Otros medicamentos no corticoideos

Since the training for the cognitive bias test had to be undertaken in an adjacent experimental room which did not have adequate temperature control, the birds had to be given sufficient time to reach an age when they were less dependent on supplementary heat. So, at 19 days of age, one bird from each pen was randomly selected and tagged for training on a visual discrimination task between palatable food (standard pelleted broiler feed sprayed with water) and unpalatable food (standard food sprayed with 4% quinine, see Appendix 1) in a test cage. Thus in total eight birds from each light treatment were recruited (four males and four females). Hodgson et al. (2007) reported no sex difference in the performance of Zebra finches in spatial or visual task, so the current study did not take the sex of the bird into consideration.

The feeds used for the discrimination test were identical to that feed given to the birds in their home pen (other than the addition of water/quinine). Previous studies have reported 2% quinine to be aversive to starlings and rats (Bateson and Matheson, 2007; Burman et al., 2009) and so this was considered to be an unpalatable but non-toxic additive. However due of the nature of broiler chickens being selected for fast growth rate and consequently large appetite, we decided to use a higher dose of quinine, namely 4%.

Birds randomly selected from pens 1- 4 were trained to associate palatable food with white cones and unpalatable food with black cones, while birds from pens 5-8 were trained to associate palatable food with black cones and unpalatable food with white cones. This was undertaken to counterbalance for colour of the cone to be associated with feed type. Each cone was made of paper and had a diameter of 7.5 mm and height of 25 mm (Figure 3.1).

Before starting the training session, birds were deprived of food for a period of two hours immediately after the six hour period of darkness to increase their motivation to subsequently feed in the discrimination task and thus increasing the chances of them successfully learning the task. Birds used for the training were taken out of their home pen to the test room which had a double decked cage placed on a table. One cage served as a holding cage and the other a test cage (see Figure 3.2 and 3.3 respectively). The holding cage was divided into four portions, one bird for each light wavelength/cone colour with which they were trained to associate with palatable feed. The test and

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holding cages were adjacent to each other so that any bird undergoing training in the test cage could see other birds in the holding cage to avoid isolation. The test room was fitted with white light having an intensity of approximately 300 lux, thus a somewhat greater intensity than what the birds had in their home pen but necessary so that they could easily identify the different cone colours. To avoid any bias associated with training birds from one treatment for a longer time than another, birds were selected alternatively from each lighting treatment/colour of training cones in a clockwise manner as presented in Figure 3.4 below.

Figure 3.1: Example of white cone Figure 3.2: Holding cage

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Figure 3.4: The order of selecting birds from the holding cage for training/cognitive tests

3.2.6.2 Training on a discrimination task and cognitive tests

Day 1 (acclimatisation): feed pellets identical to what the birds had in their home pen was scattered on a piece of brown paper spread on the floor of the test pen. The bird undergoing training was allowed to eat the pellets for a period of 5 minutes before it was returned to the holding cage. Each bird had two sessions of this acclimatisation (with an interval of 80 mins) to help them become habituated to feeding in the test pen. Day 2 (pre-training): palatable feed pellets were placed inside each of six cones of the appropriate colour which had been positioned on their side so that the feed was visible to the bird. Each bird had two sessions of this pre-training per day, each session lasting for five minutes. The aim of this process was to enable the birds to associate either white or black cones with palatable feed. White cones were made of standard white A4 printer paper, whilst black cones were made from standard white A4 paper printed with 100% black shading.

Day 3 & 4 (pre-training stage 2): Palatable feed pellets were placed in each of six petri dishes (5 cm diameter) which were fixed to the floor of the test pen and covered with either a white or black cone depending on which cone colour the bird was being trained to associate with palatable feed. The feed was placed in the petri dish so that when the bird opened the cone the feed was not scattered over the floor of the test cage. Each bird

blue light (pens 1-4) palatable feed from white cone

red light (pens 1-4) palatable feed from white cone

red light (pens 5-8) palatable feed from black cone

blue light (pens 5-8) palatable feed from black cone

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had two of these sessions per day with each session lasting five minutes and an interval between sessions of 80 minutes. This stage of the training was to teach the birds to flip open the cones to access the feed underneath.

Day 5, 6 & 7 (training): On each of these three days, each bird had two sessions with an interval of 80 minutes. On day 5 and 6, the birds were given eight cones in each session, four palatable and four unpalatable. On Day 7 the number of cones used in each session was increased to twelve (i.e. six palatable and six unpalatable) so that the birds were faced with a greater number of choices and also to prepare them for cognitive tests when they would be presented with equal number of the three cone types. Data from Day 7 was analysed and used for selecting birds for the cognitive test. The number of palatable cones out of the first six cones opened by each bird per session and the order in which the cones were opened (i.e. 1st palatable and 1st unpalatable) was determined. Birds that opened eight or more palatable cones across two sessions, i.e. birds which opened at least 66.6% palatable cones, were considered to have passed the learning criterion. Three birds had a score less than 66.6% (one bird from the red wavelength treatment and two birds from the blue wavelength), so 13 birds continued with the cognitive tests.

Day 8 (Cognitive tests): The aim of these tests was to explore how birds responded to an ambiguous (intermediate) cone when presented either alone (50% with palatable feed or 50% empty) or simultaneously with the palatable and unpalatable cones (at this time the ambiguous cone was empty). The ambiguous cone was grey in colour and of same dimensions as the palatable or unpalatable cones. For cognitive test 1, birds were presented with twelve ambiguous grey-coloured cones, formed from printing the standard white A4 paper with 50% shading. Six of these ambiguous cones had palatable feed while the other six were without feed, so that the birds might learn that opening the intermediate cone has only a 50% chance of obtaining a palatable food reward. Each bird had one session of this test which lasted for up to three mins but data was collected on the number of cones opened in the first minute. This test was carried out to assess the reaction of the birds to the ambiguous cone.

For cognitive test 2, birds were simultaneously presented with four cone types (palatable, unpalatable, ambiguous cone without feed) for a period of three minutes. Palatable feed was placed only under the palatable cones, whereas the ambiguous cones had no feed underneath them. This test was done to assess the decision of broiler

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chickens about which cones to open. The number of each of cone type opened for the first six cones was recorded and used for data analysis. For cognitive test 2, the order in which the cones were opened was also recorded for the 1st palatable, 1st ambiguous and 1st unpalatable cones.