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Conformation and Its Relation to Milk Producing Capacity in Jersey Cattle¹

Maine Experiment Station, Orono, Maine

ABSTRACT

This paper presents a biometrical analysis of the relation of conformation to the milk producing capacity of the Jersey cow. Exceptional data have been made available to this Station for the solution of this problem by the courtesy of Mr. R. M. Gow. These data give the exact scores of 1674 registry of merit Jersey cows as determined by about 140 judges.

The mean conformation as measured by score is given for the cow as a whole and for the parts into which it is divided. Within this group of Jersey cows the average score was 89.848 ± 0.073. The average Jersey cow was therefore about 10 points below the ideal Jersey cow. When this measure of the conformation as a whole is analyzed in terms of its parts, it was found that the fore udder differed most from the ideal type.

When considered in abstract terms it was found that the most seriously defective parts of the body in the minds of the judges had to deal with the mammary system, its size and blood supply. Of those parts which dealt with the body proper the least ideal was the barrel.

The variation of the different body parts is compared by means of the standard deviation and the coefficient of variation. The most variable part of the body included the eyes, horns, and muzzle, the least variable the size of the body.

The variability is further compared with characters of similar nature to those of conformation save that the variability was determined on data measured or weighed accurately in English or metric units. Bone material was in general found to vary less than the scores assigned to parts of the body depending chiefly on variations in bone length. The amount of this difference was slight, however. The variation of the udder parts was found to be at the lower end of the range of variation of other soft parts of the body.

Correlation coefficients for milk yield with the conformation as a whole and for the various parts were determined. The correlation coefficients ranged from—0.0697 ± 0.0165 to 0.1941 ± 0.0160. Out of the nineteen correlations only one was minus in value; seventeen were more than three times their probable error. The total score had the highest correlation with milk yield. The parts of the conformation having a distinctly significant relation to milk production of the cow were the milk veins, size and condition of udder, the size and shape of rear udder, the shape and size of barrel and the general appearance of the cow.

The relative merits of conformation as a guide to the milk producing capacity of a cow and a short time milk record are considered. The results show that a seven day test has a correlation coefficient with the year milk yield of the cow of approximately
times that of the conformation or any part of the conformation. The short test consequently is superior to the conformation as a guide to milk production.

Constants for the regression of each correlation table are calculated and the regression shown to be linear.The raw data are given in appendix tables 5 to 23.

¹ Paper from the Biological Laboratory of the Maine Agricultural Experiment Station, No. 129.