| Popis: |
Summary Data are presented on comparative body weights, body dimensions, and the measured surface area of Jerseys and Sindhi-Jersey (F 1 ) crosses. The mean body weights of the crossbreds are greater than those of the Jersey dams at comparable ages and stages of lactation. This difference, which may be attributable to "hybrid vigor" in the crossbreds, is most evident from birth to 15 months of age. Body measurements made at 6, 12, and 18 months of age and during first lactation show that at the earlier ages the crossbreds 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 measurements, other than weight, between the two groups diminish to a nonsignificant value or actually become reversed. The crosses exceed 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 are substantially the same for both groups. The surface area was measured on 32 Jersey and 23 Sindhi-Jersey crossbred cows with a surface integrator. These areas were compared with body weights. Neither the ratio of surface area to body weight nor the ratio of surface area to the two-thirds power of body weight shows a significant difference between the two groups. In these animals a statistical analysis indicated that the surface area is related to the square root of body weight but to no appreciable extent to total body length. |
