Sometimes deep bruises can occur that may not be obvious to people assessing bruises visually. Helen Kline, Ph.D., my former graduate student, conducted an extensive study of bruising at five commercial slaughter plants. The facilities processed both fed feedlot beef, cows and bulls. In all five of these plants, skilled trimmers had learned that a slight pinkish area or small spot could hide a large amount of bruised meat. I called this the “iceberg effect,” because icebergs appear small above the surface and large under the surface. The light pinkish area was too pale to be scored with standard commercial bruise scoring charts. Kline reported that bruising in deep tissues was not being detected on many carcasses.
I want to emphasize that all five plants processed both older cattle and fed beef. There is a possibility that trimmers in a plant that exclusively process fed beef may be less likely to discover the “iceberg effect.”
In Kline’s study, each sample animal was individually marked when it walked off the truck. Sample animals were chosen from each compartment of standard pot belly double-deck cattle trailers. A total of 617 cattle were marked and followed through five different plants to assess bruising. Fifty-six percent of all the sampled cattle had visible bruises that were visually scored with a bruise scoring chart. Trimming the “iceberg effect” increased the percentage of bruised carcasses to 76 percent. When the cattle were separated by type, visual scoring indicated that among finished feedlot beef 36 percent had bruises, cows 53 percent and bulls 64 percent.
Bruises were then tabulated by truck trailer compartment and body location. One surprising finding was a large number of bruises located on the back or top of the rump. Another finding, which has shown up in other studies, were numerous bruises in the center of the back along the spine. These are caused by tall cattle hitting the bottom deck during either entry or exiting from the trailer.
Bruises on the rump
The next step in analysis of this data is to separate the fed beef from the old breeding cows and bulls. This will be required to determine the cause of the bruises on the rump. Rump bruises are definitely not caused by hitting part of the trailer during entry or exit. If the rump bruises are occurring in fed steers and heifers, I provide a possible explanation. There are problems with lame feedlot cattle. Reports from feedlot consultants indicate problems with both founder and damaged knee joints. The question I ask is: Are cattle with sore feet or legs leaning against the inside of the trailer in an attempt to relieve pain? There is an easy way to detect sore legs at packing plants. When cattle lie on their chest (sternal recumbency) the normal position is for both front legs to be tucked under the body. If one front leg is extended out straight, the animal is sore.
Trailer compartment bruises
The doghouse had the most bruises with 56 percent. This is the reason why one fed beef company welded the doghouse shut. The percentage of bruises by trailer compartment were:
- Belly – 47 percent
- Top deck – 33 percent
- Nose – 45 percent
- Back tail compartment – 49 percent
A possible reason for a high percentage of bruises in the tail is that severely compromised cows are often transported in this compartment.