Embryo Production by Superovulation and Dual Siring in Alpacas

Alpacas have a gestation length of nearly one year, and therefore females can only produce one offspring per year. In order to accelerate the genetic gain of a herd, superovulation and embryo transfer techniques can be used to produce multiple embryos from genetically superior females. We hypothesized that the use of superovulation and dual siring results in the production of multiple embryos sired by both of the males. Our objectives were: 1)to determine the parentage of embryos produced from multiple ovulations on females bred by two males, and 2) to determine the effects of the time of breeding (first vs second) on the frequency of paternity. Females received an ovulation induction agent (hCG; 1000 IU, IV or GnRH; 100ug, IM) when a preovulatory follicle >7 mm was present to induce ovulation and emergence of a new follicular wave. Starting at 60 h post-hCG/GnRH, females received twice daily intramuscular injections of FSH at decreasing doses (i.e. Day 1 = 50mg; Day 2 = 40 mg; Day 3 = 30; Days 4 to 7 = 20 mg). Administration of FSH was discontinued when half of the follicles in the growing cohort were = 7 mm in diameter, or after seven days. On the last day of FSH administration, females received cloprostenol (187 µg, IM, twice) to induce luteolysis. Receptive females were bred to proven fertile males, once in the AM by one male and once in the evening by the other male and received hCG or GnRH at time of the first breeding. Embryo collections were performed 8 to 9 days after breeding by transcervical uterine lavage without manipulating the reproductive tract per rectum. Statistical analysis was performed on data using t-test and Fisher’s exact test. Significance was set at P < 0.05 and data are presented as mean ± SD. Growth of multiple dominant follicles was successfully achieved in 20/21 cycles. The mean number of days of FSH administration was 5.5±1.4. Sixteen females (80%) were receptive after FSH treatment and were bred by two males (A and B). Embryo collection was performed on 15 cycles and 11 collections recovered one or more embryos. A total of 46 embryos, 23 from breeding A-B and 23 from breeding B-A, were recovered for an average of 3.13 ±3.1 per flush. DNA amplification was performed on 23 embryos (6 from A-B, 17 from B-A). Twenty-two of the 23 embryos (96%) were determined to be sired by male B, six from breeding A-B and 16/17 from breeding B-A. A single embryo from mating B-A was sired by male A and was significantly different from the 22 embryos sired by male B. In conclusion, FSH can be used to promote growth of follicles and multiple embryos can be collected. However, differences in male fertility may have an effect on the number of embryos sired by each male.