The growth of Ayrshire cattle: an analysis of linear body measurements

Abstract

SUMMARYThe growth of 12 linear body measurements in Ayrshire cattle was analysed by least-squares methods. Measurements were taken at 3-monthly intervals up to 48 mo of age. Adjustments were made for month and year of birth and for type of birth (twin-born animals comprised 40% of the data). The state of pregnancy or lactation in heifers was also taken in account. Growth curves were fitted to the mean values at the 16 ages and were found to give a close fit. Residual deviations, though small, did show a systematic pattern. The estimated degree of maturity at birth ranged from about 25% for measures of width to 50% for measures of height, body length being intermediate at 40%.To a large extent the different body measurements maintained a uniform pattern of maturing and their ranking for earliness of maturity tended to remain constant throughout the growth period. The application of allometry to the measurements is examined and the error introduced by extrapolating an allometric relationship between characters of different maturing rates is illustrated.