Weather: Most people will be glad to see temperatures return to more normal levels by the weekend.
While the hottest days are likely to be behind us, Thursday and Friday will continue to be very hot.
Giving cows lots of access to clean water is critical. Slow-filling troughs is really unacceptable – you need to do whatever is needed to make sure cows have lots of water.
Heat stress will be evident above 24°C, but becomes more severe above 26°C.
Cows will naturally go for shade when temperatures are at their warmest, so keeping them in fields with lots of shade is very important. Where cows are congregating together closely, such as in a collecting yard, the ambient temperature will rise. The same can happen in a shed where cows are housed, particularly where there is poor ventilation. All farmers, but particularly those in confinement-type systems, need to be very alert in these conditions.
Grass growth: While temperatures are set to reduce, there’s no sign of rain coming, at least not in the next week. Evapotranspiration will be very high in the heat, so we can expect widespread severe soil moisture deficits by early next week. Grass growth rates are set to slow considerably over the coming days and grass is already wilting away on many farms. In times like this, it’s important to use up what grass is available before it disappears. I’d be very slow to introduce a lot of supplement now and instead continue to graze away as normal on a 20- to 25-day round length and let average farm cover drop if growth drops.
High levels of meal and/or silage should be avoided, as all this will do is slow down the rotation length, meaning more grass is wasted and more supplement will be fed. Cows are extremely content grazing what is often stemmy grass in dry weather. Remember that grass dry matter is very high in the heat at over 20%. Cease all fertiliser spreading until after the rain comes. Spreading nitrogen now will not make the grass grow any faster, but it can lead to an increased risk of leaching. There was a big deterioration in water quality after the 2018 drought, so everyone needs to be more conscious of leaching after a dry spell.
Cow health: Pica, which was a big problem earlier this year, is still lingering on some farms. If supplementing phosphorus or other minerals in the water, make sure you get the allocations correct, as cows’ water intake will have increased enormously in the dry weather.
There are two types of worms that can affect dairy cows. These are ostertagia (stomach/gut worms) and lungworm (hoose). Ostertagia can be identified in bulk milk testing or through dung samples. Only dose if there is a problem. Some farmers will only dose younger cows, but if doing this, only use an injectable and not a pour-on to prevent animals that aren’t dosed from licking the product off the dosed cows’ backs. Lungworm is more serious, particularly in the current hot weather. Identifying lungworm through diagnostic testing is difficult and vets will often suggest immediate dosing where cows are coughing. Talk to your vet about whether pour-ons or injectables are more effective.