Interaction of lipid supply and carbohydrates in the diet of sheep with digestibility and ruminal digestion

Abstract

SUMMARYTwo groups of nine wethers, three of which were fitted with rumen cannulas, were used in a digestion trial at the INRA centre in Theix, France, in 1988. Group 1 received 65% maize silage and 35% concentrates; group 2 received 65% hay and 35% concentrates. Concentrates were based on either cereals rich in starch, or by-products rich in fibre and were given either alone or supplemented with lipids as calcium soaps. The fatty acid content of lipid-supplemented diets wasc.9·5 and 8·5% of dry matter, of which 85 and 89% was provided by calcium soaps, for maize silage and hay diets, respectively. For each group, the four diets were tested in four successive periods from January to June 1988.Total digestibility of dry and organic matter, acid detergent fibre (ADF) and neutral detergent fibre (NDF) was measured in six wethers of each group by total faeces collection. On cannulated wethers, volatile fatty acid content and composition, pH and NH3-N in rumen liquor were determined four times a day;in saccodegradability of dry matter, ADF and NDF of the forage eaten by the wethers was estimated by the kinetics of incubation in the rumen.In vivoandin saccoresults showed that dry matter and organic matter digestibilities were not modified by the nature of concentrates. Cell wall digestibility was higher for fibre concentrates than for starchy concentrates, by 4·1 and 6·2 percentage units for NDF in maize silage and hay groups, respectively. Volatile fatty acids (VFA) and ammonia concentrations were higher and pH was lower with the maize silage than with the hay diet.Lipid supply slightly increased cell wall digestibility in the group fed maize silage by 7·5 and 2·0 percentage units for starch and fibre concentrates, respectively. This surprising increase was related to an improvement inin saccodegradability. In all diets, lipid supply increased pH, but variations in VFA concentration and pattern were low. Interactions between the nature of concentrate and lipid supply were moderate, but were higher in the group fed maize silage than in the group fed hay, especially for total digestibility.

Microbial protein net synthesis in sheep fed hay-concentrate diets supplemented with different source and level of fat

“…Also Tackett et al (1996) suggested that the type of fibre influenced the degree of negative effects caused by ruminally active fats. Elmeddah et al (1991) did not demonstrate a significant interaction between the nature of the diet and fat. According to Elliot et al (1995) replacement of NSC with supplemental fat decreases the amount of energy that is available for growth of ruminal microorganisms and may decrease microbial protein synthesis.…”

Effects of ruminal or postruminal fish oil supplementation on intake and digestion in dairy cows

“…Generally, the addition of lipids to ruminant diets decreases DM and especially cell-wall digestibility, or does not modify them (Palmquist and Jenkins, 1980;Jenkins, 1993). In some cases, slight increases in digestibility have been observed with different lipid supplements (Mir, 1988;Elmeddah et al, 1991). With hydrogenated fish oil, DM and/or fibre digestibility was either depressed (Sundstol, 1974) or unmodified (Doreau, 1992 No comprehensive explanation can be proposed to understand the variation in digestibility observed in our trials.…”

The Rumen Microbial Ecosystem

“…The effects of fat on ruminal pH and VFA concentration are generally minor (Hatch et al, 1972;Czerkawski, 1973;Chalupa et aI., 1984Chalupa et aI., , 1986Broudiscou et al, 1990b;Elmeddah et al, 1991;Grummer et al, 1993;Pantoja et al, 1995). The effects of fat on ruminal pH and VFA concentration are generally minor (Hatch et al, 1972;Czerkawski, 1973;Chalupa et aI., 1984Chalupa et aI., , 1986Broudiscou et al, 1990b;Elmeddah et al, 1991;Grummer et al, 1993;Pantoja et al, 1995).…”