Effect of gender, gonadectomy and oestradiol-17β on growth in lambs under grazing conditions

O. Mahgoub, G. K. Barrell, A. R. Sykes

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

To identify separate effects of gender, castration and exogenous oestrogen on growth, castrated lambs of both sexes and entire male lambs (n = 8) were implanted subcutaneously with-three sizes of oestradiol-17β implants, or not implanted, and grazed on ryegrass and white clover pasture for 180 days. A group of non-implanted entire female lambs (n = 8) was run together with the others. Non-implanted entire male lambs grew faster, had heavier heads, less internal, non-carcass fat and more protein and less fat and water in the carcass than non-implanted entire females. In addition, they had higher 12th vertebral spine, thicker tibia, and heavier and larger humerus than entire female lambs. Castration of male lambs reduced live-weight gain, weight of head and content of protein in the carcass whereas it increased carcass fat content. In addition, it caused lengthening of cannon bones and reduced height of 12th vertebral spine and length of tibia. In females, gonadectomy increased height of 12th vertebral spine and diameter to length ratio of the radius. Oestradiol treatment increased live-weight gain, reduced total internal and carcass fat, and increased water and protein content of the carcass in gonadectomized animals of either sex, and increased weight of carcass and head in spayed ewe lambs. Oestradiol treatment inhibited longitudinal growth of cannon bones and stimulated that of vertebral column and ribs, but had little effect on the dimensions of limb bones apart from increasing their diameter. Oestradiol treatment had no effect on muscle length but increased muscle girth and weight except for m. splenius in ram lambs where muscle weight was reduced. Effects of oestradiol on skeletal measurements in most cases were linearly related to dose of oestradiol. It was concluded that the variable effects of sex steroids on the skeleton were related to the differential pattern of skeletal maturation. In early maturing bones acceleration of the growth process by an exogenous sex steroid caused elongation to cease prematurely, whereas in late-maturing bones the acceleration effect on elongation did not result in premature cessation. This observation may explain the often contradictory reports in the literature on the effects of sex steroids on linear growth of bone.

Original languageEnglish
Pages (from-to)351-364
Number of pages14
JournalJournal of Agricultural Science
Volume137
Issue number3
Publication statusPublished - 2001

Fingerprint

estradiol
Estradiol
lambs
grazing
gender
Bone Development
spine (bones)
Spine
Growth
Fats
bones
Weights and Measures
Steroids
Head
steroids
Tibia
Muscles
Weight Gain
Bone Lengthening
liveweight gain

ASJC Scopus subject areas

  • Agricultural and Biological Sciences (miscellaneous)

Cite this

Effect of gender, gonadectomy and oestradiol-17β on growth in lambs under grazing conditions. / Mahgoub, O.; Barrell, G. K.; Sykes, A. R.

In: Journal of Agricultural Science, Vol. 137, No. 3, 2001, p. 351-364.

Research output: Contribution to journalArticle

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