28 July 1995

Heat-stressed rams can put freeze on flock performance

HEAT stress in sheep, particularly in rams set to work in mid-summer, can seriously undermine flock performance.

Early lambing flocks which have already turned out rams must take steps to cut the effects of hot weather or face the risk of infertility and low lambing percentages.

Ram libido and sperm damage can be one of the main causes of reduced output from early lambing flocks through lack of attention to rams working in hot temperatures.

ADAS sheep specialist Lesley Stubbings has just completed a MAFF booklet Heat Stress in Sheep – Solving the Problem. She says rams should always be shorn early and shade and water should always be easily available.

"Many flocks suffer reduced performance because of the red-uced ram libido caused by hot daytime temperatures," says Miss Stubbings. "It is too much to ask a ram to work at 100% efficiency in high temperatures in open fields in blazing sunshine."

She recommends early lambing flocks consider keeping tups indoors during the day and turning them out in the evening to enable them to work through the night. "It can make a big difference to lambing percentages," she says.

The need for rams to serve lots of ewes over a short period of time where flocks are synchronised can be a debilitating factor in mid-summer mating.

Early lamb producers should remove excess wool from the scrotum – preferably several weeks before rams are needed – provide shade and keep peak mating time to early morning and evening.

Even ewes should be handled carefully in hot weather. Gath-ering over long distances must be undertaken at a "gentle pace". Moving ewes from high to low ground can often spark off a disease outbreak such as pasteurellosis, of which heat stress is a contributory factor. Ewes should also have easy access to water and be handled as little as possible in warm weather. Move ewes in the early morning or evening. &#42

Lesley Stubbings says ram libido suffers in high temperatures.