Keeping cows cool

High humidity reduces cows’ ability to effectively evaporatively cool, which is their main mechanism for keeping cool on hot days.

The immediate impact of heat stress on cows is a decrease in feed intake resulting in reduced milk production.

Long-term heat stress results in reduced in-calf rates, low milk production, low protein and fat test results, liveweight loss and other cow health problems that can negatively impact farm income.

Heat stress can be effectively managed with a proactive whole-of-year approach including changes to on-farm infrastructure, animal nutrition and breeding programs.

Farms calving in autumn also need to consider dry cows in their heat stress plan for the farm, with heat stress during pregnancy being linked to reduced milk production in the next lactation and less productive and fertile calves.

Infrastructure and water

When considering cattle heat stress on farm our main area of focus should be on infrastructure and short-term management changes on hot days, as this is where we will see the most benefit.

Sprinkler systems used in the yards on hot days can help cow comfort levels at milking, if there is a system already in place check it is putting out large droplets of water not fine misting sprays (as this will reduce the cow’s ability to evaporatively cool even further) and there is enough water to run it throughout the milking.

Ensuring there is shade in paddocks on hot days and where possible on laneways and yards is important and thinking about shade in longer-term infrastructure and farm developments.

Ample water supply is vital as cows can drink up to 250 litres each on a hot day.

Trough type and placement should also be considered.

Cows will consume 30-40 per cent of their daily water intake at the exit side of the dairy if it is available.

Large easily accessible water troughs in all paddocks will also encourage cows to graze for longer in warmer weather helping to reduce production losses.

Breeding

Not all cows are made equal, with some being more susceptible to heat and humidity than others.

Brown Swiss and Jersey cows are more heat tolerant than Holsteins, younger smaller animals are also better at dealing with high ambient temperatures than larger animals and of those in the milking herd, lower producing cows are less affected by the heat.

Within a breed, some cows are more susceptible than others.

There is a ‘Heat Tolerance’ Australian breeding value which can be considered when selecting bulls, cows with a Heat Tolerance ABV of more than 100 are better able to tolerate warm and humid conditions resulting in less production loss.

Nutrition

Metabolising food produces heat; low fibre high quality fodder produces less heat during the digestion process than high fibre fodder and is therefore a better option on hot days.

Increasing concentrate feeding can also reduce heat load from digestion, while the addition of some fats can help to fill the gap in energy intake when feed intake reduces during periods of heat stress.

However, some additives will increase heat load, so it is best to discuss this with your nutritionist.

In addition to this on hot days, the highest quality pasture should be available overnight when it is cooler and cows are more likely to graze.

There are many changes we can make both short and long term to keep our cows cool, comfortable and milking well when the weather is warm.

Some actions to consider for your milking herd for the rest of summer include:

– Lauren Foster