Studies on perinatal lamb mortality: with particular reference to immunological and nutritional factors

Abstract

This study was concerned with perinatal lamb mortality (PLM). Over a three year period, 263 ewes and 576 lambs were studied. The work was divided into three major sections.The first section was a preliminary study divided into two parts. In the first part, basic data on PLM were collected from a variety of sheep to ascertain which aspects of the topic were worthy of further investigation. In the second part, the effects of ewe nutrition during the last eight weeks of pregnancy on lamb performance were Investigated. Particular atten¬ tion was paid in both studies to mortality rates, causes of death and birth weight and growth rate of lambs. The effect of litter size and the passive immune status of the lambs were also observed.The preliminary results lead on to the second major section in which two topics were investigated. Firstly, the effect on PLM, subsequent lamb performance and the lamb's immunoglobulin status was Investigated when twin lambs were deprived of colostrum. The deprivation appeared to have no demonstrable detrimental effect. Secondly, the effect of ewe nutrition during the last eight weeks of pregnancy on PLM, the immune status of lambs and the subsequent performance of both ewes and lambs was studied. Nutritional levels affected both ewe and lamb performance.In the last major part of the work the combined effect of inadequate ewe nutrition during late pregnancy and colostrum deprivation of twin lambs was studied. A detrimental effect on lamb performance was observed when the two factors were imposed together.Throughout the various stages of this work, blood levels of 3-hydroxybutyrate, urea and albumin were used to monitor the ewe's nutritional status. The major laboratory investigations were concerned with levels of immunoglobulins (IgG₁, IgG₂> IgM and IgA) in lamb's serum and also in ewe's serum and colostrum.In addition, blood glucose, PCV and serum alkaline phosphatase levels were measured in lambs. The value of these parameters was assessed In relation to PLM.