VET VOICE HEAT STRESS
Is heat stress affecting your herd reproductive success? Words by: Lisa Whitfield Production Animal Veterinarian
H
eat stress has been mentioned a lot in the last few years and is a buzzword at discussion groups leading up to summer. It has been clearly demonstrated that heat stress has a significant impact on cow welfare and production. The reproductive impact of heat stress is not insignificant either, and consideration should be made to heat stress days which occur over the mating period. Cows
experience heat stress where energy balance from reduced feed there are ambient temperatures intake, changes in reproductive exceeding 25C, or at lower hormone levels and damaged temperatures when the follicles are all substantial humidity index is above 70%. problems when it comes to Heat stress impacts not only establishing pregnancy. the fertility of the cow and her Changes in physical activity ability to become pregnant in the include a reduction in the display of Lisa Whitfield first place, but it also reduces her heat behaviour during oestrus, which ability to maintain pregnancy. is so heavily relied on to detect when The behaviour of a cow is altered when she is ready to be bred. she is experiencing heat stress – she is Heat displays may be both weaker and of less active, spends less time grazing and shorter duration. spends less time lying down. Negative This is not only due to the physical effect
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Dairy Exporter | www.nzfarmlife.co.nz | December 2020
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