INFLUENCE OF DURATION-IN-LAY ON HEN-DAY PRODUCTION AND INTERNAL EGG QUALITY INDICES OF ISA BROWN LAYER STRAIN UNDER NIGERIAN TROPICAL CLIMATE

Abstract

The study examined how duration-in-lay affects hen-day production and internal egg quality in Isa Brown layers. Forty-eight pullets were sourced from the Federal College of Agriculture, Moor Plantation Ibadan, and raised in a deep litter system. The birds were divided into six groups based on duration-in-lay; 0-6 weeks, 7-12 weeks, 13-18 weeks, 19-24 weeks, 25-30 weeks, and 31-36 weeks. Parameters measured included percent hen-day production (%HDP), total egg weight (TEW), average egg weight (AEW), total feed intake (TFI), daily feed intake (DFI), Haugh unit (HU), albumen index (AI), yolk index (YI), percent shell weight (%SW), and shell thickness (ST). A completely randomized design (CRD) was used. Results showed that duration-in-lay significantly influenced production performance, with percent hen-day production peaking at 87.10% and total egg weight reaching its maximum (17,658.13 kg) during weeks 19-24. Daily feed intake (121.47 g/bird/day) and total feed intake (244.86 kg) peaked at weeks 25-30, indicating reduced feed efficiency as production declined. Average egg weight increased steadily from 47.26g to 58.35g by week 13, then stabilized through week 36 (59.38g). Internal egg quality declined progressively with laying duration, as evidenced by the highest Haugh unit (86.28) recorded at 0-6 weeks. Duration-in-lay showed strong negative correlations with Haugh unit (r = -0.809), albumen index (r = -0.763), and yolk index (r = -0.854), confirming significant deterioration in egg freshness and internal quality over time. Shell thickness remained unaffected by duration-in-lay (r = 0.007), while percent shell weight declined moderately (r = -0.449). These findings demonstrate that early laying phases produce superior egg quality, while the 19–24 weeks period represents the optimal window for peak production, after which feed efficiency declines despite continued egg output.