Food and water intake, growth, and adiposity of Sprague-Dawley rats with diet board for 24 months.

Ad libitum (AL) feeding of rats leads to obesity and increased result variability, as well as premature morbidity and mortality. It may also alter metabolism and responses to foreign compounds. Moderate dietary restriction (DR) reduces these untoward effects without compromising the sensitivity of rodent bioassays. The diet board (DB) is a novel method for achieving moderate DR in group housing. Food pellets are firmly attached into grooves in an aspen board, and rats have to gnaw the wood in order to eat. Food is available continuously, but due to the effort involved rats eat less. This study simulated a chronic safety test to assess the long-term effects of DB feeding. A total of 146 male and female outbred Sprague-Dawley rats, nine weeks old at onset, were housed in groups of three and fed either AL or with DBs for two years. Food and water consumption were measured at six time points. The rats were weighed every one to two weeks. Body and tibial lengths and epididymal fat weight were measured at necropsy. Modified body mass index was calculated at five time points after one year of age. DB feeding reduced body weight and fat tissue moderately, more so in males. DB males ate less than AL males, but no differences were seen in the total food consumption in the females. There was no consistent difference in the within-group variations of the measured parameters. DB is a workable DR method, albeit some modification could enhance and standardize its DR effects, especially in female rats.

Comparison of ear tattoo, ear notching and microtattoo in rats undergoing cardiovascular telemetry.

Individual and permanent identification of experimental animals is a common and often essential research practice. There is little information available on the short-term effects of these procedures on the animals. In this study, seven rats were implanted with telemetric devices. The effects of three different identification methods (ear tattoo, ear notching and microtattoo) were compared. Cardiovascular data were collected for 24 h after the procedures. Time periods of 0-1, 1-4, 4-16 h (dark) and 16-24 h after the procedure were analysed separately. The most pronounced differences in measured parameters were observed during the first hour after the procedures were performed. Mean arterial pressure (MAP) was significantly higher (P < 0.012) following the ear tattoo than the microtattoo procedure by a difference of approximately 5 mmHg. Heart rate (HR) was significantly elevated (P < 0.001) after ear tattoo compared with both ear notching (Δ = 31 beats per minute [bpm]) and microtattoo (Δ = 44 bpm). During the 1-4 h period and the following dark period, the MAP was highest in the ear notching group, but no differences were observed in the HRs. During the following dark period (4-16 h) and the next day (16-24 h) differences in MAP and HR were minor. In conclusion, microtattoo appears to cause the mildest changes in HR and blood pressure. Based on these results, ear tattoo and ear notching should be replaced by microtattoo whenever possible.

A novel dietary restriction method for group-housed rats: weight gain and clinical chemistry characterization.

Laboratory rodents are usually fed ad libitum. Moderate dietary restriction decreases mortality and morbidity compared with ad libitum feeding. There are, however, problems in achieving dietary restriction. Traditional methods of restricted feeding may interfere with the diurnal rhythms of the animals and are not compatible with group-housing of rodents. We have invented a novel method, the diet board, for restricting the feed intake of laboratory rats. The use of the diet board moderately decreased weight gain of rats when compared with ad libitum-fed animals. The diet board retarded skeletal growth only minimally, whereas major differences were found in body fat depositions. Serum free fatty acid, triglyceride and cholesterol values were lower in diet-restricted rats, while the opposite was true for serum creatine kinase. There were no differences in total protein, albumin or alanine aminotransferase. Moreover, differences in interindividual variances in parameters were not detected between the groups; hence this study could not combine the diet board with reduction potential. The diet board provides mild to moderate dietary restriction for group-housed rats and is unlikely to interfere with the diurnal eating rhythm. The diet board can also be seen as a cage furniture item, dividing the open cage space and increasing the structural complexity of the environment. In conclusion, the diet board appears to possess refinement potential when compared with traditional methods of dietary restriction.

The diet board: welfare impacts of a novel method of dietary restriction in laboratory rats.

Laboratory rats are commonly fed ad libitum (AL). Moderate dietary restriction (DR) decreases mortality and morbidity when compared with AL feeding, but there are several obstacles to the implementation of DR. Traditional methods of restricted feeding disrupt normal diurnal eating rhythms and are not compatible with group housing. We have designed a novel method, the diet board, to restrict the feeding of group-housed rats. Animals fed from the diet board had 15% lower body weight than the AL-fed animals at the age of 17 weeks. The welfare effects of diet board feeding were assessed by comparing the stress physiology of diet board fed animals with that of AL-fed animals. Diet board feeding was associated with higher serum corticosterone levels and lower faecal secretion of IgA, suggesting the diet board causes a stress reaction. However, the AL-fed group had larger adrenal glands with higher adrenaline and noradrenaline content than the diet board animals. No gastric ulcers were found in any of the animals at necropsy. The diet board thus appears to cause a stress reaction when compared with AL-fed rats, but no apparent pathology was associated with this reaction. The diet board could help to solve the health problems associated with AL feeding, while allowing the rats to be group-housed and to maintain their normal diurnal eating rhythms. The diet board can also be seen as a functional cage furniture item, dividing the cage into compartments and thus increasing the structural complexity of the environment. In conclusion, the diet board appears to possess refinement potential compared with traditional methods of DR.

Pair housing of rabbits reduces variances in growth rates and serum alkaline phosphatase levels.

New Council of Europe regulations mandate housing of two rabbits in the same cage space currently used to house one, provided the animals are socially compatible. This study was designed to assess changes in growth and selected serum chemistry parameters due to pair housing or single housing of rabbits. Six sets of four female siblings of Crl:KBL(NZW)BR rabbits were used. The animals were seven weeks old on arrival. Two siblings of each set were allocated to pair housing, two to single housing. The animals were housed in stainless steel cages (120 cm x 60 cm x 60 cm) with a perforated floor, including a shelf (60 cm x 30 cm) at 30 cm height from the floor. The rabbits were provided with an aspen cube (5 cm x 5 cm x 5 cm), one item per animal. The rabbits were weighed and blood samples were taken from the auricular central artery at four different times during the study. Blood sera were assayed for a set of routinely assayed clinical chemistry parameters: alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (APHOS), blood urea nitrogen (BUN), cholesterol (CHOL) and protein (PROT). Mean and variance profiles over the study period were statistically analysed by multivariate analysis of variance. No differences in mean profiles were detected; however, weight (P = 0.0002) and APHOS (P = 0.017) variances were significantly lower in pair-housed animals. The reduction in variance on growth and APHOS attributable to pair housing appears to be rather large. During the 21-week study, occasional fighting was seen between the pair-housed rabbits. After sexual maturity, further major fighting bouts resulted in significant trauma that necessitated the cessation of the study. In conclusion, pair housing appears to have a decreasing effect on growth and APHOS variance, but antisocial behaviour such as fighting remains a serious problem.

Distension of pulmonary vein--left atrial junction: heart rate responses in conscious and anesthetized dogs.

The cardiac chronotropic effects of distension of pulmonary vein-left atrial junction were investigated in conscious dogs and in dogs anesthetized with intravenous alpha-chloralose (100 mg/kg) or pentobarbital (30 mg/kg). All the experiments were made on trained, chronically instrumented, closed chest animals held in horizontal position. Inflation of a single small balloon in the junction elicited a tachycardic response both in conscious and chloralose-anesthetized dogs, while in pentobarbital anesthesia no change in heart rate was found. Contrary to reports of other investigators, no transient bradycardia was found, nor any correlation between predistension heart rate and the increase in heart rate due to the distension. It is suggested that the choice of anesthetic can be done only after its modifying effect on the parameter studied is known. Only the use of trained, chronically instrumented and conscious dogs will reveal this effect.

The effect of spontaneous diabetes mellitus on fatty acid oxidation, beta-hydroxybutyrate dehydrogenase activity and respiratory coupling of hepatic mitochondria in the guinea-pig (Cavia porcellus).

1. The purpose of this study was to determine whether hepatic mitochondria of guinea-pigs with spontaneous diabetes mellitus differ from those of non-diabetic guinea-pigs in the oxidation of fatty acids, the activity of beta-hydroxybutyrate dehydrogenase, or respiration-linked oxidative phosphorylation. During the course of the study, a third group of animals (referred to as the unclassified group) was discovered which, on the basis of the clinical chemistry and histological changes in the pancreas, appeared to be in a pre-diabetic or post-diabetic state. 2. No differences in the respiratory control ratios were found between any of the three groups. Fatty-acid oxidation in hepatic mitochondria was greater in both the unclassified and diabetic groups than in the non-diabetic group. Beta-Hydroxybutyrate dehydrogenase activity, however, was increased only in the diabetic group. These findings suggest that increased fatty acid oxidation is probably an intermediate change in the development of or the recovery from diabetes mellitus, whereas the activity of beta-hydroxybutyrate dehydrogenase is affected only in more advanced stages.