Changes in body composition of mature dry cows of Holstein, limousin and charolais breeds during fattening. I. Skeleton, muscles, fatty tissues and offal

Abstract

The effects of fattening period on changes in the weight of tissues and offal in Holstein (HF), Limousin (LM) and Charolais (CH) 6–12-year-old mature dry cows were investigated. A group of animals of each breed was slaughtered and completely dissected at the beginning and the end of a 123–153-day fattening period. The empty body weight at the beginning of the experiment was 421, 452 and 513 kg in HF, LM and CH cows, respectively. It increased by 114, 106 and 130 kg (respectively 0.74, 0.86 and 0.98 kg day −1) during the fattening period. The weight of total skeleton 61, 62 and 79 kg, respectively, in HF, LM and CH breeds at the beginning of the experiment, did not change significantly ( P > 0.05). The weight of muscles, 182, 225 and 244 kg, respectively, in HF, LM and CH breeds in the initial groups, did not change significantly ( P > 0.05) in HF cows, but increased by 19 and 26 kg (i.e. 0.15 and 0.19 kg day −1) in LM and CH animals, mainly in the front part of the musculature (neck, thorax and fore limb). The weight of total body fat was similar (33–35 kg) in the three breeds at the beginning of the experiment. It increased by 87, 72 and 85 kg (i.e. 0.57, 0.58 and 0.64 kg day −1), respectively, in HF, LM and CH breeds during the fattening period. Fat deposition was greatest in intermuscular fat, but subcutaneous and omental fat had a higher relative change, indicating a higher metabolic activity. These results show that a fattening period in mature cows mainly increased total body fat, but did not greatly improve muscle weight. It is not known whether this potential muscle growth varies with the age of the animals. It may also be questioned whether this limited muscle growth is accompanied by changes in muscular characteristics related to meat quality, such as collagen or muscle fiber types.