Effect of a drastic and extended underfeeding on digestion in Barbary ewe

Four adult Barbary ewes fitted with ruminal cannulas were used to evaluate the consequences of a severe feed restriction on digestive processes. Ewes received hay at 100% of energy requirements for 10 weeks, then the same hay at 20% of energy requirements for 12 weeks, followed by a 4-week refeeding period at the first level. Digestion measurements were made at the end of the two sequences at high intake (H1 and H2), and in the 4th (L1), 8th (L2) and 12th (L3) week of the underfeeding period. Underfeeding resulted in a decrease in OM digestibility from 55.9 in H1 to 40.0% on average in the underfeeding period. After refeeding, OM digestibility increased to 62.0% in H2. The low intake level decreased ruminal content, which also was more liquid, and increased solids retention time in the rumen and the total tract (211 in L1 versus 77 h in H1). Contrary to what happens at intake levels higher than maintenance, the increase in solids retention time did not result in an increase in digestibility. Underfeeding did not modify in situ degradability but decreased protozoal (13700, 7000 and 3700 ml−1 in H1, L1 and L3, respectively) and VFA concentration, and increased the proportion of acetate at the expense of butyrate. Further research has to be done in order to improve the knowledge of mechanisms which could explain these digestive disturbances.