Digestibility of pelleted rations containing diverse potato flour and urea

The aim of this study was to evaluate ruminal in situ degradability and in vitro digestibility of dry matter (DM) in concentrate supplements containing diverse potato flour pelletized with urea (0%, 4%, 8%, and 12% DM). Samples of feeds were incubated for 0, 2, 4, 8, 12, 24, 36, and 48h in the rumen of four fistulated sheep. Level of urea added had no significant effect (P>;0.05) on the soluble fraction (a) or potentially degradable fraction (b) of the pellets and ranged from 2.1% to 12.2% and 72.9% to 87.5%, respectively. Quadratic effects (P=0.03) of the rate of degradation of fraction "b" ranged from 4.75% h-1to 7.39% h-1; the estimated maximum value at 7.4% h-1was obtained when 5.9% urea was added to the pellet. Quadratic effects (P≤0.02) of the level of urea added to the pellets on the effective degradability (ED) of DM were evaluated after considering rumen passage rates of 2.5% h-1and 8% h-1; the maximum values of ED calculated under these rumen passage rates were estimated at 6.3% to 7.3% urea in the pellets. The in vitro digestibility of DM of the pellets showed a quadratic effect (P=0.02) at different levels of urea, with a maximum value of 96.9% achieved when 7.9% urea was added to the pellets. Our results suggest that the addition of 6-8% urea to pelleted feed promotes an increase in the in vitro digestibility and ED of DM.