The effects of feeding level and roughage/concentrate ratio on the measurement of protein degradability of two tropical forages in the rumen of goats, using the nylon bag technique

Experiments were conducted with rumen fistulated goats to measure the effect of level of feeding (50, 100 and 150% of maintenance) and roughage/concentrate ratio on the rumen degradability of protein from the forages green panic (Panicum maximum Jacq. var. trichoglume Eyles) and phasey bean (Macroptilium lathyroides (L.) Urb.), using the nylon bag technique. For both forages, a high level of feed intake caused a significant reduction in protein degradability compared with that for a low level of intake. Protein degradability was higher when incubated in the rumen of goats receiving alfalfa haycubes as a sole diet than when the goats received alfalfa haycubes and a concentrate mixture. The decrease in degradability of forage protein was associated with reduction in pH of the rumen fluid. Rumen degradability of the protein of green panic was much lower than that of the phasey bean at an early stage of incubation (6-12 h incubation). There was a high positive correlation between protein degradability and dry matter disappearance in the rumen (r = 0.996).