Influence of polygamous versus monogamous mating on embryo production in four different strains of mice after superovulatory treatment.

We determined the effect of monogamous or polygamous mating with 2 females on vaginal plug (VP) rate, embryo donors (ED), 2-cell embryo production, and male performance after superovulation of females aging 24d or 45-48d. C57BL/6NCrl (B6N), BALB/cAnCrl (BALB/cN), FVB/NCrl (FVB/N), and Crl:CD1(ICR) (CD-1) females received 5 IU eCG and 5 IU hCG (24d) or 7.5 IU eCG and 7.5 IU hCG (45-48d) 48 h apart. After the hCG injection, females were paired with males, which alternated weekly in monogamous or polygamous mating. Significant differences in the percentage of VP-positive females between monogamous and polygamous mating were observed for B6N (71% vs. 49%), FVB/N (77% vs. 51%), and CD-1 (90% vs. 67%) at 45-48d. BALB/cN and CD-1 showed higher VP rates than B6N and FVB/N. A significantly higher percentage of ED was found for monogamous than for polygamous mating for FVB/N (87% vs. 61%) at 24d and for B6N (91% vs. 53%) and CD-1 (90% vs. 68%) at 45-48d. In all strains of mice and in both age groups, no significant differences were observed in the number of intact 2-cells per VP-positive female, ED or treated female between monogamous and polygamous mating except in the B6N strain where monogamous mating resulted in a significantly higher number of intact 2-cell embryos per treated female than polygamous mating at both ages. The present results imply that polygamous mating can be implemented for 2-cell embryo production in all strains studied except for B6N when all females are euthanized. However, when only VP+ females are sacrificed polygamous mating can be employed for all 4 strains studied.