2% and replaced with 0.25% L-Lys-HCl in diets 3 and 4. Daily gain was lower (P>0.01) in pigs fed diet 3 than in pigs fed diets 1, 2 and 4. Average backfat thickness was higher ( P<0.01) and PUN lower ( P<0.01) in pigs fed diets 3 and 4 compared with pigs fed diets 1 and 2. Other carcass traits were not affected ( P>0.10) by diet. Low-protein, Lys-supplemented S-SBM diets may be deficient in Thr for growing-finishing pigs.