Original article Influence of drastic underfeeding on ruminal digestion in sheep

Abstract — The effect of severe underfeeding on ruminal digestion was studied in sheep. Six wethers fitted with ruminal cannulae were used in a replicated 3 · 3 Latin square design. They received the same hay at three intake levels corresponding to energy maintenance requirements (M), 60 % (0.6 M) and 20 % (0.2 M) of these requirements. Fibre digestibility was higher at 0.2 M than at the other two levels. Ruminal neutral detergent fibre retention time did not vary between M and 0.6 M, but increased at 0.2 M. When intake was low, rumen fill decreased and contents became very liquid. No variation in in situ microbial activity or in enzymatic activities of microbial polysaccharidases or glycosi-dases was observed. Protozoa concentration decreased with intake, but total bacterial mass did not vary when intake decreased. Adherent bacterial mass expressed as a proportion of solid phase was higher at low intake. Volatile fatty acid pattern showed a shift from butyrate towards acetate when intake decreased. It is concluded that (i) changes in digestion are slight between M and 0.6 M, and (ii) microbial activity is not impaired at very low intake level. underfeeding / sheep / digestion / rumen Résumé – Effet d’une très forte sous-alimentation sur la digestion ruminale chez le mouton. Six béliers castrés munis de canules du rumen ont été utilisés dans un double carré latin 3 · 3. Ils ont reç