By contrast to bulls, fattening cull cows deposite large amounts of fat in the carcass. Furthermore, the live weight gain are low. Methionine (M) is a limiting amino acid for muscle growth in Belgian blue cattle (Hornick et al., 1997). Supplementation with M in fattening diets for cattle could therefore improve weight gain or feed conversion ratio. An experiment was thus conducted in Belgian Blue cull cows in order to assess the effects of M in fattening diet on characteristics of tissue deposition.
Twenty four Belgian Blue females from double muscled type -8 heifers (H), 8 cows with 2 calving (C2) and 8 cows with 4 calving (C4)- were used. In each group, 4 animals received a control fattening diet (M0) based on maize silage complemented with cereals, sugar beet pulp and protein from vegetable origin (10.3 MJ ME and 160 g/ kg CP per kg DM), while 4 other received similar diet but with 3.5 g of rumen protected methionine (M1).