The effect of high temperatures in the UK this summer may affect the performance of the in-utero calf, but this may not be evident until the animal is in milk production. So says Cargill calf and heifer specialist Bianca Theeruth.
Speaking at UK Dairy Day this week, she told visitors that there may be consequences on some UK dairy units, and production could be below target. “This is an epigenetic affect,” she explained, “where conditions affecting the pregnant dam ‘change’ the performance of the offspring.”
Ms Theeruth referred to trial work carried out at the University of Florida’s dairy unit that demonstrated how heat stress on the dam, resulting from high temperatures in summer months, affected the performance of the offspring.
Carried out across five consecutive summers, from 2007 to 2011, one group of pregnant cows was cooled in the dry period with sprinklers that were activated when the ambient temperature hit 23.9oC. The other group were not cooled and subjected to daily temperature increases.
Results showed that the calves born from cows cooled during their dry period – before calving – consistently produced more milk throughout their first lactation than calves born from cows that were subject to heat stress.
“The difference was more than 5kg of milk per day,” she says. “And this illustrates the longer-term effect of dry cow care on their offspring. It is an example of epigenetics.”
Ms Theeruth added that the temperatures experienced during this trial would be on par with those experienced in the UK this summer and, on some units, we could see the effect further down the line when this summer’s calf crop comes in to production.
Heat stress, dry-cow nutrition and calving difficulty can all affect the performance of the new-born calf, as well as calf management. “When conditions are challenging – like they were during the summer and how, with pressure on forage stocks, they may be this winter – producers must ensure that dry cows are well managed and any stress factors are minimised.
“Creating stress-free environmental conditions and meeting the cow’s nutritional needs, with a high quality dry-cow diet, will prepare her for her next lactation and safeguard the performance of the unborn calf later in life,” she adds.