Responses of adult laying hens to abstract video images presented repeatedly outside the home cage

Previous studies reported that domestic chicks showed progressively greater attraction towards biologically neutral video images (screensavers) with repeated exposure [Jones, R.B., Carmichael, N., Williams, C., 1998. Social housing and domestic chicks' responses to symbolic video images. Appl. Anim. Behav. Sci. 56, 231-243; Jones, R.B., Larkins, C., Hughes, B.O., 1996. Approach/avoidance responses of domestic chicks to familiar and unfamiliar video images of biologically neutral stimuli. Appl. Anim. Behav. Sci. 48, 81-98]. The potential existence of an adult parallel was examined here by studying the responses of laying hens to similar screensaver videos when these were presented repeatedly in front of their home cage. In Experiment 1, individually housed, 31-week-old laying hens were exposed to either the video image of a computer screensaver (SS) programme (Fish), a blank but illuminated television monitor (B), or a black plastic hide (H) presented approximately 50 cm in front of their home cages for 10 min/day on each of 5 consecutive days. The bird's position in the cage and the orientation of its head were recorded every 15 s during the-10 min exposure period in order to assess approach and interest, respectively. Interest was scored by summing the numbers of observations at which the hen was either facing the front or had its head out of the cage. Birds in the B and H treatment groups showed few deviations from neutrality in their approach or interest. Conversely, although SS birds avoided the video stimulus on the first day their responses had reached neutrality (neither approach nor avoidance) by the third day and they showed significantly more approach than would be expected by chance at the fifth presentation. They also showed significantly more interest than chance on each test day; this score increased progressively and showed no sign of waning even at the fifth presentation. To determine whether or not such interest would be maintained indefinitely, the responses of previously untested hens were examined when the same video (Fish) was presented for 10 min/day on each of 20 consecutive days (Experiment 2). A blank, lit television (B) was again used a control. An unfamiliar video (Doodles) was presented to the SS birds on day 21 to determine the effects of stimulus change. After avoiding the stimuli upon their first presentation, both SS and B birds achieved neutrality by day 3. Approach scores then fell in B birds but rarely deviated from neutrality in SS ones. The SS video attracted markedly more interest than did the blank screen. On this occasion, SS hens showed significantly greater interest than would be expected by chance as early as the third presentation and this was still evident upon the eighth presentation; thereafter it waned gradually. However, interest was reinstated fully when the unfamiliar SS image was shown on day 21. The present findings clearly demonstrate that abstract video images, presented in front of the home cage for 10 min on consecutive days, reliably attracted and sustained the interest of individually housed laying hens for as long as 8 days. These results are consistent with those obtained when chicks were repeatedly exposed to similar screensaver videos, i.e., this phenomenon is not dependent on the stage of development. Our results also confirm the importance of considering the environment outside as well as inside the cage in future environmental enrichment programmes.     

Rats have trouble associating all three parts of the time-place-event memory code

The ability of animals to associate an event with predictable time and place information confers a major biological advantage. The current research uses a variety of procedures and paradigms (e.g. place preference, radial arm maze, Morris water maze, T-maze, go no-go) to show that rats, unlike pigeons [e.g. Anim Learn Behav 22 (1994) 143] do not readily make an event-time-place association. They do make associations between event-time and event-place information, however. These findings are in disagreement with Gallistel's (The Organization of Learning, MIT Press, Cambridge, MA ) theory that claims that animals automatically store a memory code that has these three pieces of information. The present research is in line with the work of others who also find that rats do not readily make daily time-place associations [Behav Processes 23 (1997) 232; Behav Processes 52 (2000) 11; Behav Processes 49 (2000) 21; Anim Learn Behav 28 (2000) 298]. An interesting finding that did emerge from the present research was that at least some rats can use a circadian timer to solve a time-of-day discrimination if the task is a go no-go discrimination.     

Timing of omitted events: an analysis of temporal control of inhibitory behavior

This paper reviews research designed to investigate the temporal control of inhibitory responding using rats as subjects. One area of investigation has focused on the role of temporal variables in conditioned inhibition produced using Pavlov's [Pavlov, I.P., 1927. Conditioned Reflexes. Oxford University Press, London, 430 pp.] procedure. These studies have found that evidence of conditioned inhibition obtained by negative summation testing is strongest when the conditioned inhibitor signals the omission of the unconditioned stimulus (US) at the same temporal location as a transfer excitor signals presentation of the US [e.g., Barnet, R.C., Miller, R.R., 1996. Temporal encoding as a determinant of inhibitory control. Learn. Motiv. 27, 73-91]. Similarly, retardation of acquisition of behavioral control by a previously inhibitory conditioned stimulus (CS) is maximal when the inhibitory CS is paired with the US at the same temporal location as the inhibitor had previously signaled US omission [Burger, D., Denniston, J.C., Miller, R.R., 2001. Temporal coding in condition inhibition: retardation tests. Anim. Learn. Behav. 29, 281-290]. Other lines of research designed to assess the associative structure of temporal control of inhibition [e.g., Denniston, J.C., Blaisdell, A.P., Miller, R.R., 2004. Temporal control in conditioned inhibition: analysis of associative structure of inhibition. J. Exp. Psychol. Anim. Behav. Process. 30, 190-202] are reviewed, as is the assessment of temporal control of inhibition produced through extinction [Denniston, J.C., Miller, R.R., 2003. The role of temporal variables in inhibition produced through extinction. Learn. Behav. 31, 35-48]. These collective observations are discussed in terms of the temporal coding hypothesis [Matzel, L.D., Held, F.P., Miller, R.R., 1988. Reexamination of simultaneous and backward conditioning: Implications for contiguity theory. Learn. Motiv. 19, 317-344].     

Effects of an acute stressor on fear and on the social reinstatement responses of domestic chicks to cagemates and strangers

Genetic selection for appropriate levels of sociality (motivation to be with conspecifics) could benefit poultry welfare and performance. Runway tests that require chicks to traverse a corridor in order to reach other chicks in a goal box are commonly used to measure this behavioural trait. However, we need to determine if the chicks' responses in such tests are sensitive to certain experiential variables before we can recommend possible selection criteria for future breeding programmes. The present study focused on fear and on the identity of the stimulus birds. Broiler chicks either remained undisturbed or were exposed to an acute stressor (mechanical restraint) before their tonic immobility fear responses were measured 1h later in Experiment 1. Exposure to the stressor significantly prolonged tonic immobility and, hence, presumably, underlying fear levels. In Experiment 2, the responses of stressed chicks and undisturbed controls were assessed when they were tested individually in a runway with a goal box containing either familiar or unfamiliar chicks of the same age. Our finding that stressed chicks emerged from the start box sooner and spent longer near the stimulus birds suggests that exposure to a frightening event increased social reinstatement motivation. Furthermore, social affiliation was more pronounced when the goal box contained familiar cagemates rather than strange chicks, regardless of prior treatment. This finding demonstrates that broiler chicks that were housed in groups of twelve can discriminate between familiar and unfamiliar conspecifics encountered in novel surroundings. Thus, sociality was positively associated with fearfulness and broilers clearly showed social discrimination in runway tests. These findings highlight the dangers of disregarding variables, such as fear and the capacity for social recognition in tests of social motivation. We strongly recommend that exposure to frightening events prior to test should be avoided and that the identity of the birds in the runway goal box should be standardized, i.e. either familiar or unfamiliar, and noted.     

Corticosterone levels in host and parasite nestlings: Is brood parasitism a hormonal stressor?

Parasite chicks from non-evictor species usually try to monopolize host parental care, thereby increasing considerably the level of food competition in the nest. Here, we propose that brood parasitism is an important stressor for host and parasite nestlings and explore this hypothesis in the non-evictor great spotted cuckoo (Clamator glandarius) and its main hosts, the same-sized black-billed magpie (Pica pica) and the larger carrion crow (Corvus corone). We experimentally created 3-nestling broods of different brood compositions (only cuckoo chicks, only host chicks, or cuckoo and host chicks together) and measured baseline corticosterone levels of nestlings along their developmental period (early, middle and late). We found that brood parasitism increased corticosterone levels in magpie nestlings in the mid and late nestling period compared to those raised in unparasitized nests. Interestingly, carrion crow nestlings from parasitized nests only increased their corticosterone levels in the mid nestling period, when the competition for food with the cuckoo nestling was highest. Our results suggest that brood parasitism could be a potential physiological stressor for host nestlings, especially during the developmental stages where food requirements are highest. Conversely, cuckoo nestlings could be physiologically adapted to high competition levels since they did not show significant differences in corticosterone levels in relation to brood composition.     

Do female broiler breeder fowl display a preference for broiler breeder or laying strain males in a Y-maze test?

In recent years, the commercial broiler breeder industry has reported problems of male aggression towards females [Millman, S.T., 1999. An investigation into extreme aggressiveness of broiler breeder males. Unpublished PhD Thesis, University of Guelph]. Although this aggression is shown by the males and is apparently a defect in their behaviour [Millman, S.T., Duncan, I.J.H., 2000. Strain differences in aggressiveness of male domestic fowl in response to a male model. Appl. Anim. Behav. Sci. 66, pp. 217-233], it is also possible that it stems in some way from the females. For example, broiler breeder females may not be receptive to male courtship advances, and may avoid males, thus causing frustration in otherwise normal males. The objective of this study was to examine mate preference by broiler breeder females and the effects of sexual experience on preference. A total of 24 mature, broiler breeder females were individually tested in a Y-maze, with females choosing between a broiler breeder male and a laying strain male. Females were tested using male models and tethered live males, both when the females were sexually inexperienced and after they had been housed with broiler breeder or laying strain males for 6 weeks.Females did not display a male-strain preference when tested with models, but sexually experienced females displayed some evidence of a preference for laying strain males in tests with live males, which did not reach statistical significance (P<0.10). Live males were a stronger attractant for sexually experienced females than were models (P<0.005). Individual females tested with the same pair of males showed different preferences, suggesting females used male behaviour as a basis for their choices, and not male morphology.In conclusion, we found no evidence that broiler breeder females inherently discriminate against broiler breeder males.     

Adrenocortical responses in zebra finches (Taeniopygia guttata): individual variation, repeatability, and relationship to phenotypic quality

Although individual variation is a key requirement for natural selection, little is known about the magnitude and patterns of individual variation in endocrine systems or the functional significance of that variation. Here we describe (1) the extent and repeatability of inter-individual variation in adrenocortical responses and (2) its relationship to sex-specific phenotypic quality, such as song duration and frequency and timing of egg laying. We measured adrenocortical responses to a standardized stressor in zebra finches (Taeniopygia guttata) at two life history stages: approximately day 16 (nestlings) and 3 months of age (sexually mature adults). Subsequently, we assessed phenotypic (reproductive) quality of all individuals as adults. Marked inter-individual variation in the adrenocortical response was seen in both sexes and ages, e.g., stress-induced corticosterone ranged from 2.2 to 62.5 ng/mL in nestlings and 5.0-64.0 ng/mL in adults. We found sex differences in (a) inter-individual variation in the adrenocortical response, (b) repeatability, and (c) relationships between corticosterone levels and phenotypic quality. In males, variation in nestling corticosterone was weakly but positively correlated with brood size and negatively correlated with nestling mass (though this relationship was dependent on one individual). There was no significant correlation of adrenocortical responses between two stages in males and adult phenotypic quality was significantly correlated only with adult corticosterone levels. In contrast, in females there was no relationship between nestling corticosterone and brood size or mass but adrenocortical response was repeatable between two stages (r2=0.413). Phenotypic quality of adult females was correlated with nestling baseline and adrenocortical response.     

Effects of qualitative and quantitative food restriction treatments on feeding motivational state and general activity level of growing broiler breeders

Growing broiler breeder chickens are fed restricted rations to limit body weight at sexual maturity. This experiment tested a proposal (Brouns, F., Edwards, S.A., English, P.R., 1994. Effect of dietary fibre and feeding system on activity and oral behaviour of group housed gilts. Appl. Anim. Behav. Sci. 39, 215-223.) that feeding motivation is reduced by using qualitative rather than quantitative food restriction, and it examined relationships among suppression of growth rate, feeding motivational state and general activity level. From 2 to 15 weeks of age, female broiler breeders were reared in six groups of 20, each with a different feeding treatment. The six treatments were: high and low levels of diet dilution (600-700 g/kg and 300-350 g/kg oat feed, ad libitum), appetite suppression (50-60 g/kg and 25-30 g/kg calcium propionate, ad libitum) and quantitative restriction (recommended daily ration and twice that amount). Birds were conditioned to an operant (PR1 schedule) feeding procedure with their respective treatment diets from 3 to 7 weeks, and this was used to measure feeding motivation in 12-min tests at three times of day (1000, 1300 and 1600 h) at 8, 10, 12 and 14 weeks. Proportions of time spent sitting were measured as an index of general inactivity in systematic observations at 9, 11, 13 and 15 weeks. Although the diet dilution and appetite suppression (qualitative) treatments did not limit growth rates as intended, they and the quantitative treatments produced a range of mean body weights to compare with feeding motivation whenever birds were tested. With body weight as a covariate, there were significant effects on numbers of operant responses in 12 min (the measure of feeding motivation) of weight, age, time of day and treatmentxtime interaction, but not treatment. Feeding motivation was positively correlated with suppression of growth rate, regardless of how that suppression was achieved. However, the experimental procedure required all test birds to be without food from 0900 or 0915 h, and motivation was lowest in the earliest (1000 h) test with qualitative but not quantitative treatments. Hence, there was some evidence that feeding motivation may be partially suppressed with qualitative food restriction; distinction can be made between short-term and longer-term feeding motivation. General activity level (inversely reflected by time spent sitting) was closely correlated positively with both suppression of growth rate and feeding motivation. As a fundamental relationship between feeding motivation and reduction of growth rate was not altered by using qualitative rather than quantitative food restriction, these results support an earlier conclusion (Savory, C.J., Hocking, P.M., Mann, J.S., Maxwell, M.H., 1996. Is broiler breeder welfare improved by using qualitative rather than quantitative food restriction to limit growth rate? Anim. Welfare 5, 105-127.) that broiler breeder welfare is not improved with qualitative restriction methods.     

Working and scrounging by zebra finches in an operant task

Groups of three zebra finches were housed in cages which could be adjoined to an operant chamber. Food was restricted and its availability was signalled by a red light projected behind an operant key (an autoshaping procedure). In addition to the shaping contingency, a single peck to the illuminated key, produced food immediately. Following the first peck to the illuminated key, by any subject in the group, the entire group was placed on a schedule of continuous reinforcement (CRF) wherein hopper operation was contingent upon a keypeck during the light. Comparison of individual's behavior revealed a differential pattern of operant working; one group member worked consistently, one worked periodically and one made few (if any) operant responses. All members consumed some reinforcers. The results suggest that zebra finches, under certain conditions, will form specialized labor roles. These data support similar demonstrations with primates (Chalmeau, R. and Galleau A., 1993. Behav. Processes, 28: 173–180), pigeons (Giraldeau, L. and Lefebvre L., 1987. Anim. Behav., 35: 387–394.) and rats (Thullier, F., Desor, D., Mos, J. and Krafft, B., 1992. Psychol. Behav., 53, 17–20).     

Fear and distress in Japanese quail chicks of two lines genetically selected for low or high adrenocortical response to immobilization stress.

Behavioral and adrenocortical reactivity to stressful stimulation was examined in 12- and 13-day-old chicks of two lines of Japanese quail selected over several generations for exaggerated (HS: high stress) or reduced (LS: low stress) plasma corticosterone (B) response to brief immobilization stress. Plasma B concentrations and tonic immobility (TI) fear reactions were measured in unstressed (control) and stressed (overnight cooping) chicks of both lines. The stress treatment was applied over a period of 12-20 hr and it involved capture by the experimenter, inescapable exposure to an unfamiliar environment and to strange conspecifics, reductions in ambient temperature and floor space, and the deprivation of food and water. Chicks of the HS line were more susceptible to the induction of TI and they remained immobile longer than did LS chicks. Therefore HS chicks were considered to be more fearful than their LS counterparts. Stress treatment elicited a marked adrenocortical response that was more pronounced in HS than in LS chicks. Stress treatment also increased susceptibility to TI but did not significantly affect the duration of immobility. These findings suggest that selecting the quail for differential corticosterone response to a particular stressor had exerted an unconscious and concomitant effect on underlying fearfulness as well as on their adrenocortical reactivity to several other stressful situations. The results are further discussed in terms of a putative relationship between adrenocortical activation and fearfulness.     

Prospective timing, attention and the switch. A response to 'Gating or switching? gating is a better model of prospective timing' by Zakay

In response to the 'Switching or gating' paper (Lejeune, H., 1998. Switching or gating? The attentional challenge in cognitive models of psychological time. Behav. Proc. 44, 127-145), Zakay argued that attention allocation to time should reflect attentional processes in general and suggested that the attentional gate model (AGM) has more explanatory power than the temporal information processing model (TIP) of Church (Church, R.M., 1984. Properties of the internal clock. In: Gibbon, J., Allan, L., (Eds.), Timing and Time Perception, vol. 423. Annals of the New York Academy of Sciences, New York, pp. 566-582). The first point might not be challenged, provided that the specificity of the temporal stimulus is taken into account. Concerning the second point, we argue that the TIP model can account for human prospective timing and discuss differences between attention versus expectancy or motivation. We prefer a 'satellite' attention allocation process, targeting the switch and reference memory (Meck, W.H., 1983. Selective adjustment of the speed of the internal clock and memory processes. J. Exp. Psychol.: Anim. Behav. Proc. 9, 171-201) to an attentional gate serially included in the TIP model of Church.     

Experimental mate-removal increases the stress response of female house sparrows: the effects of offspring value?

Vertebrates secrete elevated levels of glucocorticoids in response to various stressors, which mobilize energetic reserves but concurrently interfere with reproduction. In accordance with life-history theory, recent evidence suggests that the corticosterone response to stress is modulated according to the value of the brood. Since brood value is positively related to parental care, the stress response modulation may be either the consequence of offspring value (e.g. large broods have high fitness potential - the brood value hypothesis) or the consequence of parental workload (e.g. large broods are energetically demanding for the parents - the workload hypothesis). In this experiment, we aimed at experimentally separating the effects of brood value and workload and to confront the latter two hypotheses. To do so, we captured the male parents from breeding pairs of house sparrows (Passer domesticus) and took them in captivity for 48 h. During the absence of males, mate-removed females made more food deliveries than controls (increased workload) but were unable to fully compensate the lack of their mate, thus their chicks were in worse condition (reduced brood value) than control chicks. After the experimental period, mate-removed females responded more strongly to the standardized stressor than controls. In both groups, the corticosterone response to stress was negatively related to the nestlings' mass gain. These results provide experimental support for the brood value hypothesis, i.e. that individuals may actively modulate their stress response (either down- or upwards) with respect to the value of their current reproduction.     

Besprechungen/Reviews

Book reviewed in this article: Kaufmann, J. H. (1974): Social ethology of the Whiptail Wallaby, Macropus parryi, in northeastern New South Wales (Das Sozialverhalten von Parrys Känguruh (M. p.) im nordöstlichen Neu-Südwales). Hartley, J. C., D. J. Robinson und A. C. Warne (1974): Female response song in the Ephippigerines Steropleurus stali and Platystolus obvius (Orthoptera, Tettigoniidae) (Antwortgesänge der ♀♀ bei den Ephippigerinen St. st. und P. o.). Anim. Behav. Ligon, J. D., und D. J. Martin (1974): Piñon seed assessment by the Piñon Jay, Gymnorhinus cyanocephalus (Nacktschnabelhäher beurteilen die Güte von Piniensamen). Anim. Behav. Hurley, A. C., und P. H. Hartline (1974): Escape response in the Damselfish Chromis cyanea (Pisces: Pomacentridae): A quantitative study (Quantitative Untersuchung der Fluchtreaktion des Pomacentriden Chr. c.). Jones, C. Eu., und St. L. Buchmann (1974): Ultraviolet floral patterns as functional orientation cues in hymenopterous pollination systems (Die Bedeutung ultravioletter Muster für blütenbesuchende Hymenopteren). Powell, G. V. N. (1974): Experimental analysis of the social value of flocking by Starlings (Sturnus vulgaris) in relation to predation and foraging (Experimenteller Nachweis der Vorteile des Schwarmverhaltens von Staren bei Feindabwehr und Nahrungssuche). Krieg, D. C. (1971): The behavioral patterns of the Eastern Bluebird (Sialia sialis) (Verhaltensweisen des Rotkehl-Hüttensängers S. s.). Bulletin No. 415, New York State Museum and Science Service. (1) Campbell, B. G. (1972): Entwicklung zum Menschen. 4. amerikanische Auflage, übersetzt von G. Kurth und E. May. (2) Goerttler, K. (1972): Stimme und Sprache. Sitzungsberichte der Heidelberger Akademie der Wissenschaften, math.-nat. Klasse. (3) Portmann, A. (1971): Entwurf zum vorbereiteten Diskussionsbeitrag: Der bioloeische Beitrag zum Sprachproblem. (4) Starck, D., und R. Schneider (1968): Larynx. (5) Kipp, F. A. (1966): Indizien für die Sprachähigkeit fossiler Menschen.     

Comparing the generalized matching law and contingency discriminability model as accounts of concurrent schedule performance using residual meta-analysis

To compare the generalized matching law (Baum, W.M., 1974b. On two types of deviation from the matching law: bias and undermatching. J. Exp. Anal. Behav. 22, 231-242) and contingency discriminability model (Davison, M., Jenkins, P.E., 1985. Stimulus discriminability, contingency discriminability, and schedule performance. Anim. Learn. Behav. 13, 77-84) as accounts of concurrent schedule performance, we conducted a residual meta-analysis of response- and time-allocation data from 20 studies (n's=886 and 774, respectively). Both models were fitted to the individual-subject data from each study, and residuals were obtained. Polynomial regressions were then performed on the pooled residuals to determine whether systematic trends were present as a function of predicted values. For the contingency discriminability model, the cubic coefficients were positive and statistically significant for both response- and time-allocation data. By contrast, no statistically significant systematic trend was obtained in the residuals for the generalized matching law. These results suggest that the relationship between log response allocation and log reinforcer allocation does not deviate significantly from linearity over an approximate range of +1.25 to -1.25 log units, consistent with the generalized matching law. Although qualitative criteria are also important in comparing models of behavioral phenomena, residual meta-analysis provides a powerful quantitative methodology for model selection and should prove useful in future research.     

Effects of conjugated linoleic acids on growth performance, serum lysozyme activity, lymphocyte proliferation, and antibody production in broiler chicks

This study was conducted to investigate the effect of dietary conjugated linoleic acids (CLA) on growth performance and immune responses in broiler chicks. A total of 240 day-old Arbor Acre male broiler chicks were randomly allotted into four dietary treatments with different inclusion levels of CLA (0, 2.5, 5.0 or 10.0 g/kg) for six weeks. Growth performance, peripheral blood lymphocyte (PBL) proliferation, lysozyme activity, phagocytic activity (carbon clearance) and serum antibody titers against Newcastle disease virus (NDV) vaccine were examined. There were no significant differences in growth performance among treatments (p > 0.05). Chicks fed CLA diets produced more lysozyme activity in serum than the control group at 2 and 6 weeks of age (p < 0.05). Dietary CLA enhanced the PBL proliferation in response to concanavalin A (ConA) at the age of 42 d (p < 0.05). Phagocytic ability was also affected by dietary CLA and chicks fed CLA diets had faster carbon clearance rate (p < 0.05), but antibody titers to NDV was not influenced by dietary CLA. The results of the study suggested that dietary CLA could enhance innate and cellular immune response in broiler chicks, and not affect the growth performance.     

Neuropeptide Y effect on food intake in broiler and layer chicks

Broiler chicks eat more food than layer chicks. In this study, we examined the involvement of orexigenic peptide neuropeptide Y (NPY) in the difference in food intake between broiler and layer chicks (Gallus gallus). First, we compared the hypothalamic mRNA levels of NPY and its receptors (Y1 and Y5 receptors) between these strains at 1, 2, 4, and 8 days of age. Daily food intake was significantly higher in broiler chicks than layer chicks after 2 days of age. However, the hypothalamic NPY mRNA level was significantly lower in broiler chicks than layer chicks except at 8 days of age. In addition, the mRNA levels of NPY receptors were also significantly lower in broiler chicks than layer chicks at 2 and 4 days of age (Y1 receptor) or 2 days of age (Y5 receptor). These results suggest that the differences in the expressions of hypothalamic NPY and its receptors do not cause the increase in food intake in broiler chicks. To compare the orexigenic effect of NPY between broiler and layer chicks, we next examined the effects of central administration of NPY on food intake in these strains. In both strains, central administration of NPY significantly increased food intake at 2, 4 and 8 days of age. All our findings demonstrated that the increase in food intake in broiler chicks is not accompanied with the over-expression of NPY or its receptor.     

Food allocation in crimson rosella broods: parents differ in their responses to chick hunger

Food allocation in many asynchronously hatching bird species favours large, competitively superior chicks. In contrast, food is usually distributed equally within broods of crimson rosellas, Platycercus elegans, implying that parents do not simply feed the most competitive chick. We used two temporary removal experiments to manipulate hunger of: (1) individual first- or last-hatched chicks, or (2) the whole brood. When only a single chick was hungry, parents compensated fully and chicks gained the same mass over the day as during controls. Mothers and fathers, however, responded in different ways to chick hunger. Mothers did not strongly alter their food allocation when a single chick was hungry, and controlled the distribution of food by refusing to feed first-hatched chicks when they were hungry and by moving more during feeds. In contrast, fathers allocated more food to hungry last-hatched chicks. When the whole brood was hungry, parents were unable to compensate chicks and all chicks lost mass over the day. In these conditions, mothers preferentially fed first-hatched chicks, while fathers fed all chicks equally. Our results show that both mothers and fathers were able to discriminate and selectively feed chicks, but that parents responded differently to changes in chick hunger within the brood. Fathers responded more strongly to variation in chick hunger within the brood, suggesting they reallocate food based on short-term changes in hunger. Mothers distributed food preferentially to last-hatched chicks except when the whole brood was hungry, when they switched to favouring first-hatched chicks. This pattern is consistent with a strategy of adaptive brood reduction when food is scarce. Copyright 2000 The Association for the Study of Animal Behaviour.     

Significance of chick quality score in broiler production

The quality of day old chicks is crucial for profitable broiler production, but a difficult trait to define. In research, both qualitative and quantitative measures are used with variable predictive value for subsequent performance. In hatchery practice, chick quality is judged on a binomial scale, as chicks are divided into first grade (Q1-saleable) and second grade (Q2) chicks right after hatch. Incidences and reasons for classifying chicks as Q2, and potential of these chicks for survival and post-hatch performance have hardly been investigated, but may provide information for flock performance. We conducted an experiment to investigate (1) the quality of a broiler flock and the relation with post-hatch flock performance based on a qualitative score (Pasgar©score) of Q1 chicks and based on the incidence of Q2 chicks and (2) the reasons for classifying chicks as Q2, and the potential of these chicks for survival and post-hatch growth. The performance was followed of Q1 and Q2 chicks obtained from two breeder flocks that hatched in two different hatching systems (a traditional hatcher or a combined hatching and brooding system, named Patio). Eggs were incubated until embryo day 18, when they were transferred to one of the two hatching systems. At embryo day 21/post-hatch day 0, all chicks from the hatcher (including Q2 chicks) were brought to Patio, where the hatchery manager marked the Q2 chicks from both flocks and hatching systems and registered apparent reasons for classifying these chicks as Q2. Chick quality was assessed of 100 Q1 chicks from each flock and hatching system. Weights of all chicks were determined at days 0, 7, 21 and 42. There were no correlations between mean Pasgar©score and post-hatch growth or mortality, and suboptimal navel quality was the only quality trait associated with lower post-hatch growth. Growth was clearly affected by breeder flock and hatching system, which could not be linked to mean Pasgar©score or incidence of Q2 chicks. Q2 chicks showed lower post-hatch growth compared to Q1 chicks but effects on flock performance at slaughter weight were limited because early mortality in Q2 chicks was high (62.50% at 7 days). We concluded that chick qualitative scores and the incidence of Q2 chicks may be informative for the quality of incubation, but are not predictive for post-hatch flock performance. Culling Q2 chicks after hatch is well-founded in terms of both animal welfare and profitability.     

Effect of ACTH injection and graft of bursa of Fabricius on the adrenocortical activity of bursectomized chicks at 80 hours of incubation

Early embryonic bursectomy (BFX) disturbed the adrenocortical functioning. The stress-unresponsive period that occurred in controls, and lasted for 2-3 weeks after hatching, no longer appeared in BFX chicks. In contrast, the magnitude of the stress-induced hypercorticosteronemia was much lower in BFX than in sham-operated 5 week-old chicken. It was assumed that such adrenocortical dysfunction was due to bursal deprivation, since grafting bursal buds onto the chorio-allantoic membrane of BFX embryos restored all the parameters under study, i.e., the post-hatching stress unresponsive period and the high magnitude of stress-induced responses in adults. Factor(s) involved in such interregulation are not known but do not seem to affect directly adrenocortical cells because intramuscular injection of a moderate dose of ACTH resulted in the same hypercorticosteronemia whether 3 day-old and 5 week-old chicks had been bursectomized or sham-operated.     

Effects of fire management on northern bobwhite brood ecology

Northern Bobwhite Colinus virginianus chicks require ample invertebrates for growth and feather development. Early successional or resprouting vegetation provides invertebrates for chicks but may not provide other resources such as roosting and loafing cover that is typically provided by later successional stages. Thus, management for bobwhites provides multiple seral stages in close proximity but the effects of landscape interspersion have not been tested for bobwhite broods. During a 2-year study, we explored the effects of landscape complementation and food availability on growth and survival of bobwhite chicks. We found growth of chicks to be negatively related to home range size which was negatively correlated to the amount of area burned. We also found survival of chicks to be positively related to the amount of burned area (i.e., foraging area) within brood home ranges. To maximize the growth and survival of bobwhite chicks, it would be necessary to increase access to foraging areas while decreasing the size of brood home ranges. Access to foraging areas can be created through frequent prescribed fire at small spatial scales.