Proceedings, Western Section, American Society of Animal Science INFLUENCE O F UNDEGRADABLE INTAKE PROTEIN MIXED WITH MINERALIZED SALT ON INTAKE AND FERMENTATION PROFILES O F COWS GRAZING DORMANT WINTER RANGE

Six crossbred, mature beef cows (609 kg) fitted with ruminal cannulas were used in a crossover design to evaluate the effects of small quantities of supplemental blood meal and feather meal combined with mineralized salt (40% NaCI, 41% CaHPO,, 7% KCI, 7% MgO, 5% trace minerals) on serum urea nitrogen, ruminal fermentation profiles, in situ organic matter disappearance and fecal output. Cows grazed dormant winter range in a'481 ha pasture at the New Mexico State University Chihuahuan Desert Rangeland Research Center. Mineralized salt, hlood meal, and feather meal (SBF) were combined in a 2:1:1 ratio and dosed directly through the cannula of three cows daily for 14 d at a rate of 128 g/d. while mineralized salt (MS) was dosed into another three cows at a rate of 64 gld. To determine the appropriate amount to dose, SBF was offered free choice in open tubs to 53 cows in three pastures for 60 d. In each period cows were bolused with a slow release Cr device. Fecal samples were collected and supplement and forage samples were incubated in situ for 0, 6, 12, 24, 36, 48, 72, and 96 h on d 7 to 12. Blood and ruminal fluid samples were collected at 0, 3, 6, 9, 12, 15, 18, and 24 h after supplementation on d 12. To assess forage quality, rumen exbusa was collected from two cows allowed to graze for 1 h following complete rumen evacuation. Exhusa was 7.4% CP, 53% NDF, and 14% ash. Serum ureanitrogen concentration was greater (8.4 vs. 7.7 mg/dL, P < 0.05) for SBF-treated cows. Ruminal ammonia nitrogen and total VFA concentrations, in situ DM disappearance, and fecal output, were 3.85 vs. 3.49 mg/dL ( P = 0.21), 56.0 vs 55.5 mM (P = 0.86), 2.2 vs. 2.8 %h (P=0.41), and4.61 vs. 4.48 kg/d(P= 0.21) for SBF and MS treated cows. respectively. Results suggest that the physical nature of the forage rendered supplemental protein inadequate to alter intake and : fermentation profiles. However, supplemental UIP may have increased metabolizable protein supply as evidenced by increased blood urea nitrogen.