RESPONSES OF EARLY LACTATION COWS FED WINTER AND SUMMER ANNUAL FORAGES AND UNDEGRADABLE INTAKE PROTEIN

Twenty-four multiparous Holstein cows were divided into six blocks of 4 cows based on their previous 305-d mature equivalent milk yield and were used in a 2 x 3 factorial experiment for the first 84 DIM. Object ives were to determine the effects of forage and RUP supplementation o n DM and nutrient intakes and digestibilities, milk yield and composit ion, BW change, and plasma concentrations of insulin, triiodothyronine , thyroxine, cortisol, NEFA, urea N, and protein. One cow from each bl ock was assigned to wheat or sorghum silage plus one of three concentr ates. Protein treatments were 1) all supplemental CP from soybean meal ; 2) 33.3% of supplemental CP from heated soybean meal, fish meal, and corn gluten meal; and 3) protein treatment 2 plus an additional 4.6% CP from soybean meal. Intakes of DM, CP, NDF, ADF, NE(L), and RUP were higher in cows fed sorghum silage; RUP tended to increase DMI. Milk a nd 3.5% FCM yields were higher for cows fed sorghum silage than for th ose fed wheat silage (42.3 vs. 40.0 kg/d and 41.2 vs. 38.7 kg/d, respe ctively). Milk protein, lactose, and SNF were increased by RUP. Insuli n was increased, cortisol was decreased, and thyroid hormones were una ffected by RUP. Concentrations of NEFA were highest at wk 4. For early lactation cows fed diets containing sorghum or wheat silage, RUP is a necessity.