Reproductive performance and changes in blood lipids in breeding females and in growing Watanabe heritable hyperlipidaemic and New Zealand White rabbits.

The aim of the study was to compare the reproductive performance of homozygous and heterozygous WHHL and NZW females, to record the changes in blood lipids due to gestation and lactation in the heterozygous WHHL and NZW females, and to investigate the changes in blood lipids from 4 to 11 weeks of age in homozygous and heterozygous WHHL and NZW rabbits. The conception rate of homozygous WHHL females was 14% lower than that of NZW and heterozygous WHHL females. The litter size and the weaning rate of homozygous WHHL females were significantly lower than in NZW and heterozygous WHHL females. In heterozygous WHHL and NZW females the total cholesterol was lower during the gestation and lactation while the triglycerides were higher during the gestation and were the lowest during lactation when compared to the levels at mating. In growing homozygous WHHLs of both sexes the total cholesterol did not change from 4 to 11 weeks of age. The triglycerides remained unchanged in males but decreased in females at 11 weeks of age. At this age the triglycerides were significantly lower in females than in males. In growing heterozygous WHHLs of both sexes the total cholesterol and triglycerides decreased with age. At 11 weeks of age the blood lipids were significantly higher in females than in males. The triglyceride levels in homozygous and heterozygous WHHL males and females were comparable at 4 and 6 weeks of age but significantly lower in heterozygous WHHLs at 11 weeks of age. In growing NZW rabbits of both sexes the blood lipids decreased significantly with age but no sex difference was recorded. The blood lipids in the heterozygous WHHLs of both sexes were higher than in NZWs during weaning. At 11 weeks of age the blood lipids of the males and triglycerides of the females of both strains were comparable. Only the total cholesterol remained higher in heterozygous WHHL females. The decrease with age in blood lipids in growing rabbits should be kept in mind when designing experiments beginning in animals younger than 3 months of age.

Long-term investigations of serum cholesterol, serum triglyceride, and HDL cholesterol in heritable hyperlipidemic rabbits.

The purpose of this investigation was to follow the course of the serum cholesterol, serum triglyceride and HDL cholesterol concentrations of heritable hyperlipidemic (HHL) rabbits (34 animals in total) in order to obtain an early prediction of these parameters, which appear to be highly associated with the presence of arteriosclerotic lesions. Measurements were done at 6-week intervals for one year, beginning at the 10th week of age. At week 10 the serum cholesterol concentration of females was 652.80 mg x dl-1 +/- 103.82 (standard deviation) and that of males was 648.84 mg x dl-1 +/- 146.04. The 10-week serum triglyceride concentration of males was 267.90 mg x dl-1 +/- 93.03, which decreased in two marked steps after week 10 and 40, while that of females was 246.70 mg x dl-1 +/- 67.51, which reached a maximum at 7 months and then decreased. Both the serum cholesterol and the serum triglyceride concentrations decreased significantly in males and females during the investigation period. The 10-week HDL cholesterol concentrations (males: 18.08 mg x dl-1 +/- 12.81; females: 14.61 mg x dl-1 +/- 8.56) remained relatively constant in both sexes during the investigation period. We consider one or two samplings, usually at weaning and at the beginning of an investigation, to ensure reliable biochemical parameters for the state of the animals.