Keeping dairy cows cool

Keeping it cool

Whether your cows were housed or outside in the field, it’s likely that milk yields took an unexpected drop last month.  And to make matters worse, milk butterfat percentage was probably impacted as well.  If this sounds familiar, it’s likely that your cows were suffering from heat stress during the July heatwave. 

The reason for the drop in milk production relates to how cows regulate their body temperature.  Healthy cows normally maintain a body temperature around 38.5°C, and rumen fermentation is their main source of central heating.  However, if body temperatures begin to rise above 40°C, cows will quickly reduce their forage intake to limit rumen heat production.  The downsides however are that this limits the supply of energy for milk production as well as the building blocks for milk fat.  

The ideal temperature for a dairy cow is between 5-20°C, but as temperatures rise above 20°C, both eating behaviour and milk production are quickly affected.  At 25°C, the milk drop can amount to 2.5 kg/day, rising to more than 4 kg/day at temperatures above 30°C.  Even under mild heat stress conditions, butterfat levels typically fall by around 0.2-0.4 percentage units, and milk protein by up to 0.2 units.  

While the July heatwave may have passed, some forecasters are predicting it may return in August.  So it’s important to be aware of some measures that can be taken to help alleviate the effects of heat stress, even if only for a few days:

1) Keep shed doors open to encourage air flow.

2) Check drinkers to ensure the water pressure is keeping up with increased demand. Consider putting temporary drinkers into fields, feed passages or spare cubicles to increase capacity.

3) Prioritise grazing in fields where there are trees to provide shade.

4) Increase concentrates feed rates and feed a rumen protected fat (250-500 g/cow/day) to help compensate for lower dry matter intakes.  Fermentation of concentrates produces less heat than forages, while rumen-protected fats generate no heat at all.  

5) Feed a rumen buffer, such as Thompsons’ Rumitech365, to help maintain proper rumen function on lower forage diets. 


Posted 28,07,21 by allison.

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