WITH temperatures warming up, dairy farmers are being warned that cows are extremely susceptible to heat stress which can result in depressed dry matter intakes (DMI) and reduced milk yields.

The caution comes as heat stress is becoming a greater issue in the UK, due to a combination of rising ambient temperatures and increasing average milk yields.

And according to Mark McFarland, feed additive product manager at Lallemand Animal Nutrition, this means that on average, cows producing 60 litres of milk per day experience a 2.00 KW heat output.

“A cow enters into a state of heat stress when there is excessive heat accumulation within her body which she struggles to lose,” explains Mr McFarland.

“Alongside increased panting, an immediate coping mechanism is to reduce DMI. This results in a decrease in the availability of nutrients used for milk synthesis and can also disrupt rumen function, which can cause acidosis.”

“Ration reformulation is needed during periods of increased temperatures to account for decreased DMI and changing nutrient requirements. Maintenance of normal rumen function is also critical,” says Mr McFarland.

“Intakes fall when cows get too hot as they tend to eat less often, and in bigger amounts, which results in ‘sluggish feeding’.

“As a result, producers should maximise eating time by considering feeding cows in the evening during cooler temperatures.

“Adding a probiotic yeast to the diet can also prove very beneficial, helping to support rumen function and maintain DMI.”