Impact of the Northern Fowl Mite on Laying Hen Production and Welfare Beginning at 17 Weeks of Age
The northern fowl mite (Ornithonyssus sylviarum) is an obligate blood-feeding ectoparasite of poultry that can cause decreased egg production, profit loss, anemia, irritation to flocks and personnel, and death to hens in extreme cases. This study aimed to investigate the effects of the northern fowl mite (NFM) on laying hen performance and welfare quality beginning at 17 weeks of age. Two flocks (Trials 1 and 2) involved 800 Tetra Brown hens (n=200 per room) housed in four cage-free rooms at the Purdue University Poultry Unit. Two rooms were infested with NFM and two rooms served as controls. In Trial 1, initial NFM infestation occurred at 24 weeks on 2% (4 hens) in each of the NFM rooms. Because NFM populations were scarce, a second infestation on 2% of hens occurred at 35 weeks. A final attempt to infest with NFM occurred at 41 weeks with all hens in NFM rooms being infested. In Trial 2, initial NFM infestation occurred at 24 weeks on 2% (4 hens) in each of the NFM rooms and a second infestation took place on 2% of hens at 30 weeks of age to boost the NFM population. Egg production and mortality were recorded daily and case weights were recorded weekly. Monthly Welfare Quality® assessments were taken, as well as monthly mite counts on all birds beginning at 28 weeks. Mite checks were conducted periodically on 25% (50 hens) in all rooms between weeks 25 and 38. Data were analyzed in SAS® using the GLM procedure and an ANCOVA and all significant statistical differences were reported at P < 0.05. Proportion of hens with a mite infestation was treated as the covariate. In Trial 1, regardless of treatment, mortality increased dramatically after 21 weeks, leading to a loss of 473 hens by period 7. NFM hen-day production percentage (HD) was approximately 2% lower than the Tetra management guide and control HD was 7% higher than the Tetra management guide. In Trial 1, treatment had an effect on HD, case weights, and feather damage on the belly (P < 0.05). Proportion of hens infested with mites had an effect on percent shell and feather damage on the belly. Cannibalism and pecking in Trial 1 led to extreme feather loss, high mortality, and negatively impacted production parameters. Feather loss and high mortality contributed to the low NFM populations. In Trial 2, percent livability remained high (approximately 97% for both groups) and HD remained slightly lower than the Tetra management guide (9% and 8% lower for control and NFM), respectively. In Trial 2, treatment had an effect on eggs per hen housed, mortality, feather damage on the head and neck, and skin lesions (P < 0.05). Proportion of birds infested with mites had an effect on feather damage on the back, crop, head, and neck (P < 0.05).