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The Contribution of the Dam in Inheritance of Milk and Butterfat

Register of Merit Department, American Jersey Cattle Club, New York City

ABSTRACT

The significance of these results to practical breeding may be summarized as follows:

1. It is evident that there is some correlation between a cow's producing ability and the producing ability of her daughters. Selection of females from high record dams should result in a herd that will produce in excess of the breed average. In general the daughters show about 32 per cent as much variation from the breed average as do the dams.
   
2. There is a slight correlation between the dam's record and the records of her sons' daughters. However, it appears that very little progress can be hoped for if sires are selected solely on the basis of their dam's records. It is obvious that a production record considered by itself is a poor index for the germinal composition of the dam for the characters for production. The record of the dam is nearly twice as reliable a measure of the production of her own daughters as it is of her sons' daughters.
   
3. The records of only a very few tested maternal sisters does not alone furnish a reliable guide for predicting the transmitting ability of an untried bull.
   
4. There is some correlation between the average production of the dam's half-sisters by the same sire and the average production of the dam's sons' daughters. However, selecting a bull with but this in mind is not recommended from the results of this investigation.
   
5. In choosing any untried young bull consideration should not be limited to the sire alone but the maternal ancestry is worthy of careful study. Too much information cannot possibly be obtained. The results of the last phase of this investigation indicate that when an average is made of the dam's record, the dam's sisters' records and the dam's daughters' records the average figure obtained in this manner provides a more accurate and reliable index as to a bull's probable transmitting ability than does any one of these factors considered by itself. If the dam has no record the average of her maternal sisters' records and of her daughters' records gives just about as dependable results.
   
6. In purchasing an untried young bull it is now generally recommended, in the light of present knowledge, that first of all he be sired by a proven bull, a bull whose daughters are uniformly high producers and superior to their dams. After this fact has been verified attention should then be given not only to the dam's record but also to the records of her sisters and the records of her daughters. Selection of a bull by this method seems to provide the most possibilities for success.