EFFECT OF PERCENTAGE OF DIETARY FORAGE NEUTRAL DETERGENT FIBER AND SOURCE OF STARCH ON PERFORMANCE OF LACTATING JERSEY COWS

Five Jersey cows were used In a 5 x 5 Latin square design to determine the effects of decreasing dietary forage neutral detergent fiber (NDF ) and different sources of dietary starch on performance and nutrient digestibilities. The control diet was balanced to consist of 21% forag e NDF and 43% nonfiber carbohydrates. Four other diets were balanced t o contain 35% nonfiber carbohydrates and either 16 or 11% forage NDF; diets were arranged in a 2 x 2 factorial design with either corn or co rn and wheat as the sources of starch. Dry matter intake decreased lin early as forage NDF decreased; however, most of the decrease occurred when forage NDF was reduced from 16 to 11%. Milk production, yield of 4% fat-corrected milk, and percentages of milk fat and protein were si milar among diets. Digestibility of NDF and acid detergent fiber incre ased as forage NDF decreased, but fiber digestibilities decreased with the addition of wheat to the diets. Starch digestibility was similar among diets. Source and amount of starch may be equally important or m ore important than the percentage of forage NDF for maintaining nutrie nt digestibilities of the total tract. Forage NDF in the diets of high producing cows can be reduced to 16% when sources and concentrations of starch are adequately balanced.