Influence of supplemental monensin on gestating and lactating ewes

Abstract

Twenty-five multiparous Rambouillet ewes were used to determine the effects of feeding monensin during late gestation and early lactation on prepartum and postpartum ewe body weight, milk production, blood glucose levels, and lamb production. Ewes were grouped into singles and twins by sonogram results, allotted to pens in pairs and assigned to either an ionophore (diet I with 70 mg daily) or non-ionophore (diet 2) treatment groups in a 2 x 2 factorial arrangement. All ewes were fed according to NRC (1985)diet one or two beginning an average of 56 d prepartum. There were no differences in prepartum weight gain or postpartum weight loss between treatments (P>.05). There were no differences in lamb birth weights or postnatal body weight gain to 40 d (P>.05). Nfilk collection was conducted prior to the morning feeding by removing the lamb(s)from the pen, injecting Iml (5 USP) oxytocin intrajugular, evacuating the udder by milking machine and discarding milk. At 3 h, ewe received I ml (5 USP) oxytocin intrajugular and udder was evacuated using milking machine. In the single bearing ewes, monensin increased milk volume 35% for 4 d (P <.Ol), 35% for 10 d (P < . 10), 80% for 20 d (P < .05), 16% for 3 0 d (P < . 5) and no difference in 40 d. In the twin bearing ewes, monensin increased milk volume on IO d I 1 % (P < .3), but there were no differences in the other collections. There were no differences in milk fat, proteir4 or lactose concentrations. Data collected from this study showed that monensin increased milk production in single bearing ewes when supplemented prior to lambing and supplemented during lactation.