Abstract:
Eighteen mature, nonpregnant, and indigenous South African does were randomly divided into two groups to test if their
vomeronasal organs exert an influence on LHplasma levels during a Whitten effect experimental trial. Does in the treatment (VNO
ablated) group had their vomeronasal organs rendered nonfunctional by cauterization of the nasoincisive duct under surgical
anesthesia. Does in the control group had their nasal civities irrigated with physiological saline under surgical anesthesia. All does
were synchronized into oestrus and introduced to bucks one day prior to their expected second oestrus cycle. Successful matings
were recorded. Timely blood samples were collected during each of the five days before and five days after buck introduction.
Blood plasma concentrations of estradiol and LH were determined by radioimmunoassay. Analysis of variance between groups
demonstrated that the does in the VNO ablated group did not demonstrate any interest in mating, did not become pregnant, and
did not demonstrate the primary increase in tonic plasma levels of LH that is necessary for ovulation to occur. By contrast, all of
the does in the control group demonstrated successful matings, became pregnant, and demonstrated typical primary tonic level
increases and preovulation surges in LH. Thus, it was concluded that the vomeronasal organ modulates the primary increase in
tonic levels of LH and thus influences ovulation that occurs during the Whitten effect in South African indigenous does.
