|dc.contributor.author||Stott, Alistair W.||
|dc.description.abstract||Lamb mortality is a serious source of economic loss to the
sheep industry. Surveys have shown that up to 50% of the post-natal
losses can be due either directly or indirectly to cold exposure.
This thesis examines various ways of improving thermoregulation
in the newborn lamb. Emphasis was placed on the need to develop
methods which required little or no capital expenditure. This was
essential if the most promising techniques were to be adopted in the
less favoured hill environments.
The effectiveness of the various treatments was measured by
subjecting each newborn lamb to a standard cold exposure in a
progressively cooled water bath. Various components of heat
production and heat loss were recorded during this test. The cold
resistance of each lamb was defined as the time taken for rectal
temperature to fall by approximately 4C. The capacity for
non-shivering thermogenesis (NST) was also measured in some lambs by
recording the calorigenic response to noradrenaline administration
at a therinoneutral temperature.
Shearing of the pregnant ewe 4 weeks before parturition
increased the cold resistance of the newborn lambs. Components of
both heat production and heat loss were influenced by this
Short periods of acute cold exposure imposed daily for the last
12 days of pregnancy enhanced NST in the newborn lamb. Further work
showed that all these results were influenced by ewe age, breed,
foetal number and year effects. The implications of this, and
possible mechanisms, were discussed.
Genetic selection for cold resistance in Scottish Blackface
lambs started at ABRO in 1980. Preliminary results of this
experiment are reported here. The response was asymmetrical.
Selection for high cold resistance produced considerably more
progress than selection for low cold resistance. Heritability of
cold resistance estimated from line divergence was 0.17+0.09.
Heritability for increasing cold resistance was 0.27+0.13 and for
decreasing cold resistance it was 0.01+0.16.
The large number of lambs tested during this experiment (594)
allowed a detailed investigation of various components which
influenced water bath performance. Single lambs had a greater
we ight-specif ic heat production and reduced heat loss compared to
twins. Female lambs were better able to thermoregulate than males.
Cold resistance tended to decline with age but increase with
The genetic and phenotypic relationships between cold
resistance and components of heat production and heat loss were
analysed. The implications of these findings with regard to
thermoregulation and hence lamb mortality in the field situation
|dc.publisher||The University of Edinburgh||en
|dc.subject||resistance to body cooling||en
|dc.subject||resistance to body cooling in newborn lambs||en
|dc.subject||thermoregulation in newborn lambs||en
|dc.title||Genetic and physiological factors affecting thermoregulation and resistance to body cooling in newborn lambs||en
|dc.type||Thesis or Dissertation||en
|dc.type.qualificationname||PhD Doctor of Philosophy||en