Lipid Metabolism in Farm Animals

Vernon, Richard G.; Flint, DJ

doi:10.1079/pns19880046

Cited by 26 publications

(19 citation statements)

References 28 publications

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“…Growth and fattening of meat animals is associated with an increase in fat deposition, first in subcutaneous and later in intramuscular fat [87]. Nürnberg et al [57] studied the intramuscular fatty acid composition in three different cattle breeds (German Holstein, Galloway and Belgian Blue) during growth.…”

Section: Effect Of Fat Levelmentioning

confidence: 99%

“…For cattle and pigs, these have been estimated at moderate positive levels, indicating that reductions in carcass fatness as a result of selection are likely to be accompanied by lower intramuscular fat levels, but still allowing considerable variability in intramuscular fat content independent of carcass fatness. Since fat deposition is determined by de novo fatty acid synthesis and the uptake of exogenous fatty acids [87], it is worthwhile examining the effect of variation in fatness on the meat fatty acid composition within and between breeds. Differences in fat content and fatty acid composition between muscles and muscle types also have to be accounted for.…”

Section: Effect Of Fat Levelmentioning

confidence: 99%

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Meat fatty acid composition as affected by fatness and genetic factors: a review

2004

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-Meat fatty acid composition is influenced by genetic factors, although to a lower extent than dietary factors. The species is the major source of variation in fatty acid composition with ruminant meats being more saturated as a result of biohydrogenation in the rumen compared to the meat of monogastric animals. The level of fatness also has an effect on the meat fatty acid composition. The contents of saturated (SFA) and monounsaturated (MUFA) fatty acids increase faster with increasing fatness than does the content of PUFA, resulting in a decrease in the relative proportion of PUFA and consequently in the polyunsaturated/saturated fatty acids (P/S) ratio. The dilution of phospholipids with triacylglycerols and the distinct differences in fatty acid composition of these fractions explain the decrease in the P/S ratio with increasing fatness. An exponential model was fitted to the literature data for beef and showed a sharply increasing P/S ratio at low levels of intramuscular fat. Lowering the fat level of beef is thus more efficient in increasing the P/S ratio than dietary interventions. For pork, the intramuscular fat level also affects the P/S ratio, but nutrition will have a larger impact. The fat level also influences the n-6/n-3 PUFA ratio, due to the difference of this ratio in polar and neutral lipids. However, these effects are much smaller than the effects that can be achieved by dietary means. Differences in fatty acid composition between breeds and genotypes can be largely explained by differences in fatness. However, after correction for fat level, breed or genotype differences in the MUFA/SFA ratio and in the longer chain C20 and C22 PUFA metabolism have been reported, reflecting the possible genetic differences in fatty acid metabolism. Breed differences in meat conjugated linoleic acid (CLA) content have not yet been reported, but the c9t11CLA content in meat is positively related to the total fat content. Heritabilities and genetic correlations for the proportion of certain fatty acids have been estimated in a few studies, and correspond to the observations at the phenotypic level in relation to the intramuscular fat level. Although there is potential for genetic change, incorporating fatty acid composition as a goal in classical breeding programs does not seem worthwhile at the present. Enzyme activities have been measured in a few studies, but are not able to explain between-animal variation in fatty acid composition. Biochemical and molecular genetic studies should be encouraged to unravel the mechanisms responsible for differences in the metabolism and incorporation of specific fatty acids in meat. Résumé -Influence des facteurs génétiques et de l'état d'engraissement sur la composition en acides gras de la viande. Revue. La composition en acides gras de la viande est affectée par divers facteurs : des facteurs nutritionnels, mais aussi des facteurs génétiques, quoiqu'à un degré moindre. L'espèce animale est également une source de variation importante, c'est même la plus important...

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Section: Effect Of Fat Levelmentioning

confidence: 99%

Section: Effect Of Fat Levelmentioning

confidence: 99%

Meat fatty acid composition as affected by fatness and genetic factors: a review

2004

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“…The following effects have been documented: (a) an inhibition of FA synthesis through inhibition of acetyl-CoA carboxylase in both mammary and adipose tissue (Vernon & Flint, 1988); (b) an inefficient incorporation of PUFA, and particularly of the fish oil C 20 and C 22 FA and the trans-isomers derived from rumen biohydrogenation, into the 1-monoacylglycerols required as acceptors for the newly-synthesized FA (Hansen & Knudsen, 1987); (c) an inefficient incorporation of trans-v. cis-FA into small and large triacylglycerols, not mediated at the level of lipoprotein lipase activity (Gaynor et al 1994); (d) a specific reduction in insulin-dependent amino acid v.…”

Section: Effect Of Dietary Fatmentioning

confidence: 99%

“…However, the ruminant has probably developed other mechanisms for the preferential retention of PUFA. Vernon & Flint (1988) suggested limited oxidation of linoleic acid in ruminants, based on the finding that malonyl-CoA is much more effective in inhibiting carnitine acyltransferase when linoleyl-CoA is the substrate than when palmityl-CoA is the substrate in sheep liver, whereas the converse occurs in rat liver. Nevertheless, because of extensive rumen biohydrogenation, it has been suggested that ruminants can be delicately balanced in respect of their essential FA status (Ashes et al 1995).…”

Section: Preferential Retention Of Polyunsaturated Fatty Acidsmentioning

confidence: 99%

Targets and procedures for altering ruminant meat and milk lipids

Demeyer

Doreau²

1999

Proc. Nutr. Soc.

217

132

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Beef and dairy products suffer from a negative health image, related to the nature of their lipid fraction. Rumen lipid metabolism involves the presence of saturated lipids in ruminant tissues. Lipolysis, fatty acid biohydrogenation and formation of microbial fatty acids in the rumen and their effects on rumen outflow of fatty acids are discussed. Special emphasis is given to the formation of trans-fatty acids and the possibilities of decreasing biohydrogenation. Small differences in intestinal digestibilities of fatty acids are mentioned, followed by a discussion on transfer of absorbed fatty acids into milk and adipose tissue lipids. The preferential retention of polyunsaturated fatty acids as well as the balance between synthesis and incorporation of fatty acids in tissues is described. Dietary means for the modification of milk fat are listed, with special emphasis on the possibilities for enrichment in polyunsaturated fatty acids and the presence of conjugated linoleic acids. A description of the nature and development of fat depots in beef cattle is followed by a discussion of breed, conformation and feed effects on adipose tissue distribution and fatty acid composition. Special emphasis is given to the very lean Belgian Blue double-muscled breed. The review ends with a consideration of the limits to the modification of ruminant fats, involving considerations of consumer acceptance as well as animal welfare and environmental effects.

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“…When reaching the intestine, these FA are usually in the unesterified form. They are absorbed in the duodenum, esterified in the enterocyte, and used in conjunction with phospholipids and cholesterol esters in the assembly of very low-density lipoproteins and chylomicrons that pass into the peripheral blood (Vernon and Flint, 1988). Before esterification, stearic acid (18:0) can be desaturated to oleic acid (cis-9-18:1) within the enterocyte, but only to a limited extent (Bickerstaffe et al, 1972).…”

Section: De Novo Synthesismentioning

confidence: 99%

A Review of the Metabolic Origins of Milk Fatty Acids

et al. 2013

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Milk fat and its fatty acid profile are important determinants of the technological, sensorial, and nutritional properties of milk and dairy products. The two major processes contributing to the presence of fatty acids in ruminant milk are the mammary lipogenesis and the lipid metabolism in the rumen. Among fatty acids, 4:0 to 12:0, almost all 14:0 and about a half of 16:0 in milk fat derive from de novo synthesis within the mammary gland. De novo synthesis utilizes as precursors acetate and butyrate produced through carbohydrates ruminal fermentation and involves acetyl-CoA carboxylase and fatty acid synthetase as key enzymes. The rest of 16:0 and all of the longchain fatty acids derive from mammary uptake of circulating lipoproteins and nonesterified fatty acids that originate from digestive absorption of lipids and body fat mobilization. Further, long-chain fatty acids as well as medium-chain fatty acids entering the mammary gland can be desaturated via Δ-9 desaturase, an enzyme that acts by adding a cis-9-double bond on the fatty acid chain. Moreover, ruminal biohydrogenation of dietary unsaturated fatty acids results in the formation of numerous fatty acids available for incorporation into milk fat. Ruminal biohydrogenation is performed by rumen microbial population as a means of protection against the toxic effects of polyunsaturated fatty acids. Within the rumen microorganisms, bacteria are principally responsible for ruminal biohydrogenation when compared to protozoa and anaerobic fungi.

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Lipid Metabolism in Farm Animals

Cited by 26 publications

References 28 publications

Meat fatty acid composition as affected by fatness and genetic factors: a review

Meat fatty acid composition as affected by fatness and genetic factors: a review

Targets and procedures for altering ruminant meat and milk lipids

A Review of the Metabolic Origins of Milk Fatty Acids

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