Effects of forage NDF strategies on growth performance, starch digestion, ingestive behavior, and inflammatory responses in feedlot Angus × Nellore bulls
Mailza Gonçalves de Souza, Jonas Gabriel Dantas, Bianca Lombardi Soares, Matheus Prestes Barros, Matheus Copeli Garcia, Paulo César Bortoleto Júnior, Dante Pazzanese Duarte LannaLay Summary
Energy-dense feedlot diets with reduced forage levels can improve bull growth performance but may also affect digestion and feeding behavior. We evaluated four forage neutral detergent fiber (fNDF) strategies: constant 7% or 12% fNDF throughout the 100-day feeding period, or step-up (7→12%) and step-down (12→7%) strategies implemented on day 50 in Angus × Nellore bulls (n = 60). Feeding 7% fNDF increased average daily gain (ADG) by approximately 20% (1.93 vs. 1.61 kg/d) and feed efficiency by approximately 19% (0.166 vs. 0.140), compared to 12% fNDF, during the final 50 days in the feedlot but increased fecal starch by approximately 87% (10.46 vs. 5.61%) and reduced estimated starch digestibility by 2.7 concentration units (94.32 vs. 97.00%). Increasing fNDF during the feedlot improved starch utilization. Greater fNDF increased chewing and rumination time, whereas lower fNDF increased idle time. No consistent systemic inflammatory responses were observed.