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Effects of pinealectomy on wool growth and wool follicle density in Merino sheep
Author(s) -
McCloghry Elizabeth,
Foldes Andrew,
Hollis David,
Rintoul Allan,
Maxwell Colin,
Downing Jeff,
Baker Peter,
Kennedy John,
Wynn Peter
Publication year - 1992
Publication title -
journal of pineal research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.881
H-Index - 131
eISSN - 1600-079X
pISSN - 0742-3098
DOI - 10.1111/j.1600-079x.1992.tb00068.x
Subject(s) - wool , pinealectomy , follicle , melatonin , zoology , prolactin , endocrinology , medicine , pineal gland , biology , hormone , archaeology , history
There is evidence to indicate that pinealectomy may enhance wool growth in the sheep. The aim of this study was to determine the effect of pinealectomy on wool growth and wool follicle density in Merino sheep. Castrated Merino rams (4 months old) were either pinealectomized (P), sham‐pinealectomized (S) or not treated (C). Wool growth on mid‐side patches was measured every 4 weeks and follicle density was monitored in skin biopsies collected before treatment and at regular intervals for 60 weeks. Venous blood samples were taken on each of these occasions for prolactin analysis. Melatonin concentrations were determined in venous blood collected pre‐ and posttreatment from samples taken over a 24‐hr period during the winter solstice. Pre‐ and posttreatment plasma melatonin levels (mean ± SEM) 65 ± 17 and < 13 pg/ml for P, 86 ± 21 and 69 ± 20 pg/ml for S, and 94 ± 41 and 122 ± 37 pg/ml for C, respectively, indicated that the pineal glands had been successfully removed. Wool growth, total follicle density and liveweight (mean ± SEM) did not differ between treatment groups. Measurements at week 60 were 3.9 ± 0.3, 4.1 ± 0.2, and 3.8 ± 0.3 gm clean wool/100 cm 2 ; 66 ± 6, 69 ± 7, and 64 ± 3 follicles/mm 2 ; and 50.4 ± 1.3, 50.8 ± 1.4, and 52.6 ± 1.1 kg liveweight for groups P, S, and C, respectively. There was no difference in plasma prolactin levels between the groups during the experiment (P:179 ± 37, S:183 ± 37, C.189 ± 37 ng/ml), but the expected seasonal prolactin rhythm was absent in all animals. These results indicate that the removal of endogenous pineal hormones by pinealectomy has no effect on wool growth and wool follicle density in Merino lambs.