Serum Gonadotrophin in Welsh and Shetland Ponies

Cole [1938] observed that the concentration of gonadotrophin in the serum of mares during pregnancy was greater in small breeds than in large breeds; the maximum concentration in Welsh ponies was stated to be about four times that in draught breeds. In an earlier publication we [Day & Rowlands, 1940] recorded the time and rate of appearance of gonadotrophin in six Welsh ponies, a New Forest pony, and a Shetland pony. The maximum concentrations obtained were 43–186 i.u./ml. in the Welsh ponies and 84 and 344 i.u./ml. in the New Forest and Shetland ponies. No attempt was made to deal with individual or breed variation in the potency of the sera. A considerable body of new information has accumulated in the past five years from two series of collections of serum gonadotrophin. One was made from a large number of Welsh ponies in Radnorshire and the other was made annually