Does Exposure to Blue Light (Peak at 455 nm) to 15 or 17 weeks Impact Leghorn Pullet Production, Health, and Welfare?

The objectives of this study were to determine the effects of three light treatments (L) on the health, production, and welfare of two Lohmann strains (S). The tested L were white light to 17 weeks of age (wk) (W17), blue light (peak 455 nm) to 17 wk (B17), or blue light to 15 wk then 2 wk of white light (B15). And the two S were Lohmann LSL-Lite (LW) and Lohmann Brown-Lite (LB) (n=1,800/S). This study involved two replicated trials, following a 3x2 factorial arrangement in a randomized complete block design (Trial=block). Each trial included six light-tight rooms (2 rooms/L per trial) with six floor pens per room (3 pens/S/room per trial). Pullets were reared in floor pens from 0 to 17 wk, with a perching system, two tube feeders, and a drinker line in each pen. Production data collected included bodyweight (BW), feed disappearance, mortality, ocular measurements, flock bodyweight uniformity, and age at first egg. Welfare data included pecking behaviour, location of pecks, heterophil/lymphocyte (H/L) ratios, responses to novel object (NO) tests and tonic immobility (TI) tests, and comb scores. Data were tested for normality and transformed (log +1) if necessary. Light was nested within room. Blue light treatments (B15 and B17) were identical prior to 15 wk and were therefore combined as one L (Blue), then were separated after 15 wk when the B15 rooms were switched to white light. Data were analyzed using Proc Mixed (SAS 9.4) to determine the impacts of L, S, and LxS interactions. Tukey’s range test was used to separate means when differences were significant (P≤0.05). Blue light resulted in heavier pullets at 4 wk than those under W17 (P