Compiled
by Dr. Andrew Mercola We recommend his
excellent website, www.mercola.com/beef,
where
he describes many of the benefits of Grass Fed Beef
Potential
effect of cattle diets on the transmission of pathogenic Escherichia coli to
humans.
Grain feeding seems to promote the
growth and acid resistance of Escherichia coli in fattening beef cattle, and
acid-resistant E. coli are more likely to survive the human gastric stomach.
When cattle were fed hay for only five days, the number and acid resistance of
E. coli decreased dramatically
Microbes
Infect 2000 Jan;2(1):45-53
Manipulating
meat quality and composition.
Meat quality describes the
attractiveness of meat to consumers. The present paper focuses on two major
aspects of meat quality, tenderness and flavour. Both aspects of quality can be
influenced by nutrition, principally through its effects on the amount and type
of fat in meat. In several countries, high levels of intramuscular fat
(marbling fat), are deemed necessary for optimum tenderness, although poor
relationships between fat content and tenderness have generally been found in
European studies, where fat levels are often very low.
Muscle lipid may be a marker for red
oxidative muscle fibers which are found at higher concentrations in tender
muscles and carcasses. Nutritional treatment can be used to manipulate the
fatty acid content of muscle to improve nutritional balance, i.e. increase the
polyunsaturated (PUFA): saturated fatty acid value and reduce the n-6:n-3 PUFA
value.
When 18:3 levels are raised in lamb and
beef because of grass feeding, the intensity of the flavours increases in
comparison with grain-fed animals which consume and deposit relatively more
linoleic acid (18:2). In ruminants, very high levels of 18:2 produced by
feeding protected oil supplements cause the cooked beef to be described as
oily, bland or pork-like.
Proc
Nutr Soc 1999 May;58(2):363-70
Effects
of forage vs. grain feeding on carcass characteristics, fatty acid composition,
and beef quality in Limousin-cross steers when time on feed is controlled.
Steers were used to compare forage vs.
grain feeding on carcass composition and palatability attributes of beef when
time on feed was controlled. Grain feeding generally increased (P < .01)
carcass weight, grade fat, and intramuscular fat content when compared with
forage feeding at similar times on feed. Palatability attributes of ribeye roasts
and ground beef were generally unaffected (P > .10) by diet with the
exception of slightly less beef flavor and more off-flavor in forage-fed vs.
grain-fed beef. Higher (P < .01) concentrations of linolenic acid and lower
(P < .10) concentrations of oleic acid in forage-fed beef may be partially
responsible for diet differences in flavor.
J Anim
Sci 1998 Oct;76(10):2619-30
Fatty
acid composition, including conjugated linoleic acid, of intramuscular fat from
steers offered grazed grass, grass silage, or concentrate-based diets
The effects of grazed grass, grass
silage, or concentrates on fatty acid composition and conjugated linoleic acid
concentrations of fat of steers fed to achieve similar carcass growth rates
were investigated. Fifty steers were divided into 10 blocks based on body
weight and assigned at random from within blocks to one of five dietary
treatments. The experimental rations offered daily for 85 days preceding
slaughter were:
·
1) grass silage
for ad libitum intake plus 4 kg of concentrate
·
2) 8 kg of
concentrate plus 1 kg of hay
·
3) 6 kg of
grazed grass DM plus 5 kg of concentrate
·
4) 12 kg of
grazed grass DM plus 2.5 kg concentrate
·
5) 22 kg of
grazed grass DM
The concentration of polyunsaturated
fatty acids (PUFA) in fat was higher (P < .05) for steers offered ration 5
than for those given any other ration. Decreasing the proportion of concentrate
in the diet, which effectively increased grass intake, caused a linear decrease
in the concentration of saturated fatty acids (SFA) (P < .01) and in the
n-6:n-3 PUFA ratio (P < .001) and a linear increase in the PUFA:SFA ratio (P
< .01) and the conjugated linoleic acid concentration (P < .001). The
data indicate that i.m. fatty acid composition of beef can be improved from a
human health perspective by inclusion of grass in the diet.
J Anim
Sci 2000 Nov;78(11):2849-55
Factors
influencing fatty acids in meat and the role of antioxidants in improving meat
quality.
Meat has been identified, often wrongly,
as a food having a high fat content and an undesirable balance of fatty acids.
In fact lean meat is very low in fat (20-50 g/kg), pork and poultry have a
favourable balance between polyunsaturated and saturated fatty acids (P:S) and
grazing ruminants produce muscle with a desirable n-6:n-3 polyunsaturated fatty
acid ratio.
In all species, meat fatty acid
composition can be changed via the diet, more easily in poultry where the
linoleic, alpha-linolenic and long-chain polyunsaturated fatty acid content
responds quickly to raised dietary concentrations. In ruminants the challenge
is to increase the P:S ratio while retaining values for n-6:n-3 found in cattle
and sheep fed on forage diets. The saturating effect of the rumen can be
overcome by feeding polyunsaturated fatty acids which are protected either
chemically, by processing, or naturally e.g. within the seed coat. Some
protection occurs when grain-based or grass-based diets are fed normally,
leading to relatively more n-6 or n-3 fatty acids respectively.
These produce different flavours in
cooked meat due to the different oxidative changes occurring during storage and
cooking. Inpoultry, high n-3 fatty acid concentrations in meat are associated
with fishy flavours whose development can be prevented with high dietary
(supranutritional) levels of the antioxidant vitamin E. In ruminants,
supranutritional vitamin E delays the oxidative change of oxymyoglobin to brown
metmyoglobin and may also influence the characteristic flavours of beef and
lamb.
Br J
Nutr 1997 Jul;78 Suppl 1:S49-60
Forage systems for beef production from conception to slaughter: III. Finishing
systems.
Fall-weaned calves grazed or were fed
different forages during winter followed by 1) N-fertilized tall fescue
(Festuca arundinacea Schreb.) grazed alone, 2) bluegrass (Poa pratensis
L.)-white clover (Trifolium repens L.) sequence grazed with tall fescue-red
clover (Trifolium pratense L.), or 3) bluegrass-white clover sequence grazed
with alfalfa (Medicago sativa L.)-orchardgrass (Dactylis glomerata L.). Heifers
were supplemented with grain at 1% of BW from April until slaughter in July.
One-half of steers were supplemented with grain at 1% of BW from July until
slaughter in October.
Remaining steers were fed no grain but
were finished on corn silage supplemented with .9 kg of soybean meal per steer
daily, from October until slaughter in late January. Including
alfalfa-orchardgrass in systems during the finishing phase resulted in higher
daily and total gains during the grazing period, and carcasses had more
marbling and higher USDA quality grades at slaughter compared with carcasses of
cattle on systems using fescue-red clover. Correlation of final weight with
carcass characteristics was low (r < .5).
Performance and carcass characteristics
were influenced as much or more by forage consumed during the previous
wintering phase as by forage fed during the finishing phase. Wintering cattle
on stockpiled fescue-alfalfa or alfalfa-orchardgrass hay generally resulted in
higher BW at slaughter and more desirable carcass characteristics than systems
using tall fescue alone or in combination with red clover. This was
particularly notable in steers that grazed without grain until October and were
finished on corn silage plus supplement. Final BW and carcass characteristics
in all cattle were improved by full season grazing followed by feeding corn
silage, compared with cattle finished with grain on pasture
J Anim Sci 1996 Mar;74(3):625-38