Determination of rearing practices combinations increasing the carcase weight according to the heifers slaughter age by the decision tree method

Abstract

This work aims to identify the rearing practices which increase the carcase weight according to slaughter age. For this purpose, an innovative statistical method, the decision tree method, was used to identify the most influential action levers on the carcase weight, with associated thresholds values and modalities, among the rearing practices applied throughout the animals’ life. The data of 636 heifers carcases were collected from the slaughterhouse and the rearing practices from 45 farms by survey. Firstly, classifications were done to define slaughter-age classes and carcase-weight classes. Three slaughter-age classes (younger, mid-age, older) and 3 carcase-weight classes (lighter, intermediate, heavier) were defined, then these two classifications were crossed. The decision tree method highlighted that the influence on carcase weight of the life periods of the animals (i.e. suckling, growth, and finishing periods) and the related rearing practices were different according to the slaughter age of the heifers. For the younger-slaughtered animals, the most influential rearing practices on the carcase weight were the suckling duration, the concentrate supply during growing, the distributions of compound feed and grass silage in-stall during growing. For the mid-age slaughtered animals, the rearing practices identified as the most influential were the concentrate amount distributed in-stall during finishing, the meal supply in-stall during finishing and the cereals supply at pasture during growing. For the older-slaughtered animals, the compound feed supply at pasture during finishing and the concentrate amount distributed in-stall during growing were the most influential on the carcase weight.