By Gofaone Motsamai

Heat stress is among the most urgent climate-related challenges affecting beef cattle productivity, requiring South African cattle breeders to adopt climate-smart strategies to bolster food security under changing environmental conditions.

“Heat stress is becoming a major threat to livestock productivity,” said Prof Giel Scholtz of the Agricultural Research Council (ARC) in an online guest lecture hosted by the North-West University’s (NWU’s) Faculty of Natural and Agricultural Sciences on 24 April 2025.

Prof Scholtz is a specialist researcher in applied animal breeding at ARC Animal Production and a researcher focused on sustainable livestock systems.

He explained that when humidity levels rise above 80%, the temperature threshold for heat stress in beef cattle drops from 30°C to 27°C. This heat stress reduces feed intake, delays growth, impairs fertility and affects meat quality.

Heat stress can also lead to reproductive inefficiency in both male and female cattle, Prof Scholtz said. “If the temperature goes above 27°C, semen quality decreases and some sperm die. It takes eight weeks for new sperm to be formed, meaning even one day of extreme heat can influence bull fertility.”

He presented data showing how indigenous breeds such as the Afrikaner and Nguni are more resilient than exotic breeds. “In 2015/16, the hottest and driest year recorded, Angus and Simmental types showed a 70% decrease in growth rate during heat waves, while the growth rate of Afrikaner and Nguni only dropped by 9%.”

The importance of feed efficiency under climate pressure was also raised. “We saw bulls eating less but weighing more, probably due to increased water intake,” he noted. “Nguni bulls increased water intake by up to 50%, while the Afrikaner bulls did not change their water intake at all.”

Prof Scholtz stressed the importance of using indigenous or adapted breeds for future breeding strategies. “Our indigenous breeds are our heritage for food security,” he said. “They are better adapted to survive and reproduce under harsh environments.”

He concluded the lecture by calling for new breeding priorities focused on smaller body size, lighter hair colour, darker skin pigmentation and the effective use of crossbreeding. “We need animals that are resilient, that recover quickly, and that can bounce back after extreme climatic events.”

Prof Giel Scholtz