Recent research by DADO- SENN et al. 2022 in Florida confirmed that heat stress of the cow before calving has an impact on the behaviour of calves after birth. Besides reduced feed intake and weakened immune system, heat stress also affects thermoregulatory behaviours.

Prenatally stressed calves showed a higher rectal body temperature. Thus, high temperature stress is higher for these calves than for calves that were not prenatally stressed. This led to these calves standing more often. When standing, more heat can be released due to increased body surface area.

Postnatal heat stress led to altered lying behaviour. The calves were found to lie more often on their sides than on their chests.

Trials indicate that calves out of dry cows that were not suffering from heat stress, show higher birth weights. Although this difference is relatively small compared to calves born with a favourable birth weight, there is a long term advantage: calves with an ideal birth weight show an increased growth performance, due to increased water- and feed intake and a more efficient exploitation.

This also positively influences later milk performance. Unborn calves not suffering from heat stress of the mother cows showed up to 5 kg more milk as later heifers, compared to those out of heat stresses mother cows. This can partly be explained by the fact that higher birth weights positively influence later milk performance of the animals.