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Improving Dietary Amino Acid Balance Reduces Heat Production in Lactating Sows Exposed to Heat Stress

Zhang, S., J. Johnson and N. Trottier

We hypothesized that lactating sows fed a reduced CP (RCP) diet with supplemental AA to improve AA balance produce less metabolic heat (HP) compared with feeding a conventional diet (control). The objective was to measure HP of sows (n = 24) fed control (19.6% CP) or RCP (14.2% CP) under thermoneutral (TN, 21±1.5°C) or cycling heat stress (HS, 32±1.5°C daytime and 24±1.5°C nighttime).

Diets contained 0.90% SID Lys and 2,580 kcal/kg. Positive pressure indirect calorimeters were used to measure gas exchange in individual sows with litters (sow + litter), and individual piglets on lactation d 4, 8, 14 and 18, and HP determined overnight (1900–0700) and during daytime (0700–1900). Sow and litter weights were recorded on d 1, 10 and 21. Sow HP was calculated by subtracting litter HP from sow + litter HP based on BW0.75. Model included the fixed effect of diet, random effects of block and sow, sow feed intake as a regression variable and day as the repeated measurement. Compared to control, HP (kcal/h·kg0.75) of RCP was lower (P < 0.01) overnight (5.25 vs. 5.96 ± 0.38), during daytime (6.33 vs. 6.94 ± 0.23), and over 24-h (5.78 vs. 6.46 ± 0.24) under HS. Under TN, HP of RCP tended to differ (P = 0.107) overnight (5.20 vs. 5.90 ±0.57) and over 24-h (5.93 vs. 6.48 ± 0.50) and did not differ (P = 0.190) during daytime (6.66 vs. 7.06±0.52). Under HS, lactation day affected HP (P < 0.05) overnight and over 24-h, with HP increasing from d 1 to 14 and decreasing from d 14 to 18. Under TN, day of lactation did not affect sow HP.

Feeding RCP diet to lactating sows decreased HP, and this effect was more pronounced in sows housed under HS.

Zhang, S., J. Johnson and N. Trottier. 2019. Improving dietary amino acid balance reduces heat production in lactating sows exposed to heat stress. 2019 Midwest Section ASAS/ADSA Meeting, Abstract 84.