Evaluation of Alternative Euthanasia Methods of Neonatal Chickens

Abstract

Simple SummaryMale layer chicks do not have economic value and are humanely killed after hatching. The layer industry is seeking alternative methods to humanely kill recently hatched male chicks. This study evaluated the use of gases or negative air pressure as a means of humane and viable alternatives to maceration. The treatments included carbon dioxide, nitrogen, reduced air pressure, and a negative control. The study showed that chicks exposed to treatments, gases or negative air pressure, did not differ significantly in terms of the physiological stress response. The use of carbon dioxide resulted in a faster onset of unconsciousness and ultimately death as compared to nitrogen or negative air pressure treatments.AbstractHatched male layer chicks are currently euthanized by maceration in the United States. Public concerns on the use of maceration have led to the search for alternative methods. We hypothesized that gas inhalation and low atmospheric pressure stunning (LAPS) are viable and humane alternatives to instantaneous mechanical destruction. The objective of this study was to evaluate the physiological and behavioral responses of recently hatched male layer chicks when subjected to carbon dioxide, nitrogen inhalation, or LAPS. The study consisted of seven treatments: breathing air (NEG), 25% carbon dioxide (CO2), 50% CO2, 75% CO2, 90% CO2, 100% nitrogen (N2), or LAPS. Ten day-of-hatch, male layer chicks were randomly assigned to each treatment, and each treatment was replicated on ten different days. A custom-made vacuum system was used to reduce air pressure inside the chamber from 100.12 kPa to 15.3 kPa for the LAPS treatment. Serum corticosterone and serotonin levels were measured using commercially available competitive enzyme linked immunosorbent assay (ELISA). Latencies to loss of posture and motionlessness were determined from video recordings. The 25% and 50% CO2 treatments were discontinued after the first replication, as the majority of the chicks recovered. The chicks in the negative (NEG) group had significantly higher levels of corticosterone than the other four euthanasia treatments. On the other hand, the serotonin levels of chicks in the NEG group was significantly lower when compared to the other four euthanasia treatments. The latencies to loss of posture and motionlessness of chicks exposed to 75% and 90% CO2 were significantly shorter than those in the LAPS and N2 inhalation treatments. These data suggest that the stress responses of chicks to the CO2, N2, and LAPS treatments do not differ among each other. However, the CO2 inhalation method was faster in inducing loss of posture and motionlessness in chicks than the LAPS and N2 inhalation treatments.

Killing for purposes other than slaughter: poultry

“…More recently, exposure of chicks to LAP has been evaluated and reported to be a suitable method (Gurung et al., 2018b). In this study, preliminary trials showed that a negative air pressure of 15.3 kPa (1 kPa = 7.5 Torr) would result in 100% mortality and, therefore, the experimental chicks were subjected to a reduction in chamber pressure from 100.12 kPa to 15.3 kPa over 80 s and then held in the chamber for 5 min, resulting in death.…”

Defining characteristics of immersion carbon dioxide gas for successful euthanasia of neonatal and young broilers

“…(2018) found euthanasia with CO 2 resulted in the shortest time to insensibility and death. The authors also reported bird stress, as measured by serum corticosterone and serotonin levels, was similar for all the 3 methods ( Gurung et al., 2018 ).…”

“…Despite having National Farm Animal Care Council and AVMA approval, many hatcheries are looking for an alternative method of euthanasia to maceration owing to public concern. Recently, researchers have investigated a number of alternative methods for neonatal chicken euthanasia, including CO 2 gaseous euthanasia ( Gurung et al., 2018 ; Baker et al., 2019 ). Gaseous euthanasia is used for culling adult and neonatal poultry, during which exposure to high or prolonged concentrations of an inhalant agent, in this case CO 2 , results in insensibility and death ( Galvin et al., 2005 ; Raj et al., 2006 ; AVMA, 2013 ; Baker et al., 2019 ).…”

“…Carbon dioxide inhalation induces insensibility and death, as the elevated concentration of inspired CO 2 and reduced oxygen availability cause hypercapnia and hypoxia, respectively ( AVMA, 2013 ; Terlouw et al., 2016 ). When neonatal chick euthanasia via CO 2 was compared with euthanasia via N 2 inhalation or low atmospheric pressure stunning, Gurung et al. (2018) found euthanasia with CO 2 resulted in the shortest time to insensibility and death.…”

“…The effect of a lower CO 2 concentration in the chamber on the efficacy and welfare impact of neonatal euthanasia via immersion is unknown. Research has determined that with gradual fill, in which neonatal chicks are placed into the chamber and then CO 2 is gradually introduced, death occurs between 70 and 79% CO 2 ( Baker et al., 2019 ), and a final concentration of 75% CO 2 is sufficient to result in death ( Gurung et al., 2018 ). These concentrations are specific to gradual fill and are not directly applicable to immersion, as physiological response to the immediate and significant increase in inhaled CO 2 with immersion may differ from the response to a slow buildup of CO 2 and thus affect the minimum CO 2 concentration requirement.…”