Benefits of Utilization of Hydroxy–Methionine in Diets of Finishing Pigs Raised Under Hot Environmental Conditions

This study evaluated the effects of DL-methionine (DL-Met) and hydroxy–methionine (OH-Met) on the performance and meat quality of finishing pigs raised under intermittent hot environmental conditions. A total of 120 pigs (PIC337 × Camborough; 63.26 ± 4.49 kg initial body weight) were assigned to two dietary treatments in a randomized block design. Growth performance, carcass traits, and physicochemical meat parameters were assessed during the finishing period. Overall performance and carcass characteristics did not differ between treatments (p > 0.05). However, during finishing phase II (141–168 days), pigs fed OH-Met showed higher average daily gain (ADG; 1.027 vs. 0.957 kg/day; p < 0.05) and improved feed conversion ratio (FCR; 2.862 vs. 3.028; p < 0.05) compared with DL-Met. Meat from pigs receiving OH-Met presented a higher pH at 24 h postmortem (5.78 vs. 5.63; p = 0.022) and reduced water loss by pressure (26.14% vs. 28.78%; p = 0.047). No differences were detected for backfat thickness, longissimus dorsi depth, lean percentage, color parameters, or lipid oxidation (TBARS) (p > 0.05). In conclusion, under intermittent heat stress conditions during the late-finishing phase, diets formulated with OH-Met resulted in improved growth efficiency and reduced meat water loss compared with DL-Met diets.