Visual lateralization and development of spatial and social spacing behaviour of chicks (Gallus gallus domesticus)

We investigated whether the development of spatial behaviour of the domestic chicken is influenced by light exposure of the embryo, as is known to be the case for some other lateralized visual functions. Ninety-six chicks were incubated in the dark or exposed to light during the final days of incubation. Half of the chicks in each group had the experience of moving behind opaque screens from 10 to 12 days of age. The other half were given transparent screens as a control. Chicks were tested in a detour test and a rotated floor test and their dispersal in groups was observed in larger pens. In the rotated floor test, chicks that had had experience with opaque screens used distal cues significantly more often than chicks that had experience with transparent screens (P = 0.042), regardless of whether they had been exposed to light before hatching or incubated in the dark. There were no significant differences between treatments in the detour test or in the dispersal behaviour. Hence, visual lateralization has no influence on the development of the spatial behaviour that we tested, whereas the occlusion experience is quite specific and results in shifted attention to distal spatial cues.     

Stimulus Movement,Hen Behaviour and Filial Imprinting in Japanese Quail (Coturnix coturnix japonica)

A living hen is a very attractive imprinting stimulus compared to artificial stimuli. The present study examined to what extent this attractiveness is influenced by the behaviour of the hen. The effectiveness of a living quail hen as an imprinting stimulus was compared with that of a moving stuffed hen, a non-moving stuffed hen and an empty cage. Naive quail chicks were exposed to one of these stimuli for 2 h. Both during and after this period chicks exposed to the living hen showed the strongest attachment to the stimulus, next came chicks exposed to a moving stuffed hen, while chicks exposed to a non-moving stuffed hen showed no indication of any attachment, i.e. they behaved in the same way as chicks exposed to an empty cage. Also, among chicks exposed to the living hen a correlation was present between the strength of the attachment to the hen and the behaviour of this hen during the exposure. In particular pecking and behaviour directed at the chick seemed to stimulate the development of a filial bond. Together, these findings indicate that a living hen is attractive not just because she moved, but also because of specific qualities of this movement. The behaviour of the living hen differed in various ways from the movement of the moving stuffed hen. The influence of these differences on the filial imprinting process is discussed and compared with similar findings for sexual imprinting and song learning.     

Secondary imprinting in the domestic chick blocked by previous exposure to a live hen

Two experiments were carried out to investigate secondary imprinting in the domestic chick, Gallus gallus. Experiment 1 established that, after chicks with very limited prior visual experience had been exposed to a moving cup during the first 3 days of life, the cup when stationary would suppress distress calling. The main experiment, experiment 2, then examined the effects of various forms of prior experience on the development of this kind of imprinting. Three groups of chicks were exposed on days 1 and 2 to either a live hen (Hen group), a moving object (Windmill group) or the same object when stationary (Control group). On days 4, 5 and 6 all subjects were given training of the kind used in experiment 1; imprinting to the cup was obtained in the Windmill and Control groups, but not in the Hen group. On days 11 and 12 retention tests were given; these showed good retention of primary imprinting, in that the cup was still effective in suppressing distress calling in the Control group and likewise the windmill in the Windmill group, but no effect of secondary imprinting was detected, in that the cup no longer affected the behaviour of the chicks in the Windmill group. These results indicated that primary imprinting with certain stimuli, as in the Hen group, can subsequently exert powerful interference with secondary imprinting and they supported a previous claim that, where secondary imprinting does occur, it is relatively unstable.     

Ontogeny of magnetoreception in chickens (Gallus gallus domesticus)

Chickens are precocial birds, capable of moving independently from within a few hours of hatching, and thus provide a useful model to investigate the development of magnetoreception in young birds. Chicks show some sharply-timed behavioural changes at around 11 days of age that may be indicative of improvements in navigation ability around this age. We trained Young (<10 days, n = 7) and Old (11 days or older, n = 6) chicks to find a hidden imprinting stimulus behind one of four screens in a square arena. Once criterion was reached, the directional choices of chicks were recorded in unrewarded tests in the geomagnetic field and in an experimental field shifted by 90° clockwise. These tests were separated with rewarded training trials to avoid extinction. In the first, and the first 3 tests, no indication was found that chicks chose the correct unimodal magnetic direction. Instead, in all tests, Old chicks preferred the screens in the same magnetic axis as the training direction in tests in the geomagnetic and shifted experimental fields significantly more than Young chicks (P < 0.05). Choices of Young chicks were no different to chance in tests, whereas choices by Old chicks were significantly different from chance (P < 0.05). Our findings support the hypothesis that magnetoreception appears in the second week of life in the chicken. It is, however, unclear when a truly directional magnetic response (i.e. an unimodal, rather than axial, response in our test) develops that could be used by the chicks for accurate navigation.     

Social recognition and approach in the chick: lateralization and effect of visual experience

Chicks, Gallus gallus domesticus, tested monocularly on day 3 after hatching recognize familiar versus unfamiliar conspecifics and choose to approach one or other when they use the left eye, whereas they approach familiar and unfamiliar chicks at random when they use the right eye. In experiment 1 we investigated the effects of light exposure of embryos prior to hatching on this particular form of lateralization. Irrespective of whether they hatched from eggs incubated in the dark or from eggs exposed to light during the final days of incubation, chicks using the left eye had higher choice scores (meaning they chose to approach either a familiar or an unfamiliar chick) than chicks using the right eye or both eyes. Therefore, light experience prior to hatching did not influence the lateralization of individual recognition or choice behaviour, although it did affect latency to move out of, and time spent in, the centre of the runway. Experiment 2 showed that visual/social experience posthatching influences choice behaviour: chicks housed in a group in the light for 12 h on day 1 posthatching made a clear choice between familiar and unfamiliar chicks when tested on day 3, but chicks kept in a group in the dark on day 1 did not make a choice, instead alternating between the two stimuli. In experiment 3 we found that posthatching visual/social experience increased the choice scores of chicks using the right eye and thereby removed any lateralization of choice behaviour. The results suggest that visual experience of a social group is required before chicks using their right eye (and left hemisphere) will pay attention to the cues that distinguish one chick from another. Chicks using their left eye (and right hemisphere) recognize the difference between individuals without requiring visual experience with other chicks. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.     

Neurotransmitter Release from the Medial Hyperstriatum Ventrale of the Chick Forebrain Accompanying Filial Imprinting Behavior,Measured by In Vivo Microdialysis

The imprinting behavior of chicks was quantified as a preference score (correct response ratio) achieved in a running wheel apparatus. A total of 249 chicks were exposed to an imprinting stimulus and tested for stimulus-approaching behavior. The chicks were then classified as good learners (imprinted), poor learners (non-imprinted) and a gray-zone group, those were 46%, 31% and 23% of the total chicks respectively. Using the classified chicks, the acetylcholine (ACh) and glutamate releases from the medial hyperstriatum ventrale (MHV) of the chick forebrains were determined by in vivo microdialysis. The non-imprinted chicks were used as yoked controls. Increases of ACh and glutamate released were observed in the imprinted chicks during exposure to the imprinting stimulus, whereas there were no changes in the release of these neurotransmitters in the non-imprinted chicks during the imprinting exposure. These results might be indicated that cholinergic and glutamatergic synapses which are newly formed as functioning synapses with imprinting stimulus in the MHV are involved in the performance of imprinting behavior.     

Getting better all the time: improving preference scores reflect increases in the strength of filial imprinting

In the investigation of the neural mechanisms of filial imprinting, neurochemical measures are often correlated with preference score (PS): approach activity to the training stimulus/total approach in a test. In a previous study, domestic chicks, Gallus gallus domesticus, that had a PS under 65% were classed as 'poor learners' and those with a PS greater than 65% were called 'good learners'. We tested the effects of continued imprinting training in chicks from these two categories. After exposure to an imprinting stimulus for 30 min on day 1 after hatching, preferences were tested and then the chicks were exposed to the same stimulus for either 90 min, 3 h or 4 h on the next day, followed by a second preference test. In all these experiments there was a significant improvement in mean PS in the 'poor learners' between the first and second test, such that these chicks acquired a significant mean preference for the training stimulus. There was no such improvement in chicks that did not receive further training on day 2. When absolute approach was analysed, there was no significant difference between 'poor learners' and 'good learners' at the second test, after 4 h of retraining. Overall, mean preference scores increased with length of training. These results suggest that 'poor learners' are better characterized as 'slow learners', and that their initially low PS is not caused by, for example, a lack of motivation to express a preference. Preference scores reflect the strength of learning during imprinting. Copyright 2000 The Association for the Study of Animal Behaviour.     

Effect of pens with an elevated platform on space utilization,skin lesions and growth performance in nursery pigs

Environmental enrichment, adequate space and the ability to separate a living area into suitable functional areas are key elements for pig welfare. In this study, a two-level pen for nursery pigs was explored with the aim of analysing the use of space and the impact on pig behaviour, health and performance. Therefore, per batch, three experimental groups in pens with elevated platforms (two-level pens) and one control group in a standard pen were formed after weaning at the age of 4 weeks. Thereafter, groups were studied for a period of 6 weeks. In a total of eight batches (n = 882 pigs), the occurrence of skin lesions was determined per individual using a lesion score, and in seven batches (n = 761 pigs) individual daily weight gain was analysed. In five batches (n = 450 pigs), the individual use of space and the behaviour of pigs were investigated by direct observation (4 h per day on 2 days in weeks 1, 3 and 6 of the housing period, respectively). Results revealed that 98.9% of pigs (n = 445) were observed on the elevated platform at least once. The probability that an individual pig used the platform was significantly higher than 0.95 (P < 0.0001, confidence interval = 0.977, 1). The use of the platform was not affected by sex (odds ratio (OR) = 1.013, P = 0.937). However, the probability of observing an individual on the elevated platform increased with increasing BW during the experimental period (OR = 1.043, P < 0.0001). The presence of a platform decreased the probability of seeing a pig fighting (P = 0.014) and increased the probability of observing locomotor behaviour as opposed to lying (P < 0.0001). In two-level pens, pigs sustained fewer skin injuries than in standard pens (day 41: OR = 0.731, P < 0.0001). Over 41 days of experiment, pigs in two-level pens had higher daily weight gains than animals in standard pens (416 versus 393 g/day, P = 0.006). We conclude that usable space for nursery pigs can be effectively extended by introducing elevated platforms into the pigs’ pen. Furthermore, pigs may benefit from two-level systems by establishing spaces for activity as well as for retreat from other pen mates, thereby reducing aggressive behaviour and social stress. The installation of two-level pens is therefore encouraged, if they are intended to provide more space than legally stipulated.     

Evaluation of early feed access and algal extract on growth performance,organ development,gut microbiota and vaccine-induced antibody responses in broiler chickens

Hatching concepts such as on-farm hatching provide an opportunity to supply newly hatched chickens with optimal nutrition that support growth and development of a healthy gut. Brown algae contain bioactive compounds, especially laminarin and fucoidan that may improve intestinal health and immune responses. This study aimed to examine the effects of early access to feed and water posthatch and feed supplementation with algal extract rich in laminarin from Laminaria digitata, on growth performance, organ and microbiota development and antibody production. A total of 432 Ross 308 chicks were allotted to 36 rearing pens in a 2 × 3 factorial design with two hatching treatments and three dietary treatments. During chick placement, half of the pens were directly provided access to feed and water (Early) while half of the pens were deprived of feed and water for 38 h (Late). The chicks were fed three different starter diets until day 6; a wheat-soybean meal-based control diet, a diet with low inclusion of algal extract (0.057%) and a diet with high inclusion of algal extract (0.114%). Feed intake and BW were registered on pen basis at placement, days 1, 6, 12, 19, 26, 33 and 40. To induce antibody responses, all chicks were vaccinated against avian pneumovirus on day 10. Three chicks per pen were selected as focal animals and used for blood sampling on days 10 and 39. On days 6, 19, and 40, two birds per pen were killed and used for organ measurement and caecal digesta sampling for gut microbiota analysis using the Illumina Miseq PE 250 sequencing platform. Results showed that algal extract did not influence gut microbiota, gut development or vaccine-induced antibody responses. However, during the first 38 h, early-fed chicks consumed on average 19.6 g of feed and gained 27% in BW, while late-fed chicks lost 9.1% in BW which lowered BW and feed intake throughout the study (P < 0.05). Late chicks also had longer relative intestine, higher relative (g/kg BW) weight of gizzard and proventriculus but lower relative bursa weight on day 6 (P < 0.05). No effects of hatching treatment on microbiota or antibody response were detected. The microbiota was affected by age, where alpha diversity increased with age. In conclusion, this study showed that early access to feed but not algal extract improved the growth performance throughout the 40-day growing period, and stimulated early bursa development.     

Changes in activity and object manipulation before tail damage in finisher pigs as an early detector of tail biting

Tail damage within the production of finisher pigs is an animal welfare problem. Recent research suggests that removal of known risk factors may not be enough to eliminate tail biting, especially in undocked pigs, thus a different strategy is worth investigating. This could be early detection of tail biting, using behavioural changes observed before tail damage. If these early stages of tail biting can be detected before tail damage occurs, then tail damage could be prevented by early interventions. The first step in developing such a strategy is to identify the types of behaviour changes that emerge during early stages of tail biting. Thus, the aim of the current study was to investigate whether pen level activity and object manipulation evolved differently during the last 7 days before the scoring of tail damage (day 0) for pens scored with tail damage (tail damage pens) and pens not scored with tail damage (matched control pens). The study included video recordings for twenty-four tail damage pens and thirty-two matched control pens. Activity level and object manipulation were observed the last 7 days before day 0 during the morning (0600 to 0800 h), afternoon (1600 to 1800 h) and evening (2200 to 2400 h, only activity level). Both activity level and object manipulation were analysed using generalised linear mixed effects models with a binomial distribution for activity level and a negative binomial distribution for object manipulation. The probability of being active was higher in tail damage pens compared to control pens during the afternoon the last 5 days before day 0 (P<0.001). This was seen due to a decrease in activity level in the control pens, which makes it difficult to identify future tail damage pens from this difference. Object manipulation was lower in tail damage pens compared to the control pens on all 7 days before day 0, but only in pens with undocked pigs (P<0.01). Thus, it is still unknown when this difference in object manipulation initiated. It was concluded that both activity level and object manipulation seemed related to ongoing tail biting and should be investigated through more detailed observations and for a longer time to establish the normal behaviour pattern for a particular pen. Thus, it is suggested that future research focusses on developing automatic monitoring methods for pen level activity and object manipulation and applies algorithms that establish and detect deviations from the normal behaviour pattern of the pen before tail damage.     

Familiarity interferes with filial imprinting

The present study was performed to investigate whether and how pre-exposure to an object affects subsequent filial imprinting to that object. In Experiment 1 junglefowl chicks (Gallus gallus spadiceus) were first exposed to either a red object alone (control group), or a red and a yellow object simultaneously (experimental group; phase 1). Subsequently, all chicks were exposed to the yellow object in the presence of a black and blue one (phase 2). At the end of phase 1, most experimental chicks had developed a preference for the red object over the yellow one. At the end of phase 2, preferences of experimental chicks were shifted away from the yellow object towards the novel black and blue object, relative to preferences of control chicks. This shows that pre-exposure may interfere with imprinting. Experiment 2 revealed that when control chicks were tested with the yellow object at the end of phase 1, filial responses were as strong as in experimental chicks. This shows that the yellow object had not acquired control over filial behaviour during phase 1, and also that the relatively impaired imprinting on that object in phase 2 was not due to reduced generalization from the red object. One possible explanation why pre-exposure may interfere with imprinting is that familiarity alters the level of attention attracted by an object, a mechanism suggested to underlie ‘latent inhibition’ in conditioning.     

Neuronal plasticity and multisensory integration in filial imprinting

Many organisms sample their environment through multiple sensory systems and the integration of multisensory information enhances learning. However, the mechanisms underlying multisensory memory formation and their similarity to unisensory mechanisms remain unclear. Filial imprinting is one example in which experience is multisensory, and the mechanisms of unisensory neuronal plasticity are well established. We investigated the storage of audiovisual information through experience by comparing the activity of neurons in the intermediate and medial mesopallium of imprinted and naïve domestic chicks (Gallus gallus domesticus) in response to an audiovisual imprinting stimulus and novel object and their auditory and visual components. We find that imprinting enhanced the mean response magnitude of neurons to unisensory but not multisensory stimuli. Furthermore, imprinting enhanced responses to incongruent audiovisual stimuli comprised of mismatched auditory and visual components. Our results suggest that the effects of imprinting on the unisensory and multisensory responsiveness of IMM neurons differ and that IMM neurons may function to detect unexpected deviations from the audiovisual imprinting stimulus.     

The effects of confinement on periparturient behaviour and circulating prolactin,prostaglandin F2α and oxytocin in gilts with access to a variety of nest materials

In a 2×2 factorial experiment, the effects of gestation and farrowing housing on (1) periparturient behaviour and circulating prolactin, prostaglandin F_2α (PGF_2α) and oxytocin in gilts with access to peat, straw and branches, and (2) correlational relationships between the periparturient behaviour and hormones were studied. The treatments consisted of housing in stalls or pens from mating to day 110 of gestation followed by farrowing crates or pens until after parturition. Landrace×Yorkshire gilts were observed from video recordings (n=25) from 20 h prepartum and blood sampled via jugular catheters (n=16) from 24 h prepartum until 2 h after the birth of the first piglet.There was an interaction between gestation and farrowing housing affecting the start of nest-building (P=0.03). Gilts that experienced a change in type of housing accommodation commenced nest-building closer to parturition than gilts that were penned both during gestation and at farrowing (both P<0.05). There were no effects of the housing environment on the timing of termination of nest-building, behaviour during parturition, or the course of parturition. However, relative to base level, crated gilts sat more from 16 to 6 h prepartum, whereas this was the case for penned gilts only from 9 to 7 h prepartum. Crated gilts also tended to change posture more often (P=0.07) and lie more in sternal recumbency (P=0.095). This suggests that familiarity with the environment in combination with space to move about and/or availability of materials is important in the timing of nest-building. Confinement during farrowing did not appear to impair feed-back from the materials and the nest, although increased number of postural changes may reflect the motivation but inability to nest-build, or general discomfort in the crate.There was a development over time in postural and nest-building behaviours as well as in plasma concentrations of prolactin, PGF_2α (measured by the metabolite PGFM) and oxytocin, but there were only few effects of housing treatments on hormones or associations between behaviour and hormones. The results suggest that nest-building occurs independently of a prepartum rise in prolactin, but that oxytocin may be associated with the termination of nest-building as there was a negative correlational relationship with nosing (P<0.01) and arranging nest-building materials (P<0.001).Farrowing crate housing appeared to have fewer effects on periparturient behaviour and course of parturition than reported in previous studies where effects of confinement and provision of nest-building materials may have been confounded. Thus, provision of nest-building materials to crated sows may have beneficial effects on sow behaviour and welfare.     

Adult aggression during the post-guard phase in the chinstrap penguin Pygoscelis antarctica

We report an observational study of aggressive behaviour by adults during the post-guard phase in the chinstrap penguin. The study was carried out in one subcolony where all the individuals (breeders, chicks and failed breeders) were banded, as well as in nine other subcolonies where individuals were not identifiable. Breeding adults were more aggressive towards unrelated chicks when they were feeding their own chicks than in other contexts. Chicks were also attacked at high rates by adults that did not belong to their own subcolonies. The evidence suggests that some aggressions to chicks by adults may function to avoid interference from unrelated chicks during food transfers, but our data also show that aggressive interactions are common in contexts other than chick feeding. However, aggression by adults did not show any clear spatial directionality or purpose of shepherding the chicks, and these tended not to move in any particular direction when attacked.     

Effects of supplementation with vitamin E on the performance and the tissue peroxidation of broiler chicks and the stability of thigh meat against oxidative deterioration

Two experiments were conducted: Expt 1 determined the optimal allowance of vitamin E in the diet for broiler chicks aged 0–3 weeks; Expt 2 investigated the effects of different dietary levels of vitamin E (α-tocopherol) on the performance and the oxidative stability of thigh meat of broiler chicks during storage. In Expt 1, 1-day-old 900 broiler chicks were allocated to five treatments, each with six replicates (cages) of 22 as-hatched chicks for performance evaluation, and another cage of 45 male chicks for determining plasma and hepatic α-tocopherol and thiobarbituric acid reactive substances (TBARS) concentration in blood and liver. The basal dietary α-tocopherol concentration was 13 mg/kg, and the five α-tocopherol acetate supplementation levels were 0, 5, 10, 50 and 100 mg/kg. For 0–3-week-old broiler chicks fed with maize–soya bean meal–soya oil type diet, supplementation of vitamin E did not influence the feed intake, but tended to improve growth and feed utilization, however there was no significant correlation between performance and vitamin E supplementation level. Significant positive correlations existed between dietary supplemental vitamin E level and plasma or hepatic α-tocopherol concentrations (P<0.05), and a negative correlation with hepatic TBARS levels no matter at what age (11, 16 and 21 days). In Expt 2, 2200 broiler chicks were randomly allocated to five treatments with four replicates (pens) in each. Chicks were fed ad libitum five pellet diets supplemented with vitamin E at 5, 10, 20, 50 and 100 mg/kg of diet, respectively. The basal dietary α-tocopherol level of grower and finisher diets were 7 and 6 mg/kg, respectively. Supplementation of vitamin E tended to improve growth and feed utilization of birds during 0–3 weeks of age, but the performance from 0 to 6 weeks of age were not influenced. The hepatic α-tocopherol concentrations of 6-week-old chicks linearly increased with the dietary vitamin E levels (R²=0.98, P<0.001). The content of TBARS in the thigh meat over 4 days of storage under 4°C was significantly decreased by increasing dietary vitamin E level (P<0.05). There was a significant inverse relationship between TBARS value in the thigh meat and the dietary vitamin E level (R²=0.93, P<0.01). Supplementation of vitamin E significantly improved the meat quality stability substantially against oxidative deterioration. Comparing the hepatic α-tocopherol levels of chicks in Expts 1 and 2, total allowance of dietary α-tocopherol of 20–30 mg/kg could sustain relatively constant hepatic α-tocopherol level at round about 2–2.5 μg/kg.     

Supplementing a yeast-derived product to enhance productive and health responses of beef steers

This experiment evaluated the impacts of supplementing a yeast-derived product (Celmanax; Church & Dwight Co., Inc., Princeton, NJ, USA) on productive and health responses of beef steers, and was divided into a preconditioning (days 4 to 30) and feedlot receiving phase (days 31 to 69). In all, 84 Angus × Hereford steers were weaned on day 0 (BW=245±2 kg; age=186±2 days), and maintained in a single group from days 0 to 3. On day 4, steers were allocated according to weaning BW and age to a 21-pen drylot (4 steers/pen). Pens were randomly assigned to (n=7 pens/treatment): (1) no Celmanax supplementation during the study, (2) Celmanax supplementation (14 g/steer daily; as-fed) from days 14 to 69 or (3) Celmanax supplementation (14 g/steer daily; as-fed) from days 31 to 69. Steers had free-choice access to grass-alfalfa hay, and were also offered a corn-based concentrate beginning on day 14. Celmanax was mixed daily with the concentrate. On day 30, steers were road-transported for 1500 km (24 h). On day 31, steers returned to their original pens for the 38-day feedlot receiving. Shrunk BW was recorded on days 4, 31 and 70. Feed intake was evaluated daily (days 14 to 69). Steers were observed daily (days 4 to 69) for bovine respiratory disease (BRD) signs. Blood samples were collected on days 14, 30, 31, 33, 35, 40, 45, 54 and 69, and analyzed for plasma cortisol, haptoglobin, IGF-I, and serum fatty acids. Preconditioning results were analyzed by comparing pens that received (CELM) or not (CONPC) Celmanax during the preconditioning phase. Feedlot receiving results were analyzed by comparing pens that received Celmanax from days 14 to 69 (CELPREC), days 31 to 69 (CELRECV) or no Celmanax supplementation (CON). During preconditioning, BRD incidence was less (P=0.03) in CELM v. CONPC. During feedlot receiving, average daily gain (ADG) (P=0.07) and feed efficiency (P=0.08) tended to be greater in CELPREC and CELRECV v. CON, whereas dry matter intake was similar (P⩾0.29) among treatments. No other treatment effects were detected (P⩾0.20). Collectively, Celmanax supplementation reduced BRD incidence during the 30-day preconditioning. Moreover, supplementing Celmanax tended to improve ADG and feed efficiency during the 38-day feedlot receiving, independently of whether supplementation began during preconditioning or after feedlot entry. These results suggest that Celmanax supplementation benefits preconditioning health and feedlot receiving performance in beef cattle.     

Improved performance and immunological responses as the result of dietary genistein supplementation of broiler chicks

The present study aimed to investigate the effect of supplemental genistein (an isoflavonoid) on performance, lymphoid organs’ development, and cellular and humoral immune responses in broiler chicks. A total of 675-day-old male broiler chicks (Ross 308) were randomly assigned to the five replicate pens (15 chicks each) of nine experimental diets. Dietary treatments included a negative (not-supplemented) control diet, two positive control groups (virginiamycin or zinc-bacitracin, 20 mg/kg), and diets containing 10, 20, 40, 80, 160 and 320 mg/kg of genistein. The cutaneous basophil hypersensivity (CBH) test was measured at day 10 of age after toe web injection with phytohemagglutinin-P. In addition, sera samples were collected after different antigen inoculations to investigate antibody responses. At day 28 of age, three randomly selected birds from each pen were euthanized to evaluate the relative weights of lymphoid organs. Results showed that dietary supplementation of both antibiotics increased (P<0.01) feed intake during 1 to 42 days of age. Furthermore, daily weight gain was influenced (P<0.01) by dietary treatments throughout the trial, so that the birds fed on antibiotics and 20 to 80 mg/kg genistein diets revealed the greater weight gains compared with other experimental groups. The best (P<0.05) feed conversion ratio assigned to the birds fed on diets containing antibiotics and moderate levels (40 to 80 mg/kg) of genistein. Although the relative weights of thymus (P<0.05) and bursa of Fabricius (P<0.01) were greater in birds fed on genistein-supplemented diets compared with antibiotics-supplemented birds, the spleen weight was not affected by experimental diets. Similarly, CBH response and antibody titers against Newcastle and infectious bronchitis disease viruses were markedly (P<0.05) greater in chicks fed on diets supplemented with 20 to 80 mg/kg of genistein. Interestingly, the higher dosages of genistein suppressed CBH and antibody responses to the levels seen by control and antibiotics chicks. Dietary inclusion of genistein increased (P<0.05) lymphocytes and subsequently reduced (P<0.01) heterophil to lymphocyte ratio. The present findings indicate that dietary genistein supplementation at the levels of 20 to 80 mg/kg not only improves growth performance, but also could beneficially affect immunological responses in broiler chicks.     

Effect of early feed restriction on physiological responses,performance and ascites incidence in broiler chickens raised in normal or cold environment

Intensive selection of broilers for faster growth and better feed efficiency resulted in greater susceptibility to metabolic disorders such as ascites syndrome, which is one of the major causes of mortality and economic loss in broiler industry. Whereas cool temperature is one of the primary triggers for ascites, early feed restriction (FDR) significantly alleviates its incidence and mortality. However, little is known about effects of FDR, cold environmental temperature and their interaction on physiological responses in broiler chickens. For this purpose, 320 one-day-old male broilers were divided into two treatment groups of Ad libitum (Ad) and feed restricted (FR) with eight pen replicates each. Chickens in FR group underwent feed access limitation from days 7 to 14 of age. On day 21 half of the birds (four pens) in each group exposed to the cold temperature (CT) and the other half (four pens) continued at normal temperature (NT). Average daily feed intake, average daily weight gain and feed conversion ratio (FCR) were measured at days 7, 14, 21, 28 and 42. At 39 and 46 days of age two chicks with a BW around the pen average were selected from each pen and slaughtered after collecting blood samples. Then, relative weight of internal organs and right ventricle weight per total ventricle weight (RV : TV) ratio were calculated. Compared with NT group, CT birds had higher daily feed intake and FCR (P<0.05) from day 28 to 42. Cumulative ascites mortality in CT chickens was higher (P<0.001) than NT chicks. Within the CT group, ascites mortality in FR chickens was reduced (P<0.001) to 1.25% compared with 8.75% in Ad chicks. Birds in CT group had significantly (P<0.05) thicker right ventricle and greater relative weight of heart, hematocrit and triiodothyronine concentration. However, none of these parameters were affected by FDR. Under cold stress conditions, FDR reduced activity of alanine aminotransferase and aspartate aminotransferase (P<0.05). Serum triglyceride, cholesterol, high-density lipoprotein and total protein were not influenced by either temperature or feeding regimen. In conclusion, these findings suggest that FDR reduces ascites incidence mainly by allowing better development of internal organs, which helps them to cope with the high metabolic pressure and suffer less damage.     

Creep-feeding to stimulate metabolic imprinting in nursing beef heifers: impacts on heifer growth,reproductive and physiological variables

This experiment compared growth, physiological, and reproductive responses of beef heifers with (MI) or without (CON) access to a creep-feeder, as a manner to stimulate metabolic imprinting while nursing their dams. On day 0, 60 Angus×Hereford heifers were ranked by BW and age (140±3 kg and 68±3 days), and assigned to pairs so all ranking criteria were similar between heifers within each pair. On day 1, pairs were randomly assigned to MI (n=15) or CON (n=15). From day 1 to 51, MI pairs and their dams were allocated to 15 drylot pens where heifers had ad libitum access to a corn-based supplement through a creep-feeder. The CON pairs and their dams were maintained in an adjacent single drylot pen. From day 52 to 111, treatments were managed as a single group on a semiarid range pasture. On day 111, heifers were weaned and allocated to two pastures (one pasture/treatment), receiving hay and a corn-based concentrate until day 326. Heifer BW was recorded before and at the end of the creep-feeding period (day 1 to 51), and on days 112 and 326. On days 0, 51, 111, 187, 261, and 325, jugular blood was collected and real-time ultrasonography for longissimus muscle depth and backfat thickness assessment was performed. Blood was also collected every 10 days from days 113 to 323 for puberty evaluation via plasma progesterone. Liver and subcutaneous fat biopsies were performed on days 51, 111, 261 and 325. Average daily gain was greater (P<0.01) for MI than CON from day 1 to 51, tended (P=0.09) to be greater for CON than MI from day 112 to 326, while BW on day 326 was similar between treatments. On day 51, MI had greater (P⩽0.01) plasma IGF-I and glucose concentrations, as well as mRNA expression of hepatic pyruvate carboxylase and adipose fatty acid synthase than CON. On days 261 and 325, plasma insulin concentrations were greater (P⩽0.03) in CON than MI. Mean mRNA expression of hepatic IGF-I and adipose peroxisome proliferator-activated receptor gamma were greater (P⩽0.05) in MI than CON. No treatment effects were detected for puberty attainment rate. In conclusion, supplementing nursing heifers via creep-feeding for 50 days altered physiological and biochemical variables suggestive of a metabolic imprinting effect, but did not hasten their puberty attainment.     

Reversibility revisited: Stimulus-dependent stability of filial preference in the chick

The reversibility of filial preferences was studied in domestic chicks, Gallus gallus domesticus, using an artificial as well as a more naturalistic imprinting stimulus. Day-old chicks were exposed for 2 h to either a rotating stuffed jungle fowl or a rotating red box. Two hours later their preferences were tested in a simultaneous choice test (test I), involving the box and the fowl. The next day, the chicks were trained and tested (test II) as before, except box-trained chicks were now exposed to the fowl and vice versa. In three different experimental groups, the relative attractiveness of the two stimuli (as measured in test I) was varied by altering the light intensity of the red box. In the chicks trained with the box and subsequently exposed to the fowl, there was a significant decrease in mean preference for the box from test I to test II. In contrast, the preference of the chicks trained with the stuffed fowl were not affected by subsequent exposure to the red box. This differential reversibility was also found when, in test I, the preference for the box was significantly higher than the preference for the fowl. These results support a model of the formation of filial preference as an interaction between acquired preference and a developing predisposition for a particular class of stimuli.