Continuous exposure to red light induces photorefractoriness in broiler breeder pullets

C. Hanlon, M. J. Zuidhof, A. Rodriguez, K. Takeshima, G. Y. Bédécarrats, Continuous exposure to red light induces photorefractoriness in broiler breeder pullets, Poultry Science, V. 102 (4), 2023, 102542, ISSN 0032-5791, https://doi.org/10.1016/j.psj.2023.102542.

broiler breeder, peer-reviewed, Publication, Research Showcase 2023, sexual maturity

PIP Author(s)

About

Publication Metrics

In birds, sexual maturation is regulated by the perception of light. A sudden increase in daylength above 12 h allows an increase in the synthesis and release of GnRH-I which results in the development of small white follicles (SWF). At the University of Alberta, a precision feeding (PF) system was developed to allocate feed in restricted portions and durations, improving the BW uniformity and synchronization of the age at sexual maturation. However, the PF system requires access beyond the 8 h of daylight traditionally provided during the pullet phase to ensure all birds can consume their daily allocation. Continuous exposure to supplemental lighting could cause desensitization to a normally stimulatory light signal. Thus, PF systems would benefit from a 24 h supplemental illumination program that does not interfere with the process of photostimulation. The aim of this study was to evaluate the impact of continuous supplemental illumination of feeders with pure green, red, and blue light on the growth and sexual maturation of broiler breeder hens.

Approach

At 2 weeks of age (woa), Ross 708 female broiler breeder chicks were distributed throughout 4 identical rooms, each containing 12 visually and optically isolated pens (n = 48 pens), with 10 chicks placed in each pen. This experiment was comprised of a 2 × 4 × 2 factorial arrangement of treatments, with 2 types of main house daytime lights, 4 supplemental light colors, and 2 intensities. At 3 woa, birds were housed in rooms with either 60% red LED daytime light (dtRED) or 60% green LED daytime light (dtGREEN). Supplemental LED strip lighting was placed around the hanging feeder which could be: monochromatic red (sRED; 630 nm), monochromatic green (sGREEN; 508 nm), monochromatic blue (sBLUE; 450 nm), or no illumination (sCON). Supplemental feeder light could be: high intensity (INT) or low INT. At 20 woa, all birds were photostimulated with 14 h at 30 lux. Each bird was individually weighed weekly. Eggs were collected and recorded daily.

Analysis of Results

Pairwise differences indicated that hens under sRED, regardless of DTL treatment, were 145-g and 198-g heavier than sBLUE and sGREEN, respectively at 26 woa but did not differ from sCON. From 27 woa through to the end of the study (30 woa), hens under sRED were significantly heavier than all other treatments (P < 0.001). This led to hens under sRED reaching a BW that was over 400 g heavier than hens under any other light. Hens under high INT were less uniform than those under low INT treatment. Age at first egg (AFE) was found to be delayed by approximately 9 d in hens under sRED light compared to all other SFL, regardless of INT. DTL had a significant effect on egg production (P = 0.008) with the rate of lay 3.15% higher throughout the study in hens under dtRED. Concurrent with the delayed entry into lay, sRED had the lowest production rate overall (20.55%; P < 0.001) compared to sBLUE (50.51%), sGREEN (49.37%), and sCON (49.32%). SFL had an effect on cumulative egg production (P < 0.001), with 14 fewer eggs produced per hen housed under sRED compared to the other treatments.

Application

In the present study, the results indicate that the implementation of 24 h red LED supplemental lighting is detrimental to sexual maturation and early reproductive performance of broiler breeder hens. Conversely, these effects of supplemental lighting on growth and reproduction were not observed under green and blue lights.

Abstract

The management of body weight (BW) in broiler breeder pullets is critical to offset the negative correlation between their growth potential and reproductive success. Therefore, a precision feeding system was developed to allocate feed individually based on real-time BW in more frequent, smaller portions. However, this system requires access beyond the 8 h daylength of the rearing period. Since green and red spectra have been shown to stimulate growth and sexual maturation, respectively, this study aimed to evaluate the impact of continuous supplemental illumination of feeders with monochromatic wavelengths on sexual maturation. Furthermore, the best combination of supplemental and daytime lighting for optimizing the pullet-to-hen transition period was investigated. This study contained a 2 × 4 × 2 factorial arrangement, with 2 daytime lights (dtRED and dtGREEN; n = 2 rooms), 4 supplemental lights (sBLUE, sGREEN, sRED, and sCON; n = 12 pens), and 2 supplemental intensities (High and Low). At 3 wk of age (woa), 480 female Ross 708 chicks were randomly distributed across treatments (n = 10/pen). All birds were feed restricted per management guidelines and maintained under 8 h of dtRED or dtGREEN. Birds were photostimulated at 20 woa with 14L:10D. All birds were weighed weekly, with age at first egg (AFE) and production rate calculated weekly per pen. Birds under sRED were heavier than all other treatments from 27 woa to the end of the study (P < 0.001; 30 woa), resulting in hens that were over 400-g heavier. This resulted from a delayed AFE and lower production rate under sRED, with higher intensity further hindering reproductive performance (P < 0.001). Interestingly, despite the inhibitory effect of continuous red lighting (sRED) on reproduction, dtRED resulted in a 3.15% higher rate of lay than dtGREEN. Therefore, this study suggests that while red light remains superior at stimulating reproduction, continuous red supplemental lighting results in photorefractoriness. Thus, we recommend green light in PF systems.