Filial Imprinting, Environmental Enrichment, and Music Application Effects on Behavior and Performance of Meat Strain Chicks

Filial Imprinting, Environmental Enrichment, and Music Application Effects on Behavior and Performance of Meat Strain Chicks

EDUCATION AND PRODUCTION Filial Imprinting, Environmental Enrichment, and Music Application Effects on Behavior and Performance of Meat Strain Chicks ...

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EDUCATION AND PRODUCTION Filial Imprinting, Environmental Enrichment, and Music Application Effects on Behavior and Performance of Meat Strain Chicks G. GVARYAHU, D. L. CUNNINGHAM, and A. VAN TIENHOVEN Department of Poultry and Avian Sciences, Cornell University, Ithaca, New York 14853 (Received September 28, 1987)

1989 Poultry Science 68:211-217

INTRODUCTION

Filial imprinting, the attachment of young birds to the first object they encounter, was first described by Lorenz (1935). It is a widely studied phenomenon and has been reviewed by a number of authors (Guiton, 1959, 1961; Bateson, 1966, 1979, 1981; Hess, 1973; Vidal, 1980). The attachment of precocial birds to an imprinting object may be expressed as physical contact (Vidal, 1980), approach response (James, 1962), orienting movements (Balthazart and de Rycker, 1979), or reduction of stress behavior (Gaioni et al., 1980). Groups of 10-day-old chicks have been shown to feed communally, and those reared with an imprinting stimulus gained more weight than those fed in isolation (Higuchi, 1976). Environmental enrichment involves the increase of stimulus value of the home environment by increasing its complexity. There is considerable evidence that environmental enrichment results in marked behavioral and physiological effects on mammals (Greenough, 1976). In contrast to the many mammalian

studies, very little is known about the effect of environmental enrichment on birds. Jones et al. (1980), however, found that environmental enrichment improved body weight gain, relative body weight gain, and gain:feed ratio in 9day-old broilers and egg strain chicks. Music has been associated with the treatment of human disease since ancient times and its many physiological and psychological effects on humans is well known (Standley, 1986). Effects of music on animals, however, has not been well studied. Popular publications have suggested that music can be used to increase milk production in dairy cows. Christensen and Knight (1975) exposed meat type chicks to different kinds of continuous music but failed to find any significant results. No significant influence of music on precocial birds has been reported to date. If changes in behavioral and performance traits of animals as a result of the independent effects of imprinting, environmental enrichment, and music occur, it is possible that these factors in combination may produce significant effects for the application of commercial

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ABSTRACT Combined effects of music, environmental enrichment, and filial imprinting were tested on meat strain chicks (broilers) from 1 to 7 days old (Study I) or from one to 8 wk old (Study II). In six experiments conducted in two separate studies, chicks were exposed to a blue plastic box (30 x 30 x 38 cm) containing speakers from which red gloves were hung at the chicks' eye level. Classical music was provided intermittently (1 h on/1 h off) from speakers located in the boxes. Approach response, feeding behavior, fear behavior, body weight, feed:gain ratio, and mortality were evaluated. Approach response tests (Study I) demonstrated that attachment to the imprinting enrichment and music (IEM) object was greater among treated chicks, whereas fear response tests indicated that IEMtreated chicks were also less fearful. Evaluation of feeding behavior (Study II) indicated that IEM chickens fed significantly more often than controls, particularly when the music was activated. Feed:gain ratios of the IEM-treated chicks in Study I were significantly improved (1.48 vs. 1.58) compared with those of controls for three of the four experiments. The exception occurred in Experiment 3, when chicks were exposed to heat stress, and nonsignificant differences for fced:gain ratios were observed. Body weight and mortality differences were not observed. Results of Study II, however, demonstrated significant influences of imprinting, enrichment, and music on body weight at 8 wk of age (2.63 vs. 2.57 kg), whereas differences in feed conversion and mortality were not significant. (Key words: imprinting, environmental enrichment, behavior, performance, music)

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MATERIALS AND METHODS

Management. For all experiments, commercial meat strain chicks (Arbor Acres) were obtained from a local hatchery. Chicks were placed on litter in the experimental area at the age of 1 day. A continuous lighting program was provided (12 lx). The feeding program consisted of a commercial starter ration (25% protein, 3,280 kcal ME/kg) for Study I and for the first 4 wk in Study II, followed by a finishing ration (20% protein, 3,250 kcal ME/ kg) for the last 4 wk in Study II. Feed and water were provided ad libitum for all experiments. Feed was provided in both studies for the first 7 days in a cardboard box measuring 45 x 65 x 4 cm on the floor of each pen or chamber. The 4-cm feeder wall effectively eliminated feed wastage even though chicks were not prevented from climbing into the feeder box. For Study II, feed was made available after the first 7 days by providing two (Experiment 1) or one (Experiment 2) hanging tube feeders (35 cm in diameter) for each pen. Water was provided by one jar waterer for the first 7 days and by suspended

cup waterers for Weeks 2 through 8. Heat during the brooding period was provided by infrared heat lamps. Study I consisted of four separate experiments, in which 16 wooden chambers (1.75 m x .50 m x 1.20 m), providing light and sound control and a common ventilation system, were used for testing the chicks. For each experiment, 16 groups (8 treated and 8 control groups) of 20 male or female chicks were raised in the experimental chambers to 7 days of age. Experiments 1 and 3 tested male responses whereas Experiments 2 and 4 tested females. Control and experimental groups were distributed serially among me chambers (i.e., experimental, control, experimental, etc.) with the sound levels of the chambers monitored by use of a Realistic model sound decibel meter to insure that control chicks were not exposed to the music treatment. Study II consisted of two separate experiments, both conducted in a light-controlled floor brooding and rearing facility containing litter pens measuring 3.6 x 3.5 m. Ventilation was controlled by thermostats attached to an automated fan system. For Experiment 1 (October 1986 hatch), eight groups (four treated and four control groups) of chicks were raised in eight experimental pens until 8 wk of age. Each group consisted of 40 mixed-sex chicks (sexes unequally represented). As it was impractical to soundproof the floor pens, the control and the treated chicks were located at opposite ends of the house using the empty center pens as a sound buffer zone. The buffer space between the experimental and control pens ensured that control chicks were not exposed to any music as determined by the use of a sound decibel meter. (Radio Shack, Fort Worth, TX). For Experiment 2 (January 1987 hatch), the number of pen replicates per treatment was doubled by dividing the floor pens into two units each containing 20 male and 20 female chicks (8 groups for each sex). For Experiment 2, control and experimental groups were distributed serially in the house, with every other pen left empty as a sound buffer zone (i.e., female/male control, empty pen, female/ male experimental, empty pen, male/female control, etc.). The randomization of me groups throughout the house reduced the sound buffer zone between treatments. Nevertheless, the use of a sound decibel meter suggested that control

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production practices. Recendy, Gvaryahu et al. (1987) have shown that large populations of meat strain chicks can be attached to an imprinting stimulus, and the imprinting objects could be used to move birds from a training area to a new location. In this initial study, blue and red plastic boxes providing auditory stimulation were used as imprinting objects in which classical music was activated intermittently. In addition to facilitating movement, imprinting was associated with the imprinted chicks distributing themselves more equally in the new area around the imprinting objects. Controls, however, attempted to return to their original pen, and many control chicks died of asphyxiation. It was also the impression of this author (Gvaryahu) that imprinting chicks appeared to be less fearful and fed more frequently than controls. Thus, the purpose of this study was to examine the influences of imprinting, environmental enrichment, and music application on selected behavioral and performance traits of a commercial strain of meat type chicks during the 1st wk after hatching (optimum period of imprinting) and for an extended brooding and growing period (8 wk).

IMPRINTING, ENRICHMENT, AND PERFORMANCE

chicks were not exposed to the music application even though total sound isolation was not possible. Total sound isolation may not be critical to the study, as the combined effects of music with an imprinting object and environmental enrichment was studied. Knowing those deficiencies, Experiments 1 and 2 were conducted to determine if results could be produced to suggest further study. Imprinting, Enrichment and Music (IEM) Procedure. Immediately after arrival from the hatchery, experimental chicks were subjected to a 7-day (Study I) or 8-wk (Study II) IEM procedure. Chicks not exposed to this process served as controls. Preliminary studies (Gvaryahu et ai, 1987) found that broiler chicks prefer to follow blue and red objects [chicks' unlearned color preferences are bimodal, with peaks at short and long wavelengths (Hess, 1956; Fisher et ai, 1975)]. It has also been shown that auditory stimulation also enhanced chicks' following responses toward the imprinting object (Manning, 1972). For this study, low level (i.e., perceptible to human ears only within 3 m of the IEM object) classical music (Vivaldi's Four Seasons) was used as the auditory stimulus. In each of the experimental pens, a blue plastic box (30 x 30 x 38 cm) was located in the pen containing a 10 x 8 x 10-cm loudspeaker (see Figure 1). Speakers were wired to a single music cassette player activated intermittently (1 h on/1 h off) from 1 until 7 days of age (Study I) or until 8 wk of age (Study II). To facilitate environmental enrichment, two red gloves (Study I) and three red gloves

(Study II) were hung from the IEM object at the chick's eye level at 10 and 40 cm and 20 cm from the edge of the box for Studies I and II, respectively. The hearing range of chickens is somewhat comparable to that of humans (Hou and Boone, 1971). Sound levels for the pens were periodically monitored by placing the sound meter in the middle of the pen floor and reading decibel (db) levels. Control chicks were routinely exposed to an ambient noise level of 65 db (fans and chick noises) whereas chicks in the experimental groups were normally exposed to a maximum of 75 db during the music periods (background noises plus music). Data Collection. In Study I all chicks from each pen were individually weighed immediately after arrival from the hatchery. Body weight gains and feed usage were measured at 7 days of age. Fear response was recorded at 6 days of age using a modification of the "Novel rod" test of Jones (1985). In this test, a black felt tip marking pen was used as the novel object and was placed at the center of the feeder. The latency of 50% of the chicks to return to the feeder was recorded. If less than 50% of the chicks returned to the feeder after 3 min, it was assumed (for statistical analysis) that they did so after 100 s. Approach response toward the imprinting object with the music playing continuously was recorded at 7 days of age. Chicks from each chamber were removed for a 3-min period to an open pen (210 x 60 cm). Chicks were placed at one end of the pen with the imprinting object located at the opposite end. The following behavioral measures were recorded: location of the chicks after 3 min and latency of the first three chicks to reach the imprinting object. The method used to score the location of the chicks was a subjective visual score ranging from 1 to 4. A score of 1 indicated that all chicks remained at one end of the pen, and 4 indicated that all chicks moved toward the imprinting object at the opposite end. Scores of 2 and 3 represented intermediates between these extremes. For the latency measure, the maximum score was 180 s. If a third chick did not reach the imprinting object, it was assumed (for statistical analysis) that it had reached this object after 180 s. In Study II 20 (Experiment 1) and 10 (Experiment 2) chicks from each pen were randomly selected, identified with wing bands,

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FIGURE 1. Imprinting, enrichment, and music (IEM) object included: blue plastic box (30 x 30 x 38 cm) containing a 10 x 8 x 10-cm loudspeaker and red gloves, which were hung from the IEM object at the chick's eye level.

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TABLE 1. Effects of IEM on approach response and fear behavior (Study I)1 Approach response2

Treatment

Flock location (1 to 4)

Latency of the third chick Fear (0 to 180 s) behavior (s)3

Control IEM

1.4 2^6*

180 124*

180 46*

and weighed immediately after arrival from the hatchery. Body weight gains and feed usage were monitored for the same chicks on a weekly basis. Mortality was recorded daily. Feeding behavior was assessed by determining the number of chicks at the feed trough in feeding activity during 28 5-min observational sessions (total of 2 1/3 h/pen). Each pen was observed by a single observer (Gvaryahu). Observational sessions occurred three to four times a week between 1000 h and 1500 h. The observer sat quietly approximately 2 m from the pen and recorded the number of chicks at the feed trough in feeding activity at the end of each minute of the 5-min observations. The total number of chicks in feeding activity was then divided by the 28 observational periods and the average score of the 5-min tests to produce a percentage of chicks feeding. The IEM-treated chicks were observed for feeding behavior during periods with and without the music (56 observational periods). Control chicks in Experiment 2 were observed for feeding behavior during the music and nonmusic hours because of their relatively close proximity to the music-treated pens. Control chicks in Experiment 1, however, were observed for only 28 periods because of their total isolation from the music treatments. Chicks were assessed for fearfulness using duration of tonic immobility (TI; Nash and Gallup, 1976; Gallup, 1977) at 6 wk of age (Experiment 1) and 7 wk of age (Experiment 2). This procedure involved restraining the bird on its back and measuring the elapsed time for the bird to right itself (Jones and Faure, 1980).

RESULTS AND DISCUSSION

Behavioral Measures. No differences were observed between males and females. Therefore, behavioral data were pooled over sexes. In Study I, during the first few days all IEM-treated chicks remained in close contact to the IEM device. The approach response tests (Table 1) demonstrate that attachment to the IEM device was greater for the IEM chicks compared with the controls. These observations as well as those of other studies with similar devices (Gvaryahu et al., 1987) provide clear evidence that chicks will imprint to this IEM device. These results are in accordance with previous studies demonstrating that social bonds between the members of a brood do not preclude the formation of a social attachment to an imprinting stimulus subsequently encountered (Gaioni et al., 1980; Gvaryahu et al, 1986, 1987). The fear behavior tests demonstrated that the IEM chicks were significantly less fearful of the novel object in the presence of the IEM device when compared with control chicks (Table 1). These results agree with those of Hoffman (1968) and Gaioni et al. (1980) that showed fewer distress calls occurring in the presence of the imprinting object, and Jones

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'IEM = Combined treatment of imprinting, environmental enrichment, and music. 2 Approach response toward the imprinting object with the music playing continuously was recorded at 7 days of age. 'Latency toward novel object placed at the feeder was recorded at 6 days of age. *P<.05.

For Experiment 1, four chicks from each pen (total of 16/treatment) were selected at random and removed to a side room to induce TI. In Experiment 2, the TI test was carried out with two chickens from each pen (total of 16/ treatment) in the home pen to minimize the effect of handling and moving. All TI tests in both experiments were done during the periods of music exposure. A chicken remaining in TI for 10 min (Experiment 1) or 5 min (Experiment 2) was given a maximum score of 600 s or 300 s, respectively. Preliminary tests demonstrated that the chicks' duration of TI in their home pens was smaller in comparison to those of chicks removed to a side room. Therefore, different maximum timings were used for Experiments 1 and 2. Statistical Analysis. Statistical analysis was carried out using the three-way ANOVA (treatment, sex, experiments) for body weight, mortality (Studies I and II), and feed usage in Study I. Two-way ANOVA (treatment, sex) was used for feed usage in Study II (Experiment 2 only). The Mann-Whitney U test was applied to the various behavioral measurements (Siegel, 1956).

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IMPRINTING, ENRICHMENT, AND PERFORMANCE TABLE 2. The effects of IEM on feeding behavior and duration of tonic immobility (Study 11)' Feeding behavior (% feeding) Experiment no.

Treatment

Music on

Music off

X

Tome immobility (s)

1

Control IEM

2

Control IEM

8.6 15.5* 10.4 15.5*

8.6 8.4 10.9 14.4*

8.6 11.9* 10.6 15.0*

246 136* 84 51

'IEM = Combined treatment of imprinting, environmental enrichment, and music. *Significant treatment effects within experiment (P<.05).

ments 1 and 2 (8.6 vs. 10.6% for controls, 11.9 vs. 15.0% for IEM) may have been due to the differences in seasonal temperatures that occurred for the two experimental periods (i.e., October to November vs. January to February). For both Experiments 1 and 2, IEM chickens fed significantly more often than the controls when the music was activated. These results suggest that even if the control chicks in Experiment 2 could hear the music (which, according to the sound decibel meter, they could not), their reactions to the music were totally different from experimental chicks and very similar to those of the controls in Experiment 1. When no music was played, significant differences in feeding behavior were found only in Experiment 2. When feeding behavior data were pooled (average between music on and music off), the differences between IEM and control were significant (P<.05) for both Experiments 1 and 2. The influence of music on feeding behavior in precocial birds has, until now, not been

TABLE 3. Effects of IEM on body weight and feed conversion (Study I)1 Feed conversion3

Body weight2 Treatment

Males4

Females

Pooled

Males4

Females

Pooled

Control IEM

131 135

109 110

120 123

1.56 1.46

1.59 1.49

1.58 1.48*

•IEM = Combined effects of imprinting environmental enrichment and music. Body weight at 7 days of age. 3 Ratio of grams of feed:grams of weight gain. 4 First experiment only. 2

*P<.05.

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(1982), that show that early environmental enrichment decreases fearfulness in fearinducing situations and may enhance the ability of animals to adapt to novelty. In Study II, differences in the duration of TI were significant only in Experiment 1 (Table 2). In Experiment 2 the TI test was carried out in the home pen to minimize the effect of handling and moving. Association with familiar surroundings appears to have reduced the fear response in both control and IEM-treated chickens, resulting in the nonsignificant differences between the two treatments. The TI results of Experiment 1 agree with those of Hoffman (1968) and Gaioni et al. (1980), suggesting that the IEM procedure may be beneficial in reducing fear in young chicks. The possible effect on older chickens is not clear. Mean percentages of chickens feeding per observation period are summarized in Table 2. Differences between mean percentages of chickens feeding per observation in Experi-

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TABLE 4. Effects of IEM on body weight and feed conversion of meat strain chicks (Study II) Feed conversion3

Body wei ght2 Treatment

Males

Females

Control IEM

2.77 2.84*

2.37 2.42

Pooled

Males

Females

Pooled

2.57 2.63*

2.09 2.02

2.16 2.14

2.13 2.08

Hcrl

'IEM = Combined effects of imprinting, environmental enrichment, and music. Refers to body weight at 8 wk of age. 'Refers to feed conversion at 8 wk of age, Experiment 2 only. *P<.05.

2

ment 1 and 2 combined) and feed conversion (Experiment 2) are shown in Table 4. Feed conversion was not recorded in Experiment 1 because of unequal representation of the sexes. Weights of IEM males alone and pooled mixed sexes were significantly heavier (P<.05) than those of controls. No significant differences were found for mortality; deaths were 12% for IEM-treated chicks vs. 14.3% for controls. Mortality rates were exceptionally high during the first 10 days. These high rates, which seem to have resulted from poor hatching effects, did not affect normal growth of survivors for the remainder of the study. In conclusion, these preliminary studies on the combined effects of filial imprinting, environmental enrichment, and music on the performance and behavior of meat type chicks, suggest the possible benefits of these procedures. Reduction of stress behaviors and improvements in feed conversion or body weight as a result of the successful application of the IEM procedure could save significant resources for the broiler industry. ACKNOWLEDGMENT

This research was supported by postdoctoral Fellowship Grant No. SI-0020-85 from BARD, the United States-Israel Binational Agricultural Research and Development Fund. REFERENCES Balthazart, J., and C. de Rycker, 1979. Effects of androgens on the behaviour of chicks in an imprinting situation. Z. Tierpsychol. 49:55-64. Bateson, P.P.G., 1966. The characteristics and context of imprinting. Biol. Rev. 41:177-220. Bateson, P.P.G., 1979. How do sensitive periods arise and what are they for? Anim. Behav. 27:470-486.

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studied. These results demonstrate a significant effect on the feeding behavior of 8-wk-old chickens exposed to the IEM procedure. Somatic Effects. In Study I, significant sex x experiment interaction effects on body weight and feed conversion traits were observed. These interaction effects were the result in Experiment 3 of males' exposure to higher (above 40 C) than normal (31 C to 34 C) temperatures during the test period. Because of the obvious heat stress effect on the results of Experiment 3, males from this experiment were removed from the analysis. The results, however, suggest that temperature may be an important factor relating to the effectiveness of IEM on performance parameters. Table 3 presents the combined results for body weight and feed conversion for Experiments 1, 2, and 4. No significant differences between body weights were found for experimental and control chicks in this study. Feed conversion, however, was significantly (P<.05) improved for the IEM female chicks, whereas IEM males showed an improvement in feed conversion (P<.08). When data were pooled over sexes, the 6 to 7% differences between feed conversion rates of IEM and control chicks was significant (P<.05). Improved feed conversion values for chicks as a result of environmental enrichment has been described by Jones et al. (1980). However, unlike results in Jones et al. (1980), growth rates obtained in this study in both control and experimental chicks were close to those obtained under commercial conditions. No significant differences were found for mortality; the death rate for IEM treated chicks was 1.5% (without Experiment 3 males) vs. 1.9% for controls. Study II results for body weight (Experi-

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Bateson, P.P.G., 1981. Control of sensitivity to the enrichment during development. Pages 432-453 in: Behavioral Development, ed. by K. Immelmann et al. Cambridge Univ. Press, New York, NY. Christensen, A. C , and A. D. Knight, 1975. Observations on the effects of music exposure to growing performance of meat-type chickens. Poultry Sci. 54:619-621. Fischer, G. J., G. L. Morris, and J. Ruhsom, 1975. Color pecking preferences in White Leghorn chicks. J. Comp. Physiol. Psychol. 88:402^106. Gaioni, S. J., P. DePaulo, and H. S. Hoffman, 1980. Effects of group rearing on the control exerted by an imprinting stimulus. Anim. Learn. Behav. 8(4):637-678. Gallup, G. G., 1977. Tonic immobility: The role of fear and predation. Psychol. Rec. 27:41-61. Greenough, W. T., 1976. Enduring brain effects of differential experience and training. Pages 225-278 in: Neural Mechanisms of Learning and Memory. M. R. Rosenzweig and E. L. Bennett, ed. MIT Press, Cambridge, MA. Guiton, P., 1959. Socialization and imprinting in Brown Leghorn chickens. Anim. Behav. 7:26-34. Guiton, P., 1961. The influence of imprinting on the agonistic and courtship responses of Brown-Leghorn cock. Anim. Behav. 9:167-177. Gvaryahu, G., N. Snapir, and B. Robinzon, 1987. Research Note: Application of the filial imprinting phenomenon to broiler chicks at a commercial farm. Poultry Sci. 66:1564-1566. Gvaryahu, G., N. Snapir, B. Robinzon, G. Goodman, M. E. El Halawani, and V. E. Grimm, 1986. The gonadotropic-axis involvement in the course of the filial following response in the domestic fowl chick. Physiol. Behav. 38:651-656. Hess, E. H., 1956. Natural preferences of chicks and ducklings. Psychol. Rep. 2:477-^83. Hess, E. H„ 1973. Imprinting. Early experience and the development psychobiology of attachment. VanNostrand and Reinhold, New York, NY. Higuchi, Y., 1976. The effect of imprinting on the feeding behaviour of chicks. Annu. Anim. Psychol. 26:87-95.

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