Water intake in domestic rabbits (Oryctolagus cuniculus) from open dishes and nipple drinkers under different water and feeding regimes

Rabbits (Oryctolagus cuniculus) increase caecal calcium absorption at increasing dietary calcium levels

Hindgut fermenting herbivores from different vertebrate taxa, including tortoises, and among mammals some afrotheria, perissodactyla incl. equids, several rodents as well as lagomorphs absorb more calcium (Ca) from the digesta than they require, and excrete the surplus via urine. Both proximate and ultimate causes are elusive. It was suggested that this mechanism might ensure phosphorus availability for the hindgut microbiome by removing potentially complex-building Ca from the digesta. Here we use Ussing chamber experiments to show that rabbits (Oryctolagus cuniculus) maintained on four different diets (six animals/diet) increase active Ca absorption at increasing Ca levels. This contradicts the common assumption that at higher dietary levels, where passive uptake should be more prevalent, active transport can relax and hence supports the deliberate removal hypothesis. In the rabbits, this absorption was distinctively higher in the caecum than in the duodenum, which is unexpected in mammals. Additional quantification of the presence of two proteins involved in active Ca absorption (calbindin-D9K CB; vitamin D receptor, VDR) showed higher presence with higher dietary Ca. However, their detailed distribution across the intestinal tract and the diet groups suggests that other factors not investigated in this study must play major roles in Ca absorption in rabbits. Investigating strategies of herbivores to mitigate potential negative effects of Ca in the digesta on microbial activity and growth might represent a promising area of future research.

Urine Output Monitoring and Acute Kidney Injury in Non-mammalian Exotic Animal Critical Care

Acute kidney injury (AKI) is a sudden, severe decrease in kidney function which can occur in any species. There are various causes of AKI, some of which are seen in domestic species and some that are unique to birds, reptiles, and amphibians. These species present unique challenges with AKI management, such as differences in anatomy and physiology, intravenous and urinary catheterization, repeated blood sampling, and their tendency to present in advanced states of illness. This article will discuss AKI, diagnosis, treatment, and prognosis for non-mammalian exotic species.

Perceptions of the rabbit as a low investment 'starter pet' lead to negative impacts on its welfare: Results of two Danish surveys

Concerns over compromised companion rabbit (Oryctolagus cuniculus domesticus) welfare are widespread. The welfare problems have been linked to the perception of rabbits as low investment 'children's pets.' To test this hypothesis and investigate the current conditions for rabbits, data were gathered from two surveys in 2021: a nationally representative survey of Danish companion animal owners (Survey I) and a detailed social media-based survey of Danish rabbit owners (Survey II). Using logistic regression, three owner-related variables (whether a child/adult was responsible for care of the rabbit, owner-opinion on rabbits' suitability as 'starter pets' and willingness-to-pay [WTP] for veterinary treatment) were employed to investigate the effect of rabbit status on owner-provision of selected husbandry conditions. The 76 (Survey I) and 4,335 (Survey II) responses suggested that most rabbits are acquired for children and are solitarily housed, and that many are kept in cages of an unsuitable size and not checked daily. Owners who perceived rabbits as 'starter pets' and with lower WTP were more likely to house rabbits in restricted space and to not provide continuous gnawing opportunities, ad libitum hay or routine healthcare. A child fulfilling the role of the rabbit's main caretaker was also associated with inadequate housing type and fewer gnawing opportunities. Thus, many rabbits live in unsuitable conditions, and owners who perceive rabbits as low investment 'children's pets' are more likely to not provide recommended resources. Changing owners' perceptions of rabbits and promoting suitable husbandry through official education programmes and minimum requirements is important if there are to be improvements made to rabbit welfare.

Urine Output Monitoring and Acute Kidney Injury in Mammalian Exotic Animal Critical Care

Acute kidney injury (AKI) is a sudden, severe decrease in kidney function which can occur in any species. There are various causes of AKI, some of which are seen in domestic species and some that are unique to exotics. Exotic animals present unique challenges with AKI management such as differences in anatomy and physiology, intravenous and urinary catheterization, repeated blood sampling, and their tendency to present in advanced states of illness. This article will discuss AKI, diagnosis, treatment, and prognosis for exotic companion mammals. The following article will discuss the same in non-mammalian patients.

Drying dynamics of pellet feces

Pellet feces are generated by a number of animals important to science or agriculture, including mice, rats, goats, and wombats. Understanding the factors that lead to fecal shape may provide a better understanding of animal health and diet. In this combined experimental and theoretical study, we test the hypothesis that pellet feces are formed by drying processes in the intestine. Inspirational to our work is the formation of hexagonal columnar jointings in cooling lava beds, in which the width L of the hexagon scales as L ∼ J^-1 where J is the heat flux from the bed. Across 22 species of mammals, we report a transition from cylindrical to pellet feces if fecal water content drops below 0.65. Using a mathematical model that accounts for water intake rate and intestinal dimensions, we show pellet feces length L scales as L ∼ J^-2.08 where J is the flux of water absorbed by the intestines. We build a mimic of the mammalian intestine using a corn starch cake drying in an open trough, finding that corn starch pellet length scales with water flux^-0.46. The range of exponents does not permit us to conclude that formation of columnar jointings is similar to the formation of pellet feces. Nevertheless, the methods and physical picture shown here may be of use to physicians and veterinarians interested in using feces length as a marker of intestinal health.

Rabbit Sedation and Anesthesia

With the increasing frequency of rabbits as veterinary patients, the expectation for high-quality, intensive veterinary care, and resultantly an understanding of anesthesia has been increasing. Sedation and general anesthesia are commonly required for many routine and emergency procedures in rabbits, and this results in the need for a strong awareness of anesthetic principles, knowledge of limitations of anesthesia, and maintenance of high standards of anesthesia.

Managing the Health of Captive Herds of Exotic Companion Mammals

Common medical problems diagnosed and treated in individual companion exotic mammals are relevant in a herd-health setting. Many of these problems are often associated with poor husbandry and/or inappropriate nutrition. Rabbits, ferrets, chinchillas, and rodents have been domesticated alongside humans and an understanding of their ethology gives veterinarians a base knowledge in making recommendations for animals in their care. This article briefly reviews the ethology and husbandry in such species, but detailed needs are beyond the scope of this article.

Associations between biochemical parameters and referral centre in pet rabbits with urolithiasis

OBJECTIVES

To determine the association between signalment, selected haematologic and biochemical parameters and referral centre in pet rabbits with imaging evidence of urolithiasis presented to two veterinary teaching hospitals in North America.

MATERIALS AND METHODS

The medical record database of two veterinary teaching hospitals was searched from 2009 to 2019 for records of pet rabbits that received both imaging studies and plasma biochemistry profiles. Information regarding signalment, bodyweight, packed cell volume, total solids, and plasma biochemistry profiles was obtained. Univariable and multivariable logistic regression models were performed to identify statistically significant parameters associated with imaging evidence of urolithiasis.

RESULTS

Of the 324 examined rabbits, 33 (10.2%) had confirmed evidence of urolithiasis on imaging. Increasing plasma calcium and sodium concentrations and referral centre were significantly associated with the presence of urolithiasis on the univariable logistic regression model. However, only plasma calcium concentration and the referral centre demonstrated significant associations on the multivariable logistic regression model.

CLINICAL SIGNIFICANCE

Results indicate that urolithiasis in pet rabbits that receive imaging is associated with mildly increasing plasma calcium concentration and referral centre. The association with referral centre may indicate there are geographic influences on urolithiasis or on imaging. However, the identified associations have low predictive value for the diagnosis of urolithiasis, indicating the need for additional diagnostic modalities.

Technical note: Influence of feed on image quality of abdominal ultrasonography in New Zealand white kits

<p class="Body">The aim of this study was to evaluate the influence of feed change on image quality of ultrasound scanning of the gallbladder, kidney and jejunum in New Zealand White kits. Thirty-nine 35-day-old rabbits were used, distributed into 4 diet groups: C, only commercial feed; CH, commercial feed and hay; C24H, only commercial feed, replaced by hay 24 h before examination; and CH24H, commercial feed and hay, with the commercial feed withdrawn 24 h before the exam. The rabbits received the diet for 42 d (from 35 to 77 d of age) and the ultrasound evaluations were performed on days 56 and 77. Ultrasonographic assessment for image quality focused on the possibility of visualisation and an image quality rating (3 scores: unacceptable, acceptable or excellent) for the gallbladder, kidneys and jejunum. The kidneys were visualised in 100% of animals of all diets and ages. There was no difference in visualisation (P&gt;0.05) of the gallbladder among the animals fed different diets on days 56 and 77. The C24H diet had a higher visualisation possibility (P&lt;0.05) of the jejunum compared to the C and CH diets on day 77. For the image quality score, there was no difference in the studied organs on day 56. However, on day 77, there was a difference for the jejunum (P&lt;0.05), and only the C24H and CH24H diets presented images classified as excellent. In conclusion, the image quality of the kidneys and gallbladder was unaffected by feed, and the jejunum had an improved image quality with the inclusion of hay and without the commercial feed 24 h before the test in New Zealand White rabbits at 77 d of age.</p>

Evidence-Based Rabbit Housing and Nutrition

Because most research on rabbit husbandry, welfare, and nutrition was performed on production animals, evidence for best practices in pet rabbits is scarce, and guidelines must be based on transfer of results, deduction, and common sense. Rabbits benefit from being kept with at least one conspecific; from large enclosures and multistory hutches; from drinking water offered ad libitum in open dish drinker systems; and from receiving hay ad libitum, with restricted amounts of fresh grass, herbs, or green leafy vegetables, and a high-fiber complete diet. Offering hay ad libitum bears several advantages and should be considered a matter of course.

Assessment and Care of the Critically Ill Rabbit

Rabbits have the ability to hide their signs and often present in a state of decompensatory shock. Handling can increase susceptibility to stress-induced cardiomyopathy and specific hemodynamic changes. Careful monitoring with a specific reference range is important to detect early decompensation, change the therapeutic plan in a timely manner, and assess prognostic indicators. Fluid requirements are higher in rabbits than in other small domestic mammals and can be corrected both enterally and parenterally. Critical care in rabbits can be extrapolated to many hindgut fermenters, but a specific reference range and dosage regimen need to be determined.

Biology and Diseases of Rabbits

Beginning in 1931, an inbred rabbit colony was developed at the Phipps Institute for the Study, Treatment and Prevention of Tuberculosis at the University of Pennsylvania. This colony was used to study natural resistance to infection with tuberculosis (Robertson et al., 1966). Other inbred colonies or well-defined breeding colonies were also developed at the University of Illinois College of Medicine Center for Genetics, the Laboratories of the International Health Division of The Rockefeller Foundation, the University of Utrecht in the Netherlands, and Jackson Laboratories. These colonies were moved or closed in the years to follow. Since 1973, the U.S. Department of Agriculture has reported the total number of certain species of animals used by registered research facilities (1997). In 1973, 447,570 rabbits were used in research. There has been an overall decrease in numbers of rabbits used. This decreasing trend started in the mid-1990s. In 2010, 210,172 rabbits were used in research. Despite the overall drop in the number used in research, the rabbit is still a valuable model and tool for many disciplines.

Bodyweight and body condition score in rabbits on four different feeding regimes

OBJECTIVES

The aim of this study was to assess the effects of four diet regimes (extruded diet with ad lib hay, muesli with ad lib hay, ad lib hay only, ad lib muesli only) on bodyweight and body condition score in rabbits.

METHODS

Thirty-two Dutch rabbits were studied over 9 months. Bodyweight and body condition score were recorded weekly.

RESULTS

All groups gained weight with age, but relative to the ad lib hay only group (mean, 1 · 77 ± 0 · 13 kg), after 9 months rabbits in the ad lib muesli only group were 146% heavier (2 · 59 ± 0 · 32 kg); extruded diet with ad lib hay group 125% heavier (2 · 21 ± 0 · 10 kg); and muesli with ad lib hay group 123% heavier (2 · 18 ± 0 · 13 kg). Median body condition score of the ad lib muesli only group was obese (4 · 5) and was higher than that in both the extruded diet with ad lib hay and muesli with ad lib hay (median = 3 · 5) groups (P < 0 · 001). Both the extruded diet with ad lib hay and muesli with ad lib hay groups had above-ideal body condition score despite having bodyweights within the breed standard range. The ad lib hay only group had a median body condition score of 3 (ideal). There was an overall positive correlation between body condition score and weight (qs = 0 · 814, P < 0 · 001).

CLINICAL SIGNIFICANCE

The feeding of muesli without hay should be avoided, to prevent obesity.

Influence of diet on calcium metabolism, tissue calcification and urinary sludge in rabbits (Oryctolagus cuniculus)

Rabbits absorb more calcium (Ca) from their diet than they require, and excrete surplus via urine, which therefore contains a typical 'sludge'. This makes rabbits susceptible to Ca-containing uroliths. But given the Ca content of diets of free-ranging specimens, and the limited reports of urinary sludge and Ca contents in free-ranging lagomorphs, we can suspect that rabbits are naturally adapted to high urinary Ca loads. We fed four groups of New Zealand hybrid rabbits [n = 28, age at start 5-6 weeks) pelleted diets consisting of lucerne hay only (L, Ca 2.32% dry matter (DM)], lucerne:oats 1:1 (LG, Ca 1.36%), grass hay only (G, Ca 1.04%), or grass:oats 1:1 (GG, 0.83%) for 25 weeks, with water available ad libitum. Diets were not supplemented with Ca, phosphorus, or vitamin D. Rabbits on diets LG and GG had lower food and water intakes, lower faeces and urine output, grew faster and had higher body mass at slaughter (mainly attributable to adipose tissue). Apparent Ca digestibility decreased in the order L-LG-G/GG. Rabbits on L had larger and heavier kidneys, more urinary sediment at sonography, and a higher urinary Ca content than the other groups. No animal showed signs of urolithiasis/calcinosis at X-ray, sonography, or gross pathology. Kidney/aorta histology only sporadically indicated Ca deposits, with no systematic difference between groups. Under the conditions of the experiment, dietary Ca loads in legume hay do not appear problematic for rabbits, and other factors, such as water supply and level of activity may be important contributors to urolithiasis development in veterinary patients. However, due to the lower Ca content of grass hay, the significantly lower degree of urinary sludge formation, and the significantly higher water intake related with grass hay feeding, grass hay-dominated diets are to be recommended for rabbits in which urolithiasis prevention is an issue.