Effect of glycerol in combination with alfalfa on in vitro gas production and microbial protein synthesis

Abstract

Alfonso-Á vila, Á . R., Charbonneau, E., Lafrenie`re, C. and Berthiaume, R. 2015. Effect of glycerol in combination with alfalfa on in vitro gas production and microbial protein synthesis. Can. J. Anim. Sci. 95: 577Á588. This study sought to determine the effect of added glycerol on microbial protein synthesis, ruminal degradation and utilization of alfalfa at different concentrations of nonstructural carbohydrates (NSC), using in vitro gas production. The 2 )3 factorial plus one treatment consisted of oven-dried alfalfa with two NSC levels [high: 17.9 (HNSC) or low: 7.4% dry matter (DM) (LNSC)] and three glycerol treatments [control without glycerol, 15% crude glycerol (CG) and 15% pure glycerol (PG)], the additional treatment was LNSC'exogenous sugars (LNSC'ES: LNSC with 5% sucrose'5% starch). Five pre-planned contrasts were evaluated from the seven treatments: (1) HNSC vs. LNSC alfalfa; (2) with glycerol vs. without; (3) interaction of alfalfa and glycerol; (4) CG vs. PG, and; (5) LNSC'ES vs. HNSC. Gas production over 24 h was higher for HNSC than LNSC (202 vs. 179 mL g(1 DM) and with glycerol than without glycerol (202.2 vs. 168 mL g (1 DM). A decrease in the acetate:propionate ratio was observed for HNSC compared with LNSC (2.87 vs. 3.27) and for the addition of glycerol vs. no glycerol (2.78 vs. 3.65). Reduced microbial mass (185.5 vs. 240.5 mg g(1 DM) was observed for CG compared with PG. The LNSC'ES treatment had lower microbial protein synthesis and propionic acid production in relation to HNSC. No significant interaction was observed between the effect of NSC content of alfalfa and glycerol utilization. When effects were studied separately, results indicate that increasing NSC in alfalfa stimulates the synthesis of microbial protein. Also, the addition of glycerol promotes the synthesis of glucose precursors. Finally, the type of glycerol has an impact on results obtained suggesting caution when extrapolating results for PG to CG.

Kinetics of thermal decomposition processes and kinetics of degradation in rumen liquor of glycerin derived from biodiesel production

“…Results from an in vitro study reported that growth of ruminal bacteria can be negatively affected by unsaturated fatty acids, although sensitivity differs among species (Maia et al, 2007). Contrary, Alfonso-Ávila et al (2015) studied effect of two types of glycerin (pure and crude) in combination with alfalfa on in vitro digestibility and observed in vitro digestibility of dry matter and organic matter were higher with crude glycerin compared with pure glycerin.…”

“…Besides, Abo El-Nor et al (2010) on in vitro studies observed an inhibitory cellulolytic effect of crude glycerol and pure glycerol. Recently, Alfonso-Ávila et al (2015) studied effect of two types of glycerol (pure and crude) in combination with alfalfa on in vitro gas production and reported that the type of glycerol added can impact rumen fermentation and observed in vitro digestibility was higher with crude glycerin compared with pure glicerin. They concluded that the addition of crude glycerol (87.35% glycerol) had a negative impact on microbial protein yield and tended to produce more methane than pure glycerol (99.5% glycerol).…”