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Ventilation Rate Measurements and Gas Emissions from a Naturally Ventilated Barn for Dairy Cows

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Paper number  131590119,  2013 Kansas City, Missouri, July 21 - July 24, 2013. (doi: @2013
Authors:   Ngwa Martin Ngwabie, Andrew VanderZaag, Claudia Wagner-Riddle
Keywords:   Ventilation rate Animal activity Emission factor Dairy cows Greenhouse gases.

Abstract. This study was aimed at evaluating the CO2 and H2O balance methods for estimating the ventilation rate in a naturally ventilated barn for dairy cows during the spring transitional season. Animal activity measured using the DeLaval activity meter system was also studied and the emission factors of CH4, N2O and NH3 were generated. Measurements were carried out in a free-stall dairy barn with cubicles. The main barn had a solid concrete floor which was mechanically scraped six times in a day. The activity of the cows showed a distinct diurnal pattern with peaks between 7 and 9 a.m. and also between 6 and 8 p.m. The lowest activity measured at about 5 a.m. was 275% lower than the peak activities. Variations in animal activity were similar to reported patterns suggesting that the DeLaval meter system might provide a high resolution measurement of animal activity and hence ventilation rates based on the CO2 balance method since all cows are considered. The average ventilation rates were fairly similar (p = 0.08) with means of 502 ± 248 m3 LU-1 h-1 and 575 ± 258 m3 LU-1 h-1 for the CO2 and H2O methods respectively (1 LU = 500 kg animal mass). The H2O method can provide a reasonable alternative for estimating ventilation rates in dairy cow barns when CO2 concentration is not measured. The mean emission factors were 12.4 g CH4 LU-1 h-1, 0.60 g NH3 LU-1 h-1 and 40.3 mg N2O LU-1 h-1.

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