Concentrations and Settling Rates of Particulate Matter in Laying Hen Barns in the Hot Climatic Region of Cameroon

Abstract

Particulate matter (PM) serves as a carrier of adhesive gaseous compounds, and may result to an underestimation of gas emissions from livestock barns when only filtered air samples are analysed. PM concentrations have hardly been studied in the unique livestock production system of Sub-Saharan Africa. This study was aimed at generating baseline data for PM (total suspended particulates) concentrations and settling rates in laying hen barns with cemented floors and wood shavings added as an initial bedding material. Measurements were conducted in two naturally ventilated laying hen barns in Cameroon; a barn with 4 months old hens that had just stated laying eggs and a barn with 18 months old egg laying hens. PM concentration was determined gravimetrically from the mass collected on a 1.2 µm diameter filter. Four plates with a surface area of 0.09 m² each, hung at a height of 1.7 m from the floor were used to gravimetrically determine PM settling rates over a fixed duration. Results revealed that PM concentrations correlated with the age of the hens. PM concentrations were 6.61 mg m^-3 (6.33 µg hen m^-3) and 10.17 mg m^-2 (16.95 µg hen m^-3) in the barns with 4 and 18 months old hens respectively. PM settling rates were 53.79 mg m^-2 h^-1 (51.5 µg hen m^-2 h^-1) and 115.52 mg m^-2 h^-1 (192.5 µg hen m^-2 h^-1) in the barns with 4 and 18 months old hens respectively. No fixed location within the barn experienced consistently high or low PM settling rates. Temporal and spatial variations in settling rates could be related to management routines and hen activity. Results also indicated that variations in PM concentrations in the air accounted for about 60% of the variations in the settling rates. This research highlights the need for PM emission mitigation strategies that are applicable to the climate and production system in Sub-Saharan Africa.