Faster effects on dressing yield, shrinkage, and pH contractile tissue in swine

It is a well established fact that hogs will usually lose weight while in transit from the farm to market or slaughterhouse. This loss in weight is commonly called shrinkage or drift and is of vital importance to all persons concerned with the swine industry. Shrinkage may be either excretory or tissue. Excretory shrinkage is defined as the loss in weight resulting from the elimination of excreta, which is usually referred to as the elimination of fill. Loss in weight due to excretion does not affect the carcass weight, therefore, the dressing percent is not changed when based on farm weight. However, tissue shrinkage is a loss in tissue weight thus lowering the carcass weight and dressing percentage.

The problem of shrinkage has long been a source of misunderstanding between farmers, transportation agents, marketing men and packers. The problem will become even more important if in the future a greater number of hogs are sold on the basis of grade and yield as is being done in such countries as Denmark and Canada. The amount and kind of shrinkage is a difficult problem to answer because of the great variation in the dressing percentage of similar hogs. Also hogs are produced, transported and marketed under a wide variety of conditions. Examples of these various conditions are the different breeds of hog, types of ration fed, market weights, amount of fill, weather and time in transit, mode of transportation, selling direct or auction or terminal market, etc.

If tissue shrinkage does not occur or is not affected materially by watering and feeding while in the marketing process, then "fill" is an economical waste to society. Dowell and Bjorka in their book Livestock Marketing makes the following statements: The packer objects to animals with heavy fill, not only because they dress a relatively small percentage of carcass but also because they are more difficult to handle during the process of slaughtering. Packers often keep the animals they buy in holding pens for a certain length of time in order that part of the fill may be eliminated. The practice (of filling hogs) is wasteful of feed, increases marketing costs, reduces the value of animals for slaughter, and tends to lower rather than increase total net returns to producers.

The purposes of this thesis were:

1. To determine the amount of tissue shrinkage as compared to excretory shrinkage during a four day fasting regime.

2. To determine, if possible, what tissues were involved in tissue shrinkage.

3. To study the effects of fasting on the pH of contractile tissue and consequent effects of cured meat.

4. To correlate dressing percentage with various carcass measurements.

5. To study the effect of length of haul on shrinkage percentages.