EFFECT OF LIGHTING DURATION ON THE BEHAVIOUR, WELFARE, AND PERFORMANCE OF BROILER CHICKEN

Abstract

The study was undertaken to investigate the effect of lighting duration on growth performance, behaviour, and welfare of broiler chickens from d1 to 30 days in the floor-rearing system. A total of 160 day-old broiler chicks of both sex (Lohmann Meat) was randomly housed into 4 lighting treatments including T1 [24 hours light (L): 0 hour darkness (D)], T2 (22L:2D), T3 (20L:4D), and T4 (18L:6D) with 4 replicates, each replication had 10 birds in a Completely Randomized Design (CRD). Chicks were exposed to different lighting regimes say 24L: 0D, 22L:2D, 20L:4D (2 x 2h darkness with a 1h lighting interval), and 18L:6D (3 x 2h darkness with 2 x 1h lighting interval) with 18-watt LED bulbs (22lux) for 30d. Data on live-weight gain (LWG), feed intake (FI), feed conversion ratio (FCR), and viability were recorded, where behavioural observation data were taken on 11d, 22d, and 29d. respectively. To evaluate the welfare, fearfulness tests including novel object (NO) test, novel environment (NE) test, response to observer (RO) test, and tonic immobility (TI) test were conducted at different periods with gait score (GS) test for leg health at 30d. At 27d, blood samples were taken to determine the heterophil-lymphocyte (HL) ratio and serum corticosteroid (CORT) level. The results showed that, LWG and FI in the 2nd week were found significantly higher (P<0.05) in T1(24L:0D) than that of 20L:4D and 18L:6D, which were reversed in the 4th week. But overall LWG, FI, FCR, and viability were nonsignificant (P>0.05) among the treatments. The results of behavioural activities of broiler showed that only inactive resting, feeding, preening, leg/wing stretching running/walking, and drinking activities were significantly influenced by lighting regimes. Broiler performed inactive resting activities significantly or more commonly in continuous lighting program than that of other treatment groups. This behaviour was less responsive when the birds were exposed to increased darkness period. Besides, increased activity of feeding and drinking time were found in reduced lighting periods. In behavioural observations, inactive resting frequencies were significantly lower in the T4(18L:6D) lighting compared to the T1(24L:0D) and T2(22L:2D) on 11d, 22d, and 29d. Feeding, preening and drinking frequencies seemed to improve in T4 (18L:6D) and T3(20L:4D) compared to the T1(24L:0D) and T2(22L:2D) lighting. According to fear test results, welfare was significantly improved in T4 (18L:6D) and T3(20L:4D) lighting compared to the T1(24L:0D) and T2(22L:2D) with lower RO value, higher NO time, better NE values, and lower TI time. The GS, HL ratio, and serum CORT were not influenced (P>0.05) by lighting treatments. It can be inferred that reduced lighting hours or providing increased darkness in the lighting regime of the broiler can improve broiler welfare and potentially boost broiler performances.