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Pre-pubertal mammogenesis in the sheep 2. The effects of level of nutrition on the plasma concentrations of growth hormone, insulin and prolactin at various ages in female lambs and their relationship with mammary development

Published online by Cambridge University Press:  02 September 2010

I. D. Johnsson ,
I. C. Hart ,
A. D. Simmonds  and
S. V. Morant
I. D. Johnsson
Affiliation:
National Institute for Research in Dairying, Shinfield, Reading RG2 9AT
I. C. Hart
Affiliation:
National Institute for Research in Dairying, Shinfield, Reading RG2 9AT
A. D. Simmonds
Affiliation:
National Institute for Research in Dairying, Shinfield, Reading RG2 9AT
S. V. Morant
Affiliation:
National Institute for Research in Dairying, Shinfield, Reading RG2 9AT
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Abstract

Female crossbred lambs were given a high energy and high protein diet in varying amounts to achieve either high (H; 220 g/day) or low (L; HOg/day) rates of live-weight gain during two consecutive periods between 4 and 20 and 20 and 36 weeks of age. Blood samples were collected via jugular catheters at either 1-h or 2-h intervals over a 28-h period from five lambs on each rearing treatment at 10, 14, 18, 26 and 34 weeks of age for the measurement of prolactin, growth hormone (GH) and insulin. In addition, samples were collected within 2 weeks of slaughter from all eight lambs on each treatment that were slaughtered at either 20 weeks (L and H treatments) or 36 weeks of age (LL, LH and HL treatments) for the assessment of mammary development.

The timing of once-daily feeding influenced the plasma profiles of all three hormones measured, but became less obvious with increasing age. Both mean plasma GH, and the influence of level of nutrition on the mean, declined with increasing age. Mean plasma insulin increased with age but did not differ between rearing treatments until 26 weeks, despite large differences in food intake. Mean plasma prolactin in H lambs increased significantly between 10 and 18 weeks, but a similar response did not occur in L lambs. The greater mammary development of L lambs was associated with increased plasma concentrations of GH and reduced concentrations of prolactin. However, the large variation in total mammary parenchymal deoxyribonucleic acid between individuals within each rearing treatment at 20 or 36 weeks of age was not consistently explained by the variation in any of the hormones measured.

Type
Research Article
Information
Animal Production , Volume 41 , Issue 3 , December 1985 , pp. 333 - 340
Copyright
Copyright © British Society of Animal Science 1985

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