Effects of degree of fat saturation on fiber digestion and microbial protein synthesis when diets are fed twelve times daily.

Abstract

Three Holstein heifers and one nonlactating cow, fitted with ruminal and duodenal cannulas, were arranged in a 4 x 4 Latin square design to determine the effects of degree of fat saturation on ruminal neutral detergent fiber digestion and microbial protein synthesis and to determine whether changes in the efficiency of microbial protein synthesis were related to protozoal populations in the rumen. Corn silage-based diets contained no added fat or 4.85% of diet dry matter as partially hydrogenated tallow, tallow, or animal-vegetable fat. Iodine values of fat sources were 12.8, 50.6, and 109.7 for partially hydrogenated tallow, tallow, and animal-vegetable fat, respectively. Cattle were fed every 2 h and consumed 1.5% of body weight as dry matter daily. Ruminal neutral detergent fiber digestibility was decreased by added fat but was not affected by increasing iodine value. Flows of microbial N and non-NH3-nonmicrobial N to the duodenum were not affected by treatment. Ruminal protozoa concentration decreased linearly as the iodine value of fats increased. The efficiency of microbial protein synthesis was increased and protozoa concentrations tended to decrease when fat was fed. Decreased ruminal protozoa concentration may have decreased intraruminal N recycling. Biohydrogenation of added fat may result in a low ruminal concentration of unsaturated fatty acids when cows are fed frequently, reducing the negative effects of unsaturated fat sources on ruminal neutral detergent fiber digestibility. Protozoa were inhibited by unsaturated fat, but it is not clear if biohydrogenation and frequent feeding lessened inhibition.

Soybean oil and linseed oil supplementation affect profiles of ruminal microorganisms in dairy cows

“…Another study showed that oleic acid at 0.25%, 0.5% and 1% decreased protozoal counts by 26%, 45% and 78%, respectively (Hristov et al, 2004). Further, Oldick and Firkins (2000) observed a linear decrease in ruminal protozoa with increasing degree of Cows were fed a basal diet (C) or basal diet supplemented with either 4.0% soybean oil (S), 4.0% linseed oil (L) or 2.0% soybean oil 1 2.0% linseed oil (SL).…”

“…two unsaturated double bonds (linoleic acid) v. three double bonds (linolenic acid). Oldick and Firkins (2000) observed a linear decrease in ruminal protozoa with an increasing degree of unsaturation of dietary fats when diets (48.5% maize silage and 51.5% concentrate) added 4.85% fat from prills of partially hydrogenated tallow, tallow or animal-vegetable fat.…”

“…Unsaturated fatty acids have been reported to have direct inhibitory effects on ruminal protozoa (Oldick and Firkins, 2000). Linoleic acid is toxic to ruminal protozoa and previous research has shown a consistent decrease in protozoal counts in vivo (Sutton et al, 1983;Hristov et al, 2004) and in vitro (Newbold and Chamberlain, 1988).…”

“…Linolenic acid was more toxic than linoleic acid, whereas eicosapentaenoic acid and docosahexaenoic acid were more toxic than linolenic acid. Although a few studies have examined the negative effect of unsaturated fatty acids on some ruminal microbiota (Ferlay et al, 1993;Oldick and Firkins, 2000), none has evaluated relative changes in the profiles of ruminal microbiota in response to dietary PUFA. Thus, the main objective of this study was to determine the effect of SBO and LSO supplementation of a high-forage diet (60% forage) on profiles of ruminal microorganisms.…”

Effects of increasing dietary concentrations of fish oil on lamb performance, ruminal fermentation, and leptin gene expression in perirenal fat

“…Marinova et al (2007) suggested that changes in propionate and acetate are related to the depression of acetate-producing bacteria, which are inhibited by polyunsaturated fatty acids. However, in high-grain diets, these bacteria do not grow (Russell et al, 2009); therefore, the changes in propionate and acetate could be related to effects on the rumen protozoa, because polyunsaturated fatty acids are also toxic to rumen protozoa (Oldick and Firkins, 2000). The microbial defaunation by high-grain diets have similar effects on the fermentation pattern (Mendoza et al, 1993).…”