Effects of methionine or arginine supplementation and environmental temperature on performance, carcass traits and meat quality of finishing pigs

A 46-d study was conducted to determine the effects of methionine (Met) or arginine (Arg) supplementation in a thermal- neutral (24°C) or heat stressed (32°C) environment on performance, carcass characteristics and meat quality of finishing pigs. Seventy-two mixed-sexed pigs (PIC x DanBred; initial BW of 69.1 ± 0.11 kg) were assigned to 6 diet regimes using a 2 × 3 factorial arrangement with 3 dietary treatments [a basal diet (BD), the BD + 0.15% DL-Met or the BD + 0.40% L-Arg], and 2 environmental temperatures (24°C or 32°C) having 6 pen replicates (2 pigs/pen) per treatment. Diets were formulated based on corn, soybean meal and corn gluten meal using the analyzed ingredient AA contents and published standardized ileal digestible (SID) coefficients to meet AA requirements for both finisher 1 (0.76% SID Lys; 70-90 kg) and finisher 2 (0.69% SID Lys; 90-112 kg) phases. Pigs were fed the finisher 2 diets until they reached a predetermined market weight (115 kg). At slaughter, 36 pigs (6 pigs/ treatment) were selected for carcass assessment. Samples of longissimus dorsi (LD) muscle were used for meat quality assessments. Data were analyzed using the MIXED procedure of SAS. There was no diet × temperature interaction for any variables (P > 0.05). Compared with 24°C, ADFI, ADG and G:F were lower (P < 0.001) under 32°C temperature during each phase and the overall 46-d period, except for the ADFI during finisher 2 period (P = 0.056). Overall, supplementing with 0.15% DL-Met or 0.40% L-Arg reduced ADFI (P = 0.033) and increased G:F (P = 0.012). Compared with 24°C, 32°C temperature increased (P < 0.05) chilled carcass yield and 24 h pH of carcass but decreased (P < 0.05) drip loss after 24 and 48 h and the number days to reach 115 kg BW. The 24 h pH of carcass tended to increase (P = 0.053) by 0.15% DL-Met addition but all other measured carcass parameters including lean percentage and backfat thickness were not affected by dietary treatments. The concentrations of cortisol and heat shock protein 70 (HSP70) in plasma and concentrations of thiobarbituric acid reactive substances and hydrogen peroxide in LD muscle were not affected by the dietary treatments or the environment temperature. These results indicate that heat stress reduces pig performance and may affect carcass quality. Additional L-Met or L-Arg supplementation in finisher pig diets may improve feed efficiency.