The effect of plane of nutrition and shearing on the pattern of the moult in Scottish Cashmere goats

Inhibition of prolactin promotes secondary skin follicle activation in cashmere goats

The aim of this study was to investigate the involvement of prolactin (PRL) on development of secondary skin follicles in cashmere goats. Goats were randomly assigned to either a bromocriptine treatment or control group. Samples of cashmere fiber, blood, and skin were collected from all goats after 1 mo. The results indicated that the length, growth rate, and diameter of fibers were not influenced (P > 0.05) by the inhibition of PRL resulting from the treatment with bromocriptine. There was a tendency for increases in total follicle number, primary and secondary follicle numbers, and in the ratio of secondary to primary follicles following treatment with bromocriptine, but these differences were not significant (P > 0.05). The percentage of active secondary follicles in anagen was increased (P < 0.05) in the bromocriptine-treated goats, but there was no effect of treatment on the percentage of active primary follicles. Bromocriptine decreased (P < 0.05) circulating concentrations of PRL and Insulin-like growth factor 1 (IGF1) and increased (P < 0.05) those of melatonin (MT), but there was no effect of this treatment on the serum concentrations of cortisol, growth hormone, tetraiodothyronine, and triiodothyronine. In bromocriptine-treated goats, mRNA expressions of PRL and MT membrane receptor 1a (MTNR1a) were decreased (P < 0.05) and mRNA expression of MT nuclear receptor (RORα) was increased (P < 0.05), but there was no effect of the treatment on expression of long PRL receptor, short PRL receptor, MT membrane receptor 1b and IGF1. It is concluded that inhibition of PRL promotes secondary hair follicle development in the anagen phase, possibly by downregulating MTNR1a and up-regulating RORα gene expression in the skin.

Relationships between blood hormonal concentrations and secondary fibre shedding in young cashmere-bearing goats at their first moult

The aim of this study was to evaluate secondary fibre shedding in relation to seasonal hormonal changes in young cashmere-bearing goats reared in southern Italy. We used 14 cashmere-bearing kids, seven males and seven females, of a Scottish breed-population of goats specialized in cashmere production. Monthly, a hair patch of 4 cm2was clipped from both left and right mid sides alternately and cashmere length and its yield were determined. Blood samples were taken every 2 weeks and plasma was assayed for prolactin (PRL), growth hormone (GH), tri-iodothyronine (T3), thyroxine (T4), progesterone and testosterone. With the same frequency, animals were monitored for onset of moult. Our data indicate that in young cashmere goats at their first moult, secondary fibre shedding is a seasonal event that is strictly related to changes in photoperiod and that PRL has a pivotal rôle in regulating this phenomenon. This corresponds with findings in adults. The observation that both thyroid hormones and sex steroids varied seasonally suggests that they are involved in the regulation of the moult cycle, but their precise rôle remains to be elucidated. Our data also indicate that GH seems to be implicated in the control of the moult cycle. The finding that maximal fibre shedding occurred earlier in males than females could be ascribed to differences in GH levels and to the earlier increase in plasma concentration of PRL observed in males.

Effects of nutrition on hormone profiles and patterns of deiodinase activity in the skin and associated patterns of hair follicle activity and moult in cashmere goats

The effects of nutrition on patterns of live-weight change, hair follicle activity, moult, hormone profiles and associated activities of monodeiodinase enzyme types II and III (MDII and MDIII) in cashmere goats were investigated. From 1 week before the winter solstice (mid December), one group of 15 animals was given a ration designed to provide 2·0 × live weight maintenance requirements (high; H) while a second, similar, group was given 0·8 × live weight maintenance requirements (low; L). After approximately 3 months, L animals had significantly lower mean live weights (P<0·01) than H animals. This was associated with lower (P<0·05) overall mean hair follicle activity in L than H animals during the March to May period and a lower overall mean moult score during March and April in L animals (P<0·01) but a similar mean date of moult onset. Mean concentrations of all of the hormones measured exhibited significant changes (P<0·01) with date of sampling. Overall mean concentrations of insulin, tri-iodothyronine and thyroxine did not differ with treatment but, compared with L animals, H animals exhibited higher mean concentrations of prolactin in April and May (P<0·05) and of insulin-like growth factor-1 in December and January (P<0·001). Rates of activity of MDII and MDIII in skin differed with date (P<0·001) but were not significantly affected by nutritional treatment. The MDIII/MDII ratio differed (P=0·05) with month but was significantly higher (P<0·05) in L than H animals in January, only. It is concluded that the reduction in hair follicle activity and the slower onset of moult associated with reduced nutrition were unlikely to be controlled, directly, by differences in activities of MDII or MDIII in skin tissue.