Preparing cattle for heat stress

Glacier FarmMedia | MarketsFarm – Cattle producers should have a plan to protect their animals from excessive heat this summer.

Livestock specialists with North Dakota State University encourage livestock owners to monitor weather forecasts and anticipate when conditions may pose a significant risk to livestock. Such conditions exist when above-average temperatures collide with increased humidity.

A temperature-humidity index chart can help ranchers identify when livestock are most at risk for developing heat stress, said NDSU Extension specialists. Cattle are in danger when the temperature is at 25 C and the humidity is 80 per cent of higher for 72 straight hours (or 30 C and 30 per cent, or 35 C with no humidity at all).

They are also in danger if for 48 hours, daytime temperatures are at 30 C with 55 per cent humidity or more (or 35 C and 20 per cent) and no lower than 25 C at 80 per cent at night. At 30 C with 85 per cent humidity or 35 C with 45 per cent humidity for two straight days, cattle are at the highest risk.

Heat stress can significantly impact animal performance, health and welfare, making it critical to prepare a proactive management plan for unavoidable heat events. Heat stress occurs when an animal’s cumulative heat load outweighs the animal’s ability to dissipate heat, causing body temperature to rise.

Here are some heat action plans:

• Each animal should have at least five centimetres of linear water trough access. For example, a pen with 200 animals should have one metre of linear water space. Evaluating water supply lines and ensuring sufficient water pressure and flow capacity to keep troughs full during peak water consumption is also important. Livestock whose sole source of water comes from tanks or troughs should be checked daily. In severe heat events, livestock without access to water for 24 hours or less can be at risk. If this has occurred, consult your veterinarian to determine a plan for gradual rehydration, which may take several days.
• Each animal should have a minimum of six metres of shade space (three metres for small ruminants) to prevent animal grouping and comingling of sick animals. Spraying for flies prior to a heat event will also be a vital step in reducing animal grouping.
• Reduce the risk of heat stress by dampening the pen with water or adding light-colored bedding (straw or corn stalks) to reduce the temperature of the ground. Sprinkler systems are a popular way to cool ground temperatures in confinement cattle operations.
• Livestock handling should be limited to the early morning hours (prior to 10 a.m.). Working facilities, including holding pens, should have ample access to water, and personnel should be dedicated to monitoring livestock stress status. Avoid working livestock in the evenings during a heat event to give livestock time to recover and cool down during cooler periods of the day.
• Livestock owners should consider moving livestock feeding time to late afternoon or evening. This will allow rumen fermentation to occur during cooler night temperatures and increase the animal lung capacity during hotter daytime temperatures.
• Ruminant livestock, including sheep and cattle experiencing extreme heat stress, will exhibit increased respiration rate and panting score, foaming around the mouth, down head and lethargic appearance. Livestock owners should keep in contact with their local veterinarian and contact them immediately if they have animals in severe distress. Animals should be gradually cooled by moving to nearby shaded areas with ample air movement. Rapid cooling (such as spraying with cold water) can have severe consequences for livestock in severe distress.