25 The impact of lower energy diets on finishing pig performance

Abstract Increasing dietary energy density greater than corn-soybean diets on pig performance is well documented. However, data characterizing pig performance consuming less energy dense diets than corn-soybean is not as prevalent. Distiller dried grains with solubles (DDGS) contains less energy in 2024 versus 2010, and soybean hulls will be more readily available due to more soybean processing capacity in the United States. Therefore, it becomes important for the USA pork producer to understand how the modern pig performs when consuming less energy dense diets. Hence, we commissioned a study to understand performance of pigs fed less energy dense diets. A total of 2,304 finishing pigs (DNA 600 x 241, initially 19.1 kg) were used in a 73-d experiment to evaluate the effects of lower energy on growth performance from approximately 9 to 20 weeks of age. A corn and soybean meal based diet was formulated as the control for each phase, with treatment diets being a combination of DDGS and soyhulls to lower the energy value of the diet to be 27.2, 54.4, 81.6, or 108.9 ME kcal/kg lower than the control. Dietary energy was allowed to fluctuate with changing fiber levels while maintaining a constant SID lysine-to-calorie ratio. Five phases of diets were utilized throughout this experiment. Pens of pigs were randomly allotted to 1 of the 5 treatments across 2 barns, with 32 pigs per pen and 14 replicates per treatment. Gender was equally represented in each pen. Data was modeled in R (R Core Team, 2020) to test for both linear and non-linear responses to energy level in the diet. Models included energy level, barn, and trial start weight, and pen being the experiment unit. Traits analyzed included average daily gain (ADG, kg/d), Gain to Feed (G:F), average daily feed intake (ADFI, kg/d), and kilocalories per kilogram of gain (kcal/gain). Overall, a quadratic response in ADG was observed, with the highest growth being the control treatment at 1.06 kg/d and the -108.9 kcal/kg treatment being the lowest growth at 0.91 kg/d (P < 0.001). With decreasing energy levels a quadratic response was observed for ADFI as the control animals consumed 2.4 kg/d while the -54.4 and -108.9 kg/kg treatments both consumed 2.55 kg/d (P < 0.001). Due to these differences, a linear reduction in gain to feed was observed (P < 0.001). Cumulatively, no differences in kcal/gain were observed in this experiment (P = 0.730). These data provide understanding of the impact of feeding energy dilution on modern pig growth performance.