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Trees for Stock Shade
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Trees For Stock Shade

The foliage and trunks of trees can block the sun, providing some measure of comfort for heat stressed stock. Heat stress has been shown to have an impact on animal production, fertility and birth weight as well as animal behaviour.

The graph below shows the estimated effect of providing shade on the milk production of dairy cows in Florida. The results show that when air temperatures are high (27oC), providing sufficient shade may increase milk production by around 20%, offsetting most of the effect of heat stress on production. In the trial, dairy cows with access to a cement pad covered with an insulated iron roof also had conception rates of 44% compared to 25% for cows not shaded.

Reference: Reid, R. and Bird, P.B. (1990),'Shelter' in Trees for Rural Australia, ed. K.W. Cremer, Inkata Press Melbourne, pp 319-335.

Research by the Department of Primary industries in Queensland compared a number of strategies for reducing heat stress in dairy herds including iron roofs, sprinklers and shade cloth. The results confirmed the USA research showing that shade reduced production losses due to heat stress and was even more effective than sprinklers alone. Shade increased milk and fat yield, pregnancy rates and weight gain whilst reducing somatic cell counts (an indication of infection).

In the hottest part of the year, the sun is more severe when high in the sky. For trees to be effective, stock must therefore be able to get under the canopy. Large spreading trees with a dense canopy held high above the ground are ideal. Having a clear trunk allows air movement below the canopy, further cooling the stock. Farmers may need to consider the impact of stock trampling on the root system of trees and rubbing or chewing on bark. In the afternoon, when the temperatures can still be high, tall trees will cast a shadow well away from the root system thereby reducing compaction by stock.

Heat and Cold Stress of Farm Animals



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