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Title: Studies on the metabolism of newborn lambs from prolific ewes
Author: McPherson, V. O. M.
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 1981
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Data from 12 experiments involving about 450 lambs in a cold, humid environment are presented in this thesis. The lambs were fed colostrum at levels varying from 12.5 to 50⁻¹ at birth and after periods of fasting ranging from 3 to 18.5 h post-partum. Their rectal temperature, packed cell volume (PCV) and plasma concentrations of free fatty acids (PFA), glucose, β-hydroxybutyrate, lactate, insulin, cortisol, thyroxine (T4) and immunoglobulin were measured over periods extending up to 4 days post-partum. Correlations between most of the variables were positive but small. Changes in rectal temperature were variable especially before feeding. A consistent pattern of rapid elevations in plasma levels of FFA, even in small lambs, within the initial 10 min of birth was observed, with near peak values being attained by 20 min and maintained for up to 3 h. Plasma glucose exhibited a transient increase in the first 30 min but pre-feeding insulin concentrations and PCV values remained relatively constant. Plasma cortisol and T4 values were significantly greater in lambs born spontaneously compared to those born after induction of parturition. Independent of the mode of delivery, there were significant decreases in plasma concentrations of these hormones and also lactate in the immediate post-partum period. After feeding, continued elevation in plasma FFA only occurred in lambs fed 30 minutes after delivery. Peak levels of circulating glucose and insulin were attained within 2 h. For most lambs that died, hypoglycaemia was a characteristic feature in spite of feeding and this was interpreted as an indication of a deficiency in their metabolism of carbohydrate. Values for PCV, cortisol and T4 in plasma decreased once feeding was initiated, while β-hydroxybutyrate tended to increase. Most of the absorption of immunoglobulin occurred in the 6 h after the start of feeding, the time of which was immaterial to the maximum level of passive immunity attained, provided that feeding was adequate. Induction of parturition did not affect the maximum level of passive immunity. Most lambs not given a supplementary colostrum feed at birth were found to have levels of plasma immunoglobulin which were similar to those of lambs fed at 50⁻¹. Evidence is presented to support the view that feeding at birth can reduce lamb losses but the level of feeding is critical. Amounts of colostrum which cause satiety may be detrimental to the attainment of maximum immune state if the feed is not large enough to compensate for the depression in the lamb's innate desire to suck. During late pregnancy, high levels of non-degradable protein intake by ewes on sub-optimal ME intakes had a positive influence on lamb birth weight, and colostrum yield but not on its composition.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available