Animal fats: Recent researches in the fats research laboratory, D.S.I.R., New Zealand

Abstract

The views recorded in the first section of this survey dealing with the relationship between the dietary and depot fats are in some cases based on the results of other investigators. In the second section the work of this Laboratory on the fatty-acid composition of butter fat has been examined in the light of the recent British discoveries on the synthetic activity of the mammary gland. Finally, the work of the Fats Research Laboratory on the isolation from animal fats of trace constituents, particularly the branched-chain fatty acids, is reviewed. I . The efect of dietary fat on the depot fats of animals The fats from animals are from two sources : (a) endogenous or ' synthetic ', made in the animal from dietary carbohydrate,' or from protein,z presumably via ' acetate ' units which are condensed to yield the long-chain fatty acids3 characteristic of natural fats ; (b) exogenous from the dietary fat.The respective contributions of the dietary fat and the ' synthetic ' fat to the depot fat are difficult to assess precisely, but useful information about the exogenous fat may be obtained by feeding diets containing fatty acids not normally found in the ' synthetic ' fat, e.g. deuterofatty acids,4 fatty acids with uneven numbers of carbon atoms,5 conjugated linoleic,s elaidic' or linolenic acid.8The composition of the ' synthetic ' fat may be deduced approximately (a) from feeding animals on ' fat-free ' diets,z (b) from comparisons between the weights of fatty acids in the diet and in the depot lo or ( c ) from the composition of ruminant depot-fat, which appears to consist almost entirely of ' synthetic ' fat.ll The fatty-acid composition of ' synthetic ' fat may be given as : oleic, 17-53 ; palmitic, 27-38 ; stearic, 4-29 ; hexadecenoic (with tetradecenoic), 2-16 ; and myristic (with lauric), 3-5 moles per cent. The traces of C,, diene and of C,,-,, unsaturated acids invariably present probably originate from the dietary fat, though the possibility of some synthesis cannot be excluded.l2 I t would seem that dietary fat has some influence on the nature of the ' synthetic ' fat. For example, rats fed on diets rich in palmitic acid will deposit less than the normal proportions of this acid.13 But the ' synthetic ' fats of pasture-fed rabbits and horses (see Table I) contain a higher-than-normal content of palmitic acid (45.8 and 36.3% respectively, calculated from linolenic acid content). Rats fed on diets with 3 3 % of fat normally deposit fat with 5-8% of hexadecenoic acid,I4 but the proportions of this acid may be increased two or three times by withdrawing fat from the dietZ or possibly by means of a hypothalamic lesion to induce obesity.15The first clear recognition of the role of dietary and of synthetic ' fat in the formation of animal depot-fat appears to be due to Callow.lB In 1935 he expressed the view that the softness and iodine value of fats in different parts of the body of the same animal, or between the same parts of different animals fed on the same diets, were determined by the rate of growth. This...

The occurrence of C13 to C31 branched‐chain fatty acids in the faeces of sheep fed rye grass, and of C12 to C34 normal acids in both the faeces and the rye grass

“…Linolenic acid (1 8 : 3), the predominant fatty acid of common pasture plants, in which it is present as mono-and digalactosyl diglycerides,20, 21 comprised 56.5 % of the total fatty acids in the rye grass lipids, while linoleic acid comprised 11.9 %. This content of linolenic acid in rye grass is in accord with the 62.7 % reported by Shorland,22 and is of the same order as that found in clover-rich pasture (58.90/,) 23 Table 1 contained appreciable proportions of positional and geometrical (trans) isomers produced during biohydrogenation in the rumen.7,14*25 Hartman et 0 1 .~~ reported contents of 12.5% and 9.3% trans acids in the faecal fatty acids from sheep and cows respectively. Of the n-unsaturated fatty acids below C18, in the rye grass only minimal amounts were odd-numbered (15: 1 trace; 17: 1 0.2:4).…”

“…Linolenic acid (1 8 : 3), the predominant fatty acid of common pasture plants, in which it is present as mono-and digalactosyl diglycerides,20, 21 comprised 56.5 % of the total fatty acids in the rye grass lipids, while linoleic acid comprised 11.9 %. This content of linolenic acid in rye grass is in accord with the 62.7 % reported by Shorland,22 and is of the same order as that found in clover-rich pasture (58.90/,)23 and in mixed grasses (61.3"/,24,25 The faecal fatty acids examined in the present work contained only 0.7% linolenic acid and the same amount of linoleic acid. Similar levels of these acids in the faeces of sheep fed pasture were reported by Hartman et aLZ6 who found 0.9 % 18 : 2, and 1.3 % 18 : 3 unconjugated acids.…”

The volatile acids of mutton fat

“…Until the present no antei8o acid with a molecular weight lower than that of 10-methyldodecanoic acid (Hansen, Shorland & Cooke, 1954a) had been shown to occur in animal depot fats. In cow milk, however, all the even-numbered normal volatile acids (C4-C12) are present (Hilditch, 1947), as are a number of oddnumbered normal, is8o, and anteiwo acids of higher molecular weight (Shorland, Gerson & Hansen, 1955a, b;Hansen, Shorland & Cooke, 1954b;Hansen & Shorland, 1951. )…”

Soaking of complete fattening rations high in poor roughage. 4. The effect on deposition and fatty acid composition of bovine fat

“…Differences in unsaturated/saturated ratios were originally thought to be a function of the body temperature differential; the temperature differential, however does not appear to be great enough to warrant these differences (Shorland, 1953). In view of this, the theory regarding growth rate and metabolic acitivity of adipose tissue was postulated (Schoenheimer and Rittenberg, 1935).…”