RELATIONS BETWEEN THE GROWTH AND BODY DEV ELOPMENT IN HEIFERS OF THE BLACK-PIED CATTLE AT 15 MONTHS OF AGE

A relation between the course of rearing and body development of heife rs was analyzed at 15 months of age. The evaluation involved a set of 133 heifers of the Black-Pied breed of domestic and foreign provenance that were born on one farm from March to October 1994. The heifers we re weighed at the time of birth and then at three-month intervals. Bod y dimensions (height at withers, height at hips, chest girth, body len gth) were measured at the time of birth and then at the age of 3, 6, 9 , 12 and 15 months within the range of +/-3 days from the set-up age. Using the Richards function in the form y(1) = A/(1 + Be--kt)(1/n), es timates of weights at the age of 0, 3, 6, 9, 12 and 15 months were cal culated and average daily weight gains were derived from them over a t hree-month period. Analysis of variance was applied to interpret the r elations of the particular developmental stages to heifer development at 15 months of age. The linear model included fixed effects of birth season, breeding group and growth factor, in the position of which wei ghts and average daily weight gains were set up over the periods of ob servation. Residual correlations of the observed traits were also calc ulated. The analyzed set of heifers showed (statistically highly signi ficant) differences in the body development of heifers at the age of 1 5 months between the below-average, average and above-average groups, as related to weight and daily weight gains. The largest differences i n weight and body dimensions were observed between the groups of heife rs established on the basis of weight at 6, 9 and 12 months of age and of weight gains in the period of 6-9 months. Correlation analysis sho wed the closest relations of the weight, height at withers, chest girt h and body length to the average daily weight gain in the period of 6- 9 months (r = 0.96; 0.47; 0.66; 0.41) and to the weight at 12 months o f age (r = 0.98; 0.52; 0.70; 0.44).