Comparison of fresh and dried Digitaria decumbens grass intake and digestion by Black-belly rams

The intake and digestion of fresh and dried Digitaria decumbens grass by ra ms was compared using a 2 x 2 factorial design. The experiment took place i n Guadeloupe (French West Indies) in 1996. Eight rams (mean liveweight: 45. 7 +/- 3.1 kg) were maintained in metabolism cages. Digitaria decumbens gras s was cut daily and distributed to four of them, the other four were fed th e following day with the equivalent forage which had meanwhile been dried f or 20 h at 60 degrees C. Chemical composition (g/kg of dry matter (DM)) of the two diets based on neutral detergent fibre (NDF, 713, S.E. 18), acid de tergent fibre (ADF, 361, s.E. 13) and crude protein (CP, 90, s.E. 4) was si milar. The DM intake (61.0 and 53.2 g/W-0.75, S.E. 2.0, P < 0.05), th, NDF (0.753 and 0.727, S.E. 0.004, P < 0.011) and CP (0.588 and 0.544, s.E. 0.01 4, P < 0.09) total tract digestibility of fresh and dried herbage were diff erent. Nylon bag estimates of effective DM degradability and fractional deg radation rates (per h) in the rumen were 0.436, 0.414 (s.E. 0.005, P < 0.00 5) and 0.048, 0.038 (s.E. 0.002, P < 0.02) for fresh and dried grass, respe ctively. Rumen digestibility of organic matter and NDF were 0.516, 0.541 (S .E. 0.021) and 0.763, 0.692 (s.E. 0.019), respectively. The rumen turnover rates of particles (per h) were 0.024 and 0.015 (s.E. 0.001, P < 0.05) for fresh and dried forage respectively. The efficiency of microbial protein sy nthesis (g microbial nitrogen/kg organic matter apparently degraded in the rumen) was similar with the two diets: 33.5 and 33.0 (s.E. 3.3, P < 0.9) fo r fresh and dried forage respectively. In conclusion, fresh Digitaria decum bens was nutritionally superior to dried. This is probably due to a faster degradation rate and a lower rumen retention time of the fresh forage.