Heat Stress in Ruminants

by Tanya Brouwers

The intense heat of the summer months can take its toll on the livestock of any farming operation. Ruminants, in particular, are sensitive to the elevated temperatures and high humidity levels associated with the summer season.

Research has shown that in ruminants, temperatures above 27oC may increase the incidence of lameness, disease associated with compromised immunity, reproductive problems and reduced milk yields. Not only does heat stress and its numerous consequences have the potential to be financially burdensome for the livestock operator it will also, if left unchecked, affect animal health and welfare.

In order to help livestock farmers identify and address this seasonal concern before it evolves into more severe conditions like heat exhaustion and sunstroke, the Organic Agriculture Center of Canada (OACC) has created a fact sheet on heat stress in ruminants. Along with a list of the early signs of stress, the publication also outlines numerous, easily implemented management practices that will help to reduce or avoid the incidence of heat stress altogether.

When summer temperatures rise, a livestock operator’s first priority should be to provide adequate shade and abundant cool, clean water. The provision of these two elements will go a long way in avoiding heat stress and improving performance. For example, demonstrated that when beef cattle were provided with at least 45 square feet of shade per animal, weight gains improved dramatically. Trees or permanent shelters that will accommodate all animals in a lying position are good examples of structures that will provide sufficient relief from the sun’s direct rays. For cattle, at least one watering station for every 20 cows is also recommended.

Other examples of practices that will prevent stress include the use of fans and sprinklers for those animals that are housed or corralled. Operators should also avoid transporting or handling animals during the heat of the day. Stressful activities like castration and vaccination, especially, should be carried out in the cool of the morning or the evening. Farmer’s might also consider shearing sheep in the spring rather than in the summer. Earlier shearing gives the fleece a chance to regrow and protect the exposed skin before the summer sun is at its hottest and most penetrating.

Despite all measures an operator might take to prevent stress, there is always the chance an animal may succumb to the heat. Overweight, dark-haired and lactating animals are, by their very nature, more susceptible than other animals to the effects of hot weather. The livestock operator, then, should be constantly on the lookout for signs that heat stress is occurring. Reduced feed intake, rapid breathing, open-mouthed breathing, increased saliva production and trembling are just some of the symptoms that an animal may exhibit when inadequately coping with elevated temperatures. The operator should provide shade and water at the first sign of any of these symptoms. It is likely, otherwise, that the condition will evolve into sunstroke or heat exhaustion.

If the symptoms of heat stress have not been treated in a timely manner and the condition has evolved into sunstroke, for example, then the operator must take immediate measures to lower the animal’s body temperature. Cold water enemas, ice applications and cold water submersions are some of the approaches that have effectively treated severe conditions of heat stress. Other operators have successfully treated sunstroke with homeopathic remedies. The Herdsman’s Introduction to Homeopathy, by Hansford and PInkus, recommends the use of Aconite 30C, Belladonna 30C and Glonine 30C to alleviate the symptoms of sunstroke. Finally, never hesitate to call on the expertise and experience of a qualified veterinarian.

With the inevitably high temperatures of the summer months comes the increased risk of heat stress in ruminants. The condition, if undiagnosed, can evolve into a scenario that is both financially debilitating for the operator and physically crippling for the animal. The OACC fact sheet Heat Stress in Ruminants lists numerous ways in which the livestock farmer can diagnose, reduce and avoid heat stress. The hope is that, with the implementation of these preventative practices, the health and welfare of the animals in an organic operation will remain unquestioned and uncompromised.


For more information, please see the Animal Welfare Task Force Fact Sheet, Heat Stress in Ruminants.


Tanya Brouwers is a Consultant for OACC. Please send comments or questions by phone to 902-893-7256 or by email to oacc@nsac.ca.


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Posted August 2009