Effects of four dim vs high intensity red color light regimens on growth performance and welfare of broilers

Objective: Broilers show clear preference towards red color light (RL). However setting of an optimum light intensity is difficult since dim intensities that favor growth reduce welfare. This experiment was conducted to test the most effective RL intensity regimen (Dim [5 lux; DI] vs high [320 lux; HI]) in combination applied at different growth stages that favors for both performance and welfare. Methods: Complete randomize design was adopted with 6 replicates. Treatments were; T1 = early DI (8-21 d)+latter HI (22-35 d); T2 = early DI (8-28 d)+latter HI (29-35 d), T3 = early HI (8-21 d)+latter DI (22-35 d), T4 = early HI (8-28 d)+latter DI (29-35 d) and T5 = control (white light; WT) (8-35 d) at medium intensity (20 lux). Body weight (BW), weight gain (WG), water/feed intake and ratio, feed conversion ratios (FCR) were assessed. Common behaviours (15) were recorded by scan sampling method. Lameness, foot pad dermatitis, breast blisters, hock burning damage were assessed as welfare parameters. Fear reactions were tested using Tonic Immobility Test. Ocular and carcass evaluations were done. Meat and tibiae were analyzed for fat and bone ash respectively. Results: On 35 d, the highest BW ($2,155.72{\pm}176g$), WG ($1,967.78{\pm}174g$) were recorded by T2 compared to WT ($BW_{WT}=1,878.22{\pm}155$, $WG_{WT}=1,691.83{\pm}160$). But, application of RL, either DI, or HI during early/latter stage had no significant effect on FCR. Under HI, birds showed much higher active behaviours. DI encourages eating. Though LI changed from DI to HI, same trend could be seen even under HI. The highest leg strength ($218.5{\pm}120s$) was recorded by T2. The lowest leg strength ($64.58{\pm}33s$) and the highest ocular weight ($2.48{\pm}1g$) were recorded by T1. Significantly (p<0.05) the highest skin weight ($162.17{\pm}6g$) but the lowest fat% in meat ($13.03%{\pm}5%$) was recorded by T2. Conclusion: Early exposure to DI-RL up to 28 days followed by exposure to HI-RL is the most favorable lighting regimen for optimizing production, better welfare of broilers and improving health benefits of meat.