This experiment sought to evaluate the influence of varying levels of neutral detergent fiber (NDF) in the diet on feed intake, nutrient digestibility, rumen conditions, and nitrogen retention in crossbred cattle. Beef cattle aged 18 months were organized into groups using a 2x (4x4) Latin square design. The NDF levels investigated were 47%, 51%, 55%, and 59% of dry matter (referred to as NDF47, NDF51, NDF55, and NDF59 treatments, respectively). While dry matter (DM) consumption per 100 kg body weight (BW) did not exhibit significant differences between treatments, Charolais crossbred cattle (2.16 kg DM) demonstrated higher intake than Black Angus crossbred cattle (2.04 kg DM). Metabolizable energy intake in Charolais crossbred cattle significantly differed from that in Black Angus crossbred cattle (17.6 and 16.7 MJ/100 kg BW, respectively). Regarding NDF treatments, NDF47 did not differ from NDF51 and NDF55, but it was significantly higher (PNDF59 treatment (18.1, 17.3, 17.1, and 16.0 MJ/100 kg BW, respectively). Although dry matter and organic matter digestibility did not significantly differ between Charolais and Black Angus crossbred cattle, variations were noted among treatments (Psignificant differences observed for NDF51 (59.8%) and NDF55 treatments (58.9%). Rumen pH, N-NH3, and total volatile fatty acid concentrations at 0h and 3h post-feeding did not exhibit significant differences (P>0.05) in this study. However, nitrogen retention in Black Angus crossbred cattle was significantly lower than in Charolais crossbred cattle (0.124 and 0.166 g/kg BW, respectively). Across treatments, nitrogen retention values were numerically higher (P>0.05) in NDF47, NDF51, NDF55, and NDF59 treatments (0.166, 0.148, 0.139, and 0.126 g/kg BW, respectively). In summary, this study determined that Charolais crossbred cattle displayed increased feed intake, crude protein digestibility, and nitrogen retention compared to Black Angus crossbred cattle. Furthermore, a dietary NDF level of 55% was suggested as suitable for practical use in terms of  feed utilization by farmers.
Keywords: Forage, crossbreeding, rumen fermentation, and ruminant.