THE EFFECT OF SEX HORMONES ON COMB GROWTH IN IMMATURE PULLETS

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Abstract
1. The effects of injecting oestradiol dipropionate (ODP), testosterone propionate (TP) and progesterone (P) in immature pullets have been studied. 2. TP evoked hypertrophy of the comb and wattles, but ODP and P were without effect. 3. The greatest comb growth was observed when all three hormones were injected; next in order were combs from birds receiving TP alone and then those given TP with either ODP or P. 4. Injections of all three hormones produced a slight increase in proliferative activity of the stratum germinativum and a decrease in the density of the connective tissue of the corium of the combs when compared with those of birds injected with TP alone. The combs of birds treated with ODP showed prominent blood capillaries in the peripheral layers of the corium when frozen sections were stained with Scharlach R. This is thought to have been due to the marked affinity of their red blood cells for the stain and indicates a high lipid content of the cell membrane. Similar differences were also noted in the combs of normal laying female as compared with normal male birds. 5. These histological differences provide a possible explanation for the known differences in shape, colour and texture between female and male combs. 6. It is suggested that the histological examination of the comb provides a means of establishing the validity of an assay of a hormonal preparation by the comb growth technique.

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