Effects of breed on kinetics of ovine FSH and ovarian response in superovulated sheep

Abstract Embryo production is a useful tool for ex situ conservation of endangered species and breeds, despite a high variability in the ovarian response to superovulatory treatments. The current study evaluated the incidence and mechanisms of genetic factors in such variability, by determining the pharmacokinetics and pharmacodynamics of a standard treatment with ovine FSH (oFSH) in two endangered Spanish sheep breeds (Rubia del Molar, R, and Negra de Colmenar, N) in comparison to Manchega ewes (M, control group). In the first experiment, pharmacokinetics of an i.m. single dose of 1.32 mg of oFSH was evaluated in seven animals of each breed. Plasma FSH concentrations reached their maximum at 4 h post-administration in all the ewes, but several of the kinetic parameters (plasma FSH concentration at 4 h post-administration, maximum plasma FSH concentration, C max , and both the area under the plasma concentration-time curve extrapolated to the infinite, AUC inf , and to the last moment of sampling, AUC last ) were higher in the N group. In the second trial, 10 animals of each breed were superovulated using eight decreasing doses of oFSH (3× 1.32 mg, 2× 1.10 mg, and 3× 0.88 mg). The R group, when compared to N and M, showed both a higher number of corpora lutea (13.7 ± 0.6 versus 10.0 ± 0.4 in N and 9.8 ± 0.6 in M, P P P