The fattening of Charolais cull cows

Abstract

Two experiments were conducted to investigate the effects of length of the feeding period (0, 70 or 109 days), age (5 or 11 years) and use of trenbolone acetate on liveweight, dry matter intake, carcass weight, carcass compositional changes and meat quality of 56 cull Charolais cows fed on silage. A total of 11 additional cows were slaughtered at the beginning of the feeding period to estimate initial body composition. During the 70 day feeding period, cows without the trenbolone acetate implant had a daily liveweight gain of 1.2 kg. The estimated daily dry matter intake was 13.7 kg, their feed efficiency was 90 g of gain per UFL ingested. The average warm carcass weight of fed cows was 385 kg and consisted on average of 66 % meat, 19 % fat and 15 % bone. Carcass weight gains averaged 63 kg for Experiment 1 with a muscle content of 37 %. An extended fattening period of 110 days resulted in an increased carcass weight (20 to 30 kg), but this consisted mostly of fat. In this experiment, there was no evidence of any negative effects of age on the level of performance during fattening. Even though, the liveweight gain, feed efficiency and the percentage yield at slaughter tended to decrease for 11 year old cows. Implantation with trenbolone acetate resulted in a greater liveweight gain of 57 kg and in an increase in the lean proportion of the carcass gain (47 % versus 41 % for the control group of the 11 year old cows). The fattening period was increased 27 days in this instance. Acceptability of the meat, as measured by tenderness, juiciness and flavour, increased for cows which were realimented, while shear mesurements decreased. Significant differences in tenderness with advancing age were obtained in the two muscles studied (values of 4.99 for old cows versus 5.45 for young cows). The age of the animal had no influence on the level of juiciness, flavour, shear measurments, pigments, water holding and intramuscular fat. No significant negative effects were determined for the trenbolone implant for any of the meat traits evalued.