Behavioural aspects of food selection in young chickens.

Abstract

BEHAVIOURAL ASPECTS OF FOOD SELECTION IN YOUNG CHICKENS MARTINE ADRET-HAUSBERGER and ROBIN B. CUMMING Summary ..- --.M Day old chlikkens of three breeds were offered the choice of 14 varieties of seeds to peck at and eat, Commercial Payer and broiler chickens both preferentially selected sorghum while feral chickens selected wheat, Once having eaten a particular seed, chickens tended to select that seed when offered the various seeds a day later, If unable to eat the preferred seed at first experience, chicks tended to peck at random when offered seeds a day later. Debeaking tended to reduce pecking activity but facilitated ingestion of the selected seeds. When in groups, certain individuals will initiate feeding more frequently than others. When learning to choice feed a grain and protein concentrate isolation housing is a disadvantage. I, INTRODUCTION In natural broods, the variety of materials in young of the mother hen, who leads materials to select (Stokes, development of ability to select food from a wide chickens is considerably helped by the behaviour her brood to profitable places and shows them which 1971). In modern husbandry situations where eggs are hatched in incubators, young chickens have to learn to select feed materials by'themselves. It has been shown that modern egg type and broiler chickens when offered a free choice of energy feeds (grains) and protein concentrates, learn to accurately balance their diets, probably on the basis of physiological feedback (Mastika, 1981). These chickens do not benefit from the hen's experience, but in most cases they are in large groups of the same age and their social experience could play a role in food selection. In this paper we will examine some of these aspects and see how individual experience can influence food selection, through visual preferences and the association of stimuli with a reward. Various breeds are compared and the role social experience plays. II. BASIC VISUAL PREFERENCES IN CHICKS p- EFFECTS OF THE BREED Several studies (Hess, 1956; Fran& 1957; Dawkins, 1968) of newly hatched domestic chicks have shown that these birds are very sensitive to particular shapes and colours and peck preferentially red regular hemispheric shapes. The preference for red seems to be related to a peak of photosensitivity in the wavelengths. Natural feedstuffs, such as grains, vary in their shape, size and colour and we investigated the response of'day old chickens to different seeds. One day old chicks from three breeds were used: 25 each of a commercial layer type (White Ieghorn x Black Australorp) and commercial broiler strain and 38 feral chicks, bred at the University of New England from birds originally caught on North West Island, Queensland, The chicks were kept in electrically heated brooders with water ad libitum but no food until the experiment. They were individually tested in cardboard boxes(60 x60,cms))where they were allowed Department of Biochemistry, Microbiology and Nutrition, University of New England, Armidale, New South Wales 2351 to peck at 14 different kinds of seeds (Table 1) for a 5 minute period. Records were made of which seeds they pecked prefeqst%a%%y..wd which one they first pecked. Table 1 Characteristics of seeds used in testing pecking preferences of youltg tikiic'll;ens Both breeds of domestic chicks showed a strong preference for sorghum; and then clover seed (Table 2). Some other seeds seem to be 'avoided' since they are pecked less often than expected; corn, grey sunflower, rye, oat, rape, lucerne and barley. The preference of naive domestic chicks for sorghum is, probably related to the structure of this seed, which corresponds to the basic preferences of chicks stated above;, round shape, brown-red colour and regularity. In general, they avoid pecking very large seeds (sunflower, corn, oat) or very small ones (rape, lucerne), as well as long and irregular seeds (barley,.ry&). / Table 2 Pecking preferences exhibited by young layer and broiler chickens, The feral chicks showed very different basic preferences and pecked mainly wheat and canary seed - both creamy in colour and long, oval in shape. They preferred to peck fairly long creamy coloured seeds (wheat, canary seed) but avoided pecking dark seeds like clover, sunflower and rape or very long ones (rye, oats). Al 1 the chicks tried to swallow the seeds they pecked but were not always able to do so because of the size of some of the seeds. III. EFFECT OF AN EARLY INDIVIDUAL EXPERIENCE ON PECKING BEHAVIOUR We next compared the pecking behaviour of debeaked and not deb:eaked domestic chicks, as debeaking may provide information on two aspects. Firstly debeaking is considered as an early stress which may disturb the chickens' feeding behaviour. Secondly - for mechanical reasons, debeaked birds can open their beaks more widely and therefore swallow bigger seeds than the not debeaked chicks. For chickens able to swallow seeds* the rewarding value of this stimulus is different from those who do not swallow a seed. Thus we are able to examine the role of such an experience by comparing their reactions to those of not debeaked Ichicks. Essentially the same experimental procedures as used previously were adopted. The chickens were commercial broilers, 25 not debeaked and 25 debeaked, the debeaking being carried out at the hatchery in Tamworth. A second test, again of 5 minutes duration, was carried out 24 hours later with the aim of seeing if the experience acquired in test 1 (one day old) could influence the choices in test 2 (two days old). In the first test (at 24 hours) the number of pecks observed in 5 minutes was lower and the first peck was recorded after a longer latency period in debeaked birds (Table 3). Although 24 hours had elapsed between debeaking and the first test, this operation still had an effect on pecking behaviour, in terms of a greater emotivity in isolation and/or a lower motivation to peck. Again the chickens preferred sorghum to the other seeds and more debeaked chickens successfully swallowed the sorghum seeds than the not.debeaked chickens. Table 3 Comparison of the effect of debeaking on pecking in day old chickens test 1 (Table 4). Both groups of birds showed a strong pecking preference for sorghum at However, clear differences appeared 24 hours later as the not debeaked chicks pecked sorghum less frequently than some other seeds, whereas the debeaked. birds maintained their preference for that seed. This suggests that the experience acquired at test 1 (rewarding in terms of ability or not to swallow the sorghum) influenced the choices 24 hours later. out. In order to verify this hypothesis further, a third experiment was carried Again it was basically the same as experiment 1, but only 3 seeds (sorghum, Japanese *and white millet) were used and they were stuck to the cardboard. Thus neither the debeaked nor the not &beaked chicks could swallow them. There were 50 birds used for each group. Table 4 Comparison of debeaking on the evaluation young chickens of pecking preferences in Again the chickens pecked mainly at the larger sorghum grains in test 1, but both groups of chicks switched their preferences at test 2 and pecked mainly the smaller seeds (Table 5). This switch appeared at the first seed observed to be pecked in test 2, thus the influence of the experience gained in test 1 1 was immediately apparent. Table 5 Pecking preferences of chickens exposed to seeds which cannot be swallowed . We therefore conclude that swallowing is a rewarding value necessary for the chick to maintain its basic visual preference. IV. SOCIAL INFLUENCE ON THE ABILITY TO BALANCE THE DIET Finally we examined how living in a group can influence the food selection in young chickens. For this we used another aspect of food selection - the ability to balance a diet based on a choice between a grain (energy) and protein concentrate. One week old broilers were placed in groups of 5 in wire pens for three weeks. Each pen was fitted with two feeders, one filled with sorghum and the other with a protein concentrate (38% crude protein). Feed and water were given ad libitum. The groups were observed during the three weeks to determine whether there were leaders which tended to initiate certain activities more than others. A variety of behaviours was recorded. The birds were then placed in individual cages, still on choice feeding, where they were weighed twice a week for a further two weeks. Control birds were placed in individual cages with the same choices of food as the experimental ones from one week of age for the whole experimental period. Their body weights were similarly recorded. The observations of social for each activity, one particular in that activity (Table 6). The reveal that birds which initiate in the group (Table 6). Table 6 relations in the groups revealed clear leadership individual tending to be followed by the others body weights recorded over the final two weeks feeding tended to be the heavier individuals Initiation of feeding and body weight in chickens in groups of five birds, v. DISCUSSION The experiments on the pecking at seeds indicate that very young chickens have inate tendencies to peck at various seeds, with definite preferences. If such pecking results in the successful ingestion of a seed and a satisfactory physiological feedback occurs, these chickens will subsequently (24 hours later) concentrate on these specific seeds. This suggests that they realise by associative learning that the morphological characteristics of a particular seed material is related to a beneficial physiological response if ingested. This allows the chicken to develop an efficient pecking system and to correctly orientate their basic visual preferences. When the seeds were stuck down chickens were unable to build up this seeds almost at random when tested 24 the very first experience of pecking size and colour. and it was impossible to swallow them, the association. They then tended to peck hours later. This suggests therefore that should be at food that is of suitable form, The fact that breeds demonstrate preferences for different seeds at day old is interesting. 'The preference that the ferals demonstrated for wheat is in line with the observations of Tomaszewska (pers. comm.) that grown feral fowl on North West Island could only be caught in traps baited with wheat and that they ignored sorghum baited traps. It is difficult to explain this preference as no wheat or similar grains are known to grow on North West Island. Subsequently the captured feral birds preferred sorghum grains in captivity (Gumming, unpublished). The preference demonstrated by the broiler chickens for sorghum is in agreement with previous observations (Cumming, 1983). Debeaking is generally considered a stressful procedure in day old chickens and significantly retarded the pecking of seeds by the day old chickens. However it is indeed surprising that debeaking appears to facilitate feed intake in this situation. The role of leaders in initiating feeding emphasises the importance of group feeding and the learning process that takes place. The poor performance of the birds individually housed from one week of age is in agreement with earlier observations of Mastika (unpub. data). Marked breed differences have been recorded with broilers tending to be less able to balance their diets when housed individually. VI. ACKNOWLEDGEMENTS The assistance of Dr. J. Lynch and Dr. L. Rogers in this work is gratefully acknowledged. The work was supported by the Australian Chicken Meat Research Committee. VII. REFERENCES CUMMING, R.B. (1983). In 'Recent Advances in Animal Nutrition in Australia 1983' (ed. D.J. Farrell) pp. 313-316. University of New England, Armidale. DAWKINS, R. (1968). 2. Tierysychol. 25: 170-186. FANTZ, R.L. (1957). J. Comp. Psychol.yhysiol. a: 422-430. HESS, E.H. (1956). Psychol. Reports 2: 4770483.~ STOKES, A.W. (1971). Auk. &: 21-29.-