Protect your cows from heat stress this Summer

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Grass growth falls but potential milk from forage rises.

The average GB grass growth rates, produced by Trouw Nutrition, fell to 59kg DM/ha/day last week. This is 10kg down on the previous week and is below the same time last year. Scotland and North West England saw growth rates of 67/68kg DM/ha/day and Yorkshire 54kg.

On the plus side, high temperatures increased the average dry matter of grass back up to 19%, which will have improved potential intakes. With a typical energy content of 11.8 ME this means, on average, grazing could support M + 14 litres although in many places this potential will have been offset by very high temperatures leading to heat stress in cows and reducing forage intakes.

Reasonable levels of fibre in grass and a low acid loading have reduced the risk of low butterfats but, as above, this will have been offset by potential heat stress.

In the USA and Canada, cows are housed to help protect them from heat stress in summer, the barns are equipped with fans which come on at 68 degrees F (20 degrees C) and many have water sprinklers in the feed passages which come on at 72 F (22 degrees C) Last week there will have been many cows in GB grazing outdoors in temperatures of 86 F (30 degrees C). I must emphasise that we are not saying cows should be kept indoors, just that when grazed outdoors in high temperatures, shade and good access to water are very important for cow health and welfare as well as production.