Effects of multiple ovulation and litter size on maternal and foetal physiology: prenatal and postnatal consequences

Abstract

This review examines the consequences of large litter size on the physiology of the ewe and lamb and subsequent reproductive efficiency, and highlights that there are major difficulties in managing litters of more than two lambs. The paper addresses the impact of high ovulation rates on subsequent embryo loss, and on placental and foetal development. It identifies that increases in eggs shed are linked to increases in embryo and foetal mortality and also with reduced placental capacity per lamb. The review reports that increased litter size also impacts on ewe energy reserves, particularly in late pregnancy when there is also a reduction in alimentary tract weight in ewes carrying three or more lambs. The postpartum outcomes of high litter size are also seen in reduced neonatal survival and lower colostrum and milk availability per lamb.