Preference of internal light environment of nest box by layer breeders in natural mating colony cages

Abstract: Commercial enriched colony cages have become commonplace for the natural mating of layer breeders in China in recent years. It is now generally accepted that a nest box is essential to ensure the welfare requirements of laying hens in the internal environment of colony cages. Specifically, the LED light environment of a laying nest depends on various factors, including the position, color, substrate, enclosure, and light intensity in the nest box. Therefore, the utilization rate of a nest can be improved via the evaluation on the preference selection of layer breeders in the internal light environment of a nest box. Taking a commercial layer breeder farm in Handan, Hebei province, China, as a research object, this study aims to investigate the effects of 3 LED light colors (white 400~700 nm: WL, red 585~690 nm: RL, blue 460~490 nm: BL) and 2 light intensities (5 lx: L1, 30 lx: L2) in the nest box on the nest choice of hens using preference selection index method. The nests with no light were termed as the control group (DK). The experimental house was with 4 rows of 4-tier double-sided colony cages (304 cages in total) along the length of a house. Each cage was in the size of 4.80 × 1.20 × 0.71 m (L × W × H), holding 10 roosters and 90 laying hens. 28 identical cages were selected to evaluate at the fourth tier in the house. 7 treatments were divided into WL-L1, WL-L2, RL-L1, RL-L2, BL-L1, BL-L2, DK, to compare that in a randomized block design, where each row had a replicate for each treatment. The specific measurements were made on the number of eggs laid in the nest and on the floor, as well as the nesting and agonistic behavior in the nest. The results showed that there were significant effects of light color, light intensity and their interaction on the number of nest eggs, and the agonistic behavior of egg laying (P<0.05). 1) The proportion of nest eggs in the WL-L2 and BL-L2 treatment was much higher than that in other light treatments (P<0.05), whereas, in the RL groups, the number of nest eggs was much lower than that in the control group (P<0.05). At the end of 33 weeks, the proportion of nest eggs in the WL-L2 and BL-L2 groups were 91.5±3.4% and 93.2±4.5%, respectively. However, there was no significant difference in the egg production among all groups. 2) The WL-L2 and BL-L2 treatment significantly improved the percentage of hens in the nest, the number of sitting events, the frequencies of scratching and rotating, as well as the duration of hens without egg laying. Nevertheless, the number of nest visits, the ratio of nest visits/nest eggs, and the duration of exploring were much lower than that in other groups (P<0.05). 3) In the BL-L2 treatment, the frequencies of threats and aggressive pecks were higher than that in WL-L2, but not significant correlation, whereas, the frequencies of feather pecking reached the highest among all groups (P<0.05). In the WL-L2 and BL-L2 treatments, the frequencies of fights and displacements in the nest were much higher than that in other groups. 4) The percentages of eggs laid varied over time during each hour from the time lights came on, regardless of the treatment with the highest number laid between 06:30 and 08:30 (P<0.05). The highest rates of agonistic behavior occurred with the peak time of lay in the nest. In the WL-L2 and BL-L2 treatments, the distribution of laying times for nest eggs was much less evenly than that in other groups (P<0.05). Therefore, the change of internal light environment in a nest box can be used to enhance the nest utilization rate. A stronger preference for the layers can be the high intensity of LED white and blue light. There were different requirements for the light environment in different behavioral demands of layers. It is suggested to select the sub-area illumination according to the behavioral requirements of layer breeders in the natural mating colony cages.