Impact of dietary electrolyte balance on performance, inflammation, and gut integrity of lactating sow under heat stress

초록

Objective: Heat stress adversely affects feed intake, milk production, and overall reproductive performance. One suggested nutritional strategy to mitigate these adverse effects is the optimization of dietary electrolyte balance (dEB) with bicarbonate supplementation, which regulates acid-base homeostasis and thermoregulatory responses. This study aimed to evaluate the effects of different dEB levels on lactating sow reproductive performance during heat stress. Methods: A total of 40 lactating sows were assigned to four dietary treatments with varying dEB (mEq/kg) levels (230: sodium chloride 0.47%; 250: sodium chloride 0.34%+sodi-um bicarbonate 0.14%+potassium bicarbonate 0.05%; 270: sodium chloride 0.25%+sodi-um bicarbonate 0.26%+potassium bicarbonate 0.09%; 290: sodium bicarbonate 0.52%+ potassium bicarbonate 0.13%) to evaluate the effects on reproductive performance, hair cortisol, the acid-base balance, inflammation, gut integrity, behavior, and intestinal micro-biota of lactating sows during heat stress. Results: Increasing dietary dEB levels during heat stress (temperature: 26.0 degrees C-31.1 degrees C; temperature to humidity index: 78-84) linearly increased average daily feed intake of sows during lactation and improved piglet weaning weight. Blood pH decreased linearly with rising dEB levels, while hair cortisol content showed a decreasing trend. interleukin (IL)-1 beta tended to decrease with increasing dEB levels, and IL-10 showed a trend to a quadratic peak at 250 mEq/kg before declining. Behavioral analysis showed a quadratic response in standing behavior, peaking at 250 mEq/kg, while position changes decreased linearly with increasing dEB. Beta diversity analysis revealed differences in unweighted UniFrac principal coordinate analysis between 230 and 290 mEq/kg dEB groups. The abundance of the actinobacteriota phylum tended to decrease linearly; however, the abundance of major phyla including the firmicutes and bacteroidota was unaffected. Conclusion: In conclusion, increasing dietary dEB from 230 to 270-290 mEq/kg with bicarbonate supplementation improved feed intake and piglet weight at weaning, suggesting that a dEB around 270 mEq/kg is optimal for supporting sow reproductive performance under heat stress.

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