Metabolic changes during the perinatal period in dairy sheep in relation to level of nutrition and breed. I. Late pregnancy

Abstract

SummaryThe effects of level of nutrition during pregnancy on the development of the mammary gland, on various biochemical parameters, on feed intake and on body weight were investigated in Chios (CH) and Karagouniko (K) ewes. Thirty pregnant ewes of both breeds were randomly assigned to groups A and B, which received 110% of their energy requirements for maintenance plus pregnancy for two foetuses and 90% of their maintenance energy requirements, respectively. In a second experiment, 34 pregnant Chios ewes were assigned and fed as in the first trial, but they were slaughtered on day 140 of pregnancy to study udder characteristics. The feed intake and the body weight in pregnancy were higher in ewes of group A and K ewes than of groups B (p 0.001) and CH (p 0.01), respectively. Plasma glucose concentration tended to be higher in group A than group B. Group A ewes had significantly decreased plasma free fatty acids (p 0.001) and β‐hydrobutyric acid (p 0.05), but higher insulin (p 0.01) concentrations, whereas serum T4 concentrations were higher in K than in CH ewes (p 0.01), during the last 10 days of pregnancy. The fat cell diameter and the NADP‐isocitrate dehydrogenase activity of the adipose tissue were higher in ewes of group A than group B, on the day 7 before lambing. In the second experiment, the underfed CH ewes had significantly lower empty udder weight (p 0.05), smaller udder (p 0.05), smaller teat length (p 0.01), lower mammary gland weight (p 0.05), less total content of DNA (p 0.05) and less fat percentage of mammary gland (p 0.01) in comparison with the well‐fed CH ewes. It is concluded that undernutrition during pregnancy causes considerable changes in the ewe's metabolism, mainly in the adipose tissue. Furthermore, the level of nutrition significantly affected udder development.