Abstract
Heat stress occurs when animals are exposed to environmental temperatures in excess of 25oC (the upper critical temperature), particularly in combination with high relative humidity or direct sunshine. Prevention is by providing plenty of good-quality drinking water, providing shade (natural or artificial), and using 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. This paper 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 cows at greater risk of the above-mentioned digestive disorders.
Highlights
Like all other mammals and birds, cattle are ‘warm-blooded’ homeothermic animals
High heat loads lead to depressed feed intake, decreased milk yield, milk fat and protein percentages, and elevated somatic cell counts (SCC) [4]
Cows need ample access to drinking water to allow for increased intakes in order to compensate for increased losses from sweating and increased respiration rates
Summary
Jos J Vermunt Adjunct Professor (Cattle Health and Production), College of Public Health, Medical and Veterinary Sciences, James Cook University, Townsville, QLD, Australia *Corresponding author: Jos J Vermunt, 80 Russell Robertson Drive, Havelock North 4130, New Zealand.
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