Blood metabolite levels in late pregnant ewes as indicators of their nutritional status

Abstract

A study was conducted to determine whether the measurement of blood metabolite levels in fasted 110-day pregnant ewes could provide a more accurate identification of those requiring nutritional supplementation in late pregnancy than that provided by identification of pregnancy status (single versus multiple) alone. Border Leicester x Romney ewes (195), aged 2-8 years and pregnant to one of two synchronised matings, were studied. At 110 (range 108-112) days of gestation they were weighed and blood-sampled by jugular venipuncture after a 24-h fast. Blood plasma was analysed for concentrations of glucose, non-esterified fatty acids (NEFA), β-hydroxybutyrate, urea, and creatinine. Ewes were set-stocked immediately before lambing and sex, birthrank, and birthweight of their lambs recorded. Two-year-old ewes had significantly lower plasma concentrations of glucose and creatinine, and higher concentrations of β-hydroxybutyrate, than older ewes. Ewes mated in Cycle 2 had lower concentrations of glucose, urea, and creatinine but higher concentrations of β-hydroxybutyrate than ewes conceiving to the second cycle, probably because they were removed from pastures with low residual herbage masses before fasting. Ewes carrying multiple pregnancies (twin or triplet), as measured by number of lambs born, had reduced concentrations of glucose but elevated βhydroxybutyrate and NEFA concentrations, relative to those carrying singles. Plasma glucose, NEFA, and β-hydroxybutyrate concentrations were significantly related to total weight of lamb born, but they did not significantly improve the 63% of variation in this trait explained by pregnancy status. Maternal plasma urea and creatinine concentrations were not related to total weight of lamb born to each ewe. It is concluded that, in ewes of medium fecundity, measurement of blood metabolites at 110 days of pregnancy does not enhance the accuracy with which those requiring additional nutrition in late pregnancy can be identified, compared with identification on the basis of pregnancy status alone. © 1990 Taylor & Francis Group, LLC.