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Mammary uptake of amino acids and glucose throughout lactation in Friesland sheep

Published online by Cambridge University Press:  01 June 2009

Ivan R. Fleet  and
T. Ben Mepham
Ivan R. Fleet
Affiliation:
Department of Physiology, AFRC Institute of Animal Physiology, Babraham, Cambridge CB2 4AT, UK
T. Ben Mepham
Affiliation:
Department of Physiology and Environmental Science, University of Nottingham Faculty of Agricultural Science, Sutton Bonington, Loughborough LE12 5RD, UK
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Summary

Changes in mammary blood flow, arterial and venous plasma concentrations of glucose and individual amino acids, udder volume, and milk yield and composition were measured at intervals throughout lactation in four Friesland ewes. Milk yields peaked 50–80 d post partum and declined by 40% within 3 months. Neither mammary blood flow (43·3 ± 5·8 (s.e.m.) ml/100 cm3, min) nor udder volume changed significantly throughout the period of study, but for three ewes the ‘mammary blood flow:milk yield’ ratio increased from 300 (peak yield) to 570 (late lactation). Mammary glucose uptake remained essentially constant throughout lactation despite a 50% decline in lactose output. Arterial concentrations of glucose were much lower at peak yield than in late lactation. Mammary amino acid uptake conformed quite closely to ‘essential’ and ‘non essential’ categories previously defined for goats and cows, the degree of balance with output in milk protein being similar at all stages of lactation. For several amino acids arterial concentrations and arteriovenous differences were significantly positively correlated: the changes in arterial concentrations with lactation stage were also correlated for some amino acids. Apart from the intrinsic value of such studies on a breed of ewe increasingly used for dairy purposes, the Friesland ewe appears well suited for use in quantitative metabolic studies on lactation.

Type
Original Articles
Information
Journal of Dairy Research , Volume 52 , Issue 2 , May 1985 , pp. 229 - 237
Copyright
Copyright © Proprietors of Journal of Dairy Research 1985

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References

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