Breeding For Marbling To Improve Tenderness
Breeding For Marbling should result in an indirect improvement in tenderness,
although the phenotypic relationship between marbling and tenderness is not especially high. Increased marbling
results in a dilution effect on the connective tissue (collagen) in meat and provides lubrication in
the chewing process, both of which aid in the improvement of tenderness. Increased marbling is most important when
meat is cooked to relatively high endpoint temperatures. Several research studies have shown that the risks of
having steaks of undesirable tenderness increase significantly as USDA quality grades decrease from Prime to Choice
to Select to Standard. Breeders of several purebred breeds have been selecting for increased marbling through
progeny testing of sires and(or) ultrasound evaluation of progeny of sires. Some studies have shown that the
genetic correlation between marbling and tenderness tends to be higher than the phenotypic correlation.
Because of its high level of heritability (38 %), progress
can and has already been made by selecting for increased marbling. Several breed associations are now using
ultrasound information obtained by certified technicians and images interpreted by Iowa State University for
development of EPDs for marbling as well as ribeye area and fat thickness. Using beef breeds that are noted for
high marbling in crossbreeding programs generally results in meat that has a desirable level of marbling. Current
pricing systems for carcasses and meat reward higher levels of marbling; therefore, the economic incentive for
increased marbling likely will continue to be important in the future.
We should point out the relationship between marbling and percentage of meat yield is
antagonistic. In other words, as marbling increases, percentage of meat yield generally decreases, unless both
traits are selected for simultaneously. We also should reemphasize that the phenotypic relationship between
marbling and tenderness is not especially high, although favorable. Consequently, some cattle with relatively high
marbling will produce meat that is unacceptable in tenderness, and some cattle with low levels of marbling will
produce meat that is very desirable in tenderness. The ideal situation would be to select directly for tenderness
(or against toughness) and simultaneously select for increased marbling and improved percentage of meat yield.
However, direct selection for tenderness (or against toughness) has not been feasible because tenderness can be
evaluated only on cooked meat obtained from progeny groups of cattle. Even when tenderness information is obtained,
it has not been available in “producer friendly” tenderness EPDs.
Producing beef of desirable tenderness requires utilizing beef cattle breeds or
composites that are known for producing meat of acceptable tenderness, selecting for a calm temperament, selecting
for tenderness within breeds, utilizing optimum management for different biological types, proper handling of
finished cattle from the feedlot to the processing plant, utilizing optimum postmortem technology for carcasses and
meat, and utilizing optimum cooking procedures. Of course, the beef cattle industry can control only the first
three or four of these important variables.
Commercial cattlemen first should utilize breeds in their production system that match
the environment and feed resources, but also must give considerable attention to utilizing those breeds that are
known to produce meat of acceptable tenderness. When EPDs become available, seedstock producers should breed for
improved tenderness (or against toughness) as well as marbling and desirable carcass cutability, so that commercial
cattlemen can select sires within breeds to improve tenderness and meet market demands for marbling and carcass
When other technologies are proven accurate and reliable, such as testing for DNA
tenderness markers, seedstock producers can make even more progress in improving tenderness, both from the
standpoint of selecting sires earlier and from the standpoint of selecting among more sires.
Commercial cattlemen must castrate bulls at a young age, match the appropriate
nutritional regimen with the type of cattle they are producing, feed cattle a high grain diet at least 100 days,
utilize growth promotants according to manufacturers’ recommendations, slaughter cattle at an optimum endpoint for
their biological type, and handle cattle in a way to minimize excitement and stress.
The beef industry also must utilize technology and management to optimize tenderness,
and the end users of beef must cook it properly. When both genetic selection and optimum management are utilized,
tenderness of beef can be improved significantly, and beef’s market share likely will increase.