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Effects of modified circulating prolactin levels on seasonal wool growth in Romney ewes

Published online by Cambridge University Press:  27 March 2009

C. E. McCloghry ,
A. Foldes ,
A. J. Rintoul ,
C. A. Maxwell ,
D. E. Hollis ,
P. J. Baker ,
J. P. Kennedy  and
P. C. Wynn
C. E. McCloghry
Affiliation:
Division of Animal Production, CSIRO, PO Box 239, Blacktown, NSW 2148, Australia
A. Foldes
Affiliation:
Division of Animal Production, CSIRO, PO Box 239, Blacktown, NSW 2148, Australia
A. J. Rintoul
Affiliation:
Division of Animal Production, CSIRO, PO Box 239, Blacktown, NSW 2148, Australia
C. A. Maxwell
Affiliation:
Division of Animal Production, CSIRO, PO Box 239, Blacktown, NSW 2148, Australia
D. E. Hollis
Affiliation:
Division of Animal Production, CSIRO, PO Box 239, Blacktown, NSW 2148, Australia
P. J. Baker
Affiliation:
ZIAPP Biometrics Unit, CSIRO, PO Box 239, Blacktown, NSW 2148, Australia
J. P. Kennedy
Affiliation:
Department of Wool and Animal Science, University of New South Wales, PO Box 1, Kensington, NSW 2033, Australia
P. C. Wynn
Affiliation:
Department of Animal Science, University of Sydney, Camden, NSW 2570, Australia
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Summary

The study investigated the effects of chronic elevation or suppression of circulating prolactin levels on seasonal wool growth in Romney sheep. Ewes (n = 10/group) were housed indoors under natural lighting (latitude 34 °S) and received either 50 mg bromocriptine i.m./ewe/28 days (Group B), 1 mg spiperone s.c./ewe/day (Group S) or no treatment (Group C) commencing in summer. Wool growth and liveweight were measured every 4 weeks and venous blood samples were collected for prolactin determination. Plasma prolactin levels (mean±s.E.) in Group C exhibited a gradual seasonal decline from 121±29 ng/ml to 35±9 ng/ml. Bromocriptine suppressed prolactin levels rapidly from a pretreatment value of 118±2 ng/ml to below 12±7 ng/ml for the duration of the study. Prolactin levels in Group S were not significantly higher than Group C, with the exception of the first 14 days following the initial treatment. A seasonal reduction in wool growth of c. 25% was observed in all groups; however, no significant treatment effect was evident. Mean liveweight of all animals increased from 50·4±0·8 to 56·8±0·7 kg during the study. These results indicate that perturbation of the annual cyclic secretion of prolactin does not affect wool growth in the Romney ewe.

Type
Animals
Information
The Journal of Agricultural Science , Volume 120 , Issue 3 , June 1993 , pp. 391 - 395
Copyright
Copyright © Cambridge University Press 1993

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References

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