Impacts of Reducing Dietary Crude Protein with Crystalline Amino Acid Supplementation on Lactating Sow Performance, Nitrogen Utilization and Heat Production

摘要

As the swine industry continues to compete (with human food production) for protein rich ingredients, the implementation of crystalline amino acids (CAA) have become a staple cost-saving alternative in growing and finishing diets. The inclusion of CAA has proven to decrease total diet crude protein (CP), reduce ammonia emissions and decrease total heat production in finishing swine. Very little research has been conducted on the implementation of low CP diets in sows and its effects on ammonia emitted and heat balance of the lactating sow and her litter. This then became the overarching objective of this M.S. degree research effort. Research was organized into two experiments.;In the first experiment, the hypothesis tested stated that lactation performance of sows would not differ if fed diets containing about 3 and 6 percentage points less intact CP than the standard corn/soy lactation diet and supplemented with crystalline amino acids (CAA) to meet the AA standardized ileal digestible (SID) requirement of a diet solely based on protein-bound AA. Multiparous purebred Yorkshire sows (n=48) were allocated to one of three dietary treatments: 17.16% CP (Control), 14.48% (MCP) and 11.82% CP (LCP), in a randomized complete block design. Diets were formulated to meet an SID Lys requirement of 0.78%. Control diet did not contain CAA and exceeded all AA SID requirements. The MCP and LCP diets contained L-Lys, L-Thr, L-Trp, and L-Val, in addition to L-Ile and L-Phe for LCP diet only. Voluntary feed intake was measured daily. Sow and piglet BW were recorded on d 0, 3, 6, 9, 12, 15, 18 and 21, and milk samples collected on d 4 and 16. Voluntary feed intake, and piglet ADG of MCP and LCP did not differ when compared to control. Milk urea-nitrogen (MUN) decreased (P < 0.001) for MCP and LCP, and was 8.57, 6.85 and, 2.94 mg/dL (+/- 0.93) for Control, MCP, and LCP, respectively. Feeding reduced CP diets with CAA supplementation did not impact sow lactation performance and reduced MUN.;The second experiment tested the hypothesis: that in a hot environment, feeding the LCP (low crude protein) from experiment 1 would reduce heat production by the sow, improve her utilization of N, and reduce short-term ammonia emission from her excreta and urine without negative impacts on lactation performance.;Thirty-six multiparous sows were allocated to a 2 x 2 factorial arrangement of two temperatures, thermo-neutral (21°C; TN) and heat stress (31.5°C; HS), and two diets, 17.16 (Control) and 11.82% CP (Low), in a randomized complete block design. The HS sows were acclimated during late gestation to increasing temperature from 21 to 31.5 °C. During lactation, temperature for HS sows were incrementally changed (24 to 31.5°C and 31.5 to 24°C) from 0500 to 1500 and 1800 to 0500, respectively. Control diet met SID Lys requirement with no added CAA and Low diet contained added crystalline Lys, Thr, Trp, Val and Phe. When compared to Control, piglet ADG, sow feed intake, true milk protein, and sow weight loss of Low sows did not differ. MUN and ammonia emissions decreased for sows fed Low (P < 0.0001). Change in backfat depth, body temp (BT), and days from weaning to estrus did not differ between diets. Compared to TN, BW loss, HR and RR of HS sows were greater (P < 0.05). Compared to TN, piglet ADG of HS sows were less (P < 0.05). There were no diet-by-environment interactions observed. Heat production was not impacted by diet. Heat production was significantly greater from sows exposed to HS (P < 0.05).;In conclusion, this work suggests replacing protein-bound ingredients with CAA to the proportions studied herein, does not impact lactation performance of sows under either thermo-neutral or thermal heat stress environments. The reduction of dietary CP with aggressive CAA inclusion in lactating sow diets optimizes dietary nitrogen utilization and lessens ammonia emission. However, the reduction of dietary CP with CAA supplementation does not reduce metabolic strain or total heat production of the lactating sow and litter.