CHARACTERIZATION OF HOLSTEIN, MONTBELIARD E AND TARENTAISE HEIFERS

Live weight and skeletal development, along with the onset of puberty, were described for 72 heifers belonging to 3 dairy breeds (Holstein, Montbeliarde, and Tarentaise), reared in a mountainous environment. At birth, the Montbeliarde heifers were heavier (P < 0.05) than their Ho lstein counterparts (41 vs 38 kg). Between the ages of 12 and 24 month s, the Holstein heifers were around 20 kg (P < 0.01) heavier and the T arentaise around 30 kg (P < 0.01) lighter than the Montbeliarde. For t he 32 animals having calved 4 times, these differences remained simila r until the 4th calving. The growth curves were then adjusted accordin g to age, by using a descriptive growth model (Brody), giving a mature live weight that was closely similar (NS) for Holstein and Montbeliar de (665 vs 641 kg) and higher (P < 0.05) than that of Tarentaise heife rs (618 kg). The maturing rate, estimated with this model, of Holstein and Montbeliarde females (0.0017) was similar and faster (P < 0.05) t han that of the Trentaise (0.00143). At any given age, except 6 months , most of the measurements were different (P < 0.05) between the 3 bre eds and the animals ranked in the following decreasing order: Holstein , Montbeliarde and Tarentaise; especially for wither-height and chest- depth as well as width between trochanters. The Holstein heifers reach ed puberty at a younger age (305 d) than Tarentaise (475 d) and Montbe liarde (504 d) heifers (P < 0.01).