Effect of supplementing napier grass (Pennisetum purpureum) with poultry litter and sunflower meal based concentrates on feed intake and rumen fermentation in Friesian steers

Intake of nutrients and rumen fermentation values were determined in a 4×4 Latin square design using four rumen fistulated Friesian steers. In Trial 1, steers were fed medium (MNG) or old (ONG) maturity napier grass (Pennisetum purpureum) supplemented with 3.65 kg of DM of sunflower seed meal based concentrate (SFBC) or poultry litter based concentrate (PLBC) while in Trial 2, steers were fed MNG only or MNG supplemented with 0.91, 3.65 or 6.35 kg of DM of the PLBC. In Trial 1, intakes of crude protein (CP) (15.3 vs 11.1 g kg−1 W0.75) and organic matter (OM) (127.1 vs 124.7 g kg−1 W0.75) were higher on MNG vs ONG diets while intakes of CP and OM were 3% higher on SFBC vs PLBC diets. Rumen pH was higher (7.1 vs 6.7) on ONG vs MNG (P<0.05) but similar on SFBC vs PLBC diets (P>0.05). Concentrations of ammonia (NH3-N) were higher on MNG vs ONG (101.0 vs 51.2 mg l−1) but 12.5% lower on SFBC vs PLBC diets while concentrations of VFA were higher on MNG vs ONG (123.8 vs 101.8 mmol l−1) and 2.5% higher on SFBC vs PLBC diets (P<0.05). Supplementing ONG with PLBC resulted in sub-optimal feed intake and digestion. In Trial 2, the substitution rate of MNG was negative at 0.91 kg/day of PLBC but positive, and higher (P<0.05) at higher levels of supplementation. Intakes of OM were 100.8, 111.6, 128.6 and 132.3 g kg−1 W0.75 while intakes of CP were 10.6, 12.2, 15.6 and 17.5 g kg−1 W0.75 for treatments 0, 0.91, 3.65 and 6.35 kg/day of PLBC, respectively, (P<0.05). Although rumen concentrations of NH3-N increased to 6.35 kg/day of PLBC (P<0.05), optimal feed intake and digestion were obtained at 3.65 kg/day.