The effects of shade and shearing date on the production of Merino sheep in the Swartland region of South Africa

Abstract

A total of 497 Merino ewes were allocated to one of four experimental groups for the period 1996 to 1998. The treatments were designed to provide data on the effect of shade during an autumn lambing season and the effect of shearing prior to joining in September or prior to lambing in February. Dietary intake in shaded and control paddocks was similar, but animals in shaded paddocks consumed less water than those in control paddocks. Lambs born in shaded paddocks tended to be heavier at birth than those born in control paddocks. Survival of lambs was unaffected by the provision of shade, but lambs born in shaded paddocks were 3.8 % heavier at weaning than contemporaries born in control paddocks. Lambs born to ewes that were shorn prior to lambing tended to be lighter than those from ewes shorn prior to joining. Lamb survival prior to weaning tended to be higher in lambs born to ewes shorn prior to lambing than in those shorn prior to joining. Shearing of ewes prior to lambing had a beneficial effect on lamb survival during 1997, when the survival of progeny of ewes shorn prior to joining was low. Annual lamb survival data obtained in the present experiment were combined with that from two previous experiments conducted at the same site. The response in lamb survival of the progeny of ewes shorn prior to lambing depended on the average lamb survival observed in the control group. Multiple-born progeny of ewes shorn prior to lambing grew faster to lamb marking than contemporaries born to ewes shorn prior to joining. No difference was detected in single lambs. The clean fleece weight of ewes shorn prior to lambing was heavier than that of contemporaries shorn prior to joining. Similar benefits were found for staple strength and the frequency of mid-staple breaks. It was concluded that the shearing of ewes prior to lambing might be advantageous under certain conditions, particularly when lamb survival is likely to be low.

Age trends in economically important traits of Merino ewes subjected to 10 years of divergent selection for multiple rearing ability

“…Given that staple strength is known to be reduced by reproduction (Hinch et al, 1996;Cloete et al, 2000), this result was not entirely unexpected. The reason why it only involved 4-year old ewes is, however, not clear.…”

“…demonstrated that wool of ewes subjected to pre-lamb shearing was more sound (P < 0.05) than that of ewes shorn before joining, with fewer mid-staple breaks (Cloete et al, 2000). The practice of pre-lamb shearing employed in the resource population used may thus well have contributed to the general soundness of the wool tested.…”

“…In the sense that fibre diameter is one of the most important determinants of wool price (Purvis, 1995) this result is pleasing. It should, however, be kept in mind that higher reproducing ewes are known to produce finer fleeces than lower reproducing contemporaries (Cloete et al, 2000). Genetic trends in the resource population used were inconclusive in this respect, although H line progeny tended to become stronger while L line progeny tended to become finer (Cloete & Olivier, 1998).…”

Microscopic sperm head damage and abnormalities as heat stress indicators in Australian Merino rams <i>(Ovis aries)</i> in Northern Patagonia, Argentina

“…According to previous research sheep with 1 inch fleece are more comfortable than sheep with less wool because wool fibres dissipate heat more rapidly. Sheep with long wool were reported to be less sensitive to solar heating than newly shorn animals (CLOETE et al, 2000;PICCIONE et al, 2010).…”

Effects of Night Grazing, Watering Regime, Time of the Day and Season on Respiration Rate and Rectal Temperature of Sudan Desert Sheep Ewes.

“…However, present-day strains and types may differ in respect of basal nutrient requirements, making them more susceptible to heat stress (Cloete et al, 2000).…”