Can Early Environmental Enrichment Buffer Stress from Commercial Hatchery Processing in Laying Hens?

Abstract

Under commercial conditions, laying hen chicks are exposed to a range of stressful events immediately after hatch. Here, we studied whether environmental enrichment was able to reduce the stress sensitivity of these chicks. A total of 50 hatchery chicks (HC) and 50 control chicks (CC) were raised in enriched pens (E), while 53 HC + 53 CC were raised in standard non-enriched floor pens (NE). HC weighed less on day one, but there was no effect of hatchery treatment at later ages. HC were more pessimistic in a cognitive judgement bias test and emitted more distress calls when socially isolated, indicating that hatchery stress affected behaviour and stress sensitivity. However, enrichment did not affect the behaviour in any of these tests. We found no effects of hatchery stress in a novel environment, but indications that enrichment may have increased fearfulness of HC. The sensitivity of the hypothalamic-pituitary-adrenal (HPA) axis was reduced in HC-E compared to HC-NE, indicating that enrichment buffered the physiological stress sensitivity in HC; however, the opposite pattern was found in CC. In conclusion, our results show complex and somewhat contradictory effects on the ability of enrichment to buffer the consequences of stress in commercial hatcheries.

Early and late cognitive and behavioral aspects associated with range use in free-range laying hens (Gallus gallus domesticus)

“…Latencies to approach the chick/pullet and morph stimuli were intermediate. These results are similar to those obtained in previous studies ( Salmeto et al, 2011 ; Hedlund et al, 2021 , 2022 ), and corroborates that chicks are able to perceive the stimuli differently and adapt their behavior accordingly.…”

“…To assess whether our cognitive bias test produced results consistent with previous studies employing the same testing paradigm ( Salmeto et al, 2011 ; Hedlund et al, 2021 , 2022 ), we initially conducted an analysis of the first cognitive bias test alone, before range access, on the latency birds took to reach the virtual line. This analysis considered the influence of the stimuli themselves (mirror, chick/pullet, morph, and owl) and the presentation order of stimuli (either chick/pullet or owl during the second trial) as fixed effects.…”

“…The cognitive bias test drew inspiration from a methodology that had already been validated for assessing cognitive bias in domestic chicks ( Salmeto et al, 2011 ; Hedlund et al, 2021 , 2022 ). Our rationale for evaluating the cognitive bias of birds both before and after gaining access to the range stemmed from the understanding that the range, being a less predictable environment than the barn, requires birds to continually assess and respond to various stimuli they may encounter ( Rodriguez-Aurrekoetxea et al, 2014 ; Campbell et al, 2018a ; Ferreira et al, 2020b ).…”

Commercial hatchery processing may affect susceptibility to stress in laying hens

“…To mitigate negative consequences, various attempts have been made to improve the long-term welfare of laying hens, for example, by enriching the rearing environment in order to stimulate a wider range of natural behaviour [ 4 , 9 , 10 ]. Some of the experiments do indeed reveal a positive effect, and there are indications that early enrichment may also buffer some of the stress from commercial hatching by making chickens more resilient against stress later in life [ 11 ], although the results are somewhat ambiguous.…”

Environmental Enrichment as Part of the Improvement of the Welfare of Japanese Quails

“…In the context of bird welfare, research hitherto conducted has identified several factors that can disrupt bird welfare to varying degrees. These occur at all stages of rearing, from the time of hatching [ 5 ] through to beak-correction treatments [ 6 ] and treatment associated with moving the birds between production buildings, or concerning changes to their housing systems [ 7 ].…”