Increased air velocity in the lying area improves pen hygiene and reduces ammonia emissions from houses with partly slatted pens for growing/finishing pigs

Abstract

Partly slatted pens can offer growing/finishing pigs a better house environment than pens with fully slatted floors. Under thermoneutral conditions, pigs prefer to rest on a solid area and some litter can be provided as enrichment. Ammonia emissions are lower in systems with partly slatted pens, provided the pens are kept clean. However, under high-temperature conditions, pigs in partly slatted pens may begin lying on the slatted area and fouling on the solid floor area, resulting in increased ammonia emissions. This study examined the effects of increasing the air velocity (IAV) in the lying area from max 0.5 m s−1 to max 1.0 m s−1 on conditions for pigs in partly slatted pens during warm periods. Air velocity was increased by redirecting the inlet air from the ceiling inlets down into the animal zone.The study was performed in a commercial growing/finishing house with 10 identical rooms, each containing 16 pens for 9-14 pigs growing from 25-30 kg to 115-120 kg live weight. Pigs were introduced simultaneously into two parallel rooms, one with IAV in the lying area and one without (control treatment). During two summers with six batches, concentrations of carbon dioxide (CO2) and ammonia (NH3), pig activity and choice of lying area in the pen, pen fouling and NH3 emissions were recorded in both rooms on four measuring occasions (M1-M4) during the growing period. Gas concentrations were measured by photoacoustic analyser, pig activity and pig choice of lying area by machine vision techniques, and pen fouling by visual inspection. Climate parameters (air temperature, relative humidity) were logged continuously during the growing period. Ammonia emissions were calculated from the ventilation rate (determined by the indirect CO2 tracer gas method) and the difference in ammonia concentration between outlet and inlet air.Under high ambient temperatures, pigs in the IAV treatment were observed lying significantly more often (p<0.05) in the part of the lying area with the highest air velocity. Pigs tended to lie less in the slatted area (p=0.052) in the IAV treatment than in the control. Problems with pen fouling were significantly reduced with increased air velocity in the lying area and NH3 emissions were reduced by 21% (p=0.009), from 8.4 to 6.6 g pig−1 day−1, during the late growing period (M4).In conclusion, increasing air velocity in the lying area of partly slatted pens from max 0.5 to max 1.0 m s−1 influenced pigs´ choice of lying area, improved pen hygiene and reduced ammonia emissions.