The welfare impact of increased gavaging doses in rats

Textbook recommendations for gavaging rats vary between 1-5 mi for an adult mt. Rats weighing either 130 g or 250 g were gavaged with varying dosages of barium sulphate (BaSO4). After closing, radiographs were taken at 0, 15 and 60 min. Animals showing a section of the small intestine totally filled with BaSO4 were scored as displaying spontaneous release. Other mts of the same sizes were gavaged with similar doses and subsequently tested in an o pen-field arena for behavioural abnormalities that might indicate stress or pain resulting from the procedure. Body temperature before and after treat ment was recorded using microchip transponders, None of the 250 g rats in t he I mi dosage group showed spontaneous release through the pyloric sphinct er. In the 2 mi and 4 mi dosage groups, only one out of five animals showed spontaneous release. In the 6 ml dosage group, half of the animals showed spontaneous release. lit the 8 mi and 10 mi dosage groups, Jive out of six and four out of five, respectively, showed spontaneous release. If doses we re higher than 12 mi, no animal was able to keep all of the BaSO4 in its st omach. In the rats weighing 130 g, the 3 mi dosage group showed only one ou t of four rats with spontaneous release, whereas in the 5 mi and 7 mil dosa ge groups, all animals showed spontaneous release. After 15 min, all of the rats in both weight groups showed BaSO4 in the duodenum. Ambulation, reari ng up onto the hind legs and defecation, as well as body temperature immedi ately after dosing correlated very strongly with the close (ml kg(-1)); inc reasing the dose resulted in reduced ambulation, rearing defecation and bod y temperature. However, 10 min after performance of the open-field test, ne ither body temperature, serum corticosterone nov sevum glucose showed any c orrelation with dose. This study indicates that high doses tie doses up to 10 ml for a 250 g vat) might be safe to use,. however, if an adverse impact on the mt is to be avoided use of much lower doses should be considered-fo r example, closes that do not enforce opening of the pyloric sphincter in a ny mt. This would be less than 4 ml kg(-1) in a 250 g rat.