28 Chapter 2
higher the phospholipid concentration (Larick
et al. 1989 ). Feedlot - fi nished cattle have a
different fatty acid profi le from forage - fed
cattle. Meat from forage - fed beef contains
more linolenic acid, and less oleic and lin-
oleic acids than that from concentrate - fed
beef (Elmore et al. 2004 ). Intense pasture
rotation systems of millet and grain have
been shown to alter concentrations of diter-
penoids and lactones (Maruri and Larick
1992 ). Lactones correlate positively with
roasted beef fl avor and negatively with
gamey/stale off - fl avor; diterpenoids posi-
tively correlate with gamey/stale off - fl avor.
Differences in oleic, linoleic and linolenic
acids, diterpenoids, and lactones may be
responsible for fl avor differences. Nelson et
al. (2004) found that adding restaurant grease
to cattle diets to increase energy intake
increased initial tenderness and had no effect
on drip or cook loss, sustained tenderness,
juiciness, and beef fl avor.
Feeding antioxidants has been of signifi -
cant interest with respect to maintaining post -
harvest meat quality (Guo et al. 2006 ).
Vitamin E locates in the cell membrane in
proximity to phospholipids. It can prevent
development of free radicals in membranes
ante - and postmortem (Onibi et al. 2000 ).
Garber et al. (1996) reported that vitamin E
supplementation increased muscle alpha -
tocopherol levels, delaying metmyoglobin
formation (beef) and lipid oxidation in a
dose - dependent manner. Boler et al. (2009)
found that feeding natural sources of vitamin
E to fi nishing pigs was more effective in
reducing lipid oxidation of pork during sub-
sequent storage and display than were artifi -
cial sources. Yang et al. (2002) found that
meat from pasture - fed cattle contained as
much alpha - tocopherol as grain - fed cattle
supplemented with 2500 IU vitamin E. It
contained a higher percentage of linolenic
acid, a lower percentage of linoleic acid, and
was less prone to lipid oxidation and devel-
opment of warmed - over fl avor. Diet can also
affect color of the resultant meat. Vitamin Ecarcass fat that is soft and oily. In addition,
carcass fat that is higher in PUFA content is
more susceptible to oxidation during storage
than fat that contains more saturated fat.
Palm oil and whole linseed supplements
increase muscle levels of alpha - linolenic
(C18:3) and EPA (eicosapentaenoic acid
[C20:5]); fi sh oil increases EPA and DHA
(docosahexaenoic acid [C22:6]; Elmore et al.
2004 ). The effects of changes in dietary fat
source on pork fat are more apparent if they
occur during the last few weeks before
slaughter than if they occur 1 to 2 months
before slaughter.
Lampe et al. (2006) reported that while
fi nishing diet (yellow corn, white corn, 1/3
yellow corn and 2/3 white corn, 2/3 yellow
corn and 1/3 white corn, or barley) altered
saturated, mono - and poly - unsaturated fatty
acid content in the subcutaneous fat of pigs,
energy source had little effect on the eating
quality of pork. However Wood et al. (2004)
reported that a low - protein fi nishing diet
increased tenderness and juiciness but
decreased fl avor quality of pork.
Rosenvold et al. (2001) reported that
feeding fi nishing diets low in digestible car-
bohydrate can reduce muscle glycogen stores
in slaughter pigs without compromising
growth rate. This diet reduced μ - calpain
activity and increased calpastatin activity,
indicating less muscle protein degradation in
the muscles compared to muscles of control
animals. In an effort to improve the nutri-
tional profi le of pork, Janz et al. (2008) fed
pigs a plant - based diet containing conjugated
linoleic acid, selenium, and vitamin E. The
dietary treatments had some effects on meat
quality, but the overall effects on appearance
and palatability were small.
Diet can shift the bone/muscle/fat ratio of
beef carcasses. Grain feeding (high - energy
diet) usually increases carcass weight and
intramuscular fat content, and produces more
intense fl avor in red meats than do low -
energy forage and grass diets (Melton 1990 ).
The longer the animal is in the feedlot, the