by Temple Grandin, Ph.D.
Colorado State University
Fort Collins, CO, 80523
If a bruise is occurring in the plant it will usually occur on the same location on cattle from many different sources. In one beef plant they started to notice bruises on the left shoulder. They were occurring on cattle from many different feedlots and they were gradually getting worse. The cause of the shoulder bruises was worn out broken metal in the restrainer entrance. Cattle are very abrasive and over a period of several years they wore through the metal side of the restrainer and a sharp edge was created. The first place one should look if there is a bruise on cattle from many origins is broken or damaged parts in the chutes, restrainer or stunning box. Rough handling can also cause bruising to increase. Back bruises caused by slamming stunning box doors on cattle are an indicator of rough handling. Some of the pork plants have eliminated back bruises caused by guillotine gates by cutting off the bottom of the metal door and replacing it with a curtain made from conveyor belting. The animals think that the conveyor belting is solid and they will not attempt to go through it.
Tracking down bruises which occur outside the plant will require a little more detective work. Somebody has to observe many carcasses on the line to determine if a particular type of bruise is occurring only on cattle from a specific origin. For example, there may be a severe bruise on the right loin of cattle from Feedlot A. A trip to the feedlot indicated that there was a sharp metal strip that protruded in their loading ramp. One over looked factor is the variable of truck driver. Poor driving habits, such as slamming on the brakes and sudden acceleration can increase bruising because cattle are thrown off balance. Check to make sure that, a truck driver is not the cause. Suspect a truck driver if some of the cattle from Feedlot B have bruises and other loads of cattle from this same feedlot have low levels of bruising. This may indicate that one driver is causing bruises and the other drivers are doing a good job. Several feedlots have banned the use of electric prods for truck loading. This has resulted in less bruising and fewer dark cutters. Another cause of bruising from a particular origin is excessively wild cattle. Wild cattle that are not accustomed to a person on foot will often have more bruises and dark cutters. Cattle should be exposed to people on foot long before they arrive at a packing plant.
In another case, pork loins had bruise damage and the plant manager thought that the bruises were caused by the stunner. The loin damage had yellow mucous on it and had happened about a week ago when the pigs were sorted. When I looked at the carcasses on the kill floor I observed marks where the pigs had been beaten with metal gate rods. The gate rod marks were in the same location as the yellow mucous on the loins.
Ye1low mucous which is an indicator of an old injury can remain on the carcass for months. At a fed beef plant I observed some faint traces of yellow mucous on the legs at the point where the meat hooks are inserted. When I called the feedlot I learned that these cattle had been severely abused during handling at a stocker operation prior to entering the feedlot. The manager told me that many of the cattle fell down when they exited from the squeeae chute.
Tracking down the cause of bruises will take some time, but you will be rewarded by reducing losses and improving animal welfare.
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