Effect of dietary near ideal amino acid profile on heat production in lactating sows exposed to thermal neutral and heat stress conditions

Authors: ZHANG, SAI - Michigan State University; Johnson, Jay; TROTTIER, NATHALIE - Michigan State University

Submitted to: Journal of Animal Science and Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/3/2020
Publication Date: 7/9/2020
Citation: Zhang, S., Johnson, J.S., Trottier, N.L. 2020. Effect of dietary near ideal amino acid profile on heat production in lactating sows exposed to thermal neutral and heat stress conditions. Journal of Animal Science and Biotechnology. https://doi.org/10.1186/s40104-020-00483-w.
DOI: https://doi.org/10.1186/s40104-020-00483-w

Interpretive Summary: The welfare and productivity of lactating sows is reduced during summer months when heat stress is a concern. Heat stress causes a variety of behavioral and physiologic changes that assist sows in surviving the stress but reduce their productive potential. These can include a reduction in feed intake, decreased milk production for piglet consumption, and increased body temperature. In addition, genetic advancements made by the swine industry have made sows more sensitive to the negative effects of heat stress. Therefore, there is an urgent need to develop mitigation strategies that can improve the lives of sows in our care. The study objective was to evaluate the effects of feeding sows diets with reduced crude protein under heat stress or thermoneutral conditions. We hypothesized that decreasing crude protein would improve sow health and productivity under heat stress conditions. It was determined that feeding reduced crude protein diets with a near ideal amino acid profile alleviated the increased body temperature of sows under heat stress conditions. Results from this study suggest that producers may be able to feed sows reduced dietary crude protein with a near ideal amino acid balance to reduce the physiological stress response of sows to heat and improve overall welfare and productivity.

Technical Abstract: The hypothesis of this study was that lactating sows fed a low crude protein (LCP) diet with supplemental AA to improve AA balance would have less total heat production (THP) compared to those fed a high crude protein (HCP) diet under both thermal neutral (TN) and heat stress (HS) conditions. Thirty-two lactating sows were allotted to HCP (19.3% CP) and LCP (14.0% CP) diets under thermal neutral (TN, 21±1.5°C) or cycling heat stress (HS, 32±1.5°C daytime and 24±1.5°C nighttime) conditions. All diets contained 0.90% SID lysine and 10.8 MJ/kg net energy. Positive pressure indirect calorimeters were used to measure gas exchange in individual sows with litters and in individual piglets on lactation days 4, 8, 14 and 18. These data were used to determine THP overnight (1900-0700) and during the daytime (0700-1900). Sow and litter weights were recorded on days 1, 10 and 21 of lactation. Sow THP was calculated by subtracting litter THP from sow + litter THP based on BW0.75. Under HS, sows BW and body protein (BP) loss was greater for LCP diet compared to HCP diet in peak lactation (P < 0.05 and P < 0.01, respectively) and throughout the entire lactation period (P < 0.05 and P = 0.056, respectively). For the HCP diet, when compared to TN, sows under HS had higher (P < 0.05) rectal temperatures at 1300 (P < 0.05) and 1900 (P < 0.01), and higher respiration rates at 0700 (P < 0.05), 1300 (P < 0.05) and 1900 (P < 0.05). For the LCP diet, sows under HS tended to have higher (P = 0.098) rectal temperature at 1300 and had higher respiration rate at 0700 (P < 0.05), 1300 (P < 0.05) and 1900 (P < 0.05). The relationship between daily THP and days in lactation of sows fed LCP diet was quadratic (P < 0.05), with an ascending trend until day 14 and a descending trend from days 14 to 18. Under HS, compared to HCP diet, sows fed LCP diet had lower daily THP at day 18 (P < 0.001). To conclude, feeding LCP reduced THP and this reduction was mainly associated with THP on day 18 of lactation under HS conditions. Feeding LCP diet alleviated the increased body temperature in sows under HS throughout lactation, which was accompanied by a reduction in respiration rate. Total heat production is associated with days in lactation, in particular under HS conditions with THP appearing to peak between days 14 and 18.