Some Effects of Thyroid and Gonadotrophic Preparations in the Fowl

Extracts of Horse, Sheep, and Pig Pituitary, Pregnant Mare's Serum and Chorionic Gonadotrophin were administered to hens prior to and during the moulting period. Dried thyroid powder was fed during the non‐productive phase. 2. Injections of P.M.S. to laying hens resulted in cessation of egg production within 5 days, and the onset of a heavy moult. The combs increased in size during treatment. Apart from a slight increase in comb size in the group receiving Pig Pituitary extract, no reaction to the other gonadotrophins could be detected at the dosage‐level employed. 3. In non‐laying hens P.M.S. had little effect; Pig Pituitary appeared to cause a temporary reactivation of the reproductive organs, but in no case did ovulation occur. The other gonadotrophins were again inactive. 4. Consistent symptoms of ovarian stimulation resulted from the administration of thyroid, and a number of birds resumed egg production following this treatment. Variations in the degree of response obtained appeared to be related to the media in which this hormone powder was fed.