Dairy producers worldwide experienced the warmest year on record last year, putting milk production, fertility and the overall comfort of their animals at risk, reported Cargill.
This trend in warm weather is becoming something producers quickly have to adapt to, as the last three years have brought three of the four warmest periods around the world, said Guillermo Schroeder, that company’s global ruminant R&D director.
Heat stress is linked to ambient temperature as well as to relative humidity, which increases the impact of heat. The temperature–humidity index, or THI, is a common indicator of heat stress.
And a dairy cow’s performance will be undermined when the THI reaches 68, said Schroeder.
“Fortunately, there has been a huge amount of research, at both academic and industry level, into this challenge over the past five years. We understand so much more about heat stress and ruminants now than we did 10 years ago. Every year we have more and more data. As a global business, we are able to glean statistics from Europe to Central and South America on heat stress," he told us.
Schroeder said high heat and humidity limit the ability of the cow to keep cool. “This is especially true for high-yielding cows, which generate a lot of heat through their own digestion and metabolism.”
Indicators of stress
Signs of heat stress in dairy cows will include shallow breathing, sweating, lower feed consumption and a drop in milk production of anywhere between 10% and 30%, he continued.
Heat stress can also increase reproductive problems and increase susceptibility to disease in dairy cows, said the ruminant expert.
“If a cow is only exposed to heat stress for a limited period, say one week, milk production can recover to normal levels within one to two weeks but that is a rare event. Long term exposure will depress the immune system and undermine the animal’s ability to fight diseases,” he explained.
What is happening with heat stress, said Schroeder, is that the cow diverts blood away from her core to her surface, in an effort to dissipate heat, and this can impair gut function and nutrient absorption.
“It is a lot more cost effective to alleviate the impacts of heat stress that deal with the consequences of no intervention,” he said.
In terms of nutritional strategies for producers, he said they “can improve feed efficiency by adapting the feeding approach, by concentrating the diet to provide nutrients in lower amounts a few weeks before warmer weather kicks in. They should also modify the amino acid composition of the diet and ensure mineral balance.”
He said Cargill’s heat stress targeted feed additive, which includes an osmolite compound, works on the cellular level to maintain the structural integrity of proteins sensitive to changes in body temperature, moderate the elevation of body temperature in ruminants during heat stress, and mitigate the effects of heat stress on acidosis, milk quality and pregnancy rate.