USE OF IN-VITRO GAS-PRODUCTION TO EVALUATE RUMEN FERMENTATION OF UNTREATED AND UREA-TREATED FINGER MILLET STRAW (ELEUSINE-CORACANA) SUPPLEMENTED WITH DIFFERENT LEVELS OF CONCENTRATE

Measurement of gas produced during in-vitro fermentation was used to assess the fermentability of urea treated and untreated finger millet straw to which various levels of concentrate (maize/wheat bran/groundnut cake 35:32:30) had been added. Data obtained from this technique were compared with in-vitro digestibility data obtained earlier on the same feeds. Similar trends for the effect of supplementation on digestibility were observed in both in-vitro and in-vivo measurements. Linear correlation equations were obtained between gas produced and the proportion of dry matter disappearing, enabling in-vitro gas production to be expressed in in-vitro digestibilities. A single pool exponential equation was fitted to the gas production data enabling estimates to be made of the time when in-vitro digestibilities best matched in-vivo digestibility data. These times were 45.8 and 47.9 h of untreated straw, 43.5 and 61.0 h for treated straw for trials 1 and 2, respectively. Statistically significant (P < 0.05) interactive effects between supplement and both treated and untreated straws were observed. The digestibility of untreated straw was particularly stimulated by small quantities of supplement. The digestibility of treated straw was higher than that of untreated straw and less stimulated by supplementation. These findings are consistent with the hypothesis that fibre digestibility can be increased by providing a supplement which provides sufficient nutrients to stimulate the activity of rumen micro organisms.