Abstract
Milk yield, lamb birth weight and weaning weight responses to shearing during winter in sheep were investigated. A total of 46 Karayaka ewes were allocated into two treatment groups. Pregnant ewes in one group were shorn on day 100 of gestation (Shorn, n=24) and the remaining ewes were left unshorn to serve as controls (Unshorn, n=22). The ewes were maintained on pasture during the day and housed in the evenings. Lamb birth weight, weaning weight and ewes' daily milk yield in fifteen dayintervals until weaning (75 days) were recorded. Shearing ewes on day 100 of pregnancy increased gestation length (p<0.01) compared to unshorn ewes (147.8±0.45 vs. 145.9±0.42 days). Birth weights of lambs from shorn ewes on day 100 of their pregnancy were higher (p<0.01) than those from unshorn ewes (3.7±0.11 vs. 3.2±0.07 kg). Shearing pregnant ewes increased (p<0.05) the lamb weaning weight at day 75 post-lambing (23.6±1.10 vs. 19.5±0.91). It also increased milk yield (p<0.05). Milk yields on day 75 of lactation were 302±33 and 425±25 g per day for unshorn and shorn ewes on day 100 of pregnancy, respectively. Lamb survival at weaning was higher (p<0.05) in lambs from shorn ewes compared to those from unshorn ewes. In conclusion, shearing pregnant ewes in winter months enhanced milk yield, lamb birth weight, lamb weaning weight and lamb survival. It is suggested that increasing both lamb birth weight and subsequent milk yield of dams by shearing ewes on day 100 of pregnancy during winter may improve postnatal lamb viability. (Asian-Aust. J. Anim. Sci. 2004. Vol 17, No. 12 : 1669-1673)
Highlights
INTRODUCTIONShearing ewes during pregnancy with a view to increasing lamb survival rate has been shown to increase lamb birth weight in a number of studies (Vipond et al, 1987; Black and Chestnutt, 1990; Morris and McCutcheon, 1997; Morris et al, 2000; Revell et al, 2000; Kenyon et al, 2002a,b; Revell et al, 2002)
Shearing pregnant ewes has been shown to be associated with the changes in fetal glucose concentration (Thompson et al, 1982) and maternal concentrations of glucose, corticosteroids, glycerol, non-esterified fatty acids (Thompson et al, 1982), thyroid hormone (Clarke et al, 1997; Morris et al, 2000), insulin (Symonds et al, 1986; Revell et al, 2000) insulin like growth factor 1 (IGF-1) and IGF binding protein (IGFBP; Revell et al, 2000)
H and 16.30 h) at fifteen- day intervals until lamb weaning on day 75 of lactation and daily milk yield on test-days was The objectives of the present study, were to recorded. test the hypotheses that pregnancy shearing to increase lamb birth weight increases dams’ milk yield in subsequent Statistical analysis lactation and lamb survival at weaning
Summary
Shearing ewes during pregnancy with a view to increasing lamb survival rate has been shown to increase lamb birth weight in a number of studies (Vipond et al, 1987; Black and Chestnutt, 1990; Morris and McCutcheon, 1997; Morris et al, 2000; Revell et al, 2000; Kenyon et al, 2002a,b; Revell et al, 2002). Shearing pregnant ewes has been shown to be associated with the changes in fetal glucose concentration (Thompson et al, 1982) and maternal concentrations of glucose, corticosteroids, glycerol, non-esterified fatty acids (Thompson et al, 1982), thyroid hormone (Clarke et al, 1997; Morris et al, 2000), insulin (Symonds et al, 1986; Revell et al, 2000) insulin like growth factor 1 (IGF-1) and IGF binding protein (IGFBP; Revell et al, 2000) These metabolites may change partitioning of nutrients towards gravid uterus and mammary gland development as reported by Jopson et al (2002) that pregnancy shearing can alter body composition as well as lamb birth weight. It is possible that shearing pregnant ewes may increase milk yield in the subsequent lactation
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