Milk Production of Ayrshire Cattle

THE critical genetic study of a character such as that of milk production in cattle, which is highly subject to environmental influences, cannot be carried out effectively until a fairly comprehensive knowledge of the normal variation of the character has been acquired. To this end Prof. Raymond Pearl and Mr. J. R. Miner have carried out a biometrical analysis of the normal individual variation in the milk flow and the fat content of the milk of Ayrshire cattle, the results of which are summarised in a contribution to the Journal of Agricultural Research (vol. xvii., No. 6). Their study is based on the records of Ayrshire cattle for the years 1908 and 1909 published in the reports of the Ayrshire Cattle Milk Records Committee of Scotland, more than three thousand records in each year being used for the purpose. Amongst the many important conclusions arrived at mention may be made of the indications that about one-half of the observed variation in milk-production results from the varying genotypic individuality of the animals with respect to this character, the remainder resulting from varying environmental influences. The udder as a secreting organ is compared with the oviduct of a hen, and it is shown that the latter operates with somewhat less variability than the former, having regard to the absolute weight of the product in the two cases.