A systems approach to evaluate nitrogen utilization efficiency and environmental impacts of swine growing-finishing feeding programs in U.S. pork production systems

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Abstract
Traditionally, swine diets have been formulated to meet nutrient requirements at the lowest cost with little regard toward minimizing environmental impacts. The overall objective of this study was to evaluate the relative differences among four grower-finisher feeding programs, using precision diet formulation practices, on growth performance, carcass composition, nitrogen utilization efficiency, and environmental impacts. In experiment 1, four 4-phase growing-finishing feeding programs consisting of diets containing corn and soybean meal (CSBM), low protein CSBM supplemented with crystalline amino acids (LP), CSBM with 30% distillers dried grains with solubles (DDGS), and DDGS supplemented with crystalline Ile, Val, and Trp (DDGS + IVT) were fed to 288 mixed sex pigs (initial body weight [BW] = 36.9 ± 4.2 kg) for 12 wk to determine effects on growth performance and carcass characteristics. Pigs fed with CSBM had greater (P < 0.05) final BW than those fed with LP and DDGS, and greater gain efficiency than pigs fed with LP. Pigs fed with DDGS + IVT tended to have greater (P = 0.06) backfat depth than pigs fed with DDGS, and less (P < 0.05) loin muscle area than pigs fed with CSBM. In experiment 2, nitrogen (N) and phosphorus (P) balance of barrows (n = 32; initial BW = 59.9 ± 5.1 kg) fed with each of the phase-2 diets from experiment 1 was determined in a 12-d metabolism study (7 d adaptation and 5 d collection). Pigs fed with CSBM had a greater (P < 0.05) amount of N retained than pigs fed with other diets, but also had a greater (P < 0.05) amount of urinary N excretion and blood urea N than pigs fed with LP and DDGS + IVT diets. Pigs fed with LP tended (P = 0.07) to have the greatest N utilization efficiency but the least (P < 0.05) P retained as a percentage of P intake among dietary treatments. Diet composition and data collected from experiments 1 and 2 were used to calculate life cycle assessment environmental impacts using Opteinics software (BASF, Lampertheim, Germany). The CSBM feeding program had the least impact on climate change, marine and freshwater eutrophication, and fossil resource use. The LP feeding program had the least impact on acidification, terrestrial eutrophication, and water use, while the DDGS feeding programs had the least impact on land use. These results indicate that feeding CSBM diets optimized growth performance and carcass composition while simultaneously reducing impacts on climate change, marine and freshwater eutrophication, and fossil resource use compared with the other feeding programs evaluated. Developing and evaluating feeding programs that optimize growth performance and carcass composition, while minimizing cost, nutrient excretion in manure, and environmental impact is essential for achieving sustainable pork production systems. Four growing-finishing feeding programs consisting of typical corn-soybean meal (CSBM) diets, low protein CSBM diets containing supplemental crystalline amino acids (LP), CSBM diets containing 30% corn dried distillers grains with solubles (DDGS), and DDGS diets containing supplemental crystalline Ile, Val, and Trp were evaluated to compare their effects on growth performance, carcass composition, nitrogen and phosphorus utilization efficiency, and several environmental impact measures. Pigs fed CSBM diets had greater final body weight than those fed the LP and DDGS diets, and greater gain efficiency than pigs fed the LP diets, but there were no differences in the percentage of carcass lean among feeding programs. However, pigs fed the LP diets had the greatest nitrogen utilization efficiency and the least impact on acidification, terrestrial eutrophication, and water use among these feeding programs. The CSBM feeding program had the least impact on climate change, marine and freshwater eutrophication, and fossil resource use, while the DDGS feeding programs had the least impact on land use.
Funding Information
  • United Soybean Board (2140-352-0507-I)

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