The utilization of dietary fats by ruminants:II. The effect of fatty acid chain length and unsaturation on digestibility

Abstract

The effect of fatty acid chain length and unsaturation on digestibility in sheep were examined using partially purified samples of lauric, myristic, palmitic, stearic, oleic and linoleic acids. The digestibility of the fatty acids was relatively constant with only a very slight decrease on increasing chain length. There was an extensive hydrogenation of the unsaturated fatty acids.The corrected digestibility coefficients for lauric acid was 91%, myristic 86%, palmitic 87 % and stearic acid 81-83 % whereas the corrected digestibility coefficients for oleic and linoleic acids were calculated at 87 and 93 % respectively. The digestibility coefficients for the saturated fatty acids are higher than similar estimates that have been reported for non-ruminants. It is suggested that the ruminant is better able to utilize saturated fatty acids than the non-ruminant.The efficient formulation of high energy diets containing fat for ruminant animals presupposes a knowledge of the relative merits of different types of fatty materials. Since fats in a diet serve essentially as sources of energy, a quantitative evaluation of fats in this respect can be made in terms of units of digestible energy.It was reported by Andrews & Lewis, 1970, that beef tallow, HEF, herring oil, soyabean and maize oil were well digested by sheep, and furthermore that corrected digestibility coefficients for these products covered a relatively narrow range. This is in marked contrast to the situation with respect to non-ruminant animals in which plant and marine oils have an appreciably higher digestibility than fats of animal origin, and suggests that those factors which are instrumental in determining the digestibility of a fat by such species are of less significance in the ruminant. One important factor in this respect is fatty acid chainlength. Studies with nonruminants have clearly demonstrated that the digestibility of a fat decreases as the mean molecular weight of its component fatty acids increases.In respect of unsaturation, it is now well established that the predominant factors affecting the digestibility of a fat by non-ruminant animals include the degree of unsaturation of the fat and its content of unesterified fatty acids. Since dietary fats ingested by these species arrive in the small * Present address:

Effect of lecithins partly replacing rumen-protected fat on fatty acid digestion and composition of cow milk

“…The first assumption is more likely, because total C18 fatty acid digestibility was numerically highest with raw conola lecithin, but C18:0 digestibility was not extraordinarily low at the same time. In general, the apparent total tract digestibility of total C18 fatty acids exceeded total fatty acid digestibility and corresponded in level with results of other experiments [26].…”

“…For C18:0 a negative apparent digestibility coefficient was found which is typical when significant amounts of unsaturated C18 fatty acids and low amounts of C18:0 are fed because the unsaturated C18 fatty acids are transformed to C18:0 to a large extent by biohydrogenation in the rumen [26]. Due to partial C18:1 hydrogenation in the rumen [20] also with Ca soaps the apparent digestibility of the C18 fatty acids is affected [27], but the slightly less negative C18:0 digestibility in control nevertheless indicates a better rumen-protection of the Ca fatty acids [28] as of the fatty acids in the other lipids used.…”

Effect of full-fat hemp seed on performance and tissue fatty acids of feedlot cattle

“…Inconsistencies in the response to added lipid are particularly perplexing when DMI is not affected. Although fats have more than twice the energy content of the carbohydrates they typically displace, digestibility and utilization may be moderately influenced by chain length and degree of saturation (Andrews and Lewis 1970). As well, long-chain polyunsaturated fatty acids (PUFA) are potentially toxic to ruminal microbes, particularly protozoa and cellulolytic bacteria (Palmquist and Jenkins 1980), contributing to a reduction in microbial activity and subsequent digestion.…”

The utilization of dietary fats by ruminants:I. The digestibility of some commercially available fats

“…In the first instance a procedure has been developed for the examination of dietary and faecal lipids which made possible the estimation of the digestibility coefficients of some commercially available fats; and secondly (Andrews & Lewis, 1970) a study was made of the effect of fatty acid chain length and unsaturation on digestibility.…”