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The relationship between pecking behaviour and growth rate of ostrich (Struthio camelus) chicks in captivity
APPLIED ANIMAL BEHAVIOUR SCIENCE
Applied Animal Behaviour Science 46 ( 1995) 93-101
The relationship between pecking behaviour and growth rate of ostrich (Struthio camelus) chicks in captivity M.S. Lambert”, D.C. Deemingb7”~*, R.M. Siblya, L.L. AyresC “School of Animal ~&Microbial
Sciences, University of Reading, Whit&nights, P.O. Box 228, Reading, RG6 2AJ, UK ‘School of Biological Sciences, University ofManchester, Manchester, Ml3 9PT, UK “Hangland Farm Ostriches Ltd., Upper Wardington, Banbury, OX1 7 ISU, UK
Accepted 30 May 1995
Abstract Captive ostrich (Strut& cum&s) chicks kept in ‘mixed weight’ groups grow more slowly than chicks kept in ‘similar weight’ groups. It has been suggested that this was a result of aggressive pecking of smaller chicks by larger birds, reducing the growth rates of the former by prevention of feeding. Here we test the hypothesis that position in a peck order correlates with growth rate in chicks. Two groups of 12 chicks, one group of birds of a similar weight and one group where chick weight was mixed, were kept under quarantine conditions for 5 weeks. Pecking behaviour and growth rate of individual birds were recorded. Chicks pecked the toes and heads of their companions although the rate of pecking varied between birds. At the end of the study period chicks in the mixed weight group were larger than birds in the similar weight group. The correlations between pecking rate (of both heads and toes) and growth rate were negative for both groups of birds. Pecking at companions in ostrich chicks was limited to individual birds who may be less successful at feeding and so grow more slowly. The hypothesis that growth of some ostrich chicks was reduced because of harassment by larger birds was not supported by the data and the study leaves unexplained the finding that chicks in mixed weight groups grow more slowly than chicks in equal weight groups. Keywords: Ostrich; Chicks; Behaviour; Growth
1. Introduction
Although some information is available on the conditions required for the successful rearing of ostrich chicks under farming conditions (Deeming et al., 1993; Deeming and *Corresponding author at: Hangland Farm Ostriches Ltd., Upper Wardington, Banbury, OX17 1SU. UK. Tel.: 01295 712204; fax: 01295 710628. 016%1591/95/$09.50 0 1995 Elsevier Science B.V. All rights reserved SSDfO168-1591(95)00640-O
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Ayres, 1994), problems still exist in the rearing of chicks. In particular, development of healthy ostrich chicks is characterised by variations in growth rate (Gandini et al., 1986; Guittin, 1987; Degen et al., 1991; Deeming et al., 1993) which can adversely affect the value of a bird for breeding or slaughter. Although this variance with increasing age may be due in part to inherited factors (Du Preez et al., 1992)) gender (Deeming et al., 1993) or diet (D.C. Deeming, P. Powell, A.C.K. Dick and L.L. Ayres, personal observations), the physical and social environment of birds is probably also important. Some behaviours of ostriches in the wild have been described (Sauer and Sauer, 1966a,b; Bertram, 1992)) but with the exception of two reports (Degen et al., 1989; Bubier et al., 1995) little is known of their behaviour in captivity. By contrast, the development of social behaviour in domestic fowl (Gallus gallus) is well described and position within a pecking order can affect rates of feeding and drinking (Guhl, 1953, 1958; Wood-Gush, 1955). To investigate possible social factors affecting ostrich growth rates, Deeming and Ayres ( 1994) sorted chicks into four groups according to weight and found that small chicks removed from the influence of larger companions grew faster than the largest chicks. Birds in groups of similar weight grew better than chicks in groups of mixed weights. Deeming and Ayres ( 1994) observed that some large birds pecked smaller companions and hence proposed that, in a mixed weight group of chicks, dominant birds were suppressing the growth rates of their subordinates by preventing them from feeding as much as they would otherwise have done. It was suggested that harassment of the subordinates was alleviated when the size differential within a group was reduced. Here we test the hypothesis that pecking behaviour correlates with growth rate by examining the associations between individual growth rates and the extent to which birds delivered or received pecks from their companions.
2. Materials and methods Incubation of the eggs and rearing of ostrich chicks was carried out under class 1 quarantine restrictions imposed by the Ministry of Agriculture, Fisheries and Food (MAFF) . Eggs were imported from commercial ostrich farms in Zimbabwe and incubated in a single stage incubator-hatcher (Deeming, 1995a). Upon hatching, each chick was fitted with a numbered VelcroTM leg band, identifying the chick with its egg, and was transferred to the rearing barn. The quarantine period started when the last chick had hatched ( 17 December 1993). Postmortem examinations of any chicks were carried out at the MAFF Veterinary Investigation Centre, Luddington, Stratford-upon-Avon. No chicks tested compromised the quarantine conditions. 2.1. Rearing environment The central electric rearing
rearing barn was divided into ten stalls, each measuring 2.3 X 3.7 m*, leaving a gangway with five stalls on either side. Each stall was equipped with underfloor heating and two overhead ceramic heat lamps. The temperature regimen of the barn was as described by Deeming et al. ( 1993) and light was provided by overhead
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Animal Behaviour Science 46 (1995) 93-101
Table 1 The effects of neck banding on the pecking behaviour of ostrich chicks Behaviour
Head directed pecks Toe directed pecks Pecks to band
Neck banded chicks
No neck banded chicks
Group 1
Group 2
Group 2
Group 1
6 44 0
3 222 5
5 208 0
4 77 0
fluorescent strip lighting ( 10 h light, 14 h dark). During the light hours the chicks were not left unattended. The concrete floor of each stall was swept and scrubbed each morning with a solution of virucidal disinfectant (Virkon S) and dung was removed from the stalls regularly throughout the day. A solution of disinfectant (MacroKil 200) was used for cleaning food bowls and water containers. The chicks were given fresh water several times daily and fed ad libitum with pelleted food formulated for ratites (Mazuri Zoo Foods). All chicks were weighed each morning using an electronic top pan balance. At the earliest opportunity, the sex of each chick was determined by cloaca1 examination (Gandini and Keffen, 1985). The health of the chicks was continuously monitored and any medication or other treatment required by the birds was noted. Nine of the study chicks died of various ailments before the end of the study period; four from group A and five from group B. Post mortem examinations showed that four birds had yolk sac infections with one of these also having an intestinal blockage caused by the build-up of urate solids. Three chicks were culled due to a rotational deformity of either tibiotarsus. 2.2. Neck banding Coloured neck bands of 150 X 10 mm2 strips of VelcroTM covered by strips of coloured insulation tape were used to identify individual birds. Green tape was not used because of the high level of interest it stimulated (Bubier et al., 1995). Initial trials investigated the effect of neck bands on pecking. Two sets of six birds were chosen at random from those that were 1 day old on 17 December 1993. The birds in group 1 were given neck bands, those in group 2 were not. Each group was then placed in its own stall and the frequency of pecking towards the head or neck was recorded for periods lasting 1 h. The next day the neck bands were swapped between the groups and the frequency of pecking behaviour in each of the two groups was recorded again. The presence of neck bands did not cause undue neck and head directed pecking although group 2 exhibited more pecking behaviour than group 1 (Table 1) . In neither stage of the experiment did neck banded chicks peck at heads significantly more than non neck banded controls (x2 = 0.4, P > 0.05, d.f. = 1 and 0.5, P> 0.05 for groups 1 and 2, respectively). 2.3. Observations
of aggressive
chick interactions
On Day 3 of quarantine (20 December 1993 - 4 to 5 days old post hatching) chicks were selected for two experimental groups which were housed in identical adjacent stalls. Twelve
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chicks weighing between 700 and 800 g were assigned to group A (similar weight) whereas the remaining birds, weighing between 500 and 900 g, were in group B (mixed weight). Initial observations showed that intragroup interactions were frequent. Two behaviours were prevalent and deemed to be worthy of investigation; these were: (i) toe directed pecking; the ‘aggressor’ repeatedly pecked at the toes of a “recipient’ until the recipient moved out of range; and (ii) head directed pecking; the ‘aggressor’ took the ‘recipient’ by the head, usually holding the recipient’s eyelid or head feathers. This normally resulted in the recipient immediately moving out of range. From a vantage point between the two experimental stalls the observer could record almost all incidents of toe and head pecking in both stalls, noting the ‘aggressor’ and ‘recipient’ in each case. Care was taken to frequently switch attention between stalls to minimise biases from unequal allocation of attention between the two experimental groups. Data were collected for a total of eight 3-h recording sessions over the statuary quarantine period of 35 days.
3. Results 3.1. Observations
of chick interactions
Toe and head pecking were observed throughout the whole of the study period, but they were mostly initiated by, and often limited to, a few individual birds (Table 2). Birds that pecked others frequently are here referred to as habitual peckers. Habitual toe peckers were observed in each group to actively seek the toes of stall mates and peck them repeatedly and were rarely seen feeding. Toe pecking was normally continued until the recipient moved out of range of the pecker. Any bird unable to move out of range suffered almost incessant toe pecking. Although there was normally only one or two habitual toe peckers within each group at any one time, toe pecking was sometimes stimulated in other chicks by the actions of a habitual toe pecker although the period and intensity of pecking was much less. Thus, the frequency of toe pecking within each group was high while habitual toe peckers were present whereas when habitual toe peckers died, such behaviour within that group ceased. For example, the death of chick 273 led to a complete cessation of toe pecking in group B, but the survival of chick 56 in group A meant that toe pecking persisted to the end of quarantine (Fig. 1) . All head pecking within a group was due to one, or sometimes two, birds. For this reason no attempt was made to construct a peck order. The companions of a head pecking bird did not approach the recipient of a head peck. Pecking always resulted in the withdrawal of the recipient, whereon the pecker would, more often than not, seek another bird. 3.2. Growth rates Following hatching, all chicks underwent an initial decrease in weight, with the lowest weight for each chick being recorded around Day 7 of quarantine after which almost all birds gained weight. Variation in chick weight within both experimental groups increased throughout the study period (Table 2). By Day 3.5, birds in group A had attained significantly
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Table 2 Weights of ostrich chicks (g) on Day 3 of quarantine (20 December 1993) and Day 35 of quarantine (21 January 1994) together with average growth rates (g day-’ from Day 3 to Day 35). Missing data indicates that the bird died before the end of quarantine. Hours of observation, and the number of toe and head pecks given and received (per hour of observations) are indicated for each bird Chick
Weight 20 December
1993
Weight 21 January
1994
Growth rate
Hours observed
Toe pecks
Head pecks
given
received
given
received
9 24 24 24 18 24 24 24 18 24 24 12
0.0 0.9 10.5 4.4 8.8 2.5 2.3 0.9 1.2 0.5 0.8 1.5
1.3 5.9 0.3 1.4 0.8 1.3 2.9 5.2 6.9 2.6 4.5 0.4
0.1 0.1 0.1 0.1 0.1 0.9 12.4 0.2 0.4 0.2 0.0 0.1
2.0 1.3 1.3 1.3 1.2 1.3 0.5 1.2 3.2 1.1 1.2 2.6
24 24 24 24 24 24 12 18 24 6 9 9
2.1 0.0 0.1 1.6 0.1 0.2 1.1 0.1 0.1 0.5 48.8 2.9
2.0 1.8 1.7 1.1 6.0 2.1 2.8 2.1 4.0 6.4 0.4 3.1
4.5 0.0 0.0 0.3 0.0 0.3 4.9 14.6 0.0 0.0 2.3 0.2
3.0 2.1 1.9 1.9 3.3 1.6 1.2 1.8 3.1 1.0 0.4 0.9
A - Similar weight group 17
780
36
710
56
715
86
775
93
773
109
725
110 138 150 212 301 312
710 740 730 742 731 757
B -Mixed
weight group 815 585 635 715 765 680 885 845 532 779 595 624
2 6 45 61 66 81 119 166 176 265 273 274
3400 2990 3040
84 71 71
3015 1825 3215
72 33 77
4160 3675
107 92 _
2295 2445 2215 1130 2625 3095
46 58 49 13 58 75 -
2785
70 _
higher absolute .weights than the birds in group B (3 165 f 673 and 2370 f 624 for groups A and B, respectively; two sample r-tests, P = 0.035). Growth rate (g d-’ between Days 3 and 35 of quarantine was greater for birds assigned to group A (similar weight) than those in group B (75.83 f 2.67 and 52.96 f 2.93 for groups A and B, respectively; two sample ttests, P= 0.055). There were no gender differences in growth rate, nor were there between group, or gender, differences in pecking behaviour. These results are consistent with the finding that chicks in ‘mixed weight’ groups grow more slowly than chicks in ‘similar weight’ groups (Deeming and Ayres, 1994). At the start of the study period, three birds (6 1,66 and 265), allocated to group B were within the same weight range as the birds allocated to group A. The two surviving birds at the end of quarantine (61 and 66) attained lower final weights and lower growth rates than all but one of their group A counterparts.
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3.3. Correlation between pecking behaviour and growth rate The total numbers of toe and head pecks delivered, and received, by each chick in the entire study period are shown in Table 2. Contrary to prediction, the correlations between the number of pecks received and growth rate were positive in all cases (toe pecks: r = 0.242 and 0.446 for groups A and B, respectively; head pecks: r = 0.682 and 0.168 for groups A and B, respectively). Also contrary to prediction, growth rate was negatively correlated with pecks given (toe pecks: r = - 0.286 and - 0.686; head pecks: r = - 0.820 and - 0.172; in both cases the group A correlation is given before that for group B) . Growth rates of individual birds were associated with their behaviour. Bird 273, a habitual toe pecker in group B died on Day 8 of quarantine. Postmortem examination revealed no pathogens but showed that its yolk sac weighed only 2.2 g which, at 3.5% of the total weight of the chick, was 10% of the yolk recorded in other chicks which died at a similar age (Deeming, 1995b). Chick 176 in group B, despite being heavily toe pecked and the second smallest chick on Day 3, survived to Day 35 of quarantine when it was the second largest chick in the group (Table 2). Bird 110 in group A pecked other birds most and it initiated almost every pecking encounter. On Day 35 of quarantine this bird was the smallest in its group and it achieved the smallest growth rate (Table 2).
30.
20
0 H -o- Toe pecks
P I? P 0
+
Head pecks
10
0 Days in quarantine
M.S. Lambert et al. /Applied
Animal Behaviour Science 46 (1995) 93-101
99
30.
\
I-
I
0 Fig. 1. Changes in pecking behaviour bird per 3 h recording session.
I
-z-
Toe pecks
+
Head pecks
&----T
20 10 Days in quarantine
over time in groups A( a) and B(b)
1
30
Pecking rate is measured as pecks per
4. Discussion This study was designed to test the hypothesis that birds subjected to more aggressive pecking (of which there might be more in a mixed weight group) grow more slowly because they have reduced access to food (Deeming and Ayres, 1994). The results, however, did not support this hypothesis. Pecking behaviour did not correlate with growth rate and indeed the trends were in the opposite direction. Thus growth rate was negatively correlated with the number of toe/head pecks delivered by a bird and positively correlated with the number of toe/head pecks received. It seems that in contrast to domestic fowl (Guhl, 1953), where aggression leads to greater dominance, aggressive ostrich chicks seem to be disadvantaged. Several birds which habitually toe or head pecked companions had very poor rates of growth or, in extreme cases, died. The smallest birds in both groups A and B ( 110 and 61) were the most aggressive within the group and had the lowest rates of growth. ‘Victims’ of toe pecking survived to the end of quarantine with little effect on their rate of growth. The reason why habitual toe or head peckers have such poor rates of growth or even die may lie in the pathological development of their feeding behaviour: pecking at companions may be misdirected feeding. If such birds do not take in sufficient feed they cannot maintain
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their metabolism and grow. One chick 273 died during the study period at a point when its yolk sac could not support its habitual toe pecking activity. The small size of chicks 110 and 61 may also be attributed to pathological behaviour which prevented sufficient feed intake. Head pecking is a precursor to fighting for dominance in domestic fowl chicks. Aggressive pecking is usually observed by the third week post hatching, avoidance of aggressive chicks and fighting by Week 6 (Guhl, 1958). In domestic fowl, dominance relationships are not fully established until at least 8 weeks of age (Guhl, 1953). This is presumably when the chicks can reliably recognise each other and thus avoid dominant individuals. At 5 weeks of age, ostrich chicks appeared not to recognise each other, or if they did it was of little consequence to them. Pecking birds were not avoided until pecking was initiated. All birds were periodically harassed by one or two aggressive chicks which appeared to peck at other chicks at random. We conclude that dominance hierarchies were not established by 5 weeks of age in our ostrich chicks and ‘subordinate’ birds were not present. The present study sought to explain the differences in growth rates between chicks in similar weight groups and those in mixed weight groups by examining behavioural components to growth. Despite demonstrating that the behaviour of particular birds can affect their rates of growth it is still unclear how separating chicks by weight can facilitate differences in growth.
Acknowledgements Many thanks to Allan Dick, MRCVS, of the Croft Veterinary Centre and Ann Courtenay of the Veterinary Investigation Centre, Luddington for their expertise in veterinary care and pathology required during the course of this study. We would like to thank Frank, Dene and Victoria Ayres and Sally Andrews of Hangland Farm for their kind assistance.
References Bertram, B.C.R., 1992. The Ostrich Communal Nesting System. Princeton University Press, Princeton, New Jersey. Bubier, N.E., Lambert, M.S., Deeming, DC., Ayres, L.L. and Sibly, R.M., 1995. Observations on the behaviour of ostrich (Struthio camelus) chicks in captivity. Br. Poult. Sci., in press. Deeming, D.C., 1995a. Factors affecting hatchability during commercial incubation of ostrich (Struthio camelus) eggs. Br. Poult. Sci., 36: 51-65. Deeming, D.C., 1995b. Possible effects of microbial infection on yolk utilisation in ostrich chicks. Vet. Rec., 136, 270-27 1. Deeming, D.C. and Ayres, L., 1994. Factors affecting the growth rates of ostrich (Srrurhio camelus) chicks in captivity. Vet. Rec., 135: 617-622. Deeming, D.C., Ayms, L. and Ayres, F.J., 1993. Observations on the commercial production of ostrich (Struthio camelus) in the United Kingdom: mating of Chicks. Vet. Rec., 132: 627-631. Degen, A.A., Ram, M. and Rosenstrauch, A., 1989. Time-activity budget of ostriches (Struthio camelus) offered concentrate feed and maintained in outdoor pens. Appl. Anim. Behav. Sci., 22: 347-358. Degen, A.A., Ram, M., Rosenstrauch, A. and Plavnik. I., 1991. Growth rate, total body water volume, dry matter intake and water consumption of domesticated ostriches (Struthio camelus). Anim. Prod., 52: 225-232.
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Du Preez, J.J., Jarvis, M.J.F., Capatos, D. and de Kock, J., 1992. A note on growth curves for the ostrich (Struthio camelus). Anim. Prod., 34: 150-152. Gandini, G.C.M. and Keffen, R.H., 1985. Sex determination of the South African ostrich (Struthio camelus). J. S. Afr. Vet. Assoc., 56: 209-210. Gandini, G.C.M., Burroughs, R.E.J. and Ebedes, H., 1986. Preliminary investigation into the nutrition of ostrich chicks (Struthio camelus) under intensive conditions. J. S. Afr. Vet. Assoc., 57: 39-42. Guhl, A.M., 1953. Social behaviour of the domestic fowl. Kansas Agric. Exp. Sm., Tech. Bull., 73. Guhl, A.M., 1958. The development of social organisation in the domestic chick. Anim. Behav., 6: 92-l 11. Guittin, P., 1987. Croissance de l’autruche en part zoologique. Can. J. Zool., 65: 3056-3061. Sauer, E.G.F. and Sauer, E.M.. 1966a. The behaviour and ecology of the South African ostrich. Living Bird, 5: 45-75. Sauer, E.G.F. and Sauer, E.M., 1966b. Social behaviour of the South African ostrich (Struthio camelus australis). Ostrich, Suppl. 6: 184-191. Wood-Gush, D.G.M., 1955. The behaviour of the domestic chicken: a review of the literature. Br. J. Anim. Behav., 3: 81-110.
Applied Animal Behaviour Science 46 ( 1995) 93-101
The relationship between pecking behaviour and growth rate of ostrich (Struthio camelus) chicks in captivity M.S. Lambert”, D.C. Deemingb7”~*, R.M. Siblya, L.L. AyresC “School of Animal ~&Microbial
Sciences, University of Reading, Whit&nights, P.O. Box 228, Reading, RG6 2AJ, UK ‘School of Biological Sciences, University ofManchester, Manchester, Ml3 9PT, UK “Hangland Farm Ostriches Ltd., Upper Wardington, Banbury, OX1 7 ISU, UK
Accepted 30 May 1995
Abstract Captive ostrich (Strut& cum&s) chicks kept in ‘mixed weight’ groups grow more slowly than chicks kept in ‘similar weight’ groups. It has been suggested that this was a result of aggressive pecking of smaller chicks by larger birds, reducing the growth rates of the former by prevention of feeding. Here we test the hypothesis that position in a peck order correlates with growth rate in chicks. Two groups of 12 chicks, one group of birds of a similar weight and one group where chick weight was mixed, were kept under quarantine conditions for 5 weeks. Pecking behaviour and growth rate of individual birds were recorded. Chicks pecked the toes and heads of their companions although the rate of pecking varied between birds. At the end of the study period chicks in the mixed weight group were larger than birds in the similar weight group. The correlations between pecking rate (of both heads and toes) and growth rate were negative for both groups of birds. Pecking at companions in ostrich chicks was limited to individual birds who may be less successful at feeding and so grow more slowly. The hypothesis that growth of some ostrich chicks was reduced because of harassment by larger birds was not supported by the data and the study leaves unexplained the finding that chicks in mixed weight groups grow more slowly than chicks in equal weight groups. Keywords: Ostrich; Chicks; Behaviour; Growth
1. Introduction
Although some information is available on the conditions required for the successful rearing of ostrich chicks under farming conditions (Deeming et al., 1993; Deeming and *Corresponding author at: Hangland Farm Ostriches Ltd., Upper Wardington, Banbury, OX17 1SU. UK. Tel.: 01295 712204; fax: 01295 710628. 016%1591/95/$09.50 0 1995 Elsevier Science B.V. All rights reserved SSDfO168-1591(95)00640-O
94
M.S. Lambert et al. /Applied
Animal Behaviour Science 46 (:995) 93-101
Ayres, 1994), problems still exist in the rearing of chicks. In particular, development of healthy ostrich chicks is characterised by variations in growth rate (Gandini et al., 1986; Guittin, 1987; Degen et al., 1991; Deeming et al., 1993) which can adversely affect the value of a bird for breeding or slaughter. Although this variance with increasing age may be due in part to inherited factors (Du Preez et al., 1992)) gender (Deeming et al., 1993) or diet (D.C. Deeming, P. Powell, A.C.K. Dick and L.L. Ayres, personal observations), the physical and social environment of birds is probably also important. Some behaviours of ostriches in the wild have been described (Sauer and Sauer, 1966a,b; Bertram, 1992)) but with the exception of two reports (Degen et al., 1989; Bubier et al., 1995) little is known of their behaviour in captivity. By contrast, the development of social behaviour in domestic fowl (Gallus gallus) is well described and position within a pecking order can affect rates of feeding and drinking (Guhl, 1953, 1958; Wood-Gush, 1955). To investigate possible social factors affecting ostrich growth rates, Deeming and Ayres ( 1994) sorted chicks into four groups according to weight and found that small chicks removed from the influence of larger companions grew faster than the largest chicks. Birds in groups of similar weight grew better than chicks in groups of mixed weights. Deeming and Ayres ( 1994) observed that some large birds pecked smaller companions and hence proposed that, in a mixed weight group of chicks, dominant birds were suppressing the growth rates of their subordinates by preventing them from feeding as much as they would otherwise have done. It was suggested that harassment of the subordinates was alleviated when the size differential within a group was reduced. Here we test the hypothesis that pecking behaviour correlates with growth rate by examining the associations between individual growth rates and the extent to which birds delivered or received pecks from their companions.
2. Materials and methods Incubation of the eggs and rearing of ostrich chicks was carried out under class 1 quarantine restrictions imposed by the Ministry of Agriculture, Fisheries and Food (MAFF) . Eggs were imported from commercial ostrich farms in Zimbabwe and incubated in a single stage incubator-hatcher (Deeming, 1995a). Upon hatching, each chick was fitted with a numbered VelcroTM leg band, identifying the chick with its egg, and was transferred to the rearing barn. The quarantine period started when the last chick had hatched ( 17 December 1993). Postmortem examinations of any chicks were carried out at the MAFF Veterinary Investigation Centre, Luddington, Stratford-upon-Avon. No chicks tested compromised the quarantine conditions. 2.1. Rearing environment The central electric rearing
rearing barn was divided into ten stalls, each measuring 2.3 X 3.7 m*, leaving a gangway with five stalls on either side. Each stall was equipped with underfloor heating and two overhead ceramic heat lamps. The temperature regimen of the barn was as described by Deeming et al. ( 1993) and light was provided by overhead
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Animal Behaviour Science 46 (1995) 93-101
Table 1 The effects of neck banding on the pecking behaviour of ostrich chicks Behaviour
Head directed pecks Toe directed pecks Pecks to band
Neck banded chicks
No neck banded chicks
Group 1
Group 2
Group 2
Group 1
6 44 0
3 222 5
5 208 0
4 77 0
fluorescent strip lighting ( 10 h light, 14 h dark). During the light hours the chicks were not left unattended. The concrete floor of each stall was swept and scrubbed each morning with a solution of virucidal disinfectant (Virkon S) and dung was removed from the stalls regularly throughout the day. A solution of disinfectant (MacroKil 200) was used for cleaning food bowls and water containers. The chicks were given fresh water several times daily and fed ad libitum with pelleted food formulated for ratites (Mazuri Zoo Foods). All chicks were weighed each morning using an electronic top pan balance. At the earliest opportunity, the sex of each chick was determined by cloaca1 examination (Gandini and Keffen, 1985). The health of the chicks was continuously monitored and any medication or other treatment required by the birds was noted. Nine of the study chicks died of various ailments before the end of the study period; four from group A and five from group B. Post mortem examinations showed that four birds had yolk sac infections with one of these also having an intestinal blockage caused by the build-up of urate solids. Three chicks were culled due to a rotational deformity of either tibiotarsus. 2.2. Neck banding Coloured neck bands of 150 X 10 mm2 strips of VelcroTM covered by strips of coloured insulation tape were used to identify individual birds. Green tape was not used because of the high level of interest it stimulated (Bubier et al., 1995). Initial trials investigated the effect of neck bands on pecking. Two sets of six birds were chosen at random from those that were 1 day old on 17 December 1993. The birds in group 1 were given neck bands, those in group 2 were not. Each group was then placed in its own stall and the frequency of pecking towards the head or neck was recorded for periods lasting 1 h. The next day the neck bands were swapped between the groups and the frequency of pecking behaviour in each of the two groups was recorded again. The presence of neck bands did not cause undue neck and head directed pecking although group 2 exhibited more pecking behaviour than group 1 (Table 1) . In neither stage of the experiment did neck banded chicks peck at heads significantly more than non neck banded controls (x2 = 0.4, P > 0.05, d.f. = 1 and 0.5, P> 0.05 for groups 1 and 2, respectively). 2.3. Observations
of aggressive
chick interactions
On Day 3 of quarantine (20 December 1993 - 4 to 5 days old post hatching) chicks were selected for two experimental groups which were housed in identical adjacent stalls. Twelve
96
M.S. Lambert et al. /Applied
Animal Behaviour Science 46 (1995) 93-101
chicks weighing between 700 and 800 g were assigned to group A (similar weight) whereas the remaining birds, weighing between 500 and 900 g, were in group B (mixed weight). Initial observations showed that intragroup interactions were frequent. Two behaviours were prevalent and deemed to be worthy of investigation; these were: (i) toe directed pecking; the ‘aggressor’ repeatedly pecked at the toes of a “recipient’ until the recipient moved out of range; and (ii) head directed pecking; the ‘aggressor’ took the ‘recipient’ by the head, usually holding the recipient’s eyelid or head feathers. This normally resulted in the recipient immediately moving out of range. From a vantage point between the two experimental stalls the observer could record almost all incidents of toe and head pecking in both stalls, noting the ‘aggressor’ and ‘recipient’ in each case. Care was taken to frequently switch attention between stalls to minimise biases from unequal allocation of attention between the two experimental groups. Data were collected for a total of eight 3-h recording sessions over the statuary quarantine period of 35 days.
3. Results 3.1. Observations
of chick interactions
Toe and head pecking were observed throughout the whole of the study period, but they were mostly initiated by, and often limited to, a few individual birds (Table 2). Birds that pecked others frequently are here referred to as habitual peckers. Habitual toe peckers were observed in each group to actively seek the toes of stall mates and peck them repeatedly and were rarely seen feeding. Toe pecking was normally continued until the recipient moved out of range of the pecker. Any bird unable to move out of range suffered almost incessant toe pecking. Although there was normally only one or two habitual toe peckers within each group at any one time, toe pecking was sometimes stimulated in other chicks by the actions of a habitual toe pecker although the period and intensity of pecking was much less. Thus, the frequency of toe pecking within each group was high while habitual toe peckers were present whereas when habitual toe peckers died, such behaviour within that group ceased. For example, the death of chick 273 led to a complete cessation of toe pecking in group B, but the survival of chick 56 in group A meant that toe pecking persisted to the end of quarantine (Fig. 1) . All head pecking within a group was due to one, or sometimes two, birds. For this reason no attempt was made to construct a peck order. The companions of a head pecking bird did not approach the recipient of a head peck. Pecking always resulted in the withdrawal of the recipient, whereon the pecker would, more often than not, seek another bird. 3.2. Growth rates Following hatching, all chicks underwent an initial decrease in weight, with the lowest weight for each chick being recorded around Day 7 of quarantine after which almost all birds gained weight. Variation in chick weight within both experimental groups increased throughout the study period (Table 2). By Day 3.5, birds in group A had attained significantly
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Table 2 Weights of ostrich chicks (g) on Day 3 of quarantine (20 December 1993) and Day 35 of quarantine (21 January 1994) together with average growth rates (g day-’ from Day 3 to Day 35). Missing data indicates that the bird died before the end of quarantine. Hours of observation, and the number of toe and head pecks given and received (per hour of observations) are indicated for each bird Chick
Weight 20 December
1993
Weight 21 January
1994
Growth rate
Hours observed
Toe pecks
Head pecks
given
received
given
received
9 24 24 24 18 24 24 24 18 24 24 12
0.0 0.9 10.5 4.4 8.8 2.5 2.3 0.9 1.2 0.5 0.8 1.5
1.3 5.9 0.3 1.4 0.8 1.3 2.9 5.2 6.9 2.6 4.5 0.4
0.1 0.1 0.1 0.1 0.1 0.9 12.4 0.2 0.4 0.2 0.0 0.1
2.0 1.3 1.3 1.3 1.2 1.3 0.5 1.2 3.2 1.1 1.2 2.6
24 24 24 24 24 24 12 18 24 6 9 9
2.1 0.0 0.1 1.6 0.1 0.2 1.1 0.1 0.1 0.5 48.8 2.9
2.0 1.8 1.7 1.1 6.0 2.1 2.8 2.1 4.0 6.4 0.4 3.1
4.5 0.0 0.0 0.3 0.0 0.3 4.9 14.6 0.0 0.0 2.3 0.2
3.0 2.1 1.9 1.9 3.3 1.6 1.2 1.8 3.1 1.0 0.4 0.9
A - Similar weight group 17
780
36
710
56
715
86
775
93
773
109
725
110 138 150 212 301 312
710 740 730 742 731 757
B -Mixed
weight group 815 585 635 715 765 680 885 845 532 779 595 624
2 6 45 61 66 81 119 166 176 265 273 274
3400 2990 3040
84 71 71
3015 1825 3215
72 33 77
4160 3675
107 92 _
2295 2445 2215 1130 2625 3095
46 58 49 13 58 75 -
2785
70 _
higher absolute .weights than the birds in group B (3 165 f 673 and 2370 f 624 for groups A and B, respectively; two sample r-tests, P = 0.035). Growth rate (g d-’ between Days 3 and 35 of quarantine was greater for birds assigned to group A (similar weight) than those in group B (75.83 f 2.67 and 52.96 f 2.93 for groups A and B, respectively; two sample ttests, P= 0.055). There were no gender differences in growth rate, nor were there between group, or gender, differences in pecking behaviour. These results are consistent with the finding that chicks in ‘mixed weight’ groups grow more slowly than chicks in ‘similar weight’ groups (Deeming and Ayres, 1994). At the start of the study period, three birds (6 1,66 and 265), allocated to group B were within the same weight range as the birds allocated to group A. The two surviving birds at the end of quarantine (61 and 66) attained lower final weights and lower growth rates than all but one of their group A counterparts.
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3.3. Correlation between pecking behaviour and growth rate The total numbers of toe and head pecks delivered, and received, by each chick in the entire study period are shown in Table 2. Contrary to prediction, the correlations between the number of pecks received and growth rate were positive in all cases (toe pecks: r = 0.242 and 0.446 for groups A and B, respectively; head pecks: r = 0.682 and 0.168 for groups A and B, respectively). Also contrary to prediction, growth rate was negatively correlated with pecks given (toe pecks: r = - 0.286 and - 0.686; head pecks: r = - 0.820 and - 0.172; in both cases the group A correlation is given before that for group B) . Growth rates of individual birds were associated with their behaviour. Bird 273, a habitual toe pecker in group B died on Day 8 of quarantine. Postmortem examination revealed no pathogens but showed that its yolk sac weighed only 2.2 g which, at 3.5% of the total weight of the chick, was 10% of the yolk recorded in other chicks which died at a similar age (Deeming, 1995b). Chick 176 in group B, despite being heavily toe pecked and the second smallest chick on Day 3, survived to Day 35 of quarantine when it was the second largest chick in the group (Table 2). Bird 110 in group A pecked other birds most and it initiated almost every pecking encounter. On Day 35 of quarantine this bird was the smallest in its group and it achieved the smallest growth rate (Table 2).
30.
20
0 H -o- Toe pecks
P I? P 0
+
Head pecks
10
0 Days in quarantine
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Animal Behaviour Science 46 (1995) 93-101
99
30.
\
I-
I
0 Fig. 1. Changes in pecking behaviour bird per 3 h recording session.
I
-z-
Toe pecks
+
Head pecks
&----T
20 10 Days in quarantine
over time in groups A( a) and B(b)
1
30
Pecking rate is measured as pecks per
4. Discussion This study was designed to test the hypothesis that birds subjected to more aggressive pecking (of which there might be more in a mixed weight group) grow more slowly because they have reduced access to food (Deeming and Ayres, 1994). The results, however, did not support this hypothesis. Pecking behaviour did not correlate with growth rate and indeed the trends were in the opposite direction. Thus growth rate was negatively correlated with the number of toe/head pecks delivered by a bird and positively correlated with the number of toe/head pecks received. It seems that in contrast to domestic fowl (Guhl, 1953), where aggression leads to greater dominance, aggressive ostrich chicks seem to be disadvantaged. Several birds which habitually toe or head pecked companions had very poor rates of growth or, in extreme cases, died. The smallest birds in both groups A and B ( 110 and 61) were the most aggressive within the group and had the lowest rates of growth. ‘Victims’ of toe pecking survived to the end of quarantine with little effect on their rate of growth. The reason why habitual toe or head peckers have such poor rates of growth or even die may lie in the pathological development of their feeding behaviour: pecking at companions may be misdirected feeding. If such birds do not take in sufficient feed they cannot maintain
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their metabolism and grow. One chick 273 died during the study period at a point when its yolk sac could not support its habitual toe pecking activity. The small size of chicks 110 and 61 may also be attributed to pathological behaviour which prevented sufficient feed intake. Head pecking is a precursor to fighting for dominance in domestic fowl chicks. Aggressive pecking is usually observed by the third week post hatching, avoidance of aggressive chicks and fighting by Week 6 (Guhl, 1958). In domestic fowl, dominance relationships are not fully established until at least 8 weeks of age (Guhl, 1953). This is presumably when the chicks can reliably recognise each other and thus avoid dominant individuals. At 5 weeks of age, ostrich chicks appeared not to recognise each other, or if they did it was of little consequence to them. Pecking birds were not avoided until pecking was initiated. All birds were periodically harassed by one or two aggressive chicks which appeared to peck at other chicks at random. We conclude that dominance hierarchies were not established by 5 weeks of age in our ostrich chicks and ‘subordinate’ birds were not present. The present study sought to explain the differences in growth rates between chicks in similar weight groups and those in mixed weight groups by examining behavioural components to growth. Despite demonstrating that the behaviour of particular birds can affect their rates of growth it is still unclear how separating chicks by weight can facilitate differences in growth.
Acknowledgements Many thanks to Allan Dick, MRCVS, of the Croft Veterinary Centre and Ann Courtenay of the Veterinary Investigation Centre, Luddington for their expertise in veterinary care and pathology required during the course of this study. We would like to thank Frank, Dene and Victoria Ayres and Sally Andrews of Hangland Farm for their kind assistance.
References Bertram, B.C.R., 1992. The Ostrich Communal Nesting System. Princeton University Press, Princeton, New Jersey. Bubier, N.E., Lambert, M.S., Deeming, DC., Ayres, L.L. and Sibly, R.M., 1995. Observations on the behaviour of ostrich (Struthio camelus) chicks in captivity. Br. Poult. Sci., in press. Deeming, D.C., 1995a. Factors affecting hatchability during commercial incubation of ostrich (Struthio camelus) eggs. Br. Poult. Sci., 36: 51-65. Deeming, D.C., 1995b. Possible effects of microbial infection on yolk utilisation in ostrich chicks. Vet. Rec., 136, 270-27 1. Deeming, D.C. and Ayres, L., 1994. Factors affecting the growth rates of ostrich (Srrurhio camelus) chicks in captivity. Vet. Rec., 135: 617-622. Deeming, D.C., Ayms, L. and Ayres, F.J., 1993. Observations on the commercial production of ostrich (Struthio camelus) in the United Kingdom: mating of Chicks. Vet. Rec., 132: 627-631. Degen, A.A., Ram, M. and Rosenstrauch, A., 1989. Time-activity budget of ostriches (Struthio camelus) offered concentrate feed and maintained in outdoor pens. Appl. Anim. Behav. Sci., 22: 347-358. Degen, A.A., Ram, M., Rosenstrauch, A. and Plavnik. I., 1991. Growth rate, total body water volume, dry matter intake and water consumption of domesticated ostriches (Struthio camelus). Anim. Prod., 52: 225-232.
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Animal Behaviour Science 46 (1995) 93-101
101
Du Preez, J.J., Jarvis, M.J.F., Capatos, D. and de Kock, J., 1992. A note on growth curves for the ostrich (Struthio camelus). Anim. Prod., 34: 150-152. Gandini, G.C.M. and Keffen, R.H., 1985. Sex determination of the South African ostrich (Struthio camelus). J. S. Afr. Vet. Assoc., 56: 209-210. Gandini, G.C.M., Burroughs, R.E.J. and Ebedes, H., 1986. Preliminary investigation into the nutrition of ostrich chicks (Struthio camelus) under intensive conditions. J. S. Afr. Vet. Assoc., 57: 39-42. Guhl, A.M., 1953. Social behaviour of the domestic fowl. Kansas Agric. Exp. Sm., Tech. Bull., 73. Guhl, A.M., 1958. The development of social organisation in the domestic chick. Anim. Behav., 6: 92-l 11. Guittin, P., 1987. Croissance de l’autruche en part zoologique. Can. J. Zool., 65: 3056-3061. Sauer, E.G.F. and Sauer, E.M.. 1966a. The behaviour and ecology of the South African ostrich. Living Bird, 5: 45-75. Sauer, E.G.F. and Sauer, E.M., 1966b. Social behaviour of the South African ostrich (Struthio camelus australis). Ostrich, Suppl. 6: 184-191. Wood-Gush, D.G.M., 1955. The behaviour of the domestic chicken: a review of the literature. Br. J. Anim. Behav., 3: 81-110.