IN-VITRO RUMEN GAS PRODUCTION VERSUS IN-SITU (IN-VIVO) RUMEN KINETICS OF SORGHUM STOVER

Abstract

Rumen kinetics of urea-treated sorghum s5over was determined using the ill-vitro rumen gas production and the ill-sitn (in-vivo) rumen degradability techniques, with a view to comparing thejr efficiency as tools for predicting nutritive value of roughages. Five, ten
and fifteen-day urea-treated and ensiled sorghum stover samples were rumen-incubated in both methods side by side with untrehted sorghum stover samples. The in-vitvo rumen gas production curves which were typicAlly centripetal in progression, did not however,
statistically differ (P>0,05). In the case of iir-sihi rumen degradability of the sorghum stover treatments, the curves did not only statistically differ (P>0.05), they were curvilinear in progression. The results generally showed a high correlation (P<0.05) between the chemical composition of the sorghum stover samples and their degradability rate constants, C and particulate and outflow rate, K. While the ill-vifro gas technique might have been less precise than the iri-sih rumen technique, it nevertheless proved more effective in establishing that much longer anaerobic urea fermentation may not bestow any significant nutritive advantage on ensiled sbrghum stover. Furthermore, since in-vitro methane (CH4) produced has been found to correspond to stoichiomevric prediction of ill-vivo production, it is practicable to estimate the amount of CH4 produced by sheep under feeding conditions. Also, despite its limitations like higher cost, the invitro gas technique is commercially viable where large samples need to be nutritionally predicted. It would, thus appear that the combination of both iir-vitro and in-sitri (illvivo) dry matter JSinetic elevation of roughages (especially where some have antinutritional compounds), may be the most accomplished way of predicting their nutritive value.