Vermunt, Jos J., and Tranter, Bill P. (2011) Heat stress in dairy cattle – a review, and some of the potential risks associated with the nutritional management of this condition. In: Proceedings of Annual Conference of the Australian Veterinary Association - Queensland Division. pp. 212-221. From: Annual Conference of the Australian Veterinary Association - Queensland Division , 25-27 March 2011, Townsville, QLD, Australia.

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Abstract

Heat stress occurs when animals are exposed to environmental temperatures in excess of 25°C (the upper critical temperature), particularly in combination with high relative humidity or sunshine. High humidity makes the sweating mechanism relatively ineffective, thereby making cattle unable to maintain their core body temperature. Affected cows attempt to reduce heat load by reducing exercise, feed intake and lactation. They actively seek shade and wet areas. As their body temperature rises animals become agitated and distressed, have laboured open-mouth breathing and eventually collapse, convulse and die. Heat stress that is not life-threatening leads to reduced milk production and impaired reproductive performance, and may predispose amongst others to subclinical acidosis. Treatment of severely affected animals is by cooling with cold water and/or fans. Prevention is by providing good-quality drinking water and shade (natural or artificial), and the use of water sprinklers and/or fans. Changes to the diet (i.e. high energy density and low protein) are also beneficial and often implemented. However, there may be some potential risks associated with the nutritional management of heat stress in dairy cattle; i.e. the animals are at increased risk of developing subacute rumen acidosis, with ensuing laminitis/lameness, and displaced abomasum. The first part of this paper provides a brief review of heat stress in dairy cattle. The second part discusses how increasing the energy density of the diet (i.e. increasing the grain/forage ratio), as part of the nutritional management of heat stress, may put the cows at greater risk of the above mentioned digestive disorders.

Item ID:	15828
Item Type:	Conference Item (Non-Refereed Research Paper)
Date Deposited:	18 May 2011 23:40
FoR Codes:	07 AGRICULTURAL AND VETERINARY SCIENCES > 0707 Veterinary Sciences > 070706 Veterinary Medicine @ 100%
SEO Codes:	83 ANIMAL PRODUCTION AND ANIMAL PRIMARY PRODUCTS > 8303 Livestock Raising > 830302 Dairy Cattle @ 50% 83 ANIMAL PRODUCTION AND ANIMAL PRIMARY PRODUCTS > 8399 Other Animal Production and Animal Primary Products > 839901 Animal Welfare @ 50%
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