Selection of Food Allotment for New Zealand White Rabbits in Developmental Toxicity Studies

Selection of Food Allotment for New Zealand White Rabbits in Developmental Toxicity Studies. CLARK, R. L., ANTONELLO, J. M., WENGER, J. D., DEYERLE-BROOKS, K., AND DUCHAI, D. M. (1991). Fundam. Appl. Toxicol. 17, 584–592. In three initial studies, female rabbits were fed 125, 150, or 230 g of Purina Certified Rabbit Chow No. 5322 (“regular” chow) per day or 150 g/day of Purina Certified High Fiber Rabbit Chow (“high fiber” chow) for at least 5 weeks prior to artificial insemination and until Day 28 of gestation when fetuses were removed and examined. Animals allotted 230 g/day of regular chow ate approximately 180 g/day and gained more weight than the 150 g/day group until Day 14 of gestation after which food consumption declined and body weight decreased. Animals fed 150 g/day regular chow ate all food provided until after Day 22 of gestation when food consumption decreased dramatically in some animals. Animals in the 125 g/day regular chow and 150 g/day high fiber chow groups ate essentially all food provided throughout gestation. Ad lib feeding in the 230 g/day groups was associated with adverse reproductive consequences consisting of decreased numbers of implants and live fetuses and decreased fetal weight. In one study involving 3 groups fed 125 and 150 g/day regular chow and 150 g/day high fiber chow, reproductive parameters were similar in all 3 groups. However, fetal weight in the 150 g/day regular chow group was 50% more variable than the other groups in association with more variable maternal body weight change late in gestation in that group. In subsequent studies using 125 g/day, there has consistently been fewer animals going off feed late in gestation and a decrease in fetal weight variance of approximately 60% compared to previously when the standard daily allotment was 150 g/day. These results establish that a daily allotment of 125 g regular chow is sufficient and preferable to 150 g/day regular chow for animals which are to be terminated on Day 28 of gestation as in developmental toxicity studies. A diet of 150 g/day “high fiber” chow offered no advantage over 125 g/day regular chow which itself has an adequately high fiber content.