The effect of fasting on tissue shrinkage and some of its mechanisms in rats

Ante-mortem fasting long has been recognized as a sound practice for meat animals. However, the length of a feasible fasting time is not well established. There are two advantages of fasting meat animals before slaughter. First, it is more difficult to thoroughly bleed and eviscerate the animal if it has been fed, watered and/or severely excited immediately prior to slaughter. In addition, fiery fat and dark-colored muscle may occur. Secondly, from a monetary standpoint, annual feed consumption, particularly in large meat packing companies, may be quite costly in preslaughter periods. In fact, the expenditure for feed and labor totals millions of dollars in the United States. A feasible fasting time, which would not produce tissue shrinkage or serious loss of meat quality, should be determined. Laboratory animals are desirable subjects in many biochemical, physiological and biological experiments. The response of laboratory animals to fasting regimes could yield useful and desirable information. Whether such information can be transposed to meat animal species should be investigated. Two kinds of shrinkage (excretory and tissue) occur during the fasting period. Excretory shrinkage does not affect the yield of edible meat, but it is important to investigate tissue shrinkage, as it does affect yields. The two most important tissues in the meat animal carcass are fat and muscle. Fat tissue is considered to be of minimum economic importance in the United States, and is only important insofar as it affects eating quality and cutability. Knowledge of muscle shrinkage during the fasting period is far more essential because of the positive relation of muscle yield to the total value of the carcass. The main objectives of this experiment were to determine the length of fasting time necessary to effect tissue shrinkage and to determine which tissues were affected most by fasting.