Feed Additives for Heat Stress

Feed additives assist cows in hot conditions in many ways. Some include:

  • rumen modifiers
  • yeast and yeast metabolites
  • betaine
  • niacin.

Rumen modifiers such as monensin, tylosin, virginiamycin, lasalocid and bambermycin may assist by beneficially altering the balance between the different populations of microbes in the rumen and the proportions of volatile fatty acids (VFAs) they produce.

For more information, see the feed.FIBRE.future fact sheet  or visit the Dairy Australia website.

Yeast and yeast metabolites increase fibre digestibility. They use-up lactic acid and break down rumen contents into glucose from propionate; a VFA commonly produced by gut bacteria. There is some evidence that suggested increasing glucose can assist cows in managing their metabolic heat loads during heat stress 

Betaine helps to maintain feed intake and reduce the amount of energy used to stay cool and continue normal metabolic processes. It can provide effective relief in heat stress situations, but only if the dosage is correct.

The dose rate for heat stress is 15-20 grams per cow per day, but a nutritional advisor should be consulted to get the balance right. There are some situations where betaine would not be advised. 

Vitamin B3, or niacin, has been shown to play a role in energy metabolism, so additional niacin supplementation may be helpful in the warm seasons.  

The most important thing with your summer nutrition program is to provide a diet which includes high quality forage fibre, adequate protein, slowly fermenting starch sources, fats, buffers and minerals.

Consult your nutrition adviser for more information on what place these or other feed additives may have in your summer nutrition program.


Essential salts provide potassium, sodium and magnesium

Electrolytes are essential salts that all mammals need to balance water intake and keep hydrated. Cows lose electrolytes through sweating and urination, so their feed intake may require supplements.

Cows lose large amounts of potassium (K+) in hot conditions through sweating. Potassium bicarbonates provide a good source of dietary potassium for dairy herds. Between 1.3-1.6% potassium in the diet (DM basis ) is recommended during the hotter seasons.

Cows urinate in response to increased water intake and excrete more sodium (Na+). Sodium bicarbonate is the preferred source of dietary sodium, but sodium chloride works as well and is cheap. Approximately 0.45 – 0.6% sodium in the diet (DM basis) is recommended during the hot season.

Magnesium inputs should also be increased during the hot season because it’s an essential co-factor for many metabolic processes, particularly extra fat supplementation. Approx. 0.35% magnesium in the diet (DM basis) is recommended.

A nutritional advisor will have a solid knowledge around the existing salt and electrolyte content of your current feedstocks and provide advice on adjustments during warmer months.


Are buffers necessary?

Cows normally produce more than 2.5 kilograms of bicarbonate-rich saliva every day. Bicarbonates act as an effective buffer against changing stomach acidity and keeps rumen pH within an optimal range. A stable pH range supports the cow’s gut bacteria; an essential component in breaking down the rumen contents.

Hot conditions make cows drool from their mouth instead of letting saliva flow into the rumen. On top of that, heat-stressed cows will have lower concentrations of bicarbonates in their saliva.

A drop in the flow and the bicarbonate concentration means the natural buffering activity is reduced. At the same time, the cow may be consuming less effective fibre and more grain or feed concentrate. This also increases the risk of a fall in rumen pH and ruminal acidosis problems.

Therefore, dietary supplementation with a buffer is good insurance during the hot season. Recommended daily feed rates vary depending on what is fed and how it is fed.

Consult your nutrition adviser.