Early infection with Histomonas meleagridis has limited effects on broiler breeder hens' growth and egg production and quality.

A study was conducted to determine differences between Histomonas meleagridis-infected and control pullets based on disease signs, hen growth, and egg production and quality. Ross 708SF females were weighed and then placed in pens on the day of hatch (92 chicks/pen). At 25 D, 4 pens were infected with H. meleagridis in the cloaca, whereas 4 pens were control. At 5, 10, and 20 D after inoculation, 5 birds per pen (2 birds per pen at 20 D) were subjectively scored for blackhead disease. Birds were feed restricted based on BW and/or egg production. Individual BW were collected at 3, 5, 13, 15, 20, and 64 wk. Egg production was recorded at 24-63 wk. Egg quality was measured at 30, 34, 39, 42, and 56 wk and included shell and vitelline membrane strength, shell thickness, egg weight, and Haugh units. Hatchability was measured at 27, 37, and 60 wk and fertility at 27 and 37 wk. Treatment effects were determined by JMP Pro 14 using GLM with means separated using the Student t test (P ≤ 0.05). Cecal lesions were apparent on 5, 10, and 20 D and liver lesions on 10 and 20 D for the infected birds. The control had no histomoniasis lesions. Flock uniformity differed on wk 13 and 20 (P = 0.04; 0.04). Infected birds weighed less at 64 wk (P = 0.002). The onset of lay was not delayed. Infected birds produced more eggs during 1 period (P = 0.02). The infected birds produced heavier eggs at 30 wk (P = 0.04), eggs with a stronger and thicker shell at 42 wk (P = 0.05, 0.03), and eggs with a stronger vitelline membrane at 56 wk (P = 0.049). Hatchability and fertility did not differ (P > 0.05). H. meleagridis was observed in the infected birds' cecal samples at trial termination. This study indicates early infection with H. meleagridis has limited effects on pullet egg production and quality.