The composition, structure and function of lipids in the tissues of ruminant animals.

Digestion, absorption and transport of lipids in ruminant animals.

Section A. Physiology. Ruminant metabolism in relation to the synthesis and secretion of milk fat

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This chapter discusses the composition, structure, and function of lipids in the tissues of ruminant animals. The lipid components of ruminant tissues are similar in nature to those of nonruminants, although there are important differences in the proportions of individual lipids in specific tissues. The fatty-acid components of tissues from ruminants certainly differ markedly in composition from those of nonruminants. The complex metabolic origin is from hydrogenation or partial-hydrogenation of dietary fatty acids in the rumen, by synthesis de novo by rumen bacteria or within the animal itself, by oxidation of other dietary components, and by modification of absorbed fatty acids by α- or β-oxidation, by desaturation, or by chain elongation. As a result, the fatty acids of ruminant tissues are characterized by comparatively high concentrations of odd-chain and branched-chain fatty acids and of positional and configurational isomers of mono- and diunsaturated fatty acids, and, at the same time, by comparatively low concentrations of polyunsaturated fatty acids.

The composition, structure and function of lipids in the tissues of ruminant animals

The effect of age on the fatty acid composition of depot fat of Jersey cattle has been investigated. Serial samples of subcutaneous fat were obtained by biopsy of the same animals from 3 months to 2 years of age. Samples of depot fat were also obtained from various anatomical locations of animals slaughtered between birth and 11 years of age.In subcutaneous fat at biopsy the percentage stearic acid remained constant to 1 year of age and then declined from 20% to 5% during the period 1–2 years post partum.In perinephric fat the stearic acid content increased from 10–15% at birth to 40% at 1 year of age, and then declined during the period 1–2 years post partum.Changes in the percentage stearic acid above the 10% level were accompanied by inverse change in octadecenoic (C18:1) acid, and below 10% mainly by change in hexadecenoic (C16:l) acid.There was a gradient of unsaturation between subcutaneous and internal body fats, and also within the subcutaneous fat itself.Evidence is presented to suggest that the decrease in the unsaturation of depot fat during the period 1–2 years post partum is associated with the deposition of more unsaturated fatty acids during the fattening phase of development.

Fatty acid composition of adipose tissue of Jersey cattle during growth and development

SUMMARY Samples of prefemoral, thoracic and intestinal duct lymph have been collected under acute conditions from three cows grazing pasture and the lipid composition compared with that of plasma. The concentration of lipids in peripheral lymph was 16–36% of that found in plasma; the fatty acid compositions of peripheral lymph lipids were similar to those of plasma. Of the fatty acids present in intestinal and thoracic lymph 86 and 76% were esterified as triglycerides, 10 and 13% as phospholipids and 3 and 5% as cholesterol esters, respectively. Saturated and mono-unsaturated fatty acids were preferentially esterified as triglycerides whereas di- and tri-unsaturated acids were associated more with phospholipids. The content of di- and tri-unsaturated fatty acids was greater in the triglycerides and phospholipids derived from the intestine than in those found in plasma. The di- and tri-unsaturated fatty acids in intestinal and thoracic lymph were transported mainly in the form of triglycerides (45–62%) and phospholipids (21–33%). Cholesterol esters were quantitatively of minor importance in the transport of these fatty acids in lymph. The intestine does not appear to play any major role in the formation of the high concentration of cholesterol ‘linolenate’ found in bovine plasma. The process of lipid digestion in the cow appears to be similar to that found in sheep.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/ED65E94BAF49C35DE3D4BDA403767E35/S0021859600014635a.pdf/div-class-title-lipid-composition-of-lymph-and-blood-plasma-of-the-cow-div.pdf

W. M. F. Leat

Papers

Lipid composition of lymph and blood plasma of the cow