Keeping dairy cattle cool
Heat stress can have a substantially negative effect on milk productions and is an animal welfare concern. Simple steps can help reduce this impact.
Dairy cattle can be impacted when temperatures rise above 25° C, especially when combined with high humidity¹ and warm nights. The primary effect is a reduction in milk yield. When cows experience heat stress, their intake of feed decreases, resulting in lower energy intake. Energy is also diverted towards regulating body temperature, leaving even less available for milk production.
Milk production can drop by as much as 20 percent during periods of moderate to severe heat stress.²
Mitigating heat stress
» Provide ample shade: Access to shade is one of the most effective ways to reduce heat stress. Shade from trees or purpose-built structures, such as shade cloths, can reduce temperatures by several degrees.
» Optimise water supply: During periods of heat stress, dairy cattle can increase their water intake by up to 50 percent. Equal access to a plentiful supply of cool water, with multiple troughs per paddock, is recommended to prevent dehydration and support milk production. Further troughs along race ways, feed pads, and the milking areas may be added.
» Energy dense feeds: Quality summer crops can help to support cow energy requirements over summer. Concentrates such as grains (barley, maize) and high-energy pellets provide quick and efficient sources of energy to meet cow requirements, despite reduced feed intakes.
» Rumen bypass fats: A concentrated energy source that does not increase the heat load from fermentation.
» Yeast cultures: Saccharomyces cerevisiae can improve rumen fermentation efficiency³ and help stabilise the microbial environment during periods of heat stress, leading to better fibre digestion, higher nutrient absorption, and less digestive heat production.
» Vitamin E and selenium antioxidants: Heat stress increases oxidative stress in cattle⁴, which may impair immune function and reduce milk yield. Antioxidants like vitamin E and selenium neutralise free radicals and support immune function.
Contact your local PGG Wrightson Technical Field Representative to learn more about implementing heat mitigation strategies.
WRITTEN BY LAURA PATTIE (BVSC DIST, MANZCVS) PGG WRIGHTSON
TECHNICAL EXPERT – ANIMAL PRODUCTION
¹ West, J. W. (2003). Effects of Heat-Stress on Production in Dairy Cattle. Journal of Dairy
Science, 86(6), 2131-2144
² National Animal Disease Information Service (NADIS) UK. Heat Stress in Dairy Cows.
Available at: NADIS Heat Stress Guide
³ Desnoyers, M. et al (2009) Meta-analysis of the influence of Saccharomyces cerevisiae
supplementation on ruminal parameters and milk production of ruminants. Journal of
Dairy Science, 92(4),1620-1632
⁴ Abeyta, M. et al (2023) Effects of dietary antioxidant supplementation on metabolism
and inflammatory biomarkers in heat-stressed dairy cows. Journal of Dairy Science 106(2)
1441-1452
