Two experiments were conducted to evaluate a commercially available supplemental N source for beef cattle (Fermenten®; Church & Dwight Co., Inc., Princeton, NJ, USA). The first experiment evaluated kinetics of in vitro NH3-N release using batch cultures of rumen fluid incubated with: control (no N added), soybean meal, urea, and Fermenten®. Ammonia-N was measured at 0, 0.5, 2, 4, 6, 8, 12 and 24 h after incubation began. A treatment by time interaction (P<0.01) occurred in which, during the initial 2 h, Fermenten® cultures had the highest (P<0.01) NH3-N but, from 4 to 24 h, the highest (P<0.01) NH3-N concentrations were with urea-incubated cultures. The total increase in NH3-N concentrations from 0 to 24 h of incubation was less for Fermenten® (P<0.01) than for the soybean meal and urea. The second experiment assessed effects of Fermenten® supplementation on growth, blood parameters, voluntary forage intake and reproductive performance of beef heifers. Sixty heifers, stratified by initial body weight (BW), were randomly allocated to one of two treatments that consisted of iso-nitrogenous grain-based supplements containing either Fermenten® (72 g/kg, as-fed) or urea (9.7 g/kg, as-fed). Supplements were offered three times weekly at a rate of 2.4 kg of dry matter per heifer daily. Shrunk BW was measured on days 0 and 112 for calculation of daily body weight gain. Body volume measurements were completed on days 0, 28, 56, 84 and 112, whereas pelvic area was assessed on days 0, 56 and 112. Blood samples were collected on days 28, 56, 84 and 112 for analysis of metabolites and hormones. On day 56, 2 heifers, which were randomly selected from each pasture, were placed in individual feeding stations for 26 days to determine treatment effects on voluntary forage intake. On day 112, all heifers were grouped by treatment and exposed to bulls for 60 days. Fewer heifers offered the Fermenten® supplement attained puberty (P<0.05) and became pregnant during the study compared to heifers fed urea (0.60 and 0.93, respectively; P<0.01). Addition of Fermenten® to batch cultures of rumen fluid rapidly increased NH3-N concentrations, whereas further increases occurred in a slower and steady rate. Beef heifers fed a supplement containing Fermenten® had similar growth and development, but inferior reproductive performance, than heifers fed a supplement containing urea.
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- Beef heifers