Effects of dietary non-ionic surfactant and forage to concentrate ratio on bacterial population and fatty acid composition of rumen bacteria and plasma of goats

This study was conducted to investigate effects of alkyl polyglycoside (APG) in diets that varied in forage to concentrate ratio (F:C) on ruminal microbial and plasma fatty acid (FA) composition and bacterial population in goats. A 2 × 2 factorial experiment was arranged within a 4 × 4 Latin square design using four wether goats fitted with permanent ruminal fistulae. Treatments included two levels of dietary F:C (40:60 vs. 60:40, on an air dry basis) and APG (no APG vs. 6.5 g APG per day per animal). Dietary APG inclusion increased the proportion of iso-14:0 (P=0.03), and decreased the proportions of anteiso-17:0 (P=0.04) and monounsaturated fatty acids (MUFA) (P=0.04) in solid associated bacteria (SAB), but had no effect on FA in liquid associated bacteria (LAB) or in plasma. In addition, APG decreased (P<0.05) the Ruminococcus albus population. The major effects of APG were independent of F:C ratio. High dietary F:C decreased the proportions of 17:0 (P=0.01) and 9c12c18:2 (P=0.05) in LAB, decreased iso-13:0 (P=0.04) in SAB and 9c12c18:2 (P=0.05) in plasma, increased the proportions of anteiso-13:0 (P=0.04) in LAB, and 17:0 (P=0.0003) and 9c18:1 (P=0.03) in plasma, but had no effect on the ruminal bacterial population. These results indicate that, in both low and high F:C diets, dietary APG alter the FA composition of ruminal bacteria, which further imply a change in function and survival of rumen bacteria.