The dark cutter issue
No issue is probably more consternating to cattle feeders and packers than dark cutters. Dark cutters, of course, are carcasses that cannot be sold through normal retail channels, and are subsequently severely discounted.
Dark cutters are caused by a build up of lactic acid within muscle tissue, which will not allow meat to turn the characteristic bright, cherry red color, when exposed to oxygen. Thus, the term "dark cutters."
Lactic acid is the end product of glycogen utilization, which normally occurs when the animal is stressed or exercised. However, lactic acid build up can also occur due to being off-feed for a significant length of time. In this case, it is glycogen depletion (the storage form of immediate energy) that causes the lactic acid build up.
This latter cause is the one I'm particularly familiar with. I do a great deal of work for small feedlots in isolated areas, and this is something we must be acutely aware of.
Many feedlots are a long way from packers, and therefore the details for shipment become crucial. In most cases, this means we must have trucks available at daylight to get cattle to the plant and slaughtered by that afternoon.
If trucks are delayed, that may mean cattle will be held overnight and slaughtered the next day. That can mean a significantly greater percentage of dark cutters because the cattle have been standing overnight off-feed and/or have also been off-feed the entire day before. A similar situation sometimes occurs with small feeders who sell on a grade-and-yield basis. Occasionally, they'll get the idea that since fill is not an issue, they can economize by withholding feed the day the cattle are shipped. That decision can result in a disastrous number of dark cutters.
Psychological Stress Has An Impact As a nutritionist, I primarily key on the nutritional aspects. The reality, however, is that psychological stress is the principal factor in most cases. One large Southwestern feeder has a database showing a correlation to yield grade. It shows that Yield Grade 1 and 2 carcasses have a greater incidence of dark cutters than 3s and 4s.
In truth, my best guess is that instead of yield grade, the correlation is to Bos indicus breeding. These breeds tend to have less fat cover and, of course, are more excitable (than Bos taurus).
Obviously, hot shots and rough handling are major contributors. Mechanical noise and kill floor odors are most certainly factors, too.
In some plants cattle move quietly and obliviously into the kill floor area. In others, cattle tremble violently with fear and excitement just before slaughter. Although I've never seen any data, I'm sure that some plants have a higher incidence rate of dark cutters than others.
In years past, the legal requirement to withhold MGA(r) prior to slaughter created dark cutters. Here, the withdrawal often meant the whole pen would be in heat at slaughter, resulting in a significantly greater number of dark cutters.
Several years ago, however, FDA removed the withdrawal requirement. My best guess is that today MGA(r) would reduce the number of dark cutters (since none of the heifers would be in heat at slaughter).
Implants are an interesting issue. Intuitively, I would not expect implants to have much effect. The reason: blood analysis shows that for virtually every implant on the market, the release of hormone is exceedingly low by 60-65 days. Since most cattle are implanted 75-120 days before slaughter, I'd expect any influence of the implant to be minimal.
Surprisingly, the available data shows that implants are a small, but significant, factor. What has raised awareness of this issue is the fact that a major packing company has begun discounting cattle implanted with a particular product. I won't name the product since from data available to me I am not sure this particular implant is much different than others in its class.
Packer Perceptions >From time to time, packer buyers have singled out individual items and practices as "bad" and attempted to apply a discount. (I even once had a packer tell a client his cattle were to be discounted because wheat was in the ration.) Some have questioned the motives, and to a certain extent some of these attempts to "discount" have no doubt been disingenuine.
However, most people do tend to think in black-and-white terms. When there's an unusual amount of sickness, often the vaccine is blamed. If a different vaccine is used the following year and there is less sickness, that vaccine is deemed "best." The reality, however, is the difference is more likely due to stress.
The same goes for dark cutters. Reduce the stress and the incidence of dark cutters will likewise decline. Certainly, implants have an effect. Those that give us the greatest gain may also be more predisposing. But, it's simplistic and misleading to label one product as the "dark cutter" implant.
Cattle are not intelligent, but they are highly emotional. Forget that for a moment and we'll have dark cutters regardless of what they're implanted with.
(Correction: Last month, the term "toxoid" was used incorrectly. The correct term is "anti-toxin.")
David P. Price is a consulting nutritionist specializing in feedlot and range cattle. A number of his books and a subscription newsletter are available through BEEF magazine by contacting Marilyn Anderson at 800/722-5334, ext. #710.