In dairy cows, the first short-term impact of heat stress is the reduction of milk yield ,about 10 to 35% reduction is usually recorded and acidosis risks are also increased. While in beef, fattening cattle are the most sensitive to heat stress with consequences such as increased acidosis risks and the reduction of feed intake, especially lower fiber consumption, which translates into lower growth performance and behavioral changes as producers often see less calm but more nervous animals.
A study shows that fattening heifers in the shade had a 100 g/day increase in average daily weight gain, as compared to those with no shade, due to higher feed intake in the shade. Moreover, these animals were less stressed and showed less carcass defaults such as dark meat.
The Long term consequences can arise on animal health, immune function or reproduction, especially as heat stress generally increases the production of free radicals, leading to oxidative stress.
Oxidative stress in dairy cows can lead to increased mastitis frequency and higher somatic cell counts in milk. It can also cause decreased fertility, increased embryo mortality, post-partum retained placenta and early calving, with consequences on the calves’ live weight, mortality and health.
Rumen specific live yeast Saccharomyces cerevisiae I-1077, considered as a rumen modifier, can help alleviate the impact of heat stress. In particular, its ability to help stabilize rumen pH and enhance fiber degradation in the rumen is particularly adapted to respond to heat stress challenges. Several trials showed good results in both dairy and beef cows.
Trials with a nutritional supplement , an antioxidant combination containing organic selenium, and a natural primary antioxidant source showed that the animal’s total antioxidant status (TAS) is improved, translating into: reduced somatic cell count in milk by 40-60%, a sign of enhanced immunity (also shown on dairy goats) and improved meat quality parameters in cattle.
There are other nutritional recommendations that can help combat heat-stress in cattle ,these are:1) Increase the energy density of the diet.
2) Add more starch or added fat to the diet as fat is not fermented in the rumen, hence does not release heat during digestion.
3) Mineral electrolytes balance must be maintained as excessive sudation, or panting, leads to losses of sodium and potassium.
4) Provide clean fresh water at all times but most especially after milking.
source Dairy Global.
