Managing Heat Stress in Dairy Cows
This is just a republish from my original a year ago. The impact of heat stress happens at different temperatures depending upon what the cows ‘normal’ is. Details below on potassium and magnesium levels make a huge difference, but don’t forget to watch the sugar levels in the diets too.
Heat stress in cows if not managed, costs production output, conception rates and increases variable costs (treatment etc)
There are many practical influences to you make to the environment and many different housing systems. There is no right or wrong opinion on this, all work if set up correctly, all fail if not.
Assuming a number of ‘must do’ such as adequate clean water availability, multiple feedings, 60% of diet at night when cooler, bunker management etc…
Simple nutritional changes on a TMR diet will counteract the effects on heat, there is no reason to see lower fertility or production.
Long fibre needs to be reduced but fibre levels need to be maintained from other sources. Generally some substitution from carbohydrates to energy from fat is beneficial. Keep NDF 28 -30% and ADF greater than 18%
Micro managing diet minerals will make the biggest differences. Potassium is the key mineral – source must be a carbonate and not a chloride aim for 1.5%. Magnesium oxide coverers any shortfall in magnesium levels, maximum level of 0.4%, I find around 0.35% effective. The main objective being to raise the DCAD of the diet to positive 25 / 30 or greater. Normal buffers such as bicarbonate soda and limestone need to keep under 400 g / day in order not to reduce DMI (0.35% to 0.6%). Salt in TMR at 100g naturally drives thirst and encourages drinking. Finally betaine which is an osmolyte, is a very effective addition which can be adjusted as per external temperature, generally has a 3 to 4 day lag between feeding and being effective. Rumen protected Niacin is another effective tool.
As per most farms, no two are the same so there is no one fix suits all. There is still however, no reason that heat stress cannot be effectively managed within a sensible budget and to the benefit of the cow.