Interactive effects of the feed-borne mycotoxin deoxynivalenol and a mixed-species Eimeria challenge on layer pullets during the transition to lay

The pullet-to-layer transition involves reproductive maturation, increased feed intake, and relocation stress, which may increase susceptibility to feed-borne mycotoxins and enteric pathogens. A study was conducted to investigate the individual and combined effects of a naturally deoxynivalenol (DON) contaminated diet and Eimeria challenge on performance, health, and timing of sexual maturity in layer-type pullets. A total of 288 Hy-Line W36 pullets were fed either a control diets (1.7-2.1 mg/kg DON) or naturally contaminated diets (13.0-13.6 mg/kg DON) from 15 wk of age. At 18 wk, birds within each diet were randomly assigned to either a non-challenged or an Eimeria-challenged group in a 2 × 2 factorial arrangement. Measurements were obtained during the acute and early-recovery phases following challenge. Dietary DON alone did not affect body weight, feed intake, and feed conversion prior to Eimeria challenge (P > 0.05), but delayed the onset of lay for 6 d. Following challenge, Eimeria significantly reduced feed intake and body weight during the acute and early-recovery phases (P < 0.001), transiently increased gut permeability (P < 0.001), induced villus atrophy and crypt hyperplasia across intestinal segments (P < 0.01), reduced bone mineral density and body fat percentage (P ≤ 0.011), and altered jejunal barrier-related gene expression. Eimeria challenge also delayed onset of lay by 10-d and reduced hen-day egg production (P = 0.019). Dietary DON did not exacerbate Eimeria-induced reductions in growth performance, egg production, intestinal morphology, and systemic oxidative status (P > 0.05). However, DON was associated with increased E. tenella-related cecal lesion severity (P = 0.025) and modulation of splenic and mucosal CD4⁺:CD8⁺ T-cell ratios during the early-recovery phase. In conclusion, Eimeria primarily impaired performance and delayed sexual maturity, whereas DON showed limited production effects but intensified cecal pathology and altered immune responses. Therefore, managing both feed-borne mycotoxins and environmental Eimeria is important during the pre-lay and early-lay periods to ensure uniform sexual maturity and optimal lifetime productivity in layer flocks.