Digestion of fatty acids in ruminants: a meta-analysis of flows and variation factors. 1. Total fatty acids

Abstract

A database built from 95 experiments with 303 treatments was used to quantify the ruminal biohydrogenation (BH) of fatty acids (FA), efficiency of microbial protein synthesis (EMPS), duodenal flow and intestinal absorption of total FA and of FA with 12 to 18 C units, in response to variations in dietary FA content, source or technological treatment of fat supplement. Flows of FA were expressed relative to dry matter intake (DMI) to compile data from bovine and ovine species. BH tended to increase curvilinearly with FA intake, whereas dietary FA did not affect EMPS. A linear relationship between FA intake and duodenal flow of total FA was obtained, with a coefficient of 0.75 6 0.06 g duodenal FA/kg DMI for each g FA intake/kg DMI. Between experiments, positive balances of total FA (intake -duodenum) were related to low EMPS. Relationships between duodenal flows of FA with 12 to 18 C units and their respective intakes were linear, with a coefficient that increased with the number of C units. Duodenal flow of bacterial FA was linearly related to FA intake (coefficient 0.33 6 0.13), whereas contribution of bacterial lipid to duodenal flow decreased as FA intake increased. For each FA with 12 to 16 C units, prediction of FA absorption from its respective duodenal flow was linear. For total FA and FA with 18 C units, apparent absorption levelled off at high duodenal flows. All these relationships were discussed according to current knowledge on microbial metabolism in the rumen and on the intestinal digestibility of FA in the intestine.

Quantification of the main digestive processes in ruminants: the equations involved in the renewed energy and protein feed evaluation systems

“…The prediction of total FA at the duodenum (FAduo = 46.5 ± 19.7, min = 14.2, max = 101.5 g/kg DM) and apparently digested in the intestines (FADint = 33.7 ± 11.7, min = 13.9, max = 61.3 g/kg DM) are based on equations already published by Schmidely et al (2008). These equations have been derived by meta-analysis Schmidely et al, 2008).…”

“…The prediction of total FA at the duodenum (FAduo = 46.5 ± 19.7, min = 14.2, max = 101.5 g/kg DM) and apparently digested in the intestines (FADint = 33.7 ± 11.7, min = 13.9, max = 61.3 g/kg DM) are based on equations already published by Schmidely et al (2008). These equations have been derived by meta-analysis Schmidely et al, 2008). The database used concerned digestion trials where intake, duodenal and fecal flows of FA were measured in experiments where dietary FA ( = 44.5 ± 20.5, min = 9.1, max = 99.4 g/kg DM) was an experimental factor.…”

Impacts of feeding lipid supplements high in palmitic acid or stearic acid on performance of lactating dairy cows

“…Decreases in lipid digestion when lipid intake increased were associated with a decrease in the digestibility of saturated FA (Wu et al 1991;Pantoja et al 1996aPantoja et al , 1996b. Recently, Schmidely et al (2008) did an exhaustive meta-analysis of FA digestion. In their appendix 1 table that describes the database input variables, apparent intestinal digestibility in dairy cows was 746 and 734 g kg -1 for C16:0 and C18:0, respectively, while for the overall data set that included sheep and growing cattle apparent intestinal digestibility was 767 and 754 g kg -1 for C16:0 and C18:0, respectively.…”

“…However, there are concerns with respect to digestibility of the medium-and long-chain FA by lactating cows related to carbon chain length and saturation (Doreau & Ferlay 1994;Pantoja et al 1996b;Dohme et al 2004;Glasser et al 2008;Schmidely et al 2008) that are associated with rumen inert fats. Even with more common feed fats, for example tallow and yellow grease, there was decreased postruminal digestibility of FA in particular saturated FA (Avila et al 2000).…”

Meta-analyses of experimental data in animal nutrition

“…For example, alteration in feeding practices impact feed efficiency, product quality, the environment, animal welfare, etc., and significant progress can be made in this type of holistic research using meta-analyses. There are numerous examples of such applications of meta-analytical methods in recent nutrition publications, such as the quantification of the physiological response of ruminants to types of dietary starch (Offner and Sauvant, 2004), to the supply of dietary N (Rico-Gomez and Faverdin, 2001), to dietary fats (Schmidely et al, 2008) and rumen defaunation (Eugè ne et al, 2004). Others have used meta-analyses to quantify phosphorus flux in ruminants (Bravo et al, 2003) estimates of initial conditions of state variables.…”