Dairy farmers are being advised to look for signs of heat stress, which could knock performance in the coming months, according to Adam Clay, Ruminant Manager with Trouw Nutrition GB.
Heat stress is caused by a combination of higher temperatures and raised humidity. It can have a significant impact on performance by reducing milk yields, largely due to the depression of feed intakes.
“Last year we saw depressions in milk yield, milk quality and pregnancy rates when climatic conditions induced heat stress, reducing margins and potentially profits,” explained Mr Clay.
“Temperatures do not need to be very high before heat stress becomes an issue. Cows start to be affected by heat stress when the temperature reaches just 20°C (68°F) so it is easy to see how grazing cows are at risk of heat stress.”
Mr Clay added that in the week ending June 20, the peak temperature of 21°C combined with 83% humidity, a stress risk of up to 70%.
Visible symptoms of heat stress include a more rapid respiration rate and panting, lethargy, reduced feed intake and rumination, and lower yields.
Mr Clay added that heat stressed cows also exhibit changes in rumen function, with less frequent cud chewing and reduced saliva production. These factors increase the risk of acidosis by disrupting the usual rumen buffering effect of rumination.
Farmers are advised to act promptly at the first signs of heat stress, as the rumen can take a long time to adjust and effects can be seen a long after weather conditions have improved.
Against usual advice, Mr Clay suggests that cows suffering from heat stress should also be fed less forage in the diet. He said: “Forages are actually a source of considerable heat production in the rumen which can exaggerate the impact of heat stress.
“Their fermentation produces seven times more heat than concentrates, so under heat stress conditions it will pay to reduce forages and increase concentrates, particularly high fibre concentrates.”
“Also make sure cows have access to plenty of clean, fresh water, as when thirsty water intakes will increase markedly. This problem will be worse when forages are reduced,” added Mr Clay.
Source: Western Morning News