Heat stress has multiple negative impacts on animal metabolism and physiology and is thought to cost the swine industry more than $360 million per year (St-Pierre et al., 2003). Heat stress can impair the ovarian function as seen on most farms as an increase in wean-to-estrus intervals following weaning and reduced conception rates during the summer months. Betaine is a commercially available feed additive that can have multiple functions such as acting as a methyl-donor or osmoprotectant. The objectives of this trial were to have a better understanding of the underlying metabolic and physiological changes during heat stress in lactating sows and to evaluate to what extent betaine supplementation can reduce the effects of heat stress. Twenty sows were housed in either a heat stress or a thermoneutral environment and fed either 0% or 0.22% betaine supplement in their diets. Respiration rates, rectal and skin temperatures were recorded. Following weaning, sow’s ovaries were ultrasounded every 12 hours to determine follicular growth rates and timing of ovulation. Respiration rate, rectal and skin temperature were increased under heat stress conditions. At the same hours post-weaning follicle size was larger in sows housed at TN conditions. Betaine supplementation reduced the rectal temperature and increased the follicular size in sows. These results show some initial data that is promising for the potential for betaine supplementation during lactation to partially alleviate the impacts of heat on sow reproductive performance. However, further study is required using a larger sample size to detect differences in variables with high variability.
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