Factors Affecting Body Weight, Scrotal Circumference Hip Height and their Relationships with Birth Weighl Preweaning and Postweaning Gains in Young Bulls

Abstract

Morsy, N.H.A., Hassan, H.A., Makarechian, M. and El-Feel, F.M.R. 1998. Factors affecting body weight, scrotal circumference, hip height and their relationships with birth weight, preweaning and postweaning gains in young bulls. J. Appl. Anim. Res., 13: 81–92. Records of 125 bulls from two synthetic breed groups; Beef Synthetic (SYX, n = 64) and Dairy Synthetic (DSX, n = 61) fed two levels of energy (high concentrate, 85% grain or low concentrate, 55% grain) throughout 140-d feedlot test period were used in this study. The records were analysed by stepwise regression analysis to study the relative influence of birth weight (BW), preweaning daily gain (PWG) und postweaning daily gain (POG) on final body weight (WT), scrotal circumference (SC) and hip height (HHT) at the end of feedlot test. In addition the effects of the level of energy and breed group on the above relationships were investigated The data were analyzed by the general linear model to study the fixed effects of energy level, breed group and their interactions on final WT, SC and HHT. The results indicated that POG had the maximum associations with final WT and SC, while PWG had the highest association with HHT. The combination of PWG and POG provided the best prediction equations for final WT and SC. BW had the lowest associations with SC, HHT and final WT. The level of energy did not affect the regression coefficients of final WT, SC and HHT on BW, PWG and POG. The effects of breed group on the regression coefficients were not significant except for the regression of HHT on PWG. The level of energy in feedlot diet was a significant (P<0.01) source of variation for the growth measurements of WT, SC, HHT and their changes in feedlot test. Breed group did not have any significant influence on the growth measurements. The results indicated that in general final feedlot weight and testicular size could be predicted fairly accurately from the growth measurements of bulls from birth to yearling regardless of the level of energy and breed group effects on these relationships.