Performance, Behaviour and Welfare Aspects of Broilers as Affected by Different Colours of Artificial Light

Abstract

The objective of this experiment was to assess the behaviour, performance, water/feed intake pattern and welfare parameters of broilers reared in deep litter system upon red (RD:650-750nm), white (WT:325-750nm), green (GR:530-545nm) and blue (BL:450-470nm) light under tropical environment. Based upon previous studies, it was hypothesized that certain colours of light would contribute to superior performance upon exposure at early stage of the life. It was also hypothesized that changes of the behaviour pattern under different colours of light would have effect on the welfare parameters of the broiler chickens. METHODOLOGY Animals and Husbandry Day old broiler chicks (Cobb) were obtained from a commercial supplier and distributed randomly into six replicate brooders for each colours of artificial light (ALC) treatment red (RD:650-750nm), white (WT:325-750nm), green (GN:530-545nm) and blue (BL:450-470nm) by balancing weight. Feed/water intakes (FWI), temperatures of each replicated brooder were measured daily and weight gains (WG) were measured weekly. At 14d, birds were weighed and 3 birds were placed into one experimental cage (3"x2") and continued the exposure to same ALC throughout the lifetime. Complete Randomize Design was adopted with 6 replicates. Each experimental cage was separated by double layered black polythene and those were photophically separated. Each experimental unit was provided with a feeder and a bell shaped drinker to ensure adlib. feed and water. Birds were remained in their allocated light treatment from 1-35d of age. Temperature and humidity were recorded daily. Chicks were fed with a commercial broiler starter (ME=2980 kCal/kg and CP = 21.5%) and finisher(ME=3050kCal/kg and CP=19.5%) diets. Vitamin C was provided at a rate of 5g/l of water to prevent from heat stress from 28d onwards. Light Environment RD, WT, GN and BL colour incandescent bulbs were used. WT served as the control. During the brooding period, artificial light was provided for 24 hours using 40W coloured incandescent bulbs and the light intensity was 60 lux at bird"s eye level. During growing period it was reduced to 20 lux (5W) and provided from 22:00h to around 0700-0730 hours of the following day (9 hours and 30 minutes) until the light intensity of the poultry shed reached 150 lux by day light. The light sources were adjusted to equal intensity by changing the heights, according to the recommendations of FAWC, UK, 1997. The light bulbs were wiped weekly in order to minimize dust built-up, which would have reduced the intensity and spectra. Measurement of Feed/Water Intake Pattern and Production FWI measured daily. To get an understanding of FWI pattern during 3 sessions of the day [(day time (07:30-18:00h), dark period (18:00-22:00h) and night time under artificial light (22:00-07:30 h)]; FWI were measured separately 4days/week covering those sessions. The FWI were recorded by subtracting the weight of the leftover feed/water every day and the every session. The growth of the birds was determined by weighing the birds weekly. All the birds were weighed and the average weights were recorded. Mortalities and their causes (if known) were recorded. On 36d, 6 birds/treatment were slaughtered humanely by neck dislocation. Each de-feathered carcass was dissected into skin, shank, internal organs (gizzard, crop, liver, heart) muscle/bone (right drumstick and the thigh) and weighed them separately. Behaviour Recordings The undisturbed behaviour of the chicks in the rearing room was recorded once a week in the morning [MN], evening [EV] and night [NT] for 3 consecutive hours at each session by adopting scan sampling method (Martin and Bateson, 1993) using an ethogram (Table 1). Twenty one most common behaviours performed by broilers were evaluated. Behaviours were evaluated on 3 focal birds/ pen, by direct visual scans for 15 minutes intervals. Behaviours were recorded by one-zero measurements (presence or absence) of each behaviour. It was recorded the number of birds in each experimental unit engaged in each of the activity defined by the ethogram. 39