Addition of Protease to Standard Diet or Low-Protein, Amino Acid-Supplemented, Sorghum-Soybean Meal Diets for Growing-Finishing Pigs

摘要

Low-protein diets supplemented with amino acids help to reduce nitrogen excretion from pig facilities; the exogenous enzymes improve the feedstuffs utilization. So, two experiments were conducted to evaluate the effects of a protease added to sorghum-soybean meal standard or low-protein diets on Average Daily Gain (ADG), Average Daily Feed Intake (ADFI), Feed: Gain Ratio (FGR), Fat Free Lean Gain (FFLG), Backfat Thickness (BT), Longissimus Muscle Area (LMA), Lean Meat Percentage (LMP) and Plasma Urea Nitrogen (PUN) concentration of growing and finishing barrows. Weekly data (ADG, ADFI and FGR) were analysed with PROC MIXED; other data were analysed with PROC GLM. In experiment 1, 32 growing (29.18±5.05 kg initial weight) barrows were individually alloted into 1.2×1.5 m pens in a complete block design with factorial 2×4 arrangement of two levels of CP (16 and 11.5%) and four of protease (0.00, 0.25, 0.50 and 0.75 kg t 1), with eight treatments (T) and four replicates per treatment. Diets (CP% and kg t 1 protease) were as follows: T1) 16, 0.0; T2) 16, 0.25; T3) 16, 0.5; T4) 16%, 0.75; T5) 11.5, 0.00; T6) 11.5, 0.25; T7) 11.5, 0.5; and T8) 11.5, 0.75, respectively. There was no effect of protein nor of enzyme level on all variables, except for PUN that was reduced as CP was lowered in the diet. The interaction of factors tended to affect FFLG. The mixed effect analysis showed an effect of time (week) on ADG, ADFI and FGR. In experiment 2, 32 finishing (56.77±5.38 kg initial weight) barrows were used in a completely randomized design with a factorial 2×4 arrangement of two levels of CP (14 and 9.5%) and four of protease (0.00, 0.25, 0.50 and 0.75 kg t 1), with eight treatments (T) and four replicates per treatment. The initial weight was used as a covariate for statistical analysis of data. The treatments (CP% and kg t 1 protease) were as follows: T1) 14, 0.0; T2) 14, 0.25; T3) 14, 0.5; T4) 14%, 0.75; T5) 9.5, 0.00; T6) 9.5, 0.25; T7) 9.5, 0.5; and T8) 9.5, 0.75, respectively. The CP reduction negatively affected ADG and FFLG and reduced PUN concentration, but increased FGR. Increasing the protease level increased the PUN. The interaction of both factors affected PUN of pigs. The mixed procedure showed a fixed effect of initial weight on ADFI and ADG; of time (week) on ADFI, ADG and FGR; and of protein level on ADG. These results indicate that protease supplementation to standard- and low-protein, sorghum-soybean, amino acid-supplemented diets, does not improve the growth performance of growing-finishing pigs; that the protein level does not affect the carcass characteristics and that the plasma urea nitrogen concentration is reduced when dietary protein is reduced.