FIBER REQUIREMENTS OF DAIRY-COWS - OPTIMUM FIBER LEVEL IN LUCERNE-BASED DIETS FOR HIGH PRODUCING COWS

Data from an experiment with high producing dairy cows were used to obtain regression relationships for neutral detergent fiber (NDF) and acid detergent fiber (ADF) as single dependent variables, with dry matter intake (DMI) and digestibility (DMD), rumination and total chewing activities, percent milk fat, 4% fat-corrected milk (FCM) and body weight change. Diets were comprised of alfalfa hay at four stages of maturity, fed with 20, 37, 54 or 71% concentrate. Diet dry matter levels of NDF and ADF ranged from 18.3 to 48.6% and 12.3 to 35.1%, respectively. The relationships of fiber components with body weight and 4% FCM yield suggest that during the period of 10-26 weeks post-partum, levels of fiber less than 29% NDF and 20% ADF were required to sustain a 4% FCM yield of more than 35 kg and maintain a positive body tissue balance. Furthermore, at the same level of dietary NDF, an advance in alfalfa maturity adversely affected (P < 0.05) yield of 4% FCM. Associated with an advance in maturity was a daily change in NDF of 0.86 percentage units and a decrease in FCM of 0.39 kg/day.