Maximising efficiency against heat stress in cattle

Farmer's Weekly|May 22 - 29, 2020

Maximising efficiency against heat stress in cattle
Expected temperature increases due to the effect of global warming will have a negative impact on the productivity of livestock. According to animal science researchers at the Agricultural Research Council, beef farmers will have to follow certain breeding objectives to lessen this effect.
Annelie Coleman

Livestock production systems are the world’s largest users of land resources, and the situation in Southern Africa is no different. Approximately 84% of the surface area of South Africa is available for agriculture, of which only about 13% is arable. The greater part of South Africa is suitable only for extensive livestock production. The livestock value chain has a responsibility to be fully aware of these facts and that the industry stands to suffer as a result of global warming.

MITIGATION OF HEAT STRESS

Temperature, solar radiation, humidity and wind all affect animals directly, with temperature having the greatest direct effect on livestock production.

Most livestock perform at their best at a temperature between 4°C and 24°C. Given the effects of global warming, the temperature in large parts of Southern Africa are expected to rise more frequently above this comfort zone. It therefore makes sense to select animals that are adapted to high temperatures, according to Prof Michiel Scholtz, specialist researcher at the Agricultural Research Council’s (ARC) Animal Production Institute.

Fast Facts

Global warming is a reality that livestock producers in southern Africa need to take cognisance of.

Heat stress directly affects the fertility of livestock and, ultimately, production levels.

Research results show that crossbreeding mitigates the impact of heat stress on beef cattle production.

The climate across Southern Africa varies from arid conditions in the west to humid and subtropical conditions in the north and east, while much of the central part is semi-arid.

Heat stress is a common cause of reproductive inefficiency, especially in beef cattle, as it negatively effects the fertility of a bull by decreasing semen quality. This is a measure of the ability of semen to accomplish fertilisation, and semen quality does not return to normal for about eight weeks after exposure to heat stress due to the duration of the spermatic cycle. Heat stress influences reproduction and will, in the long run, become evident in a decrease in the number of calves born in an affected herd. Georgette Pyoos-Daniels, a junior researcher at the ARC Animal Production Institute, writes that even a single day of heat stress may reduce the semen quality and potential fertility of a bull. This is why early, seasonal warning systems are set to become more important in the quest to mitigate the effects of global warming in future.

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May 22 - 29, 2020