Effect of different sources and levels of nitrogen on in situ degradability of sugarcane tops (Saccharum officinarum) in cattle
The research was carried out in Mexico, the objective was determined the amount of nitrogen (N) needed to maximize the M degradability in steers consuming sugarcane tops (SCT) (Saccharum officinarum). Four Zebu steers fitted with rumen cannulae were allocated in 4 experiments fed SCT as basal forage. The N sources were Taiwan grass (TG) (Pennisetum purpureum) at 0, 10, 20, and 30%; Poultry manure (PM) 0, 10, 20 and 30%; Urea 0, 0.8, 1.6 and 2.4% and high N/energy supplement (HNES) 0.0, 0.5, 1.0 and 1.5 kg fresh matter/animal/d. Ruminal ammonia concentration (NH3) was similar to TG treatments, fractional degradation rate and total intake increase with addition of TG, however, SCT intake decrease. VFA and Microbial nitrogen production (MNP) (g/d) were not affected (P<0.05). Inclusion of PM increased total VFA, NH3 concentrations, MNP, fractional degradation rate (P<0.05) and SCT intake. PM intake was 10% for all treatments. Inclusion of urea increased DMI, NH3 VFA concentrations and MNP (P<0.05). The fractional degradation rate increased with addition of urea. Addition of HNES increased NH3 concentration forage intake (P<0.05). THE NHES increased total VFA concentration (P<0.05). Fractional degradation rate and MNP were affected positively by HNES (P<0.05). The MN/kg DOMR varied from 12.73 up to 15.81. In all experiments the better results of fractional degradation rate, MNP and intake were at 100 mg NH3/l. These trials confirmed that SCT are a potential source of forage for cattle, but as sole food were deficient in N, however it is possible to supply this N by 10% PM, 0.8 % urea or 0.5 kg HNES to satisfy the needs of rumen microorganisms for fermentable N in SCT diets.