Update of feeding recommendations for fattening of culled cows. Development of a model for the estimation of the composition of weight gain and associated requirements

Abstract

Culled cows account for a large part of beef consumption in France and are a significant proportion of the income for dairy (10%) and suckling farmers (up to 30%). On-farm observations highlight large variation in culled cow phenotype in terms of age, frame size, sanitary and physiological state and body condition. Consequently, an important issue for producers of culled cows is the management of feed supply during the finishing period to obtain a satisfactory condition score and conformation for slaughter.

Feeding recommendations established in 1988 consider the live weight and the live weight gain to estimate the energetic requirements for fattening. They do not allow for the age, the frame size or the body condition score. In order to update the feeding recommendations for growing and fattening bovine, we have developed a predictive model, called VDR, in order to estimate the requirements for fattening culled cows. This paper outlines the factors that contribute towards the variations of live weight gain and gain composition for culled cows. The paper goes on to describe the VDR model by summarising the developments from previous modelling approaches and outlining the assumptions and equations of the model. The VDR model combines a growth model for the cow during its productive period and a model for the fattening period. Parameterisation was done for Charolais, Limousine and Holstein cows. Validation using data from Charolais cows shows that VDR explains about 80% of the variability in energetic requirements. Acomparison with the recommendations from 1988 quantifies the improvements obtained with VDR. The last section describes the construction of a table that allows the energy requirements for culled cows to be estimated easily.