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Metabolic adaptations in goat mammary tissue during long-term incomplete milking

Published online by Cambridge University Press:  01 June 2009

Colin J. Wilde ,
David R. Blatchford ,
Christopher H. Knight  and
Malcolm Peaker
Colin J. Wilde
Affiliation:
Hannah Research Institute, Ayr KA6 5HL, UK
David R. Blatchford
Affiliation:
Hannah Research Institute, Ayr KA6 5HL, UK
Christopher H. Knight
Affiliation:
Hannah Research Institute, Ayr KA6 5HL, UK
Malcolm Peaker
Affiliation:
Hannah Research Institute, Ayr KA6 5HL, UK
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Summary

Lactating goats were milked incompletely in one gland and normally in the other gland twice daily for 24 weeks. Yields of the incompletely milked glands were adjusted so that a calculated 100 ml milk remained in the gland at the end of milking. On average this residual volume was greater by 7·6% of the total milk volume than that left after normal milking and was 25·9% greater than the capacity of the alveoli. After 24 weeks, the weekly milk yield of the incompletely milked gland was 23·8% lower than that of the other gland (P < 0·001) when expressed in relation to cell number. The metabolic capacity of secretory cells in the two glands was measured in serial tissue biopsies. Two weeks of incomplete milking had no effect on enzyme activities or metabolic fluxes in the incompletely milked gland, but after 24 weeks the activities of several key enzymes were significantly lower in this gland. This was associated with a reduced rate of synthesis of total protein and casein in expiants freshly prepared from the tissue. The rate of lactose synthesis also tended to be lower in expiants from the incompletely milked gland. Secretory cell number in the two glands was similar at the end of incomplete milking. The data indicate that incomplete milking over a long period caused partial secretory cellular involution via a local chemical feedback mechanism in the gland.

Type
Original Articles
Information
Journal of Dairy Research , Volume 56 , Issue 1 , February 1989 , pp. 7 - 15
Copyright
Copyright © Proprietors of Journal of Dairy Research 1989

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References

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