Last year, a major packer began discriminating against a particular implant on the grounds it creates more dark cutters. It was blatantly unfair and I hastily wrote a column on the causes of dark cutters.
As it turned out, I made an error in describing the biochemical aspects. While I'm embarrassed at my error, all the practical management aspects were correct. Since publication of that article, two research studies have been published verifying my comments.
My discussion on management in that original column was based on observation and experience. The new studies, however, were scientifically controlled and statistically analyzed. Most interesting was the verification of my conjecture on the difference between packinghouses.
It's been my observation that the level of management (of cattle pre-slaughter) is highly variable. Based on that, I surmised that the dark cutter rate would also be quite variable between packers.
A study published in the Journal of Animal Science confirmed it.1 The Kansas State University (KSU) project reported that the dark cutter rate varied nearly five fold between packing plants.
This study examined five different plants owned by the same company. It found the range varied from a low of 0.28% to a high of 1.24%.1 Earlier, beef quality audits found the national average substantially higher: 5% in 1992 and 2% in 1995.2
Management's Enormous Effect Such disparity between the rates clearly indicates the enormous effect of management. Aside from how the cattle are physically handled, scheduling is also important. If scheduling is disorganized and cattle are held overnight without feed and water, dark cutters rise dramatically.
In the KSU study "carry cattle" (cattle held over weekends or holidays), even though provided feed and water, had over twice the incidence rate of dark cutters (0.77% vs. 1.64%).
Another of my comments regarding the feedyard was also confirmed. At some point in time, nearly every feedlot that sells on the rail attempts to economize by withholding feed the day before slaughter. This is a prescription for dark cutters.
In an Oklahoma State University (OSU) trial, feed withdrawal increased dark cutters three fold (0.35% vs. 1.04%).3 Combine the effects of withholding feed with strange facilities, and it's easy to see how rates as high as 5% have occurred.
Not specifically addressed in these studies were the facilities leading into the plant. If cattle are allowed to hear the noise and smell the blood from the kill floor, the dark cutter rate will be elevated. I'm sure that differences in facilities were a factor in the wide variation between packing houses.
The bottom line is that cattle management is the key to reducing dark cutters. The problem is that the human psyche does not like to admit shortcomings. It's easier to blame something else, such as implants. Implants are surely a factor, but the differences between implants are small compared to management factors.
An OSU study identified implants as a factor in terms of carcass leanness.2 Lean carcasses tended to have a higher incidence of dark cutters and those implants that increase protein accretion the most would tend to produce a higher incidence of dark cutters.
Unfortunately, there are no controlled studies published comparing specific implants - cattle provided the same management with different implants. There have been, however, some unpublished studies using uncontrolled data - studies looking at cattle from different feedlots and comparing implant only.
This type of information is unreliable since management can be so variable. For example, a study by Colorado State University (CSU) found a 10-fold difference in the dark cutter rate between feedlots (0.05% to 0.64%).4
But from available data, it's generally accepted that products containing TBA do increase the dark cutter rate over estrogen-only implants in steers. The CSU study found a single TBA combination implant in steers increased the dark cutter rate by 0.11% (over estrogen-only implants).4
Performance Comes With A Price The implants that give the greatest protein accretion also give us a proportional reduction in marbling and, it would appear, an increase in dark cutters.
Even so, it seems disingenuous for a packer to discount cattle because a particular implant was used. That implant increases leanness which results in a larger ribeye and more retail cut out.
To blame a dark cutter "wreck" on a particular implant simply conveys an ignorance of the subject. When the dark cutter rate doubles or triples, it's not a matter of what implant was used. It's a breakdown in management.
1"Factors Affecting The Occurance Of Dark Cutting Beef ...," K.K. Kreikemeier, J.A. Unrah and Tom Eck, Kansas State University, Journal of Animal Science Vol. 76:388, 1998. 2"Characteristics Of Dark Cutting Carcasses," S.M. Janloo and H.G. Dolezal, et.al., Oklahoma State University Research Report, July 1998, page 28. 3"Impact Of Withhholding Feed On Performance And Carcass Measurements Of Feedlot Steers," S.M. Janloo and H.G. Dolezal, et.al., Oklahoma State University Research Report, July 1998, page 109. 4"Factors Contributing To The Incidence Of The Dark Cutting Condition ...," Final Report to NCBA by Colorado State University, J.A. Scanga, et.al.