Effect of Micro-AidŽ Supplementation on Nitrogen Losses from Cattle Manure

Abstract Text: A 2x2 factorial experiment was designed to study the effects of Micro-Aid inclusion in cattle diets on OM and N losses from manure over time.  Sixty aluminum pans (33x23x5 cm) were used to simulate feedlot pen surface, with 15 replications per treatment.  Complete manure (urine and feces) was collected from 6 ruminally fistulated steers for 5 d.  All cattle were fed a common diet with 3 of the steers ruminally dosed with 1 g Micro-Aid /steer daily for 10 d prior to the start of and throughout manure collection.  On d 1, soil and manure were weighed into each pan to equal 60% soil and 40% manure, on a DM basis.  Manure and soil were completely mixed together to simulate the hoof action of cattle; the mixture was approximately 4 cm deep within each pan.  Representative samples of manure and soil were analyzed for OM and N to calculate losses over time.  Pans were kept in a temperature controlled room (20°C) for either 30 or 60 d at which time material from the pans was ground through a 1-mm screen, subsampled, and analyzed for OM and N.  Soil was essentially devoid of N (<0.001%), thus all N in the pans originated from the manure (2.7% N on a DM basis) regardless of treatment.  Soil OM was 2% and both Micro-Aid (MA) and control (CON) manure averaged 84% OM.  Losses of OM, measured as both g lost and % lost, were greater for CON than MA at both 30 d and 60 d (P<0.01).  Losses of OM were greater at 60 d than 30 d for both treatments (P<0.01), with 68% of losses occurring by d 30 for both treatments.  Nitrogen losses for CON pans were 24.5 and 48.1% for d 30 and 60 respectively (P<0.01).  Nitrogen losses for MA pans were 32.4 and 33.7% for d 30 and 60 respectively (P=0.84).  At d 30 N losses were similar for CON and MA pans (P=0.23), but CON pans had 30% greater N losses at d 60 (P=0.03).  Of total N losses at d 60, MA pans lost 97% by d 30 while CON pans lost 50% by d 30.  Micro-Aid proved effective at minimizing OM and N losses from cattle manure during storage, which should translate into reduced ammonia volatilization and greater fertilizer value for crop production.

Keywords: manure, nitrogen, organic matter