Use of high concentrations of carbon dioxide for stunning rabbits reared for meat production

[EN] An investigation was performed to determine whether high concentrations of carbon dioxide (CO2) at 70-98% in atmospheric air are a suitable alternative for stunning rabbits compared to conventional approaches such as electronarcosis. Aversion to the gas and efficacy in causing prolonged unconsciousness and death were studied in a total of 480 rabbits by means of behavioural parameters, physiological indicators (presence of rhythmic breathing and corneal reflex) and electroencephalography (EEG, brain function). The use of any of the 4 studied concentrations of the gas caused more nasal discomfort and vocalisations than the use of atmospheric air (P<0.001). EEG activity confirmed that loss of posture is a good indicator of the onset of unconsciousness in rabbits exposed to CO2, occurring earlier (P<0.05) at 90 and 98% than at 70 and 80%. Rabbits showed signs of aversion for 15 s before the onset of unconsciousness, which occurred around 30 s after the beginning of the exposure to the gas, similar to species such as swine in which high concentrations of CO2 are also used for stunning. CO2 at 80 to 98% is suggested as a reasonable concentration range to induce a long state of unconsciousness and death in rabbits, while 70% CO2 is not recommended because it requires too long duration of exposure (more than 360 s) to ensure effectiveness. Despite the advantages in terms of pre-stun handling and irreversibility, CO2 is not free of animal welfare concerns. In consequence, a debate is necessary to ascertain if CO2 can be considered a suitable alternative to stun rabbits, considering the advantages and drawbacks cited, quantified in the present study as 15 s of aversion (nasal discomfort and vocalisations) before losing posture.The Spanish Association of Rabbit Industry Retailers (INTERCUN) provided financial support to carry out this studyDalmau, A.; Pallisera, J.; Pedernera, C.; Muñoz, I.; Carreras, R.; Casal, N.; Mainau, E.... (2016). Use of high concentrations of carbon dioxide for stunning rabbits reared for meat production. World Rabbit Science. 24(1):25-37. doi:10.4995/wrs.2016.3880.SWORD2537241Anil, M., & McKinstry, J. (1991). Reflexes and loss of sensibility following head-to-back electrical stunning in sheep. Veterinary Record, 128(5), 106-107. doi:10.1136/vr.128.5.106Bradley Bays T., Lightfoot T., Mayer J. 2006. Exotic pet behaviour: Birds, Reptiles and Mammals. Philadelphia: Saunders.Conlee, K. M., Stephens, M. L., Rowan, A. N., & King, L. A. (2005). Carbon dioxide for euthanasia: concerns regarding pain and distress, with special reference to mice and rats. Laboratory Animals, 39(2), 137-161. doi:10.1258/0023677053739747Council Regulation (EC). 2009. No 1099/2009 on the protection of animals at the time of killing. European Community Official Journal, L303:1-30Dalmau A., Rodríguez P., Llonch P., Velarde A. 2010a. Stunning pigs with different gas mixtures. Part 2: aversion in pigs. Anim. Welfare, 19: 324-333Dalmau A., Llonch P., Rodríguez P., Ruíz-de-la-Torre J.L., Manteca, X., Velarde A. 2010b. Stunning pigs with different gas mixtures. Part 1: gas stability. Anim. Welfare, 19: 315-323.EFSA. 2013. Guidance on the assessment criteria for studies evaluating the effectiveness of stunning interventions regarding animal protection at the time of killing, EFSA J.,11: p. 41.Forslid A. 1992. Muscle spasms during pre-slaughter carbon dioxide anaesthesia in swine. Fleischwirtschaft, 72: 167-168.Raj A.B.M., Gregory N.G. 1995. Welfare implications of the gas stunning of pigs 1. Determination of aversion to the initial inhalation of carbon dioxide or argon. Anim. Welfare, 4: 273-280.Raj A.B.M., Gregory N.G. 1996. Welfare implications of gas stunning of pigs 2. Stress of induction of anaesthesia. Anim. Welfare, 5: 71-78Rodríguez P., Dalmau A., Ruiz-de-la-Torre J.L., Manteca X., Jensen E.W., Rodríguez B., Litvan H., Velarde A. 2008. Assessment of unconsciousness during carbon dioxide stunning in pigs. Anim. Welfare, 17: 341-349.Velarde A., Cruz J., Gispert M., Carrión D., Ruiz-de-la-Torre J.L., Diestre A., Manteca X. 2007. Aversion to carbon dioxide stunning in pigs: effect of the carbon dioxide concentration and the halothane genotype. Anim. Welfare, 16: 513-522

Stress-induced changes in group behaviour

Testing animals in groups can provide valuable data for investigating behavioural stress responses. However, conventional measures typically focus on the behaviour of individual animals or on dyadic interactions. Here, we aimed to determine metrics describing the behaviour of grouping animals that can reveal differences in stress responses. Using zebrafish (Danio rerio) as a model, we observed replicated shoals both immediately and 24 hours after exposure to a novel environment, as an assessment of temporal change in response to an acute stressor. We quantified various standard behavioural measures in combination with metrics describing group structure, including different proximity, social, and spatial metrics. Firstly, we showed a high collinearity between most of the analysed metrics, suggesting that they describe similar aspects of the group dynamics. After metric selection, we found that under acute stress shoals had significantly higher shoal densities, a lower variation in nearest neighbour distances and were in closer proximity to the walls compared to the same groups tested 24 hours later, indicating a reduction in acute stress over time. Thus, the use of group metrics could allow for the refinement of behavioural protocols carried out in a range of research areas, by providing sensitive and rich data in a more relevant social context

Do atmospheric aerosols form glasses?

Zobrist B, Marcolli C, Pedernera DA, Koop T. Do atmospheric aerosols form glasses? ATMOSPHERIC CHEMISTRY AND PHYSICS. 2008;8(17):5221-5244.A new process is presented by which water soluble organics might influence ice nucleation, ice growth, chemical reactions and water uptake of aerosols in the upper troposphere: the formation of glassy aerosol particles. Glasses are disordered amorphous (non-crystalline) solids that form when a liquid is cooled without crystallization until the viscosity increases exponentially and molecular diffusion practically ceases. The glass transition temperatures, Tg, homogeneous ice nucleation temperatures, Thom, and ice melting temperatures, Tm, of various aqueous inorganic, organic and multi-component solutions are investigated with a differential scanning calorimeter. The investigated solutes are: various polyols, glucose, raffinose, levoglucosan, an aromatic compound, sulfuric acid, ammonium bisulfate and mixtures of dicarboxylic acids (M5), of dicarboxylic acids and ammonium sulfate (M5AS), of two polyols, of glucose and ammonium nitrate, and of raffinose and M5AS. The results indicate that aqueous solutions of the investigated inorganic solutes show Tg values that are too low to be of atmospheric importance. In contrast, aqueous organic and multi-component solutions readily form glasses at low but atmospherically relevant temperatures (≤230 K). To apply the laboratory data to the atmospheric situation, the measured phase transition temperatures were transformed from a concentration to a water activity scale by extrapolating water activities determined between 252 K and 313 K to lower temperatures. The obtained state diagrams reveal that the higher the molar mass of the aqueous organic or multi-component solutes, the higher Tg of their respective solutions at a given water activity. To a lesser extent, Tg also depends on the hydrophilicity of the organic solutes. Therefore, aerosol particles containing larger (≳150 g mol−1) and more hydrophobic organic molecules are more likely to form glasses at intermediate to high relative humidities in the upper troposphere. Our results suggest that the water uptake of aerosols, heterogeneous chemical reactions in aerosol particles, as well as ice nucleation and ice crystal growth can be significantly impeded or even completely inhibited in organic-enriched aerosols at upper tropospheric temperatures with implications for cirrus cloud formation and upper tropospheric relative humidity