Body Weights, Body Measurements, and Surface Area of Jersey and Sindhi-Jersey (F1) Crossbred Females

Abstract

Data are presented on comparative body weights, body dimensions, and measured surface area of Jerseys and F1 crosses of Red Sindhi (a Zebu breed) with Jerseys. The crosses were compared with their Jersey dams in respect to weight from birth to 21 months of age and 1st, 2d and 3d lactation. The mean body weights of the crossbreds were greater than those of the Jersey dams of comparable ages and stages of lactation. The difference is most evident from birth to 15 months of age. The size of the crossbreds was unexpected since purebred Red Sindhis are smaller than Jerseys. The difference in gain in body weight may be attributable to "hybrid vigor". Fifteen body measurements, made at 6, 12, and 18 months of age and during 1st lactation, show that at the earlier ages the cross-breds are taller and have greater body width and depth, but that their body length is less. With the advance of age, the differences for most of the body dimensions between the 2 groups diminish to a nonsignificant value or actually become reversed. The crosses exceeded the Jerseys, however, in angle of rump and length of head at all ages. The average coefficients of variation for body weight and body dimensions was substantially the same for both groups. The surface area was measured on 32 Jersey and 23 of the F1 crossbred cows with a surface integrator. These surface areas were compared with body weights. Neither the ratio of surface area to body weight nor the ratio of surface area to the 2/3 power of body weight showed a significant difference between the 2 groups. In these animals a statistical analysis indicated that surface area is related to the square root of body weight but to no appreciable extent to total body length.