Feed processing and macronutrient strategies to alleviate the effect of heat stress on the physiological and performance responses of lactating sows.

This study evaluated the effects of feed processing and dietary energy-protein strategies on physiological responses, performance, stress biomarkers, and fecal microbiota of lactating sows exposed to heat stress (HS). Fifty multiparous Landrace × Yorkshire sows were assigned to five dietary treatments as treatment a: mash diet with 3,320 kcal ME/kg, 18.0% crude protein (CP), without AA supplementation (CON). Treatment b: pellet diet with 3,320 kcal ME/kg, 18.0% CP without AA supplementation. Treatment c: pellet diet, 3,400 kcal ME/kg, 18.0% CP, no additional AA supplementation. Treatment d: pellet diet, 3,400 kcal ME/kg, 16.2% CP, no additional AA supplementation. Treatment e: pellet diet, 3,400 kcal ME/kg, 16.2% CP, with additional AA supplementation (10%+). Feed processing did not significantly affect rectal temperature, sow feed intake, body weight (BW) change, reproductive performance, stress biomarkers, or fecal microbial populations. Respiratory rate was generally unaffected by dietary treatment but increased (p < 0.05) during late lactation in sows fed the high-ME, low-CP pelleted diet with AA supplementation. Sow BW at weaning was higher (p < 0.05) in sows fed higher-CP diets, while piglet weaning weight and average daily gain were positively influenced by dietary ME and CP (p < 0.05). Inflammatory cytokines, antioxidant capacity, hair cortisol, and fecal microbiota were not altered by dietary treatments. However, malondialdehyde concentration increased (p < 0.05) with higher dietary ME. In conclusion, pelleted diets formulated with higher dietary ME (3,400 kcal/kg) and adequate CP (18.0%) supported superior piglet growth performance and improved sow BW at weaning under HS.