Effect of chitosan on mixed ruminal microorganism fermentation using the rumen simulation technique (Rusitec)

Abstract

The objective of this study was to investigate the effects of chitosan on in vitro fermentation of an alfalfa:concentrate diet (50:50, Dry matter (DM) basis) using the rumen simulation technique (Rusitec). The Rusitec system consisted of eight vessels: two received 1380 mg of chitosan (CHI-H) daily, two received 690 mg of chitosan (CHI-L), two received 16 mg of monensin (MON), and two received no additives (CTR). After an adaptation period, fermentation parameters were determined for 9 days, divided into three sub-periods. At the end of the Rusitec trial, the vessels fluid was used as inoculum and incubation medium for batch cultures (96 h), and the response in rate and extent of gas production for starch, cellulose, and the same diet used in the Rusitec trial was calculated. The apparent DM, organic matter (OM), and crude protein (CP) disappearance was decreased by CHI-H and CHI-L in a dose-dependent manner, but only CHI-H decreased neutral detergent fibre (aNDFom) disappearance. No effects of MON were found in the disappearance of DM, OM, aNDFom, or CP. CHI-H and CHI-L decreased total gas and methane production, but only CHI-H reduced methane production per gram of disappeared DM. MON reduced total gas production, but no effects were observed for methane production or methane per gram of disappeared DM. Only CHI-H decreased fermenter fluid NH 3 concentration. No effects of CHI or MON were found for total volatile fatty acids (VFA), but propionate and valerate were enhanced by CHI-H, CHI-L, and MON. Both CHI treatments increased propionate-to-acetate (C3:C2) ratio, but MON only increased this ratio in the first sub-period. CHI-H and CHI-L reduced branch-chained VFA (BCVFA) in a dose-dependent manner from the second sub-period onward. In the in vitro batch fermentation trial, MON, CHI-H, and CHI-L treatments reduced gas production compared with CTR at sampling times beyond 8 h for the alfalfa:concentrate diet and beyond 24 h for cellulose and starch. CHI-H, CHI-L, and MON reduced asymptotic gas production with the starch substrate. With the cellulose substrate, CHI-H reduced asymptotic gas production, and CHI-H, CHI-L, and MON reduced the gas production rate, but MON reduced it to a greater extent. With the alfalfa:concentrate substrate, CHI-H and CHI-L reduced asymptotic gas production, but MON reduced it to a greater extent. In conclusion, addition of chitosan exerted an effect on some fermentative processes in the rumen, which may improve in vitro energy efficiency, and this effect was maintained over the entire experimental period without any apparent adaptation.