Animal Health

Nutrition counters stress

By Dairy News

Every Australian dairy farmer knows the impact heat stress can have on their herd.

New research has found feeding protected B vitamins can help improve reproduction and achieve higher milk production.

Jefo Nutrition’s Hélène Leclerc said dairy cows adapt to heat stress by modifying metabolism to reduce heat expenditure, resulting in reduced milk production, and reproductive performance will be negatively impacted, resulting in a loss of profit.

“Supplementing a blend of protected B vitamins (folic acid, B12, pyridoxine, pantothenic acid and biotin) during lactation is an innovative option to counteract impacts of the heat stress impact and will improve milk production, component yield and reproductive performance.

“The benefit of supplementing protected B vitamins during heat stress is even higher than under non stressful condition,” Ms Leclerc said.

A study conducted during summer in the north of Mexico, where reproductive performance is drastically reduced due to heat stress, showed an improvement when the ration was supplemented with a blend of protected B vitamins, in fact, the first service conception rate increased by 19 per cent while 22 per cent more cows got pregnant early at 120 and 150 days in milk.

During another study conducted in the United States with cows under heat stress, the energy corrected milk increased by 3.8 kg/day when compared to non-protected biotin. The increase included higher milk production with 100 g more butterfat and 160g more milk protein.

The Temperature Humidity Index (THI) was developed to identify the point (68) where heat stress negatively affects performance. An example of a THI of 68 would be 24°C with a 30 per cent humidity.

A University of Arizona study showed cows producing 35 kg of milk daily dropped by 2.2 kg of milk per day when the minimum THI was on average 68 (65 to 73), the maximum impact on milk production will occur 24–48 hours following heat stress.

Cows under heat stress have depressed heat expression due to a lower production of estradiol and quality of ova. Early embryo development is impaired when the body temperature of the dairy cow reached 38.9˚C which explains lower pregnancy and conception rates during summer.

It takes 40–60 days following heat stress before fertility returns to normal.

Recent studies have also shown an association between the effects of heat stress during the breeding period and subsequent reduced milk production of progeny between 82 -399 kg over a lifetime lactation.

What can be done to reduce the
impact of heat stress on dairy cows?

The use of cooling systems and a reduction of stocking density are sound management tools along with providing clean water and some nutritional adjustment to the ration.

The take home message on heat stress

  • The dairy cow will adapt to heat stress by modifying its metabolism to reduce heat expenditure.
  • Milk production and reproductive performance will be negatively impacted resulting in a loss of profit for the dairy producer.
  • Supplementing a blend of protected B vitamins (folic acid, B12, pyridoxine, pantothenic acid and biotin) during the lactation period is an innovative tool to provide ammunitions to dairy cows to counteract the heat stress impact and will improve milk production, component yield and reproductive performance.
  • The benefit of supplementing protected B vitamins during heat stress is even higher than under non stressful condition.