Abstract
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 3-0H
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. coli
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 lambs.
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.
