Abstract
The poultry red mite (PRM), Dermanyssus gallinae, a potential vector of pathogens to animals and humans, causes impaired bird welfare. A study investigated changes in behavioural variables, physiological biomarkers, and health parameters following acaricidal treatment of PRM infestation of laying hens on a commercial farm. Mite traps determined the challenge to 12,700 hens before and after drinking water administration of the acaricide, fluralaner (Exzolt®, 0.5 mg/kg; Weeks 0 and 1). Weekly daytime direct observations and night-time video recordings monitored bird behaviours from Weeks -6 through +6. Blood samples were collected from randomly-selected birds (Weeks -6, -1, and +6). Following treatment, mite count reductions (>99%) were statistically significant (P < 0.0001), as were night-time reductions in the percent of hens showing activity, preening, head scratching (all P < 0.0001), and head shaking (P = 0.0007). Significant daytime reductions were observed in preening and head scratching (both P < 0.0001), head shaking (P = 0.0389), severe feather pecking (P = 0.0002), and aggressive behaviour (P = 0.0165). Post-treatment, comb wounds were significantly reduced (P = 0.0127), and comb colour was significantly improved (P < 0.0001). Heterophil/lymphocyte ratio was significantly reduced at Weeks 1 and 6 (P = 0.0009 and P < 0.0001, respectively). At Week 6, blood corticosterone (P = 0.0041) and total oxidant status (P < 0.0001) were significantly reduced, and haemoglobin and mean corpuscular haemoglobin significantly increased (P < 0.0001). Farm production records indicated that those post-treatment improvements were accompanied by significant reductions in weekly mortality rate (P = 0.0169), and significant recovery in mean weekly egg weights (P < 0.0001) and laying rate (P < 0.0001). The improvements in behavioural variables, physiological biomarkers, and health parameters that were observed following the elimination of PRM on a commercial farm indicate that infestations can be a cause of reduced hen welfare.
Highlights
The poultry red mite (PRM), Dermanyssus gallinae affects all poultry production types, from backyard and organic farms to more intensive, enriched cage or barn systems [1]
The study was conducted in alignment with the principles of the Good Clinical Practice VICH GL9 (GCP) (CVMP/VICH/595/98-Final) [17] on a commercial egg production farm and was approved by the Ethical Committee on Animal and Human Experimentation of the Universitat Autonoma de Barcelona
The family-owned farm was selected because it was appropriate for completing a GCPadherent study and had a history of infestation with the PRM
Summary
The poultry red mite (PRM), Dermanyssus gallinae affects all poultry production types, from backyard and organic farms to more intensive, enriched cage or barn systems [1]. Kilpinen et al observed behavioural changes of increased grooming behaviour in mite-infested hens relative to uninfested controls [14]. A corollary of those findings is that mite elimination would improve hen welfare. To test this hypothesis a study was undertaken under commercial production conditions to assess changes on a wide range of animal welfare indicators following acaricidal treatment of hens on a naturally mite-infested commercial building. The selected acaricide was fluralaner, a systemically acting compound of the isoxazoline class that has been shown to eliminate PRM infestations from hens and poultry houses [16]
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