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Injectable trace minerals: a solution to combat livestock heat stress this summer

With forecasts predicting another long hot summer ahead for southern regions, trace mineral supplementation is one effective solution to help combat heat stress in livestock over the coming months, says animal health company Virbac Australia.

“High temperatures can affect everything from conception and fertility rates to immunity, meat quality and milk production, leading to significant economic impacts for producers,” reports Virbac Australia’s Technical Services Veterinarian Dr Paula Gonzalez-Rivas. “In extreme cases, it can even lead to livestock mortality.”

Cattle begin feeling uncomfortable above 25°C – which means that heat stress will be an issue across all Australian livestock regions. For southern regions, cattle are particularly at risk of heat stress coming out of winter, and are more exposed to extreme heat events.

What’s often surprising is that it’s not only extremely high daytime temperatures that trigger heat stress. Warmer night times can have more of an impact, says Dr Gonzalez-Rivas. “Hot nights can be dangerous for livestock, as it’s harder to thermoregulate, dissipate heat accumulated during the day, and reduce their core temperature. That places them under continuous stress, increasing respiration, heart rate and water intake, and placing a strain on multiple physiological processes. In fact, recent research has revealed air temperatures rising as little as just 1.5°C above average can decrease conception rates by as much as 5%1. Even before birth, calves suffer the negative consequences of heat stress if cows were heat stressed during late pregnancy2.”

“Heat stress affects the animal’s oxidative status, it increases the production of free radicals and reduces the activity of antioxidant enzymes, leading to oxidative stress. In both beef cattle and sheep, oxidising agents present in the meat lead to lipid and protein peroxidation affecting muscle fibre structure, resulting in high drip loss, undesirable meat colour and shorter shelf life. In dairy cows, oxidative stress negatively impacts milk production and health. Cows under oxidative stress have increased incidence of mastitis, higher somatic cells count, poor responses to vaccination, decreased fertility, increased embryo mortality, abortion, premature calving, retained foetal membranes, and uterine infections.
Furthermore, oxidative stress also affects sperm concentration and viability in males3,” says Dr Gonzalez-Rivas.

It’s clear that heat stress has real potential for devastating losses in terms of both performance and production – but the good news is that it can be effectively managed. Virbac Australia advises farmers and producers to act now and will be running free webinars on ways to minimise the impact of heat stress in livestock over summer.

A pre-summer review of preparedness for heat stress is a great idea. This should include an examination of the livestock environment, including site characteristics, infrastructure and condition, to provide good shade and water sources, and even fans and sprinklers in intensive production environments. “Adequate water is essential,” Dr Gonzalez-Rivas explains. “It's worth remembering that animals under heat stress lose much more water through respiration and perspiration, often requiring up to five times more water than usual.”

Having a good summer nutrition program that includes trace mineral supplementation is also key. Dr Gonzalez-Rivas recommends using a trace-mineral injection like Multimin injection to improve antioxidant activity “Antioxidants are an ideal heat stress abatement strategy, and Multimin adds important trace minerals like manganese, zinc, selenium and copper, to help boost antioxidants, reproductive performance and immune function4, 5. We also recommend increasing energy density to compensate for reduced feed intake,” says Dr Gonzalez-Rivas – “including slowly fermentable starch to reduce the amount of heat released in the rumen during fermentation6, as well as supplemental fat that bypasses the rumen and minimises the heat released during digestion.”

High-quality forage and fibre also help optimise rumen efficiency and function, particularly for animals receiving high starch diets. If supplementary feeding, modify this strategy from once to twice-a-day feeding, and consider feeding less during the hotter hours and more at night, to allow heat dissipation7.

It can also be beneficial to balance the mineral and electrolyte content, because excessive sweating or panting results in losses of sodium, potassium and bicarbonate, increasing the risks of acidosis and mineral imbalances.  

Victorian dairy farmer, Renee Murfett, is a big believer that it pays to be preventive rather than reactive when it comes to heat stress in cattle.

“Summer can be harsh on our cows, so we make sure they’ve always got access to shade and water. We have a sprinkler system set up in our yard for hot days which not only cools the cows but also stops their frustration with flies. The first signs of heat stress we notice is heavy breathing and stock not wanting to move away from the shade. In more severe cases, they go down with exhaustion. We can lose anywhere from 500 to 1,000 litres of milk a day during a heat wave so Multimin is definitely something we are open to trialling in our cows during a heat stress event.”
As Dr Gonzalez-Rivas concludes, “a proactive approach to the management of heat stress is more effective than a reactive response once it has occurred. Right now, is a great time to begin implementing the best processes to minimise the impact of what’s set to be another blisteringly hot Australian summer and I encourage all farmers and producers to register to our free webinars.”

Get your livestock performance ready for summer. Sign up for the heat load index forecast, and heat stress alerts for beef cattle at chlt.com.au and for dairy cattle at dairy.katestone.com.au

For more information and to register to the free webinars run by Virbac Australia, visit au.virbac.com/webinars  
Beef webinar: Thursday 31st October at 6.30pm-7.30pm AEDT
Dairy webinar: Thursday 5th December at 6.30pm-7.30pm AEDT
(02) 6766 4513
[1] David Wolfenson, Zvi Roth, Impact of heat stress on cow reproduction and fertility, Animal Frontiers, Volume 9, Issue 1, January 2019, Pages 32–38.
2 Fabris, T. F., Laporta, J., Skibiel, A. L., Corra, F. N., Senn, B. D., Wohlgemuth, S. E., & Dahl, G. E. (2019). Effect of heat stress during early, late, and entire dry period on dairy cattle. Journal of dairy science, 102(6), 5647-5656.
3 Celi P. (2011) Oxidative Stress in Ruminants. In: Mandelker L., Vajdovich P. (eds) Studies on Veterinary Medicine. Oxidative Stress in Applied Basic Research and Clinical Practice. Humana Press, Totowa, NJ
4 Machado, V. S., Oikonomou, G., Lima, S. F., Bicalho, M. L. S., Kacar, C., Foditsch, C., ... & Bicalho, R. C. (2014). The effect of injectable trace minerals (selenium, copper, zinc, and manganese) on peripheral blood leukocyte activity and serum superoxide dismutase activity of lactating Holstein cows. The Veterinary Journal200(2), 299-304.
5 Teixeira, A. G. V., Lima, F. S., Bicalho, M. L. S., Kussler, A., Lima, S. F., Felippe, M. J., & Bicalho, R. C. (2014). Effect of an injectable trace mineral supplement containing selenium, copper, zinc, and manganese on immunity, health, and growth of dairy calves. Journal of dairy science97(7), 4216-4226.
6 Gonzalez-Rivas, P. A., DiGiacomo, K., Russo, V. M., Leury, B. J., Cottrell, J. J., & Dunshea, F. R. (2016). Feeding slowly fermentable grains has the potential to ameliorate heat stress in grain-fed wethers. Journal of animal science, 94(7), 2981-2991.
7 Mader, T. L., Davis, M. S., & Brown-Brandl, T. (2006). Environmental factors influencing heat stress in feedlot cattle. Journal of Animal Science, 84(3), 712-719.
Photo captions:
  1. Victorian Dairy Farmer Renee Murfett with Dr Susan Swaney
  2. Dairy cattle in Victoria