Many farmers will have cows that experienced heat-induced stress in the recent heatwave, with symptoms ranging from mild dehydration to heat stroke.

However, for autumn calvers the full effect may not be fully realised until calving, farmers are being warned.

In a press release, Nettex's technical livestock manager Nia Williams advised farmers that "cows calving this autumn are at a greater risk of producing calves with impaired immunity".

Williams advised farmers that calves may be facing greater risk of scours in the early stages of life.

Heat stress can disrupt a cow's normal feed intake levels, increase the cow's susceptibility to infections such as pneumonia, and impact mammary gland development.

Critically these can all impact the cow's ability to produce colostrum.

Commenting on the effects, Williams noted that:

She advised farmers that colostrum should be fed rapidly after birth and that farmers should monitor the effect of passive antibody transfer with a blood test between one to seven days from birth.

Teagasc

Teagasc has advised that all calves should receive 3L of colostrum within two hours of birth, from the cow's first milking.

The quicker the calf receives colostrum, the greater the absorption of antibodies (immunoglobulins) and stronger the calf's immune system.

In some cases, a cow may be leaking colostrum in the run-up to calving. If this loss of colostrum occurs more than a few hours before calving, then the quality will be at risk.

Testing this colostrum with a refractometer is a simple and quick way to ensure calves receive the best care. Quality colostrum is at a minimum of 22% on a brix refractometer, according to Animal Health Ireland.

Farmers do not need to dump colostrum below the 22% level however, as it is still exceptional feed for the calf's second and third feeds where it still exhibits high levels of immunoglobulin absorption.

Calves

According to Williams, calves suffering from heat stress may exhibit symptoms including poor suckling, low energy and open-mouth breathing.

Nutritional support may be needed to improve recovery speed.

Electrolytes are commonly used on farm and are easy to use, cost-effective, and show rapid improvements in calf health especially where calves are scouring.

If symptoms do not reduce or disappear, veterinary assistance may be required.

Cow health

Autumn calvers will be at particular risk of heat induced stress. Water consumption and appetite reduce significantly in the lead up to calving resulting in dehydration and in many cases, mineral deficiencies.

Calcium deficiency or milk fever is the most common but other subclinical deficiencies can develop such as zinc, selenium, and copper.

“During calving, cows can lose close to 60L of water through blood and uterine fluids, along with significant electrolyte losses," Williams said.

She advises farmers to support cows immediately after calving with nutritional support. The feeding of mineral, electrolyte, and vitamin dense products in solid or liquid form is increasingly common.

Boluses are also increasingly popular post-calving as well as mineral injections (where deficiency is identified) as an insurance policy that mitigates the risk of developing clinical or subclinical deficiencies post calving.

Body condition score

With August and September calving farms now beginning to plan drying off, body condition score (BCS) must be monitored. BCS for cows entering the dry period should not be below 2.75.

Heat stress can cause a cow to lose condition, so farmers must act before the reduced BCS begins to impact the calf and calving process through mineral deficiencies, impacted calf growth, and a prolonged negative energy balance.

Teagasc data points to BCS potentially dropping by 0.25 from pre-calving to post-calving, preventing where possible and mitigating heat impacts are crucial.

Low BCS (below 2.75) is easily identified by the cow having protruding hip bones, without fat tissue padding, ribs visible and backbone prominent with the rise and fall of bones evident (not smooth).