Behavioral response of weaned pigs during gas euthanasia with CO2, CO2 with butorphanol, or nitrous oxide

Simple Summary Pig farmers are forced to euthanize a significant number of pigs due to injuries, hernias, or unthriftiness. The majority of pigs are euthanized using carbon dioxide gas asphyxiation. However, the humaneness of carbon dioxide is being increasingly questioned. An alternative is the use of nitrous oxide gas. We conducted this study to compare the euthanasia of young pigs using nitrous oxide or carbon dioxide. In addition, we tested the administration of a pain relief drug prior to carbon dioxide exposure to determine if we could eliminate behaviors indicative of pain. Pigs became unable to control their muscle movement, breathed heavily, and lost posture at the same time regardless of treatment. Pigs exposed to both gases showed heavy breathing and open-mouth breathing prior to losing posture. However, pigs exposed to carbon dioxide made more escape attempts but fewer squeals than pigs exposed to nitrous oxide. Administration of pain relief prior to exposure to carbon dioxide did not alter behaviors indicative of pain. The findings are inconclusive as to whether using nitrous oxide is significantly better than using carbon dioxide, but the results show that its use is just as effective, and possibly more humane. Abstract The swine industry is often forced to euthanize pigs in the first few weeks of life due to injuries, hernias, or unthriftiness. The majority of pigs are euthanized using carbon dioxide (CO2) gas asphyxiation but concerns as to the humaneness of CO2 are increasing. This study compared the euthanasia of weaned pigs using N2O (N2O; n = 9) or CO2 (n = 9), at 50% and 25% min(-1) exchange rate, respectively. In addition, we administered an analgesic prior to euthanasia with CO2 (CO2B) exposure as a third treatment (n = 9) to elucidate behaviors indicative of pain. Pigs in the CO2 and N2O treatments lost posture at similar times (latency of 145.0 +/- 17.3 and 162.6 +/- 7.0 s respectively, p > 0.10), while the CO2B treatment pigs lost posture the soonest (101.2 +/- 4.7 s, p < 0.01). The pigs in the CO2B treatment made more escape attempts than the CO2 or N2O pigs (16.4 +/- 4.2, 4.7 +/- 1.6, 0.3 +/- 0.2, respectively; p < 0.0004). However, pigs in N2O squealed more often than either the CO2 or CO2B pigs (9.0 +/- 1.6, 2.8 +/- 1.2, 1.3 +/- 0.6, respectively, p < 0.001). Given the similar time to loss of posture and shorter time displaying open mouth breathing, N2O may cause less stress to pigs; however, the greater number of squeals performed by these pigs suggests the opposite. It was not apparent that any behavior measured was indicative of pain. In conclusion, N2O applied at a 50% min(-1) flow rate can be an alternative to CO2 for pig euthanasia.Livestock Behavior Research UnitIowa State Universit

Behavioral Response of Weaned Pigs during Gas Euthanasia with CO2, CO2 with Butorphanol, or Nitrous Oxide

The swine industry is often forced to euthanize pigs in the first few weeks of life due to injuries, hernias, or unthriftiness. The majority of pigs are euthanized using carbon dioxide (CO2) gas asphyxiation but concerns as to the humaneness of CO2 are increasing. This study compared the euthanasia of weaned pigs using N2O (N2O; n = 9) or CO2 (n = 9), at 50% and 25% min−1 exchange rate, respectively. In addition, we administered an analgesic prior to euthanasia with CO2 (CO2B) exposure as a third treatment (n = 9) to elucidate behaviors indicative of pain. Pigs in the CO2 and N2O treatments lost posture at similar times (latency of 145.0 ± 17.3 and 162.6 ± 7.0 s respectively, p \u3e 0.10), while the CO2B treatment pigs lost posture the soonest (101.2 ± 4.7 s, p \u3c 0.01). The pigs in the CO2B treatment made more escape attempts than the CO2 or N2O pigs (16.4 ± 4.2, 4.7 ± 1.6, 0.3 ± 0.2, respectively; p \u3c 0.0004). However, pigs in N2O squealed more often than either the CO2 or CO2B pigs (9.0 ± 1.6, 2.8 ± 1.2, 1.3 ± 0.6, respectively, p \u3c 0.001). Given the similar time to loss of posture and shorter time displaying open mouth breathing, N2O may cause less stress to pigs; however, the greater number of squeals performed by these pigs suggests the opposite. It was not apparent that any behavior measured was indicative of pain. In conclusion, N2O applied at a 50% min−1 flow rate can be an alternative to CO2 for pig euthanasia

Ranging Behaviour of Commercial Free-Range Broiler Chickens 1: Factors Related to Flock Variability

Little is known about the ranging behaviour of chickens. Understanding ranging behaviour is required to improve management and shed and range design to ensure optimal ranging opportunities. Using Radio Frequency Identification technology, we tracked 300 individual broiler chickens in each of four mixed sex ROSS 308 flocks on one commercial farm across two seasons. Ranging behaviour was tracked from the first day of range access (21 days of age) until 35 days of age in winter and 44 days of age in summer. Range use was higher than previously reported from scan sampling studies. More chickens accessed the range in summer (81%) than winter (32%; p p

Ranging Behaviour of Commercial Free-Range Broiler Chickens 2: Individual Variation

Little is known about broiler chicken ranging behaviour. Previous studies have monitored ranging behaviour at flock level but whether individual ranging behaviour varies within a flock is unknown. Using Radio Frequency Identification technology, we tracked 1200 individual ROSS 308 broiler chickens across four mixed sex flocks in two seasons on one commercial farm. Ranging behaviour was tracked from first day of range access (21 days of age) until 35 days of age in winter flocks and 44 days of age in summer flocks. We identified groups of chickens that differed in frequency of range visits: chickens that never accessed the range (13 to 67% of tagged chickens), low ranging chickens (15 to 44% of tagged chickens) that accounted for

Oxytocin as a welfare indicator related to the social environment

The disruption of normal social behavior is a major welfare concern for farm animals. Swine typically experience several regroupings depending on their production stages. Group-housing of breeding sows is particularly becoming more common in the United States. All these situations involve agonistic interactions to establish a hierarchy in newly formed groups. Therefore, social stress is a critical welfare aspect of animal production systems due to its detrimental effects on well-being, especially for subordinates. In contrast, positive social interactions appear to have evolved in social animals as an effective strategy to reduce the adverse effects of stress. The mechanisms through which benefits arise from positive interactions and how that enhances an animal\u27s stress-coping ability are poorly understood. In addition, the neurophysiological mechanisms of social behavior in pigs remain mostly unknown. Recent research on rodents and primates suggests that oxytocin (OT) acts as one of the main regulators of mammalian social behavior at the central level. Research on the role of OT shows anxiolytic effects and an association with positive affective states. This suggests that OT might be the physiological pathway by which animals benefit from positive relationships. No studies have investigated the role of OT in the social behavior of pigs. The first study, presented in Chapter Two, validated that OT administered intranasally was able to attenuate social separation distress 45 min post-administration in 2 wk-old suckling piglets, as evidenced by the lower activity, escape attempts, and heart rate of OT-treated piglets during a 15 min social isolation test. The response to OT was greater in gilts than barrows possibly due to an estrogen influence. This study also confirmed that intranasal administration represents an appealing, non-invasive method to study the effect of neuropeptides on the behavior and welfare of animals. The second study, presented in Chapter Three, investigated the effects of mixing sows in mid-gestation (prenatally-stressed; PNS), by introducing them into a new group weekly for 3 wk, on the response of their female offspring to social separation. Furthermore, we used intranasal OT administration to elucidate the impact of PNS on the offspring\u27s social behavior. Prenatally-stressed piglets displayed lower levels of behavioral activity and heart rate during social isolation. The administration of OT to PNS piglets reestablished vigilance behaviors such as alertness and standing. In control piglets, OT administration increased the root mean square of successive differences (RMSSD) of the heart rate, a measure of parasympathetic activity; however, PNS piglets did not respond to this effect of OT, but OT lowered their heart rate through a different mechanism. These results suggest that social stress during the second trimester of gestation alters behavior and the development of the autonomic nervous system in the sow\u27s offspring. The third study, presented in Chapter Four, investigated the long-term effects of neonatal OT administration on the pigs\u27 ability to cope with social stress. Repeated OT administration to neonatal pigs at 1, 2, and 3 d of age caused pigs to be involved in more agonistic interactions when mixed after weaning at 19 d of age and to have greater cortisol and adrenocorticotropin hormone concentrations, with a few effects persisting at mixing at 8 wk of age. A dexamethasone-corticotropic releasing hormone test revealed that neonatal OT administration resulted in a long-term dysregulation of the hypothalamo-pituitary-adrenal axis until at least 11 wk of age. We originally hypothesized that neonatal OT administration could provide long-lasting protective effects against social stress. Our results showed the opposite, as a disruption of the OT system in early life brought long-term detrimental consequences. This series of experiments show for the first time that OT is implicated in the social behavior of pigs and appears to play a role in their stress-coping abilities. Hence, OT might represent the first welfare indicator to assess the social environment. A better knowledge of the neurobiological mechanisms of the social behavior of domestic animals will help to clarify how different husbandry practices can lead to various outcomes in animal health and well-being and implement practices that meet their social and psychological needs

Effects of Oxytocin Administration on the Response of Piglets to Weaning

Weaning is often an abrupt and stressful process. We studied the effects of administering oxytocin, subcutaneously or intranasally, on the ability of pigs to cope with weaning. On a commercial farm 144, 30 day-old pigs from 24 litters were used. On the day of weaning, one male and one female in each litter were administered one of three treatments: intranasal oxytocin (24 International Unit), subcutaneous oxytocin (10 International Unit per kg of body weight), or handled as a control. The pigs were placed in one of eight weaner pens, split by sex and with an equal representation of treatments. Data included body weight and growth, physiology (neutrophil:lymphocyte ratio, plasma cortisol, C-reactive protein and Tumor Necrosis Factor-α concentrations), and behavior (feeding, drinking, social behavior). Both oxytocin treatments tended to result in higher levels of mild aggression within groups (p = 0.08), specifically between oxytocin-administered and control pigs (subcutaneous to control p = 0.03; intranasal to control p = 0.10). Subcutaneously-administered pigs tended to frequent the feeder more often than intranasally-administered pigs (p &lt; 0.10), with the latter having slightly lower body weight 38 days post-weaning (p = 0.03). However, acute oxytocin administration did not result in any noticeable physiological changes 4 or 28 h post-weaning. Hence, the use of a single administration of oxytocin prior to weaning in pigs is not recommended, at least not in the conditions studied here

Indoor side fidelity and outdoor ranging in commercial free-range chickens in single- or double-sided sheds

The ranging behaviour of broiler chickens kept in free-range housing systems remains poorly understood, despite access to the outdoor range being their main feature. We investigated the impact of allowing chickens to have range access on both sides vs. one side of the shed, using 24 flocks of approximately 40,000 Ross 308 chickens of mixed sex on one commercial farm across winter and summer. Sheds were identical and pseudo-randomly allocated to either double-sided (no modification) or single-sided (by keeping one side closed at all time) range access treatment. Flocks were first provided with range access from 15 to 17 and 21 to 27 days of age for summer and winter flocks, respectively. Live outdoor observations were conducted daily for the first week after first range access and every other day from the second week onwards until the day prior to depopulation (44 days of age), twice daily in each morning and evening during anticipated peaks of range use. Indoor side fidelity was also assessed by spray marking 320 chickens in total on the right- and left-hand side of the shed, one colour each side, and conducting two to four repeated counts of the colour-marked individuals in each location over the week following marking. Indoor count results showed that colour-marked chickens had 50% chance of being found on either side of the shed (