Wool growth of pregnant Merino ewes fed to maintain maternal liveweight

Abstract

The wool production at the midside of 15 non-mated Merino ewes was compared with that of their monoctocous (n = 20) and dioctocous (n = 13) flockmates during the second half of pregnancy. The ewes were compared under experimentally controlled feeding conditions designed to maintain the liveweight of each ewe, exclusive of the weights of fleece and conceptus, by progressively increasing the quantities of a sorghum grain and lucerne chaff diet (1:1 by weight) offered to the pregnant ewes. During the latter half of pregnancy, each non-mated ewe consumed 42.1 kg of the diet. The single- and twinbearing ewes consumed 27 and 44% more of the diet than did the non-mated ewes. The adjusted liveweight of the non-pregnant ewes increased by 0.03 kg/week, while those of the monoctocous and dioctocous ewes changed by 0.11 and -0.05 kg/week (s.e.= ¦ 0.04). These changes in liveweight were small but differed between the ewe classes (P<0.05). The rate of wool production per unit area of skin at the midside was 411 ¦g/cm2.day, with no significant differences between the ewe classes, and with no interactions between ewe classes and period of measurement. The wool produced on the midside had an average fibre diameter of 19.0 ¦m, again with no significant differences between ewe classes or periods. The length of fibre grown during the latter half of pregnancy was 26.1 mm, with no difference between the ewe classes. We conclude that a loss of wool production is not an obligate consequence of pregnancy, but can be prevented by nutritional management that recognises the additional requirements of the pregnant ewe for nutrients.