Dairy heifers rearing systems. Comparison between Holstein and Norman breeds

Abstract

The rearing of 432 heifers from the INRA herd for Genetic Research in Le Pin au Haras was studied retrospectively (births from 1978-79 to 1986-87 on mean date Dec 26). Two herds of primiparous cows had to be prepared : an early calving system intended for an intensive cow feeding system (I), and a late calving system for a sparing cow feeding system (II). In each situation, calvings occurred in the autumn. The main objective was to achieve growth performance as equal as possible in each system from year to year. Then, feeding was very uniform and rather intensive. Heifers included Holstein (2/3, born on Dec 31) and Norman (1/3, born on Dec 19) genotypes. The heifers from heifers accounted for 1/3 of the population (born on Nov 30) which included 33 twin heifers. The heifers entering system I were born on Nov 24 (n=201) instead of Jan 25 in system II (n=185). At the end of the considered period (rearing and first lactation in system I, rearing in system II), the adjusted live-weight (age effect) was lower in system I but these primiparous cows produced milk (5145 kg). Holstein and Norman heifers had similar growth rates, although Norman heifers from heifers gained less in the early stages. Normally, heifers from heifers produced more milk than heifers from cows, due to genetic and feeding advances. Twin heifers had a higher culling rate in their first lactation (system I). At culling, primiparous cows with a long lactation period (system I) and heifers (system II) provided heavy carcasses but the slaughter rate was higher in the Norman breed.