Implants do not cause dark cutters. Dark cutting carcasses
are caused by abnormal physiology after slaughter. Normally,
muscle contains glycogen, a type of starch that is used by
the muscle for energy. After slaughter, glycogen is
converted to lactic acid. Because circulation has ceased,
lactic acid accrues in the muscle and the pH drops,
producing normal beef characteristics. If glycogen is absent
at slaughter, these normal changes do not occur and the
higher than normal pH results in beef that is darker, firmer
and drier than usual. This is called a dark cutter or DFD
(dark, firm and dry) beef.
Any event that causes muscle glycogen to be abnormally low
at the time of slaughter could potentially result in a dark
cutting carcass. Usually, high incidences of dark cutters
are caused by specific stresses such as long hauls or
overnight stays before slaughter. Some cattle are more
susceptible to cutting dark than others, and there are some
times of the year that dark cutters are predictably high.
Implants can be involved, too, as some implant programs may
increase the likelihood that some cattle will cut dark. In
particular, TBA-containing implant programs occasionally
result in a higher incidence of dark cutters than implant
programs that do not contain TBA.