Growth and development with special reference to domestic animals XLI : relation between live weight and chest girth in dairy cattle of unknown age
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The relation between body weight and chest girth of dairy cattle of mixed ages may be formally represented by the equation 'Y=aXn in which Y is body weight, X chest girth. The value of the exponent n is of the order of 2.82 (that is the percentage increase in body weight tends to be about 2.82 times as great as the percentage increase in chest girth), but in the 6 groups of cattle investigated the values of n ranged from 2.72 to 2.88. There are also variations with group and with size in the value of the coefficient a. It thus appears that the relation between weight and chest girth is not altogether independent of nutritive level. However~ the relation between weight and chest girth is close enough for practical estimation of weight from chest girth and for the theoretical generalization that within certain limits weight is a power function of chest girth as indicated by the equation Y=-gXlI. This equation Y =aXn was fitted by the method of least squares to the following weight-chest pairs of measurements: 2454 Missouri Holsteins; 2235 Missouri Jerseys; 4689 combined Missouri pairs; 5866 Nebraska Holsteins; 2758 Nebraska Jerseys; 840 Nebraska Guernseys; 1457 Nebraska Ayrshires: 10,921 combined Nebraska pairs; 15,6]0, grand total of all the pairs. The fitted equations and their statistical constants are shown in Fig. 3. Tables and charts are presented for estimating live weight from chest girth of cattle of mixed ages. A later bulletin will present similar analyses for given age intervals.