EFFECTS OF SOURCE AND LEVEL OF UNDEGRADED INTAKE PROTEIN ON NUTRIENT USE AND PERFORMANCE OF EARLY LACTATION COWS

At parturition, groups of six cows (two primiparous) were assigned randomly to experimental diets composed of wheat silage, concentrate containing 11.4% yellow grease, corn, and supplemental protein sources. Protein sources were soybean meal, heated soybean meal, and a combination of corn gluten and heated soybean meals. Intakes of DM, NDF, and NE(L) were not affected by undegraded protein levels (trial 1). Milk and 4% FCM yields and percentages of CP, lactose, SNF, and total solids were not influenced by protein source. Mobilization of body tissue was accelerated by heated soybean meal. During wk 1 to 4 postpartum, efficiency of NE(L) Utilization was greater for cows receiving the combination treatment than for those receiving the soybean meal treatment. During wk 4 to 8, cows fed the heated soybean treatment utilized NE(L) more efficiently for milk yield than cows fed the combination treatment. Efficiency of utilization of absorbed protein was not affected by level of undegraded protein. At wk 9, fat was removed from the concentrate, and a second trial was conducted. Intakes of DM and NE(L) were reduced for cows fed the combination treatment. Milk yield and composition and efficiency of utilization of NE(L) and absorbed protein were not affected by level of undegraded protein.