- Email: [email protected]
Spatial Preference in the Domestic Hen
Br. vet.
J.
(1975), 131,560
SPATIAL PREFERENCE IN THE DOMESTIC HEN By B. O.
HUGHES
Agricultural Research Council's Poultry Research Centre, King's Buildings, West Mains Road, Edinburgh ERg 3JS
SUMMARY
The importance of the fowl's environment is being increasingly recognized, both from the point of view of production and that of animal welfare. More reliable methods of assessing bird-environment interactions are needed. A novel method of testing the preference of domestic fowls for space is described. Six hens of three different strains were given a choice between a spacious or a confined cage. All showed a significant preference for the larger cage; neither time of day nor strain of bird appeared to influence this preference. INTRODUCTION
One of the essential features of a system of intensive husbandry, such as a hen battery, is that it involves housing animals under restricted spatial conditions; the extent of this confinement has been questioned upon the grounds of the animals' welfare (H.M.S.O., Ig65, Ig70). Very little work, however, has been carried out on this problem; in the fowl, difficulties of interpretation are intensified by the absence of reliable physiological or biochemical measures for assessing long-term stress. An approach which has been used for many decades in the psychological field as a learning paradigm, but which is novel in this context, is to place the animal in a two-choice situation where it can express its own preference. The object of this experiment, then, was to give fowls a choice between two cages: one providing more space than the other, and to record which one was preferred. MATERIALS AND METHODS
Six adult hens, about I l years old, were used. Two were derived from Thornber gogs (birds 1,2), two were derived from Shaver 288s (birds 3, 4), and two were Brown Leghorns (birds 5, 6). One bird of each strain was placed in the test situation from ogoo-I700 hours daily (birds I, 3, 5) and the other from 1700ogoo hours (birds 2, 4, 6). The dark period was from 2100-0700 hours. When not being tested they were kept in their home cage in a battery where they had been housed for several months prior to the experiment. Food was available only in the test situation; food and water were provided in similar containers,
SPATIAL PREFERENCE IN THE HEN
in both the large and the small cages; the runway and cage design is shown in Fig. I. The small cage was 30.5 X 30.5 cm, the large cage was 91.5 X 61 cm and the birds' home cage was 46 X 30.5 cm. The runway was 1·86 m X 30.5 cm; a moveable partition converted it into aT-maze whichever starting area the bird was placed in. Other birds could be heard but not seen from the enclosure where testing took place. Each bird was given one trial per day, the preferred cage was entered through a one-way door, and once the bird had made its choice it remained there for 8 or 16 h. From the runway the bird could see that the cages were of different sizes; it could put its head and neck into the cage without actuating the trip, but as soon as it began to enter, the door came down behind it. Over an 8-day period before testing began every bird underwent eight familiarization trials of this type, when it was obliged to enter the
N
s Fig. I. Plan view of the runway and cages (to scale) used for the testing procedure. The dotted lines show the alternative positions for the movable partition and the starting boxes are marked Nand S.
large and the small cage on alternate days; it thus received an equal amount of experience of each. Birds were started from either the N or the S end of the runway in a predetermined sequence which was the same for all birds; it was N N S S N N S S and so on. Using a sequence generated from random numbers can result in one end being greatly over-represented over a short sequence, for example, N N N S N N N. If the bird had a strong preference for turning right, say, this could result in frequent entries to a particular cage for reasons unconnected with the cage itself. Equally, too regular a sequence, such as N S N S N S, would result in a bird which showed spontaneous alternation (turning right and left on successive trials) always entering the same cage. The sequence adopted avoided both these dangers, being designed to equalize the effects of spontaneous alternation or of positional preference. Between birds I and 2 the entire apparatus was rotated through 180 0 to confirm that its orientation in the pen was not an important factor.
BRITISH VETERINARY JOURNAL,
13 1 ,
5
RESULTS
The data were analysed by plotting each day's choice on a chart of the type developed by Bross (1952) for sequential trials. Testing ceased when the line crossed the upper boundary, indicating a preference significant at the 5 per cent level. The results are shown in Fig. 2, movement of the black line upwards indicates preference for the larger cage. All birds expressed a significant preference for the large as opposed to the small cage. Birds I and 3 never selected the small cage, bird 6 selected it once, bird 4 twice, bird 5 five times and bird 2 six times. A positional preference was particularly marked in bird 2. The latency to enter the cage was recorded by noting the time which elapsed between placing the bird in the runway and its passage through the door. At the beginning of the familiarization trials the latency exceeded 10 min in all birds, and in some cases amounted to several hours. By the end of testing it had decreased on
Fig. 2. The results for the six different birds shown on sequential analysis charts. Each small black square represents one daily trial. Vertical movement up the ordinate represents preference for the large cage while horizontal movement along the abcissa represents preference for the small cage. Testing continues until one of the boundaries is crossed. Crossing the upper or lower boundary represents a preference significant at the 5 per cent level for the large or the small cage respectively. If the area between the arms is entered it indicates that the sequence is not significant. (From Bross, 1952).
SPATIAL PREFERENCE IN THE HEN
average to about 5 s. After a significant preference had been demonstrated, one bird from each strain was given an additional trial, with the runway and cages rotated through 180 °. In each case the large cage was selected, with little or no increase in latency. DISCUSSION
The findings demonstrate that, under controlled conditions, hens given a choice of spending 8-16 h in a space rather smaller or alternatively considerably larger than that afforded by their home cage prefer the larger space. Different stocks were tested in case there were any strain differences in spatial preference, resulting in birds more willing to tolerate confinement. Birds were tested at the two different times of day to determine whether there was a preference shift between the more active daytime period and the resting period during darkness. However, neither the strain of bird nor the time of day spent in the test cage appeared to have an important influence on the preference. Even size of bird seemed to have little effect. The 909s, weighing about 2'3 kg, entered the small cage six times, the same number of times as the Brown Leghorns which weighed about 1'3 kg. The area of floor space per bird provided by the small cage was 930 cm2; this compares with space allowances recommended by the Codes of Practice (Ministry of Agriculture, Fisheries and Food, 1971) which vary from about 1200 cm 2 (in the case of a medium hybrid in a single cage) to 469 cm 2 per bird (when 3 or more light hybrids are housed together). The small cage therefore provides a spatial allocation within the recommended range. The fact that the large cage continued to be preferred after 180 0 rotation confirms that it was the cage itself which was being selected rather than some feature of the environment, for example, different light levels or air movements. There is a possibility that it was some feature of the large cage other than its increased space which the birds were selecting; such a possibility, however, should be remote, because every effort was made to equalize features such as construction materials, feeders, drinkers and so on. This finding has two implications. Firstly, it demonstrates that a choice situation, in which a bird can express its preference, affords a valid insight into the way it perceives its environment and permits an estimation of which features the bird is likely to regard as "important". Secondly, when a particular feature, such as spatial constraint, has been identified as important, all available indicators of stress should be examined in situations in which the environment is likely to be inadequate. For example, recent studies (Hill & Binns, 1973) show a positive linear relationship between egg production and unit area per bird. If one is justified in regarding egg production as a crude indicator of stress, this is a predictable finding. Ultimately it may be possible to specify an ideal environment and then, within economic constraints, to achieve an approximation to it. REFERENCES
BROSS, I. ( 1952 ). Biometrics, 8, 188. H.M.S.D. (1965) . Report of the Technical Committee to Enquire into the Welfare of Animals kept under Intensive L ivestock Husbandry Systems. Cmnd . 2836. London: H er Majesty's Stationery Office.
BRITISH VETERINARY JOURNAL, 13 1, 5 H.M.S.O. (1970). Welfare of Livestock. A Report by the Farm Animal Welfare Advisory Committee. London: Her Majesty's Stationery Office. HILL, A. T. & BINNS, M. R. (1973). Proc. 4th Europ. Poult. Con!, London. p. 605. MINISTRY OF AGRICULTURE, FISHERIES AND FOOD (1971). Codes of Recommendationsfor the Welfare of Livestock. Code NO.3. Domestic Fowls. (Acceptedfor publication 24 September 1974)
Preference spatial des poules dOlDestiques (Hughes) ResUlDe. L'importance de I'environnement de la volaille est reconnue de fac;:on croissante, du point de vue de la production et du point de vue du bien-etre animal. Des methodes plus stires de l'evaluation des interactions de I'environnement des oiseaux sont necessaires. Une nouvelle methode originale pour tester la preference des volailles domestiques pour I'espace est decrite. On donna Ie choix a six poules issues de trois souches differentes entre une cage spacieuse ou etroite. Toutes montrerent une preference significative pour la cage plus grande; ni Ie moment de la journee ni la souche d'oiseau ne semblait influencer cette preference. RauDlbediirfnis von Hiihnern (Hughes) ZusaDllDenfassung. Die Wichtigkeit der Umgebung von Hiihnern wird mehr und mehr begriffen und zwar sowohl vom Gesichtspunkt der Produktion wie auch des Wohlbefindens der Tiere. Aber die Notwendigkeit besteht, zuverHissigere Methoden zu finden, urn die Wirkung der Umgebung auf die Tiere zu beurteilen. Eine neue Methode wird beschrieben, mit der die Vorliebe von Htihnern fUr geraumige Unterkunft untersucht werden kann. Sechs Hennen dreier verschiedener Rassen konnten zwischen einem geraumigen und einem engen Kafig wahlen. AIle zeigten eine signifikante Vorliebe fUr den grosseren Kafig; weder die Tageszeit noch die Rasse der Htihner schien diese Vorliebe zu beeinflussen. Preferencla espaclal en la gallina dOlDestica (Hughes) ResUIDen. La importancia del medio ambiente del ave se va reconociendo mas y mas, tanto desde el punto de vista de la producci6n como del bienestar del ave. Se necesitan metodos mas confiables para estimar las interacciones entre ave y medio ambiente. Se describe un nuevo metodo de comprobar la preferencia de las aves domesticas en cuanto a espacio. Se dio a elegir una jaula grande 0 pequefia a seis gallinas de tres razas distintas. Todas mostraron una significativa preferencia por la jaula mayor; ni la hora del dia ni la raza del ave parecieren influir esta preferencia.
J.
(1975), 131,560
SPATIAL PREFERENCE IN THE DOMESTIC HEN By B. O.
HUGHES
Agricultural Research Council's Poultry Research Centre, King's Buildings, West Mains Road, Edinburgh ERg 3JS
SUMMARY
The importance of the fowl's environment is being increasingly recognized, both from the point of view of production and that of animal welfare. More reliable methods of assessing bird-environment interactions are needed. A novel method of testing the preference of domestic fowls for space is described. Six hens of three different strains were given a choice between a spacious or a confined cage. All showed a significant preference for the larger cage; neither time of day nor strain of bird appeared to influence this preference. INTRODUCTION
One of the essential features of a system of intensive husbandry, such as a hen battery, is that it involves housing animals under restricted spatial conditions; the extent of this confinement has been questioned upon the grounds of the animals' welfare (H.M.S.O., Ig65, Ig70). Very little work, however, has been carried out on this problem; in the fowl, difficulties of interpretation are intensified by the absence of reliable physiological or biochemical measures for assessing long-term stress. An approach which has been used for many decades in the psychological field as a learning paradigm, but which is novel in this context, is to place the animal in a two-choice situation where it can express its own preference. The object of this experiment, then, was to give fowls a choice between two cages: one providing more space than the other, and to record which one was preferred. MATERIALS AND METHODS
Six adult hens, about I l years old, were used. Two were derived from Thornber gogs (birds 1,2), two were derived from Shaver 288s (birds 3, 4), and two were Brown Leghorns (birds 5, 6). One bird of each strain was placed in the test situation from ogoo-I700 hours daily (birds I, 3, 5) and the other from 1700ogoo hours (birds 2, 4, 6). The dark period was from 2100-0700 hours. When not being tested they were kept in their home cage in a battery where they had been housed for several months prior to the experiment. Food was available only in the test situation; food and water were provided in similar containers,
SPATIAL PREFERENCE IN THE HEN
in both the large and the small cages; the runway and cage design is shown in Fig. I. The small cage was 30.5 X 30.5 cm, the large cage was 91.5 X 61 cm and the birds' home cage was 46 X 30.5 cm. The runway was 1·86 m X 30.5 cm; a moveable partition converted it into aT-maze whichever starting area the bird was placed in. Other birds could be heard but not seen from the enclosure where testing took place. Each bird was given one trial per day, the preferred cage was entered through a one-way door, and once the bird had made its choice it remained there for 8 or 16 h. From the runway the bird could see that the cages were of different sizes; it could put its head and neck into the cage without actuating the trip, but as soon as it began to enter, the door came down behind it. Over an 8-day period before testing began every bird underwent eight familiarization trials of this type, when it was obliged to enter the
N
s Fig. I. Plan view of the runway and cages (to scale) used for the testing procedure. The dotted lines show the alternative positions for the movable partition and the starting boxes are marked Nand S.
large and the small cage on alternate days; it thus received an equal amount of experience of each. Birds were started from either the N or the S end of the runway in a predetermined sequence which was the same for all birds; it was N N S S N N S S and so on. Using a sequence generated from random numbers can result in one end being greatly over-represented over a short sequence, for example, N N N S N N N. If the bird had a strong preference for turning right, say, this could result in frequent entries to a particular cage for reasons unconnected with the cage itself. Equally, too regular a sequence, such as N S N S N S, would result in a bird which showed spontaneous alternation (turning right and left on successive trials) always entering the same cage. The sequence adopted avoided both these dangers, being designed to equalize the effects of spontaneous alternation or of positional preference. Between birds I and 2 the entire apparatus was rotated through 180 0 to confirm that its orientation in the pen was not an important factor.
BRITISH VETERINARY JOURNAL,
13 1 ,
5
RESULTS
The data were analysed by plotting each day's choice on a chart of the type developed by Bross (1952) for sequential trials. Testing ceased when the line crossed the upper boundary, indicating a preference significant at the 5 per cent level. The results are shown in Fig. 2, movement of the black line upwards indicates preference for the larger cage. All birds expressed a significant preference for the large as opposed to the small cage. Birds I and 3 never selected the small cage, bird 6 selected it once, bird 4 twice, bird 5 five times and bird 2 six times. A positional preference was particularly marked in bird 2. The latency to enter the cage was recorded by noting the time which elapsed between placing the bird in the runway and its passage through the door. At the beginning of the familiarization trials the latency exceeded 10 min in all birds, and in some cases amounted to several hours. By the end of testing it had decreased on
Fig. 2. The results for the six different birds shown on sequential analysis charts. Each small black square represents one daily trial. Vertical movement up the ordinate represents preference for the large cage while horizontal movement along the abcissa represents preference for the small cage. Testing continues until one of the boundaries is crossed. Crossing the upper or lower boundary represents a preference significant at the 5 per cent level for the large or the small cage respectively. If the area between the arms is entered it indicates that the sequence is not significant. (From Bross, 1952).
SPATIAL PREFERENCE IN THE HEN
average to about 5 s. After a significant preference had been demonstrated, one bird from each strain was given an additional trial, with the runway and cages rotated through 180 °. In each case the large cage was selected, with little or no increase in latency. DISCUSSION
The findings demonstrate that, under controlled conditions, hens given a choice of spending 8-16 h in a space rather smaller or alternatively considerably larger than that afforded by their home cage prefer the larger space. Different stocks were tested in case there were any strain differences in spatial preference, resulting in birds more willing to tolerate confinement. Birds were tested at the two different times of day to determine whether there was a preference shift between the more active daytime period and the resting period during darkness. However, neither the strain of bird nor the time of day spent in the test cage appeared to have an important influence on the preference. Even size of bird seemed to have little effect. The 909s, weighing about 2'3 kg, entered the small cage six times, the same number of times as the Brown Leghorns which weighed about 1'3 kg. The area of floor space per bird provided by the small cage was 930 cm2; this compares with space allowances recommended by the Codes of Practice (Ministry of Agriculture, Fisheries and Food, 1971) which vary from about 1200 cm 2 (in the case of a medium hybrid in a single cage) to 469 cm 2 per bird (when 3 or more light hybrids are housed together). The small cage therefore provides a spatial allocation within the recommended range. The fact that the large cage continued to be preferred after 180 0 rotation confirms that it was the cage itself which was being selected rather than some feature of the environment, for example, different light levels or air movements. There is a possibility that it was some feature of the large cage other than its increased space which the birds were selecting; such a possibility, however, should be remote, because every effort was made to equalize features such as construction materials, feeders, drinkers and so on. This finding has two implications. Firstly, it demonstrates that a choice situation, in which a bird can express its preference, affords a valid insight into the way it perceives its environment and permits an estimation of which features the bird is likely to regard as "important". Secondly, when a particular feature, such as spatial constraint, has been identified as important, all available indicators of stress should be examined in situations in which the environment is likely to be inadequate. For example, recent studies (Hill & Binns, 1973) show a positive linear relationship between egg production and unit area per bird. If one is justified in regarding egg production as a crude indicator of stress, this is a predictable finding. Ultimately it may be possible to specify an ideal environment and then, within economic constraints, to achieve an approximation to it. REFERENCES
BROSS, I. ( 1952 ). Biometrics, 8, 188. H.M.S.D. (1965) . Report of the Technical Committee to Enquire into the Welfare of Animals kept under Intensive L ivestock Husbandry Systems. Cmnd . 2836. London: H er Majesty's Stationery Office.
BRITISH VETERINARY JOURNAL, 13 1, 5 H.M.S.O. (1970). Welfare of Livestock. A Report by the Farm Animal Welfare Advisory Committee. London: Her Majesty's Stationery Office. HILL, A. T. & BINNS, M. R. (1973). Proc. 4th Europ. Poult. Con!, London. p. 605. MINISTRY OF AGRICULTURE, FISHERIES AND FOOD (1971). Codes of Recommendationsfor the Welfare of Livestock. Code NO.3. Domestic Fowls. (Acceptedfor publication 24 September 1974)
Preference spatial des poules dOlDestiques (Hughes) ResUlDe. L'importance de I'environnement de la volaille est reconnue de fac;:on croissante, du point de vue de la production et du point de vue du bien-etre animal. Des methodes plus stires de l'evaluation des interactions de I'environnement des oiseaux sont necessaires. Une nouvelle methode originale pour tester la preference des volailles domestiques pour I'espace est decrite. On donna Ie choix a six poules issues de trois souches differentes entre une cage spacieuse ou etroite. Toutes montrerent une preference significative pour la cage plus grande; ni Ie moment de la journee ni la souche d'oiseau ne semblait influencer cette preference. RauDlbediirfnis von Hiihnern (Hughes) ZusaDllDenfassung. Die Wichtigkeit der Umgebung von Hiihnern wird mehr und mehr begriffen und zwar sowohl vom Gesichtspunkt der Produktion wie auch des Wohlbefindens der Tiere. Aber die Notwendigkeit besteht, zuverHissigere Methoden zu finden, urn die Wirkung der Umgebung auf die Tiere zu beurteilen. Eine neue Methode wird beschrieben, mit der die Vorliebe von Htihnern fUr geraumige Unterkunft untersucht werden kann. Sechs Hennen dreier verschiedener Rassen konnten zwischen einem geraumigen und einem engen Kafig wahlen. AIle zeigten eine signifikante Vorliebe fUr den grosseren Kafig; weder die Tageszeit noch die Rasse der Htihner schien diese Vorliebe zu beeinflussen. Preferencla espaclal en la gallina dOlDestica (Hughes) ResUIDen. La importancia del medio ambiente del ave se va reconociendo mas y mas, tanto desde el punto de vista de la producci6n como del bienestar del ave. Se necesitan metodos mas confiables para estimar las interacciones entre ave y medio ambiente. Se describe un nuevo metodo de comprobar la preferencia de las aves domesticas en cuanto a espacio. Se dio a elegir una jaula grande 0 pequefia a seis gallinas de tres razas distintas. Todas mostraron una significativa preferencia por la jaula mayor; ni la hora del dia ni la raza del ave parecieren influir esta preferencia.