Arousal, but not nursing, is necessary to elicit a decreased fear reaction toward humans in rabbit (Oryctolagus cuniculus) pups

Appropriate handling of pet rabbits: a literature review

Many rabbits show fear behaviours when lifted off the ground. Estimates from owner surveys suggest that around 60% of pet rabbits struggle when lifted and fear-related aggression is common. This article integrates information from both laboratory and pet rabbit studies to formulate a list of recommendations for appropriate handling of rabbits. Reduction of the frequency of the stressor can be achieved by educating owners on alternative management practices to reduce the need to carry their rabbits. However, in some situations, it is unavoidable that a rabbit is lifted. Amelioration of the stress in these instances can be achieved by a 2 pronged strategy. First, the population of rabbits can be made more resilient to infrequent stressors by selectively breeding for confident rabbits and by better socialisation of unweaned kits, and, where possible, training of individual animals to permit handling. Secondly, any unavoidable lifting can be made less stressful by educating veterinary staff in appropriate methods of holding rabbits during both consultations and inpatient care. Better understanding of appropriate interactions with rabbits will improve welfare.

Artificial feeding synchronizes behavioral, hormonal, metabolic and neural parameters in mother-deprived neonatal rabbit pups

Nursing in the rabbit is under circadian control, and pups have a daily anticipatory behavioral arousal synchronized to this unique event, but it is not known which signal is the main entraining cue. In the present study, we hypothesized that food is the main entraining signal. Using mother-deprived pups, we tested the effects of artificial feeding on the synchronization of locomotor behavior, plasma glucose, corticosterone, c-Fos (FOS) and PERIOD1 (PER1) rhythms in suprachiasmatic, supraoptic, paraventricular and tuberomammillary nuclei. At postnatal day 1, an intragastric tube was placed by gastrostomy. The next day and for the rest of the experiment, pups were fed with a milk formula through the cannula at either 02:00 h or 10:00 h [feeding time = zeitgeber time (ZT)0]. At postnatal days 5-7, pups exhibited behavioral arousal, with a significant increase in locomotor behavior 60 min before feeding. Glucose levels increased after feeding, peaking at ZT4-ZT12 and then declining. Corticosterone levels were highest around the time of feeding, and then decreased to trough concentrations at ZT12-ZT16, increasing again in anticipation of the next feeding bout. In the brain, the suprachiasmatic nucleus had a rhythm of FOS and PER1 that was not significantly affected by the feeding schedule. Conversely, the supraoptic, paraventricular and tuberomammillary nuclei had rhythms of both FOS and PER1 induced by the time of scheduled feeding. We conclude that the nursing rabbit pup is a natural model of food entrainment, as food, in this case milk formula, is a strong synchronizing signal for behavioral, hormonal, metabolic and neural parameters.

The rabbit pup, a natural model of nursing-anticipatory activity

Mother rabbits nurse their young once a day with circadian periodicity. Nursing bouts are brief (ca. 3 min) and occur inside the maternal burrow. Despite this limited contact mother rabbits and their pups are tuned to each other to ensure that the capacities of each party are used efficiently to ensure the weaning of a healthy litter. In this review we present behavioral, metabolic and hormonal correlates of this phenomenon in mother rabbits and their pups. Research is revealing that the circadian rhythm of locomotion shifts in parallel to the timing of nursing in both parties. In pups corticosterone has a circadian rhythm with highest levels at the time of nursing. Other metabolic and hormonal parameters follow an exogenous or endogenous rhythm which is affected by the time of nursing. In the brain, clock genes and their proteins (e.g. Per1) are differentially expressed in specific brain regions (e.g. suprachiasmatic nucleus, paraventricular nucleus) in relation to providing or ingesting milk in mothers and young, respectively. These findings suggest that circadian activities are modulated, in the mothers, by suckling stimulation and, in the young, by the ingestion of milk and/or the perception of the mammary pheromone. In conclusion, the rabbit pup is an extraordinary model for studying the entraining by a single daily food pulse with minimal manipulations. The mother offers the possibility of studying nursing as a non-photic synchronizer, also with minimal manipulation, as suckling stimulation from the litter occurs only once daily.

Effects of husbandry and management systems on physiology and behaviour of farmed and laboratory rabbits

The major issues regarding the welfare of both farmed and laboratory rabbits are reviewed, according to husbandry and management systems. The main stressors that can affect welfare and homeostatic responses in rabbits are also reviewed. An overview of the most widespread housing systems for both farmed and laboratory rabbits is presented. The main problems related to housing and management are identified, in particular those related to individual and group housing, space requirements and group size, as well as human-animal interaction. The effects of psychological and physical stressors on physiology and behaviour are illustrated through examples in various rearing conditions. Psychological stressors include social stress and fear, while physical stressors include environmental variables such as housing system and climatic factors, i.e. heat. Welfare indicators are identified that can be monitored to determine the effects of individual and environmental variables on the animals' possible coping strategies. Physiological indicators include the neuro-endocrine and psycho-neuro-immuno-endocrine measurements, while behavioural indicators include the behavioural repertoire and responses to behavioural tests. Some possible ways to enhance welfare are indicated, such as enrichment of the environment and improved handling procedures.

Circadian rhythm of corticosterone secretion in the neonatal rabbit

Maternal care in the rabbit is restricted to a single 3- to 5-min period of nursing each day. One to three hours prior to the arrival of the mother, pups exhibit anticipatory behavioral arousal and elevation of core body temperature. In rodents, the hypothalamic-pituitary-adrenal axis is quiescent and levels of the adrenal hormone, corticosterone (CORT), are stable and extremely low during the first days of life, which are known collectively as the stress-hyporesponsive period (SHRP). It has been proposed that the rabbit also has an SHRP. However, we decided to examine CORT changes associated with the daily nursing bout, since behavioral arousal, core body temperature, and CORT are elevated prior to the onset of feeding in many other species. We scheduled the nursing bout at 1000 h and analyzed CORT concentration using RIA in pups sampled at various intervals after suckling. CORT levels showed a circadian variation that peaked at the time of the daily nursing bout. After nursing, values steadily decreased to a nadir at 2200 h and then rose again in advance of the next scheduled nursing. The three-fold difference between the highest (1000 h) and the lowest (2200 h) CORT values suggests that either the SHRP does not exist in rabbit pups or else it has properties that differ from those described for rodents. Unlike rodents, rabbit pups show a circadian secretion of CORT synchronized to the scheduled nursing bout.