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 a ssess the fermentability of urea treated and untreated finger millet s traw to which various levels of concentrate (maize/wheat bran/groundnu t cake 35:32:30) had been added. Data obtained from this technique wer e compared with in-vitro digestibility data obtained earlier on the sa me feeds. Similar trends for the effect of supplementation on digestib ility were observed in both in-vitro and in-vivo measurements. Linear correlation equations were obtained between gas produced and the propo rtion of dry matter disappearing, enabling in-vitro gas production to be expressed in in-vitro digestibilities. A single pool exponential eq uation was fitted to the gas production data enabling estimates to be made of the time when in-vitro digestibilities best matched in-vivo di gestibility 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. S tatistically significant (P < 0.05) interactive effects between supple ment and both treated and untreated straws were observed. The digestib ility of untreated straw was particularly stimulated by small quantiti es of supplement. The digestibility of treated straw was higher than t hat of untreated straw and less stimulated by supplementation. These f indings are consistent with the hypothesis that fibre digestibility ca n be increased by providing a supplement which provides sufficient nut rients to stimulate the activity of rumen micro organisms.