The Inheritance of Milk Yield in Ayrshire Cows

Abstract

THE possibility that some of the factors governing the inheritance of milk might be inherited in a sex-linked manner has been suggested by one of the writers (l). The need was felt for further investigation. There are two main avenues by which this question may be explored: by planned experiment with cattle or by a study of the existing milk records. The former method is slow and very costly, but would probably give conclusive results. The latter does not require experiment to provide the necessary facts, but the data may be somewhat vitiated by lack of control over conditions of nutrition and husbandry which undoubtedly affect, to a great extent, the amount of milk which a cow may yield in a lactation.The statistical method uses the existing herd books and milk records, and approaches the question by studying the effect of various animals in the ancestry upon the yields of their female descendants. A sex-Linked character cannot be transmitted from a paternal grandsire to his granddaughter. The sex-linked qualities of a bull are all transferred to his daughters while, if a cow is heterozygous for them, only half her offspring will possess them.Attention must be drawn to the fact that it is not reasonable to expect that all the factors influencing milk yield may be inherited in a sex-linked manner. Milk yield must be dependent on many factors, not merely on those directly connected with secretion of milk, but also on those which govern constitution, size, weight, etc. The purpose of the present paper is to explore the subject further from the statistical aspect in order to find out whether any of the factors governing milk yield are inherited in a sex-linked manner and, if so, how they compare with the factors inherited in the ordinary autosomal manner.The material was taken from the annual records of the Scottish Milk Records Association and from the Ayrshire Cattle Herd Book. Thirty leading herds of pedigree Ayrshire cattle, all located in the south-west of Scotland and which have been continuously recorded from 1922 to 1928, were selected from their alphabetical order. One other herd, out of alphabetical order, was included', as it had a great effect on many of the other herds.In all, some 5000 records were obtained, and these eventually represented 1518 cows. The records were corrected for age on the figures of Kay and M'Candlish (2) for Ayrshire cows in the south-west of Scotland. No correction

Untersuchungen über die Vererbung der Milch‐ und Fettmenge in der Leistungsherde des Herrn von Lochow in Zieckau

“…Buchanan Smith c. s. (2) bringen in ihrer Arbeit „Inheritance of Milk Yield in Ayrshire Cows”, die 1930 im Journal of Dairy Research erschienen ist, eine sehr interessante Studie, die allerdings die gestellte Frage rein mathematisch behandelt. Die Verfasser beschränken sich darauf, zu untersuchen, ob die Erbfaktoren für Milchleistung oder einige von ihnen geschlechtsgebunden sind.…”

169. A statistical inquiry into the inheritance of milk yield in three herds of dairy Shorthorn cattle

“…To overcome this difficulty another method, devised by Dr R. A. Fisher, has been already employed by the present writer (5). Briefly the argument is as follows: the closer the blood relationship of two animals, the more genes they should have in common, the more alike they should be, and, in the case of dairy cattle, the less difference there should be between their milk yields.…”

“…Ayrshire cows (BuchananSmith & Robison, 1931). Differences in the milk yield of pairs of cows according to their relationship classification…”