Research Update: Feeding Cool Cows May 2020
Feeding Cool Cows
Feeding Cool Cows

Our ever-changing climate is a challenge for a range of agricultural industries, including dairy. For a single four-day heat event in northern Victoria in 2014, the cost at just the farmgate level was estimated at around $16 million. However, the impact at an individual cow level is very complex. One of the objectives of the DairyFeedbase Feeding Cool Cows project is to assess the cost of hot weather in terms of individual cow milk production and then devise on-farm management strategies for implementation at the herd level to minimise the impact of heat events on dairy farm productivity.

Research by the Feeding Cool Cows team confirms that, as cows are exposed to hot weather, the cow’s internal temperature increases resulting in changes to behaviour, including less time spent lying down to rest and less time spent eating or grazing. The consequence of this is reduced dry matter intake and ultimately less milk produced per cow.

Photo: Feeding Cool Cows Project Leader Dr Leah Marett

Cool Cows project leader Dr Leah Marett and her team are investigating a range of strategies to assist dairy farmers to better manage heat-related yield drops. Controlled experiments are focused on the different components of the diet of the cow: concentrates, forages and additives. Dr Marett said “so far changing the concentrate offered to cows has shown some small positive effects on production, for example maize grain in place of wheat, but there is limited economic benefit during short-term heat events due to the higher cost of maize. So now we are focusing on other components of the cow’s diet such as forages and additives.”

The focus of these short-term feeding strategy experiments is aimed at offering cows feeds that will help the cow maintain a lower body temperature during heat exposure, or that offer greater palatability so that the cow continues to eat during heat events. The most recent experiment offered chicory to cows –  a forage that  grows well during summer and could continue to offer palatable high quality grazeable feed during hot conditions. Results are still coming in, including work to define the economic impacts, but preliminary data show a higher milk production in cows fed chicory compared to pasture silage.

Another focus of the Cool Cows project has been to understand the impact of hot weather at the plant level. Partner farms in Northern Victoria allowed some of the team to access their paddocks during the hot summer of summer 2018 and collect samples of lucerne, tall fescue and perennial ryegrass. The results showed a decrease in the nutritive characteristics of all forages with increasing temperature above 25oC, highlighting the important role and impact that  home-grown feed has during summer.

The project will also focus on how to use nutrition in conjunction with genomic selection to boost profitability. “DairyFeedbase Cool Cows project is also working closely with DairyBio geneticists to improve the heat tolerance ABV that is already available to farmers,” said Dairy Australia’s Director of Major Innovation Projects and DairyFeedbase Co-director Kevin Argyle. “Farmers should be pleased that their two main innovation program investments are working together to achieve fantastic profitability and productivity outcomes.” The Cool Cows team are working towards understanding the interaction between the diet of the cow, and the cow herself, to answer the question – should heat tolerant and susceptible cows be fed differentially during summer?

“Infrastructure also has a part to play,” said Dr Marett. “The cow welfare benefit of options including tree belts, shade covers, sprinklers and ventilation are well established, and the economics of these are being assessed and will be incorporated into our final recommendations.”

The economic framework being developed by the Cool Cows team combines feeding, infrastructure, and herd assembly options to provide detailed information on the cost and benefit of a range of interventions available to farmers. The end integrated solution to minimise the impact of heat stress will be a whole-of-farm system with guidelines well supported by science.