Effects of Encapsulated Enzyme and Yeast Products on in Vitro Rumen Fermentation

Batch cultures of mixed rumen micro-organisms were conducted to evaluate the effects of encapsulated yeast （+EY） and encapsulated enzyme （+EE） using plant proteins （barley and oats grain） on rumen fermentation in vitro,investigate the abilities of encapsulated yeast and encapsulated enzyme to prevent rumen digestion in vitro.Treatments of the study were the control,+EY,+EE products (3.33 mg·mL^-1 of the incubation medium),unencapsulated yeast （-EY） and enzyme （-EE） products (0.17 and0.17 μL·mL^-1 of the incubation medium,respectively).+EY group increased dry matter disappearance （DMD,P＜0.01） and the total volatile fatty acids （TVFA,P＜0.01） at 3 h of the incubation compared with the control,regardless of encapsulation of yeast.Gas production （GP） of +EY group was higher (P=0.05,29.94 mL·mL^-1 organic matter,OM) than that of the control (25.08 mL·g^-1 OM) at 3 h of the incubation.Supplementation +EY increased DMD （P=0.04,0.394 vs 0.352,respectively） and acetic proportion (P=0.04,52.6 vs 49.8 mol·100 mL^-1,respectively) at 6 h of the incubation and increased A:P ratio （P＜0.01,3.11 and 2.86,respectively） at 24 h of the incubation,as compared to unencapsulation of yeast.Supplementation of enzyme had higher （P≤0.04） GP,DMD and TVFA at 3 and 6 h of the incubation compared with the control,regardless of encapsulation.Moreover,the addition of +EE produced greater GP at 6 (P＜0.01,92.35 vs 78.21 mL·g^-1 OM,respectively),12 (218.47 vs 159.18 mL·g^-1 OM) and 24 h (380.97 vs 297.78 mL·g^-1 OM,respectively) of the incubation,higher DMD （0.347 vs 0.313,respectively） at 3 h of the incubation as compared to-EE group.The study showed that the encapsulation might protect part of yeast and enzyme from releasing to the rumen throughout the digestion in vitro,resulting in higher or no difference of rumen fermentation parameters compared with unencapsulated groups at any incubation times.In comparison with-EY and-EE,the higher rumen fermentation parameters at the early incubation time were observed,which could be attributed to the higher concentration of yeast or enzyme.However,regardless of the encapsulation,the results indicated that both yeast and enzyme only improved the speed rather than the extent of rumen fermentation in vitro.