Cobalt In Vitro Rumen Microbial Fermentation

Effect of Cobalt on In Vitro Fermentation by Rumen Microorganisms ABSTRACT In vitro studies were carried out to examine the effect of cobalt on in vitro rumen fermentation by rumen microorganisms obtained from fistulated calves. Six rumen fermenters were divided into six groups. Control group was given a diet consisting of rice straw and concentrate and groups II , 111, N, V and VI, the above diet supplemented with 0.05,0.1,0. 15,0.2 and 0.25mg/kg cobalt,respectively. Cobalt supplementation had no significant effect on rurien PH. The ammonia-N concentration was significantly higher(P<0.05) in group 11,111 and IV as compared to control group. The ammonia-N yield increased by 18.45,14.53 ans 11 .81%(P<0.05) when 0.1,0.15 and 0.2mg/kg cobalt,respectively,was added and incubation lasted 72h. Curval correlation between the ammonia-N yield(Y,mg) after incubation for 72h and the amount of supplemented cobalt(X,mg/kgDM) was Y=-2. 157 IX + 16.299X + 87.99,r=0.95 19, n=3. In vitro digestibility of organic matter(OM) in group N,V and VI increased by 2.79,5.69 and 3.79% respectively(P<0.05). Curval correlation between in vitro digestibility of OM(Y,%) and the amount of supplemented cobalt(X,mg/kgDM) was Y=-0.0454 X2 + 0.7633X + 42.85, r0.9019, n3. Cobalt supplemented with 0.15,0.2 and 0.25mg/kg increased significantly(P<0.05) the total VFA concentration of varying levels of cobalt had no effect on molar proportion of individual VFAs. The relationship between the amount of supplemented cobalt(X,mg/kgDM) and the total VFA concentration(Y,mmolIl) the proportion of acetate,propionate and butyric acid(Y,%) were: Y(TVFA,mmol/l)=-O.7966X2+ 9.8637X + 36.909 r=0.9575 n3 Y (acetate,, %) =O.4537X + 56.217 r0.9784 n=3 Y (propionate, %) -0.101 1X + 0.4532X + 27.29 r0.9480 n=3 Y (butyric acid, %) 0.042 X ?0.5367 X + 2.0784X + 5.1867 r0.9784 n Cobalt supplementation with 0.1,0.1 5,0.2,and 0.25mg/kg increased significantly(P<0.05) the microbial nitrogen yield after incubation for 72h. The highest increase was oberved in the group supplemented with 0.2mg/kg cobalt. The microbial nitrogen yield(Y,g) were correlated to the amount of supplemented cobalt(X,mg/kgDM), and can be fitted into regression model Y=0.024 1 Ln(x) + 0.0771, r=0.9 1 06,n=3.