2010 - Volume 37 - Issue 4

237-240
Differences Between Rats and Rabbits in their Response of Feed and Energy Intake to Increasing Dietary Fat Content
by A. Alhaidary, H. E. Mohamed & A.C. Beynen

It is common practice to use an ad-libitum feeding regimen in rat studies, even when experimental diets with different energy densities are used; a prerequisite is that the diets have identical nutrient:energy ratios. It is assumed that the rats will maintain a constant energy intake so that nutrient intake will not differ between the dietary treatments. The concept that energy requirement determines feed intake is supported by the study with rats that is described in this paper. Increasing the amounts of dietary fat (coconut fat or corn oil), and thus increasing the energy densities of the diets, caused decreasing feed intakes so that energy intakes remained unchanged. However, feeding the same diet recipes to rabbits led to increasing feed intakes, and even further enhanced energy intakes, in response to increasing concentrations of corn oil in the diet. Secondly, when the diet contained coconut fat, an increase in fat content also raised feed intake, but at higher inclusion levels there was no further increase or rather a decrease in feed intake by the rabbits. It is suggested to apply restricted feeding in rabbit studies using diets with different energy densities in order to avoid additional variables such as differences in weight gain and nutrient intake.

243-250
PCR (Polymerase Chain Reaction) is Superior to Culture and Serology in Detecting Haemophilus Infection in Rats and Guinea Pigs
by R. Boot & F.A.G. Reubsaet

Based on partial sequencing of the 16S rRNA gene V-factor dependent Pasteurellaceae (Haemophilus), strains from rat and guinea pig were assigned to the Rodent cluster or the Haemophilus parainfluenzae complex. PCRs for the detection of biotype Heyl or Jawetz [P.] pneumotropica detected none of the strains and only two Haemophilus strains assigned to the Rodent cluster respectively. All Haemophilus strains were positive by a PCR developed for detection of all Pasteurellaceae taxa. The Pasteurellaceae PCR detected infection in all 76 rats and 40 guinea pigs from 3 and 6 colonies respectively reported to be free from Pasteurellaceae infection. ELISAs, using two Haemophilus antigens and culture, detected infection with similar frequency but both methods were inferior to PCR. The Pasteurellaceae PCR should be the new ‘gold standard’ for comparison of the sensitivity of other test methods for Pasteurellaceae infection in rodents.

253-259
The Association of Early Dietary Supplementation with Vitamin E with the Incidence of Ulcerative Dermatitis in Mice on a C57BL/6 Background
by J. R. Mader, M. A. Mason, L. K. Bale, N. M. Gades & C. A. Conover

The purpose of this study was to ascertain if prophylactic ingestion of a diet rich in vitamin E would prevent or impede the development of ulcerative dermatitis in mice on a C57BL/6 background. Mice were fed after weaning a standard mouse diet, vitamin E (99 IU/kg), or a mouse diet fortified with vitamin E (3000 IU/kg). Cases of ulcerative dermatitis were recorded by individuals (i.e. aware of) the diet assignment. The incidence of ulcerative dermatitis in a retrospective cohort of mice on standard diet was compared with the group on the diet fortified with vitamin E. Age was associated with ulcerative dermatitis in standard diet and vitamin E fortified diet groups, r = 0.43, p-value < 0.0001 and r = 0.18, p-value < 0.02, respectively. The average age of incidence for ulcerative dermatitis in the mice fed the standard diet was 89 weeks and for the mice fed the vitamin E diet it was 41 weeks. The unadjusted odds ratio comparing the incidence of ulcerative dermatitis between the two diet groups was 4.6 with a 95% confidence interval of (2.44, 8.58), x2 p-value < 0.0001. Therefore, there was an association between the diets and ulcerative dermatitis, with the mice on the vitamin E fortified diet having almost five times the odds of having ulcerative dermatitis compared with mice on the standard diet. Incidence of ulcerative dermatitis was not influenced by sex or genotype. Our study results show that a diet fortified in vitamin E initiated at weaning does not prevent or impede the development of ulcerative dermatitis in mice on a C57BL/6 background and on the contrary accelerate development when administered to young mice.

261-265
A Pasteurella pneumotropica Strain of Mouse Origin Colonizes Rats but is Out Competed by a P. pneumotropica Strain of Rat Origin
by Boot R

Mouse and rat Pasteurellaceae have been found to differ in phenotypic characteristics but both animal species may be infected by each other’s bacterial strains. We explored the possibility that a mouse Pasteurella strain colonizing rats would be out competed by a subsequent infection of a rat Pasteurella strain. Rats were dosed intranasally and orally with the mouse P. pneumotropica biotype Jawetz strain NCTC 8141T and exposed to pen-mates infected with the rat P. pneumotropica biotype Heyl strain SSI P331 by co-housing. Rats were tested by PCR using primer sets developed for the specific detection of each biotype respectively. The co-housing and exposure of rats initially infected by the mouse P. pneumotropica with pen-mates harbouring the rat P. pneumotropica led to disappearance of the mouse bacterium from the rats. Our results question the suitability of Pasteurellaceae from contemporary laboratory animals to elucidate associations between bacterial properties and host species.

267-270
Alopecia in Rabbits Fed Semi-purified Diets with Marginal Protein Content
by A. Alhaidary, H. E. Mohamed & A.C. Beynen

A marginal (i.e. less than optimal) protein intake by rabbits has been suggested to cause hair loss. Our recent study with rabbits offered the opportunity to test the suggestion under controlled conditions. Young growing rabbits were fed one of four semi-purified diets. The diets were high (21.6 energy % protein) or low in casein (13.0 energy % protein) with either high or low level of corn oil (21.1 instead of 5.3 energy %). On various body parts of the rabbits, the degree of alopecia was scored. Upon slaughter, the amount of hair in the stomach was assessed. The low-fat diets with either high or low protein content induced similar growth rates, indicating that the low protein level was not limiting growth. It was found that a decrease in the protein level of the low-fat diet was associated with significant alopecia on legs and belly and less hair accumulation in the stomach. It is concluded that signs of alopecia that are observed in rabbits fed experimental diets could relate to low dietary protein concentration.

275-284
Rat Strains Differ in Antibody Response to Streptobacillus moniliformis
by R Boot1, L. Van den Berg & H.A. van Lith

Rats are the natural host of Streptobacillus moniliformis. The bacterium is zoonotic which is an obvious reason for periodic monitoring of rat colonies for S. moniliformis infection. This may be done by measuring antibodies to the bacterium by for instance the enzyme-linked immunosorbent assay (ELISA). Inbred rat strains can significantly differ in antibody response to viral, bacterial and parasitic infections. We tested the hypothesis that in rats the antibody response to S. moniliformis is under genetic control. Rats of 6 inbred strains were intranasally and orally dosed with the bacterium and monitored for the development of antibodies by ELISA. Rats of all strains rapidly seroconverted to the bacterium. The rat strains differed significantly in final antibody activities and seroconversion rates. WKY and SHR rats were high responders, BN and F344 rats were low responders and LEW and BD rats were intermediate both in antibody development and seroconversion.