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A survey of 47 commercially-managed flocks in South East Scotland revealed that during late gestation 62% (29 flocks) were classified, by mean flock serum 3-OH butyrate concentration, as adequately fed, 36% (17 flocks) as moderately underfed and one flock was severely underfed. There was a wide range in the lamb perinatal mortality rate from 2% to 15%. While the incidence of simple dystocia was between 15% to 30% of births, the prompt detection and correction of such events meant that lamb birth injuries did not result. Infectious disease was not the major cause of lamb mortality. Starvation, hypothermia and E. coil endotoxaemia caused by poor husbandry standards were the most important causes of high perinatal lamb mortality rates. There was no correlation between the lamb perinatal mortality rate and the level of dam nutrition during late gestation. Prematurity was an important cause of lamb deaths on some farms due to failure of the neonate to adapt to the extra-uterine environment. Cases of joint ill, spinal abscessation and meningitis occurred in certain flocks where management practices should have ensured adequate passive antibody transfer. In these flocks entero-invasion due to an overwhelming environmental challenge was considered to be the portal of entry for bacterial pathogens. Prophylactic oral antibiotics were necessary to control watery mouth in newborn lambs in 95% of flocks studied. Ewes carrying triplets were more susceptible to severe underfeeding during late gestation which resulted in a marked reduction in litter birthweights in approximately 30% of cases. Bovine colostrum feeding to weakly lambs proved to be an excellent supportive treatment in cases of inadequate dam colostrum production and no cases of bovine colostrum-induced anaemia were observed in these lambsABSTRACT Recent research work on perinatal mortality in lambs has concentrated on patho-physiological changes that occur during second stage labour. Poor placental development and low lamb birthweights which are related to dam nutrition during distinct stages of gestation are quoted as important factors contributing to an increased perinatal mortality rate. In addition, central nervous system haemorrhages caused by dystocia resulting in an increased lamb mortality rate have been reported by several workers. Rather than investigate existing poor husbandry standards on farms with average production figures, this study examined units with excellent production data in order to identify positive practices that could be recommended to other commercial farmers. This thesis is based on routine veterinary advisory work undertaken by the author in commercial flocks. The practical nature and further application of such work is emphasised throughout this thesis. A survey of 47 commercially-managed flocks in South East Scotland revealed that during late gestation 62% (29 flocks) were classified, by mean flock serum 3-OH butyrate concentration, as adequately fed, 36% (17 flocks) as moderately underfed and one flock was severely underfed. Cases of ovine pregnancy toxaemia occurred in the severely underfed flock and the two moderately underfed flocks which contained individual ewes with serum 3-OH butyrate concentrations above 3.0 mmol/l. The occurrence of ovine pregnancy toxaemia cases was a poor indicator of overall moderate under nutrition in a flock. The mean ewe body condition score three to five weeks before lambing was not significantly correlated to the current level of nutrition within the flock and, therefore, the single assessment of condition score during late pregnancy is not an accurate indicator of nutritional status of the flock at that time.