The postpartum llama: fertility after parturition

Fertility was evaluated at various times during the postpartum period in the llama. Fifty-six parous female llamas chosen at random were bred at 10, 20, and 30 days postpartum with six intact males. Half of the females copulated only once and the other half twice within an interval of 24 h. Ovarian activity was monitored by ultrasonography and analysis of urinary estrone sulfate and pregnanediol glucuronide (PdG). At the time of copulation, all females had developed ovulatory-size follicles. Ovulation was confirmed by the presence of a CL at 8 days after breeding and PdG concentrations 1 ng/mg creatinine (Cr). Conception was defined as PdG concentrations 1 ng/mg Cr at 15 days after breeding and the presence of a CL. Pregnancy was defined as the presence of a CL, PdG concentrations 1 ng/mg Cr and an embryonic vesicle 20 days postbreeding. There were no significant differences in the proportion of females ovulating after breeding at different times postpartum; however, conception and pregnancy were significantly greater in females bred at Day 20 or 30. Ovarian follicle size was significantly larger at 30 days (9.1 mm) than at 10 and 20 days (7.9 and 8.8 mm, respectively) of breeding, with no difference in concentrations of estrone sulfate. The proportion of females conceiving as a result of breeding at 10 days postpartum (6 out of 10) was significantly less than for females bred at 20 (13 out of 15) or 30 days (16 out of 18). There were significant differences in the diameter of the uterine horns in females bred at 10 days (5.2-cm diameter) in contrast to females bred at 20 or 30 days (2.9 and 2.7 cm, respectively). These data demonstrate that the llama may ovulate as early as 10 days postpartum however, pregnancy rates from breeding at 20 or 30 days were threefold higher (61%) than those in females bred at 10 days postpartum (21%)