PSI-27 - Dietary supplementation of betaine and an antioxidant blend improved feed efficiency in commercially housed fattening pigs under heat stress conditions

Abstract: Heat stress decreases pig productivity and welfare by reducing feed intake and growth, increasing oxidative stress, and compromising gut health. Feed additives with anti-inflammatory and antioxidant properties could help pigs cope with the negative impact of heat stress. The study evaluated the efficacy of feeding diets containing betaine and a plant-based antioxidant blend (AOB) on the growth performance and carcass quality parameters of commercially housed fattening pigs under heat-stress conditions. The study design was a randomized completed block with 2 dietary treatments using 836 pigs (starting weight: 22.7±3.8 kg BW) and 22 replicate pens/treatment (19 mixed-sex pigs/pen). The treatments were a standard four-phase commercial grow-finish corn-soy based diet (Control) and Control plus 1 kg/MT each of betaine and AOB (BetAOB). Pigs were subjected to a heat stress challenge by increasing the ambient temperature from 18 to 29^oC for 8 h/d (10:00 to 18:00) from d 10 to 42 and d 85 to 106 of the study. Body weight (BW) and feed disappearance of each pen were recorded before and after the heat stress challenge and every third week to calculate average daily gain (ADG), average daily feed intake (ADFI), and feed conversion ratio (FCR). Morbidity and mortality were recorded daily. Data were analyzed using PROC GLMMIX of SAS with appropriate models for the different data distributions. Pen was the experimental unit. The overall herd mortality was 1.3% and 0.7% of pigs received medical treatment for leg problems. Treatment did not affect the percentage of pigs culled (P=0.48; Control=6.7% vs. BetAOB=5.7%). Pigs fed BetAOB tended to have a lower FCR (-0.06 kg/kg; P=0.10) during the first heat stress challenge (d 22-42). Further, BetAOB-fed pigs had a lower FCR (-0.07 kg/kg; P=0.02) and tended to have a greater ADG (+28 g/d; P=0.07) from d 43-61. Pigs fed BetAOB tended to have a lower ADFI (-89 g/d; P=0.06) from d 62-84. Consequently, pigs fed BetAOB had a lower (P=0.04) overall FCR compared to the Control (2.53 vs. 2.48 kg/kg). Treatment did not affect carcass weight (P=0.76), carcass yield (P=0.76), or any of the carcass quality parameters measured (all P >0.11). In summary, under heat-stress conditions, pigs receiving the diet containing 1 kg/MT each of betaine and AOB had better feed efficiency than those receiving the Control diet. Therefore, feeding finishing pigs diets supplemented with betaine and the antioxidant blend can help minimize the negative effect of heat stress by improving feed efficiency.