The sun can shine when calves are fed heifer start milk replacer

This summer, for a second year in a row, Bonanza calf Nutrition will add a proven additive to reduce heat stress problems in calves to its Shine Heiferstart formula.

Trial work at Milan University have found the blend of additives in Shine Heiferstart really works when it comes to making calves more comfortable, productive, and healthier during hot, humid situations, explained Dr Amanda Dunn of Bonanza calf nutrition.

Two trials were conducted to assess growth, feed efficiency, health status, respiratory rate, rectal temperature, and antioxidant status (all heat stress parameters). There were 40 heifer calves in each group from birth to weaning in conditions where the temperature humidity index (THI) was >80 (heat stress zone e.g. When temp is >28°C and humidity >80%). This THI reading would also be hit at lower temperatures (25-26’C) in the UK as the RH is often over 90%, she explained

Firstly, the use of the additive made life more comfortable pushing the critical THI out to 84 from 80 in supplemented calves which led to better technical and economic performance and improved animal health and welfare.

Results showed significant better growth performance from calves that received the additive in both trials (See Figure 1), with 16% and 30% more growth from birth to weaning in trials 1 and 2 and 18 to 27% enhanced feed efficiency.

Figure 1: Growth Performance and feed efficiency

During periods of heat stress, dry feed consumption is reduced, which coupled with higher energy demands (to dispel heat), there is often a reduction in daily liveweight gains. This can delay reaching targets and impair rumen development which can make weaning a more difficult process, says Dr Dunn.

Calves fed the additive had a much greater antioxidant capacity compared to calves fed standard MR which resulted in these calves having better resistance to oxidative stress caused by severe heat. Oxidative stress is defined as an imbalance between oxidants and antioxidants and can have detrimental effects on the calf’s immunity and health.

In terms of calf health, it was no co-incidence that additive fed calves had significantly less relapses of diarrhoea and respiratory problems and therefore reduced number of veterinary treatments compared to control group. This resulted in an reduction of £6 /calf in veterinary treatments against diarrhoea and respiratory diseases.

Respiration rate and rectal temperature are two accurate ways to measure heat stress in calves. Additive fed calves had significantly less breaths per minute (trial 1 = -7, trial 2 = -8) and lower rectal temperatures (trial 1 = -0.5°C, trial 2 = -0.55°C) than control calves (See Figure 2).

Elevated respiration is observed during periods of high temperature as this promotes evaporative heat loss. Taking a few minutes a day to stand and observe your calves can tell you a lot, says Dr Dunn.

Just like humans, calves will drink a lot more water when it is hot as lose a lot of moisture through sweat and increased respiration.

Research has shown that as the temperature of the environment rises from 0-35°C there is a fourfold increase in the amount of water calves consume, from 1.4 litres/day to 4 litres/day, in addition to their milk.

To avoid dehydration, it is therefore vital that clean water is constantly available.

During a heatwave, feeding electrolytes to calves in between milk feeds can be beneficial to provide additional water and energy.

“Often excess panting can lead to calves becoming acidotic and the electrolyte can help alleviate this,’’ Dr Dunn explains.

By including the additive in Shine Heiferstart it allows calves to feel more comfortable in their environment, perform better in terms of growth and development, they are more efficient at converting their feed which leads to better economical gain per calf.

From a health and welfare perspective during severe heat calves have a reduced respiratory rate, lower rectal temperature, and greater resistance to oxidative stress.