Prolonged hot weather across the UK is taking its toll on dairy cows, with milk yield dips reported in many herds and the likelihood of reduced fertility. And we may not have seen the end of it, according to Cargill’s ruminant specialist Donald Macleod. He’s encouraging dairy farmers to make management and dietary changes that will help mitigate the effects of this heat stress and keep cows on track.
“Daily spikes in summer temperatures will affect cow productivity and behaviour, and by early July many dairy farmers across the UK had reported reduced milk yields since the hot weather has continued,” he says.
“But prolonged periods of high temperatures will have longer lasting effects, and fertility is the key casualty. It’s highly likely that heat detection and conception rates will have dipped and we won’t see this immediately, but in a few months’ time. By this point, it’s too late to do anything except pick up the additional costs of additional fertility work and an extended calving interval.”
Heat stress has become more of an issue in high-production cows which produce a lot of metabolic heat. “Cows producing 46kg of milk a day produce 26% more metabolic heat than those producing 32kg of milk a day,” he explains.
Management tweaks and using a cooling product in milking and dry cow diets will reduce the impact of heat stress on herd performance.
“Make sure there’s a good supply of clean water and cow flow is optimised,” adds Donald. “Fresh feed should be available at cooler times of the day to encourage intakes. Dips in production are most likely a direct consequence of depressed appetite from heat stress due to sub-acute ruminal acidosis.”
Using the specialised rumen buffer Equaliser® CoolCow is also proven to mitigate the effects of heat stress in dairy cows. “I have many reports in the past five years from producers showing how this has kept production on track during high summer temperatures,” he says.
Cargill’s UK trials have also shown that the specialised buffer supports fertility. On eight farms where the temperature and humidity index (THI) was recorded and where actions were taken to reduce the effects of heat stress, including fans and Equaliser Coolcow, fertility performance was maintained in heat-stress conditions.
Results showed the best improvements were seen where fans and the rumen buffer were used with conception rates remaining more consistent and only dipping from around 40%, to 35% as the THI increased from 60 to 65 or above. This is above 22°C and 60% humidity, which is typical in a UK summer.
Added to concentrate or buffer feeds, the rumen buffer works by helping to restore a cow’s electrolyte balance and regulating her core body temperature.
“Because this specialised rumen buffer plays an important part in countering the negative effects of heat stress, which we’ve shown can affect most UK dairy herds during the summer, it’s a cost that can be easily justified,” says Donald
For close-up dry cows including the feed product CoolCalver, which also contains the specialist cooling pack found in CoolCow, valuable postbiotics and the energy-boosting, liver-priming feed supplement LiFT, the effects of heat stress can also be reduced.
“Keeping cows active and maintaining feed intake will support more consistent fertility and milk production through the summer and into autumn and reduce the risk of setbacks caused by heat stress,” he concludes.
