CHAPTER 3: EFFECTS OF STRAIN AND SEX OF BIRD ON THE BEHAVIOUR OF FREE-RANGE
3.2 M ATERIALS AND M ETHODS
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chicken strains under free-range conditions. Behaviour in these strains of chickens has not been studied before.
3.2 Materials and Methods
62 3.2.3 Treatments and experimental design
A total of 144, 20-week old PK, OV and NN chickens were used in the study. Birds were separated by sex and allocated to 4 free-range pens such that there were 12 males × 3 strains on each of 2 pens and 12 females × 3 strains on each of 2 separate pens. Strains were mixed to enable comparison of their responses under exactly the same management conditions. The pens, measuring 900 m2 each (Figure 3.1),were demarcated by 2.2 m high wire mesh reinforced by wooden and steel poles. Chloris gayana (Katambora Rhodes grass) was the dominant grass species on the pens. The birds were weighed individually on a digital crane scale, model UME CCS-150K, S/N: NXC 100020, to determine initial body weights (BW).
3.2.4 Housing, feeding and health management
Day-old chicks of OV, NN and PK strains were obtained from parent flock kept at the Agricultural Research Council (ARC), Irene, Pretoria, SA. From d 1 to d 49, chicks of each strain were reared in 2 × 1.5 m pens in a closed well ventilated poultry house which was 4 × 10 m. The house floors were covered with a 10 cm thick layer of wood shavings. Heat and light was provided using 75 W infrared lamps. The day-old chicks were maintained at a temperature of 32°C which was gradually reduced to 21°C by 21 d old. A thermometer was kept in the house just above the level of the birds and was used to monitor changes in temperature.
A broiler starter diet was offered ad libitum from standard tube feeders. Potable tap water was offered ad libitum through 4 L plastic founts. Chicks were vaccinated against Newcastle disease at 10 and 35 d of age. A foot bath drenched with disinfectant (Virukill®, Hygrotech South Africa (Pty) Ltd, Pretoria, SA) was placed at the entrance to the brooding house.
63 N
NN: Naked Neck; OV: Ovambo; PK: Potchefstroom Koekoek
From d 50, birds were given a grower meal supplied by Meadow feeds, South Africa. The nutritional composition of the feeds is shown in Table 3.1. At 20 weeks old, selected birds were moved from the poultry house and assigned to 4 free-range pens as described earlier. The Rhodes grass paddocks were located side by side and separated by fencing. During establishment, they were watered regularly and were rain-fed once established.
Pen 3 (Males) Pen 4 (Females)
NN = 12
OV = 12 Gate
PK = 12
Pen 2 (Females) Pen 1 (Males) Cage
Passage Main entrance
30m
30m
Outer boundary fencing
Figure 3.1. Free-range pen lay-out as used in the study
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Table 3.1. Chemical composition (label values) of commercial broiler starter and grower feeds
Composition Starter Grower
Crude protein (g/kg) 200.0 180.0
Metabolisable energy (MJ/g) 12.8 13.0
ME/CP ratio (MJ/g) 0.1 0.1
Fat (g/kg) 25.0 25.0
Fibre (g/kg) 50.0 60.0
Moisture (g/kg) 120.0 120.0
Calcium (g/kg) 12.0 12.0
Phosphorus (g/kg) 6.0 5.5
Lysine (g/kg) 12.0 10.0
Feed supplied by Meadow Feeds, Pietermaritzburg, South Africa.
Weeds and other invader grass species were hand-picked and eliminated from the pens. Cattle manure was used to fertilize the grass paddocks. Wooden cages measuring 2.5 × 2 m were placed in one corner of each pen to provide shelter for the birds overnight. The cages, with slatted floors elevated 1 m above the ground surface, were fitted with wire mesh doors to deter predators. Doors were left open during the day and closed at night. A standard plastic drinker was placed under shade near each cage to provide clean water. The drinkers were inspected, washed and replenished at least twice a day to ensure ad libitum access to clean water.
65 3.2.5 Observations and data collection
After placement onto the pens, the birds were allowed a 7 d adaptation period before commencement of data collection. For behavioural observations, 3 birds, one of each strain, in each of the 4 pens were randomly chosen and marked with paint on the tip of the tail 20 minutes before being let out of the cage at 07:00 h. Paint of a different colour was used each time. Two trained observers recorded the activities of one bird each, simultaneously, in 2 pens purposively chosen to represent males and females for each observation session. Two pens of males and females were observed simultaneously for 30 minutes as a result. Birds in the other 2 pens were observed immediately after. The observers switched from pens with males to females and vice- versa.
Birds in each pen were observed 3 times a day, once a week, for a total of 3 weeks (1, 3, 5) from 0700 to 0800 h; 1200 to 1300 h and 1600 to 1700 h. During behaviour observation, a distance long enough to avoid disrupting the expression of normal behaviour by the birds was maintained. The time spent on each of the following behaviours was recorded:
1). Drinking behaviour (standing over a drinker with the head towards the drinker) 2). Foraging (pecking on vegetation in the paddock or scratching the ground) 3). Preening (cleaning of feathers)
4). Dust bathing (the act of rolling or moving around in dirt) 5). Hunting (chasing after insects)
6). Standing (remaining still in inactivity) 7). Other activities
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Other general behavioural activities like panting were also noted. A stopwatch, model 870A Century clock-timer, was used to time and record specific time intervals devoted to a particular activity. Ambient temperature (°C), and relative humidity (%) were recorded on the same days that behaviour observations were made. As a result, meteorological data reported in the current study correspond to measurements made on the day of observation. These were used to compute a temperature humidity index (THI). In addition to these observations, BW were measured weekly using a digital scale (± 1 g sensitivity) as part of a separate experiment.