Pregnancy failure in cats associated with long-term dietary taurine insufficiency

The effect of long-term dietary taurine insufficiency on reproductive function was studied in adult female domestic cats (n = 11). Cats were time-mated during taurine-deficient (6 months) and refed (6 months) states, and the outcome of ovulatory cycles and breeding was analysed. Serum progesterone and relaxin concentrations were evaluated in order to characterize pregnancies, including those resulting in resorption of fetuses, and pseudopregnancies. Increased resorption of fetuses, reduced litter size, and increased incidence of stillborn kittens was observed in queens while on taurine-deficient diets, as well as after refeeding of a taurine-enriched diet. Overall, 30% of the ovulatory cycles resulted in the delivery of kittens, with mean live and stillborn litter sizes of 2.2 +/- 0.4 and 0.8 +/- 0.4 kittens (mean +/- SEM), respectively. The remaining ovulatory cycles resulted either in pregnancies in which fetuses were resorbed (38%), or in pseudopregnancies (32%). Ovulatory cycles resulting in resorbed fetuses were characterized by the appearance of relaxin on day 20 of gestation, but with a subsequent decrease to non-pregnant concentrations by day 25 of gestation. These results suggest that reproductive failure in domestic cats exposed to long-term nutritional taurine deficiency is associated with a postovulatory defect manifest within the first 10 days after implantation, and that this defect is not reversible upon refeeding of a taurine-enriched diet for 6 months.