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| Lipides
dans les muscles Longissimus provenant des animaux élevés
en pâturage ou au grain |
(Traduction partielle et texte complet
en anglais)
P. T. GARCIA and J. J. CASAL
Instituto de Tecnologia de Carnes, CICV,INTA.
CC 77, 1708 Moron, Buenos Aires, Argentina.
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Introduction
Les opinions médicales voient
dans la composition du régime l'un des facteurs qui augmente
le risque du développement de certaines maladies par son
influence sur le niveau de cholestérol dans le sang. Le potentiel
hypercholestérolemique-atherogenique d'un mets est lie à
son contenu en cholestérol et en graisses saturées.
Plusieurs études ont démontré que les tissus des animaux
élevés au fourrage sont plus maigres que celui provenant
des animaux élevés au grain (Crouse et al. , 1984).
Des études ont été menées démontrant
que la composition des acides gras dans la graisse bovine dépend
de leur régime (Rumsey et al. ,1972 ; Marmer et al., 1984).
Résultats
et débats
Certains particularités des carcasses sont résumées
sur le tableau 1. Les animaux élevés au pâturage
étaient plus gros (p.<.05) que ceux élevés
au grain d'après l'épaisseur de la graisse sous
cutanée et le pourcentage des animaux classifies comme
FD2.
Les pourcentages de graisse intramusculaire
étaient plus élevés parmi les LD élevés
au grain que dans ceux élevés en pâturage
(p.<0.05) (tableau 2 ) Ces résultats sont similaires
a ceux de Marmer et al. (1984) et Crouse et al. (1984) et démontrent
les effets du régime sur la déposition de la graisse
intramusculaire .
Le contenu
du cholestérol dans les muscles des LD élevés
en pâturage était plus bas que dans les muscles des
LD élevés au grain (p.<0.05) (tableau 2). Rhee
et al. (1982) n'ont pas trouve des différences significatives
dans le contenu en cholestérol des steaks crus avec des
différents niveaux de marbrage, sauf que les steaks "pratiquement
dépourvus" de marbrage contenaient beaucoup moins de cholestérol
que les steaks avec des pourcentages divers de marbrage.
Conclusions
L'énergie du régime
a une influence sur la graisse intramusculaire (marbrage) et le
cholestérol des muscles Longissimus des animaux. Les Longissimus
des animaux élevés au pâturage ont moins de
graisse intramusculaire et du cholestérol que ceux des
animaux élevés au grain.
Les lipides du Longissimus provenant des animaux élevés
au pâturage ont un niveau plus élevé de PUFA
et un rapport n-6/n-3 inférieur a ceux élevés
au grain.
Table 1. Some characteristics of the steers
|
| |
Grain |
Grass |
| n |
32 |
32 |
| Live
weight, kg |
| Initial |
360 |
360 |
| Final |
436 |
465 |
| Gain, g/day |
.65 |
.59 |
| Fat
thickness |
| 12th rib, cm |
.76 |
.92 |
| Fat degree 1, (%) |
31 |
22 |
| Fat degree 2, (%) |
69 |
78 |
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Table 2. Total intramuscular fat and
cholesterol in LD muscle. Mean and SD
| |
Grain |
Grass |
| IMF |
3.9 + / - 1.1 |
2.9 + / - 0.9* |
| Cholesterol
mg % |
72.2 + / -13.7 |
66.6 + / - 8.8* |
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* p < .05
Références
BOHAC C. E., RHEE K. S., 1988. Influence of
animal diet and muscle location on cholesterol content of beef and
pork muscles. Meat Sci. 23, 71-75.
BROWN H. J., MELTON S. L., RIEMANN H. J., BACKUS W. R., 1979. Effects
of energy intake and feed source on chemical changes and flavor
of ground beef during frozen storage. J. Ani. Sci. 48, 338-342.
CROUSE J.D., CROSS H. R., SEIDEMAN J., 1984. Effects of a grass
or grain diet on the quality of three beef muscles. J. Ani. Sci.
58, 619-625.
FOLCH J., LEES H., STANLEY G. H. S., 1957. A simple method for the
isolation and purification of total lipids from animal tissues.
J. Biol. Chem. 226, 497-509.
LARICK D. K., TURNER B.E., 1989. Influence of finishing diet on
the phospholipid composition and fatty acid profile of individual
phospholipids in lean muscle of beef cattle. J. Ani. Sci. 67,2282-2293.
MARMER W. N., MAXWELL R. J., WILLIAMS E. J., 1984. Effects
of dietary regime and tissue site on bovine fatty acid profiles.
J. Ani. Sci., 59, 109-121..
RHEE K. S., DUTSON T. R., SMITH G. C., 1982. Effect of changes in
intramuscular and subcutaneous fat levels on cholesterol content
of raw and cocked beef steaks. J. Food Sci. 47, 1638-1642.
ROSCHLAN P., BERNARD E. and GRUBER W., 1975. 9th Int. Congress on
Clin. Chem. Toronto. Abstr. No 1.
RUMSEY T. S.. OLTJEN R. R., Bovard K. P., Priode B. H., 1972. Influence
of widely diverse finishing regimens and breeding on depot fat composition
in beef cattle. J. Ani. Sci. 35, 1069-1074.
TU C., POWRIE W. D., FENNEMA 0., 1967. Free and esterified cholesterol
content of animal muscles and meat products. J. Food Sci. 32, 30-34.
38th ICoMST Clermont-Ferrand France 1992 pag.53
- 56
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| Lipids
in longissimus muscles from grass or grain fed streer |
(Texte complet en anglais)
P. T. GARCIA and J. J. CASAL
Instituto de Tecnologia de Carnes, CICV, INTA.
CC 77, 1708 Moron, Buenos Aires, Argentina. |
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Summary
The effect of grass or grain dietary regimen on Longissimus
intramuscular fat and cholesterol was examined using two groups
of Angus steers slaughtered at similar level of finishing. Carcasses
were graded and after a 24 hs chill the Longissimus muscle
was removed for analysis. Total intramuscular fat content, its fatty
acid composition and total muscle cholesterol were determined. Grass
steers were fatter than grain steers (fat thickness at 12th rib
were .92 and .76 cm respectively). Grain fed Longissimus
were fatter than that of grass fed (3.9 vs. 2.9%, p<.05) and
with more cholesterol (73 vs. 66 mg%, p<.05). Grass fed Longissimus
lipids presented more n-3 fatty acids and a lower relation n-6/n-3
(1.6 vs. 2.1, p< 0.05).
Introduction
The composition of the diet is seen by most medical opinion as one
factor increasing the risk of the development of certain diseases
via its influence on the level of blood cholesterol. The hypercholesterolaemic-atherogenic
potential of a food is related to its cholesterol and saturated
fat content. Several studies have shown that tissue from forage-fed
beef is leaner than tissue from grain-fed beef (Crouse et al., 1984;
Brown et al., 1979; Marmer et al., 1984). Studies have been conducted
that show that fatty acid composition of bovine fat is influenced
by dietary regimen (Rumsey et al. , 1972 ; Marmer et al. , 1984).
There are conflicting reports in the literature regarding the effect
of lipid composition modifications of animal diets on the muscle
cholesterol content (Bohac & Rhee, 1988). The low correlation
found between marbling score and cholesterol content suggests that
a large proportion of the cholesterol is present in structural lipids
(Rhee et al., 1982).
The objectives of the present study were to determine the effects
of grass or grain diets on the intramuscular fat and cholesterol contents
and in the fatty acid composition of Longissimus muscles from
Angus steers.
Materials
and Methods
Sixty-four steers Angus, at an average live-weight of 360 kg, were
assigned to two dietary treatments (32 steers each). one group was
placed on a mixed pasture and the other was fed with sorghum grain
and corn silage ad-libitum. At similar level of finishing appraised
by experts the steers were slaughtered. The steers were graded in
fat degree 1 or 2 (FD1 or FD2) according to Argentine National Meat
Board standard regulations. Samples of Longissimus muscle at
10-12th ribs were obtained, the lean tissue was finely chopped and
aliquot samples were dried and extracted with hexane during 16 h to
determine the weight of chemical fat or extracted with the Folch et
al.(1957) method for fatty acid analysis. Aliquot samples from the
chloroform extract were saponified and used for total cholesterol
determinations with an enzymatic-calorimetric method ( Roschlan et
al., 1975).
The data were analyzed using the "Lineal General Program" (SYSTAT
1987) with intramuscular fat percentages as principal fixed effect
and carcass weight as lineal covariate, and cholesterol mg% as principal
fixed effect and intramuscular fat percentage as lineal covariate.
Results
and Discussion
Some carcass traits are summarized in Table 1. The grass-fed steers
were fatter (p <.05) than the grain fed ones according to the subcutaneous
fat thickness and the percentage of steers classified as FD 2. The
percentages of intramuscular fat were higher in the grain-fed LD than
in the grass-fed (p < 0.05) (Table 2). This results were similar
to the findings of Marmer et al. ( 1984) and Crouse et al .(1984)
and shows the dietary effects on the intramuscular fat deposition.
The intramuscular fat % were lower than the values for LD. The cholesterol
content in the grass-fed LD muscles were lower than in the grain-fed
LD muscle (p < 0.05) (Table 2). Rhee et al. (1982) found no significant
differences in cholesterol content in raw steaks with different amounts
of marbling except that steaks with "Practically devoided" marbling
contained significantly less cholesterol than did steaks with any
other marbling scores. Tu et al .(1967) indicated that the total cholesterol
content of muscle increases very little as the percent lipid value
arose. The cholesterol content in muscle is lower than in intermuscular
or subcutaneous fats (Rhee et al., 1982) then total cholesterol intake
from beef may be reduced by trimming off the separable fat. The fatty
acid composition from total LD lipids in grass and grain-fed steers
is presented in Fig. 1. Significant differences were detected only
for 15:0, 17:1, 18:3 and 20:3. Marmer et al. (1984) and Larick &
Turner (1989) found similar results. Rumsey et al.(1972) show that
cattle fed forage diets have more saturated fatty acid in their fat
than cattle fed a concentrate diet. In our case, 14:0 and 16:0 decrease
but 18:0 increases in grass-fed compared to grain-fed. It can be seen
that a small but significant difference in n-3 fatty acids between
grass and grain-fed steers was detected. In grass-fed steers the diet
contain high amounts of linolenic acid (n-3). Though most linolenic
acid is partly or completely hydrogenated a small amount escapes hydrogenation
and is absorbed and converted to n-3 PUFA. In contrast in grain-fed
steers the seed's lipids contain mainly linolenic acid (n-6) and there
is a very low intake of n-3 PUFA. In Fig. 2 are presented the total
saturated, monounsaturated and PUFA fatty acids and the n-6/n-3 relation
in grain and grass steer Longissimus lipids.
Conclusions
Dietary energy affects the intramuscular fat (marbling) and cholesterol
of steer Longissimus muscles. Longissimus for grass
fed steers have less intramuscular and cholesterol than grain fed
steers. The Longissimus lipids from grass fed steers have higher
levels of PUFA and a lower relation n-6/n-3 than the grain ones.
Table 1. Some characteristics of the steers.
|
| |
Grain |
Grass |
| n |
32 |
32 |
| Live
weight, kg |
| Initial |
360 |
360 |
| Final |
436 |
465 |
| Gain, g/day |
.65 |
.59 |
| Fat
thickness |
| 12th rib, cm |
.76 |
.92 |
| Fat degree 1, (%) |
31 |
22 |
| Fat degree 2, (%) |
69 |
78 |
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Table 2. Total intramuscular fat and cholesterol
in LD muscle. Mean and SD
| |
Grain |
Grass |
| IMF |
3.9 + / - 1.1 |
2.9 + / - 0.9* |
| Cholesterol
mg % |
72.2 + / -13.7 |
66.6 + / - 8.8* |
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* p < .05
References
BOHAC C. E., RHEE K. S., 1988. Influence of
animal diet and muscle location on cholesterol content of beef and
pork muscles. Meat Sci. 23, 71-75.
BROWN H. J., MELTON S. L., RIEMANN H. J., BACKUS W. R., 1979. Effects
of energy intake and feed source on chemical changes and flavor of
ground beef during frozen storage. J. Ani. Sci. 48, 338-342.
CROUSE J.D., CROSS H. R., SEIDEMAN J., 1984. Effects of a grass or
grain diet on the quality of three beef muscles. J. Ani. Sci. 58,
619-625.
FOLCH J., LEES H., STANLEY G. H. S., 1957. A simple method for the
isolation and purification of total lipids from animal tissues. J.
Biol. Chem. 226, 497-509.
LARICK D. K., TURNER B.E., 1989. Influence of finishing diet on the
phospholipid composition and fatty acid profile of individual phospholipids
in lean muscle of beef cattle. J. Ani. Sci. 67,2282-2293.
MARMER W. N., MAXWELL R. J., WILLIAMS E. J., 1984. Effects of dietary
regime and tissue site on bovine fatty acid profiles. J. Ani. Sci.,
59, 109-121..
RHEE K. S., DUTSON T. R., SMITH G. C., 1982. Effect of changes in
intramuscular and subcutaneous fat levels on cholesterol content of
raw and cocked beef steaks. J. Food Sci. 47, 1638-1642.
ROSCHLAN P., BERNARD E. and GRUBER W., 1975. 9th Int. Congress on
Clin. Chem. Toronto. Abstr. No 1.
RUMSEY T. S.. OLTJEN R. R., Bovard K. P., Priode B. H., 1972. Influence
of widely diverse finishing regimens and breeding on depot fat composition
in beef cattle. J. Ani. Sci. 35, 1069-1074.
TU C., POWRIE W. D., FENNEMA 0., 1967. Free and esterified cholesterol
content of animal muscles and meat products. J. Food Sci. 32, 30-34.
38th ICoMST Clermont-Ferrand France 1992 pag.53 - 56
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