Évolution de la production laitière et du poids vif des vaches laitières au cours de leur carrière

Abstract

One hundred seventy-six dairy cows which had completed at least 3 lactations were used to describe and to analyse the pattern of initial milk production (mean of days 4, 5, and 6 of lactation), peak milk production and of live weight at calving during the first 3 lactations. These cows were free of health disorders during the first 2 weeks of each lactation and fed according to INRA recommendations. On average, initial production, peak production, and live weight at calving were 15.7 kg/d, 22.5 kg/d and 536 kg in 1st lactation, respectively; 21.7 kg/d, 28.0 kg/d and 576 kg in 2nd lactation; and 23.3 kg/d, 29.8 kg/d and 607 kg in 3rd lactation. When a 4th lactation was completed, live weight was 29 kg higher than that of the 3rd lactation, whereas initial production did not increase significantly. Three main patterns were identified for both initial production and live weight. The increase of performance between the first 2 lactations and between the 2nd and 3rd lactation differed among patterns. For some cows, initial production or live weight increased only between the 2nd and 3rd lactation. The increase of milk production between 2 consecutive lactations was as important as that of live weight (+2 kg milk per 50 kg live weight). Equations were proposed to predict initial and peak milk productions for parities 2 and 3 on the basis of productions of preceding lactations, breed and live weight changes. © 1995.