Management effects on the environmental footprint of swine production
Livestock production in general is a very small contributor to GHG emissions. However, swine producers will continually be faced with a series of challenges to minimize the environmental impact of swine production. The main objectives of the the studies in this thesis were to evaluate the effects of reducing dietary CP with the supplementation of synthetic AA and the effects of feeding diets with or without antibiotics on manure generation and excretion of N and C. In Exp. 1, thirty-two barrows were used in a metabolism study to evaluate the effect of feeding reduced CP, amino acid (AA) supplemented diets on nutrient excretion. Pigs were assigned to one of four dietary treatments: 1) Control: Corn-SBM-DDGS diets with no synthetic AA, 2) 1X reduction in CP, 3) 2X reduction in CP, and 4) 3X reduction in CP. Diet 4 was balanced on the 7th limiting AA, phenylalanine. Diets 2 and 3 were then formulated to have a stepwise reduction in CP between Diets 1 and 4. Diets 2-4 were supplemented with synthetic amino acids as needed to meet amino acid needs based on NRC 2012 AA minimum ratios for the 7 age phases tested. Low-CP AA supplemented diets significantly reduce N excretion by up to 45%. In addition, VFA concentrations were reduced between 9-17% when dietary CP content was reduced up to 3X levels. Overall fecal C excreted (g/pig/d) was greatest for the lowest CP (3X), largely due to the % C digested being the lowest for that diet. Both DE and ME, were linearly (P < 0.0001) decreased by approximately 6 and 5% respectively with increasing reductions in dietary CP. In Exp. 2, seven hundred twenty-three pigs were placed into eleven identical, environmentally controlled rooms for a wean-to-finish study. Pigs were allotted to one of two dietary treatments: 1) Control: Corn-SBM-DDGS diets with Antibiotics, and 2) Antibiotic Free; treatment 1 less the antibiotics but with alternative supplements. Diets were fed in nine dietary phases. There was a tendency for greater final BW and BW gain per manure pit when pigs were fed the control antibiotic treatment. No significant differences were observed between the two dietary treatments for manure volume (L), manure volume per kg BW gain, DM (g/kg BW gain), N (g/kg BW gain), and AmmN (g/kg BW gain). Manure pH tended to be lower for pigs fed the antibiotic free diet (P < 0.06) compared to the control diet. There were no differences observed for manure total C (kg), manure C per kg BW gain, manure C g/pig/d, and manure C g/pig wean-to-finish. In summary, Exp. 1 low CP diets with synthetic AA supplementation result in lower DE and ME values and C digestibility for the lowest CP diets, but significantly reduce N and VFA excretions. In Exp. 2, the antibiotic free diets had similar manure nutrient excretion and generation with lower manure pH which may affect transformation of N2O during manure land application. The adoption of technologies like these evaluated in this thesis will be of the utmost importance in remaining proactive in finding a way to meet the demands of a growing world population in a manner that is cost effective for the producer, while being environmentally sustainable.
Radcliffe, Purdue University.
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