146 Comparing feeding strategies during heat stress in finishing pigs using a stochastic swine model

Abstract

Abstract Nutritionists may feed standard diets or increase dietary net energy (NE) and/or standardized ileal digestible lysine (SIDLys) to counter reduced average daily feed intake (ADFI) due to heat stress in the late finishing phase. The objective of this work was to develop a set of statistical tools to analyze different grow-finish feeding strategies using the simulations from a proprietary stochastic swine model (Watson) when heat stress occurs during the last 2 wk of the finishing phase. Financial considerations were excluded from the study. Nutrient recommendations for maximum feed efficiency were derived from Watson and used to formulate a grower diet for 25 to 60 kg body weight (BW), and four finisher diets for 60 to 135 kg BW: a) thermoneutral (10 MJ NE/kg, 7.9 g/kg SIDLys), b) high AA (10 NE/kg, 9.2 g/kg SIDLys), c) high NE (10.5 MJ/kg NE, 7.9 g/kg SIDLys), and d) high NE and high AA (10.5 MJ NE/kg, 8.3 g/kg SIDLys). The grow-finish period was simulated by feeding the grower diet followed by the finisher diets in 5 different scenarios: 1) thermoneutral, diet a; 2) heat stress, diet a; 3) heat stress, diet a, and b during last 2 wk; 4) heat stress, diet a, and c during last 2 wk; 5) heat stress, diet a, and d during last 2 wk. Performance results were obtained by running each scenario 100 times, generating a new population per simulation. Results from scenarios 1) and 2 showed that heat stress in the last 2 wk reduced (P < 0.05) ADFI and average daily gain of pigs fed diet a by 790 g/d and 310 g/d, respectively. This resulted in a decrease of 4.79 kg in final BW, an increase of 0.64% lean yield, and a decrease of 0.80 mm back-fat at slaughter (P < 0.05). An increased dietary SIDLys (3), NE (4), or both (5) during heat stress did not affect BW compared with scenario 2 (P > 0.05). An increased NE (4) or NE and SIDLys (5) did not affect lean yield and back fat compared with scenario 2 (P > 0.1). But increased SIDLys during heat stress (3), increased lean yield (P = 0.04) and a trend in less back fat (P = 0.07) compared with scenario 2. In conclusion, pig performance was reduced with heat stress in the late finishing period. With the developed statistical tools, we determined from the simulations that none of the proposed strategies significantly increased final BW compared with the baseline (2). But feeding greater SIDLys will likely result in significantly greater lean yield and less back fat. When formulating diets with greater nutrient density attention to ingredient cost and pig prices should be considered.