The effect of withholding drinking water on wool growth and lamb production of grazing Merino sheep in a temperate climate

Abstract

Drinking water was withheld from grazing pregnant and non-pregnant Merino ewes for a period of 12 months in an experiment carried out near Armidale, N.S.W., lat. 30° S., altitude 1000 m. There was no reduction in the wool production or liveweight of, or the number of lambs born to, ewes without drinking water as compared with ewes with water supplied. There was a significant reduction in the birth weight of the lambs of ewes without drinking water. Body water turnover rates were similar in sheep with and without water in the cooler months but a combination of climatic effects resulted in considerably lower water turnover rates of the sheep without water in early summer.

Lactation, together with a low pasture water content and moderately high thermal loads in late December, resulted in a 25% mortality of the mated ewes without drinking water and the subsequent death of their lambs. Removal of the remaining ewes and lambs to green pasture immediately stopped the deaths although no drinking water was supplied. There were no deaths in the unmated ewes.

The survival of most of the ewes when deprived of drinking water reflects in part the temperate climate of the Armidale area, where mean daily air temperatures during summer do not exceed 25°C and rain usually falls in each month of the year.