Here in the West, summer has arrived with a bang this year. The first heatwave in December was one of the hottest ever, with the mercury topping 40C° for four consecutive days. This was followed by another record-breaking hot streak in January, where Perth recorded six consecutive days over 40C°. With areas such as Geraldton recording over 43C°, this summer is shaping up to be unusually hot. Whilst humans may find the heat a challenge, the impact on body condition score is one not to be overlooked in production animals.
Sheep, in particular, may exhibit changes in behaviour and dry matter intake in response to the effects of heat stress. These changes during periods of high temperatures can cause a drop in profitability of enterprises, particularly breeding and feedlot operations. A recent research summary concluded that both ewe and ram reproduction is negatively affected by moderate levels of heat stress (van Wettere et al, 2021). Interestingly, the benchmark temperature was ≥ 32C°, which is what we are now calling a ‘cool break’ in WA summers.
In production sheep, this sort of heat stress can cause a reduction in both body condition and live weight gains, as sheep redirect energy and nutrients into sustaining thermoregulation and core body temperature stability. Due to their higher metabolism, lower body mass, and shorter fleece length, lambs are also very susceptible to heat stress.
Milne Sheep Specialist, Wayne Manoni, says one of the simplest strategies to reduce heat load in sheep is to ensure access to adequate shade. Shade-seeking is a normal behaviour for sheep in response to heat stress. When considering shade, or providing a man-made shade structure, it is important to allow enough space for all sheep in the mob to have access to the shade, without overcrowding. Shade can assist animals to maintain optimum body condition, as animals in shade generally have lower body temperatures and spend less time walking.
Ensuring access to clean, quality water also aids in reducing heat load during hot, summer months. Checking water for acceptable salt levels, total dissolved solids (TDS), pH in the ~6.5-8.5 range, and making sure the whole mob have access to the water trough are good tools to ensure adequate water intake in sheep. Water consumption averages ~3-5 litres per day, but can be as high as 12-15 litres per day in peak temperatures, or when salt content in the diet is too high. Like humans, keeping sheep well hydrated is key to managing stress during heat waves, therefore monitoring water troughs is good practice.
Milne Nutritionist, Dr Josh Sweeny, says regular and frequent water consumption goes hand in hand with sustaining dry matter intake over periods of heat stress, which is where providing balanced nutrition is essential in mitigating the adverse impact that hot weather can have on sheep fertility and performance. The Milne sheep team are always on hand to discuss shade strategies and feed practices to assist sheep farmers.
