Domestic chicks' runway responses to video images of conspecifics

A review of environmental enrichment for laying hens during rearing in relation to their behavioral and physiological development

Globally, laying hen production systems are a focus of concern for animal welfare. Recently, the impacts of rearing environments have attracted attention, particularly with the trend toward more complex production systems including aviaries, furnished cages, barn, and free-range. Enriching the rearing environments with physical, sensory, and stimulatory additions can optimize the bird's development but commercial-scale research is limited. In this review, "enrichment" is defined as anything additional added to the bird's environment including structurally complex rearing systems. The impacts of enrichments on visual development, neurobehavioral development, auditory stimulation, skeletal development, immune function, behavioral development of fear and pecking, and specifically pullets destined for free-range systems are summarized and areas for future research identified. Visual enrichment and auditory stimulation may enhance neural development but specific mechanisms of impact and suitable commercial enrichments still need elucidating. Enrichments that target left/right brain hemispheres/behavioral traits may prepare birds for specific types of adult housing environments (caged, indoor, outdoor). Similarly, structural enrichments are needed to optimize skeletal development depending on the adult layer system, but specific physiological processes resulting from different types of exercise are poorly understood. Stimulating appropriate pecking behavior from hatch is critical but producers will need to adapt to different flock preferences to provide enrichments that are utilized by each rearing group. Enrichments have potential to enhance immune function through the application of mild stressors that promote adaptability, and this same principle applies to free-range pullets destined for variable outdoor environments. Complex rearing systems may have multiple benefits, including reducing fear, that improve the transition to the layer facility. Overall, there is a need to commercially validate positive impacts of cost-effective enrichments on bird behavior and physiology.

Valence and Intensity of Video Stimuli of Dogs and Conspecifics in Sheep: Approach-Avoidance, Operant Response, and Attention

Simple Summary

Animals’ judgement of stimuli’s negativity or positivity cannot always be assumed. To assess the valence and intensity of video stimuli (dogs as negative vs. conspecifics as positive stimuli) in sheep, we used three experimental approaches: (1) an approach-avoidance paradigm; (2) operant conditioning using the videos as reinforcers; and (3) an attention test. We measured sheep’s behavioral and physiological reactions. Sheep generally reacted to the videos presented. Nevertheless, we found no support with the approach–avoidance paradigm, and the attention test for dog videos were more negative than sheep videos. However, the operant conditioning indicated that sheep were more prone to avoid videos of moving dogs. Overall, we found that standard video images may not be ideal to represent valence characteristics of stimuli to sheep.

Abstract

Stimuli are often presumed to be either negative or positive. However, animals’ judgement of their negativity or positivity cannot generally be assumed. A possibility to assess emotional states in animals elicited by stimuli is to investigate animal preferences and their motivation to gain access to these stimuli. This study’s aim was to assess the valence of social stimuli in sheep. We used silent videos of varying intensity of dogs as negative versus conspecifics as positive stimuli in three approaches: (1) an approach–avoidance paradigm; (2) operant conditioning using the video stimuli as reinforcers; and (3) an attention test. In the latter, we assessed differential attention of sheep to simultaneous projections by automatically tracking sheep head and ear postures and recording brain activity. With these approaches, it was difficult to support that the sheep’s reactions varied according to the stimuli’s presumed valence and intensity. The approach–avoidance paradigm and attention test did not support the assumption that dog videos were more negative than sheep videos, though sheep reacted to the stimuli presented. Results from the operant conditioning indicated that sheep were more prone to avoid videos of moving dogs. Overall, we found that standard video images may not be ideal to represent valence characteristics of stimuli to sheep.

Chicks prefer to peck at insect-like elongated stimuli moving in a direction orthogonal to their longer axis

Spontaneous preferences towards possible prey have been little investigated using targets in motion. Preferences of domestic chicks (Gallus gallus) to peck at video-images of stimuli representing live insects moving along their longer body axis (i.e. "forwards") or along the shorter body axis (i.e. "sideways") were investigated. Chicks presented with both types of stimulus displayed a significant preference for pecking at stimuli moving sideways. This preference was already present on day 1 post-hatching, and it strengthened on day 6 for those chicks that had experienced pecking at live insects. Head angles used to fixate the stimuli prior to pecking were also analysed and were consistent (i.e. 30 degrees -35 degrees and 60 degrees -65 degrees ) with those reported for fixation of non-edible targets (larger stimuli at a distance). In a first control experiment the same video-presented stimuli were used but the insect's legs were removed to reduce flickering. In a second control experiment, paper-printed images of the whole insect were used. In both cases, the sideways direction of movement was clearly preferred. Overall, our data show that chicks have a spontaneous preference to peck at video-images resembling live insects moving along their shorter body axis. Sideways movement may constitute a crucial signal attracting chicks' attention and enhancing predatory responses possibly because of stronger stimulation of motion detectors.

The effects of hen vocalizations on chick feeding behavior

The purpose of this study was to determine if playing hen calls at the feeder affects broiler chick productivity and welfare. Hatched chicks (n = 832) were equally placed into 16 pens. Broilers in 8 treated pens received 3 min of hen-feeding calls once each hour during the first 9 d of age; broilers in the other 8 pens received no recorded hen vocalizations during the same period. After d 9, recorded hen vocalizations ceased and all birds were treated identically. Through 9 d of age, chicks receiving recorded hen vocalizations had improved (P < or = 0.05) feed conversion ratios, and these chicks weighed more (139.12+/-1.52 g vs. 133.17+/-1.59 g for control chicks; P < or = 0.01). The behavior data showed that on d 1, 4, and 7, more (P < or = 0.05) chicks receiving recorded hen vocalizations were found within 0.61 m of the speaker than control chicks. Following recorded hen vocalization cessation on d 9, birds and feed were weighed on 17, 24, 31, and 38 d of age, and carcass yield was measured on d 40. There were no differences in BW, feed efficiency, or carcass yield after recorded hen vocalization ceased. These data suggest that after d 9, differences became nonsignificant, corresponding to when recorded hen vocalization stopped. Behavior data demonstrated that chicks appear to be attracted when stimulated with recorded hen vocalizations, thus remaining in close proximity to the speaker. Evidence suggests that hen vocalization improves production and attraction to hen vocalization with known improvements in BW and feed conversion during the first 9 d posthatch.

Motivation and ability to walk for a food reward in fast- and slow-growing broilers to 12 weeks of age

Poor physical abilities of broilers may prevent them from performing behaviours for which they are motivated. The aim of this study was to measure the influence of physical ability and motivation on the performance of broilers in short physical tasks. We tested birds from a fast- and a slow-growing broiler strain in a runway to 12 weeks of age. To manipulate motivation, half of the birds of each strain was feed deprived for 3h and the other half for 24h before testing. Each bird was tested in a control and a slalom runway test once a week. With a similar motivation, slow growers had a shorter latency to start walking and walked faster through the runway than fast growers in both tests. In fast growers walking speed decreased faster with age than in slow growers. Slow growers vocalised more in both tests. In the slalom test, 24h deprived birds vocalised more than 3h deprived birds. Although the fast and slow growers have a different genetic background, the results indicated that motivation is the dominant determinative factor for walking in birds with a low body weight, while physical ability is the dominant determinative factor for walking in birds with a high body weight.