PSXII-31 Effect of dietary protein level and amino acid balance on heat production in lactating sows exposed to thermal neutral and heat stress conditions.

Abstract: Heat stress (HS) increases body temperature (BT) and reduces feed intake in pigs. Increasing the dietary protein content may correct the reduced amino acid intake provoked by HS, but it may further increase BT. The effect of dietary protein level on BT of HS pigs was analyzed with nine ileal cannulated pigs (61.7 ± 2.5 kg body weight). A thermometer set to register BT at 5-min intervals was implanted into the ileum. There were two treatments: low-protein (10.8%) wheat-free-amino acid diet (LP); high-protein (21.6%), wheat-soybean-meal diet (HP). The study was conducted in two 10-d periods; in each period, d1 to d6 was for diet adaptation, d7 to d9 was for data analysis, and d10 for ileal sample collection. Pigs were fed at 0600 h (morning), 1400 h (midday), and 2200 h (evening), same amount each time. Following, the separate contribution of ambient temperature and thermal effect of feeding on the postprandial BT increment was analyzed in fed and fasted pigs. Ambient temperature ranged from 30.1 to 35.4 °C and relative humidity from 50% to 84%. Both ambient temperature and BT followed similar patterns. The BT of HP pigs after the morning and midday meals was higher (P < 0.05) but size of the BT increments did not differ between HP and LP pigs. Midday and evening postprandial BT were higher than postprandial morning BT (P < 0.05). The BT increment was larger and longer after the midday than after the morning and evening meals (P < 0.05). The capacity of pigs to dissipate postprandial body heat depends on the accumulated thermal load received before their meals, because the thermal load before the morning meal was smaller than that before the evening meal. The estimated contribution of thermal effect of feeding (0.42 to 0.87 °C) on the total postprandial BT increment (0.69 to 1.53 °C) was larger (P < 0.05) than that of ambient temperature (0.27 to 0.66 °C). In conclusion, these data indicate that the dietary protein level has a small effect on the BT of HS pigs regardless of feeding time. Also both the thermal effect of feeding and ambient temperature impact the BT of HS pigs, although the former had a stronger effect. This information may be useful to design better feeding strategies for pigs exposed to HS conditions.

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84 Improving dietary amino acid balance reduces heat production in lactating sows exposed to heat stress

Journal of Animal Science ◽

10.1093/jas/skz122.086 ◽

2019 ◽

Vol 97 (Supplement_2) ◽

pp. 47-48

Author(s):

Sai Zhang ◽

Jay S Johnson ◽

Nathalie L Trottier

Keyword(s):

Heat Stress ◽

Amino Acid ◽

Gas Exchange ◽

Positive Pressure ◽

Metabolic Heat ◽

Lactating Sows ◽

Dietary Amino Acid ◽

Conventional Diet ◽

Diet Control ◽

Amino Acid Balance

Abstract 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.

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