Plan ahead to manage heat stress

Summer is here and with it comes the risk of heat stress in feedlot cattle.

Feedlot operators can reduce the severity of the heat load burden placed on cattle during hot conditions by implementing a range of management strategies and being mindful of some key tips, according to a leading expert in the field.

Dr Simone Holt, a consulting nutritionist with Nutrition Service Associates, Toowoomba, helped develop the current heat load model in the feedlot industry, and works with many feedlots on their heat stress management strategies.

She said there are four main components to developing a strategy – undertaking a pre-summer review, daily monitoring, developing a stress response plan, and a death loss response plan.

“In a pre-summer review, which happens typically around August and early September, feedlots need to take stock of the previous summer to assess what did or didn’t work, and change response plans if needed,” Dr Holt said.

“All feedlot staff members should be briefed on heat load and undertake some training so they can correctly identify the signs and stages of stress in animals relative to heat load.”

Dr Holt said symptoms of heat stress include excessive panting, progressing to open-mouthed panting, and cattle with their tongues out as heat increases throughout the day in a heat load event.

“Restlessness is another sign animals aren’t coping – they’ll move about a bit more than what they normally would,” Dr Holt said.

“When it comes to preparing, I’m a big advocate of making sure pen floors are as clean as possible. Pen conditions play a very important role in helping to reduce heat load, so we need to make sure floors are clean. 

“During summer, muddy hair coats can reduce the ability of the animal to dissipate heat, so it is important that pen floors are attended to as part of the pre-summer review and then regularly assessed during the summer. 

“Also in a pre-summer review, feedlots should go through a risk assessment program. Year to year yards might change their feeding program, and some years they might have more Bos indicus type cattle, and maybe other years they might have more Bos taurus cattle that are a bit more susceptible to heat stress.”

Dr Holt said daily monitoring of cattle was essential, and ensuring staff knew who was responsible for every aspect of the management strategy was vital.

“Making sure extra water tanks are on hand if they’re needed for extra water points in pens is important,” Dr Holt said.

“Often during heat stress events you’ll get animals that will just hang out around the water troughs, and although they’re not drinking, they’re standing there because of the coolness that comes off the tanks. Typically, those animals block other animals from getting in to get the water that they need. Additional water tanks ensure you can get as many cattle to water as needed.

“We make sure pen riding stops after 7am unless it’s absolutely necessary during excessive heat load events at the feedlots where I advise. We have our stock crew out very early in the morning before it gets hot. We stop all movement of cattle, so there’s no drafting or loading.

“There are several steps in place for when we start approaching a heat load event. Initially this will trigger a heat load ration, followed by extra water points, minimising stock movements and notifying processing plants in an extreme event that we’re not going to be shipping cattle.

“A heat load ration is designed to take some of the energy load out of the ration. As cattle eat they generate heat of fermentation, so we’re trying to help the cattle stabilise their intake. There is also some risk of acidosis occurrence coming in and out of heat stress events, as cattle are naturally adjusting their dry matter intake to the conditions. Typically, a higher roughage diet is fed.”

Dr Holt said in undertaking a death loss plan, feedlot managers need to be mindful of the National Feedlot Accreditation Scheme’s (NFAS) guidelines and trigger points for reporting death loss to the Australian Lot Feeders’ Association (ALFA).