Evaluation of the Impact of Light Source on Reproductive Parameters in Laying Hens Housed in Individual Cages

Abstract

Higher light wavelengths have been shown to stimulate extra-retinal photoreceptors more efficiently than lower wavelengths to promote reproduction in poultry. We developed a light emitting diode (LED) bulb that emits 60% of its light in the red spectrum (LED-R), and evaluated the effects of different light sources on growth and reproduction in commercial layer hens. Three rooms equipped with either 100 W incandescent, 15 W compact fluorescent (CFL), or 10 W LED-R bulbs were populated with 96 Lohmann LSL-Lite layers housed in individual cages from 14 to 69 weeks of age (woa). Pullets were initially maintained on a 10-h photoperiod, then photostimulated at 18 woa. Surprisingly, regardless of the light source, plasma levels of estradiol peaked at 16 woa, 2 weeks before photostimulation, and egg-laying was initiated at 19 woa. As a direct correlation between age at first egg and body weight was identified, metabolic cues most likely served as a primary trigger to initiate sexual maturation prior to photostimulation. Overall egg production and cumulative egg numbers were similar among treatments. Interestingly, a second increase in estradiol was observed at 52 woa under all treatments, suggesting an additional ovarian stimulation, possibly associated with an additional follicular recruitment at that age. Overall, changes in estradiol concentrations were more pronounced in hens maintained under LED-R light than in hens exposed to incandescent and CFL, especially for the second increase, suggesting that a higher amount of red light leads to stronger ovarian activity. Maintaining hens under LED-R bulbs also resulted in lower feed consumption, which combined with the lower energy consumption of LED-bulbs (LED-R: 306 kW; incandescent: 2,514 kW; CFL: 422 kW) could reduce the production cost.

Should I Lay or Should I Grow: Photoperiodic Versus Metabolic Cues in Chickens

“…While studies have considered the effect of food availability on reproductive success in wild species of seasonal breeders, in the domestic laying hen food availability is not a limiting factor and control of the reproductive axis is achieved mostly by modulating environmental conditions, such as photoperiod. As demonstrated in a recent trial involving Lohmann LSL-Lite, current commercial strains do not necessarily require photostimulatory cues in order to initiate the reproductive process ( Baxter and Bédécarrats, 2019 ). This suggests that sexual maturity is not exclusively triggered by photoperiodic cues, but rather hens are required to reach a critical threshold in body weight or fat composition in order to enter lay ( Zuidhof, 2018 ; Baxter and Bédécarrats, 2019 ).…”

“…As demonstrated in a recent trial involving Lohmann LSL-Lite, current commercial strains do not necessarily require photostimulatory cues in order to initiate the reproductive process ( Baxter and Bédécarrats, 2019 ). This suggests that sexual maturity is not exclusively triggered by photoperiodic cues, but rather hens are required to reach a critical threshold in body weight or fat composition in order to enter lay ( Zuidhof, 2018 ; Baxter and Bédécarrats, 2019 ). In terms of the HPG axis, this suggests that additional factors can overcome the inhibitory mechanisms in place prior to photostimulation.…”

“…However, to date, most research models describing the control of the hypothalamic-pituitary gonadal (HPG) axis have largely focused on the impact of environmental cues such as photoperiod ( Bédécarrats, 2015 ), rather than incorporating the impact of growth and metabolic status. Recent evidence suggests that modern commercial laying hens do not exclusively rely on photostimulation to initiate sexual maturation, as egg production may commence at an earlier age, prior to an increase in photoperiod ( Baxter and Bédécarrats, 2019 ).…”

Rearing cage type and dietary limestone particle size: I, effects on growth, apparent retention of calcium, and long bones attributes in Lohmann selected Leghorn-Lite pullets

“…Structural bone growth continues until the surge in estradiol at sexual maturity ( Whitehead, 2004 ; Baxter and Bédécarrats, 2019 ). The surge of estradiol shifts the bone mineralization process of osteoblast from structural to medullary ( Kalkwarf et al., 2003 ).…”

Prolonged Dark Time Within A 24-h Light Regime Improves Eggshell Quality by Enhancing Calcium Deposition in Laying Hens

“…Photoperiod is generally considered as the primary cue to stimulate reproduction of laying hen [7]. The light source [8], spectrum [9,10], intensity [11], and the uniformity of light distribution [12] all have an in uence on the laying performance. Altered photoperiod has an in uence on eggshell quality.…”