Effects of 2-Hydroxy-4-(methylthio)butanoic Acid and dl-Methionine on Broiler Performance and Compensatory Growth After Exposure to Two Different Environmental Temperatures

Abstract

The effects of previous environmental heat stress (HS; 25 to 35°C) or a thermoneutral environment (TNE; 25°C); Met source, DL-Met (DLM) or the hydroxy-analogue of Met (HMB); and Met level were measured in broilers under a TNE (25°C). Performance, carcass measurements, nitrogen retention, and compensatory growth (CG) were evaluated by removing 195 birds from each environment and placing them in individual chambers for 5 d. TNE birds were removed to the chambers at 25, 36, and 49 d of age, and HS birds were removed at 30, 43, and 56 d of age. They continued to receive the same Met source at three different levels: 0.09% DLM or HMB on equimolar basis, 0.04% DLM or HMB, or no Met supplementation. CG was regarded as the difference between a bird's actual growth rate in the chambers and predicted growth based on TNE bird data. Birds from HS exhibited CG for weight gain (WG), breast, leg, abdominal fat, and carcass weight (P < 0.001) but had negative intestinal growth (P < 0.01). There was no difference in CG between Met sources. Birds fed HMB showed better nitrogen retention (P < 0.05), and those from TNE had better WG (P < 0.05) and feed efficiency (P < 0.07) when fed HMB. Only drumstick weights of birds under previous TNE were positively affected by Met level.