Evaluation of immunocontraceptive adjuvants, titers, and fecal pregnancy indicators in free-ranging white-tailed deer

The future of the porcine zona pellucida (PZP) immunocontraceptive in white-tailed deer (Odocoileus virginianus) is dependent upon finding an adjuvant that is highly immunogenic, resulting in reproductive inhibition. Antibody measurement in plasma, fawn-doe observations, and fecal pregnancy indicators have been used to assess PZP effectiveness and reproduction in ungulates. During 1997-1998, potentially reproductive (>1 year) female white-tailed deer in a suburban Connecticut community were immobilized and received 1 of 3 treatments: 1) synthetic trehalose dicorynmycolate (S-TDCM) plus PZP, 2) Freund's Complete and Incomplete Adjuvants (FCA) plus PZP, and 3) FCA plus sterile water (control). Fawn-doe observations indicated that 5 of 9 S-TDCM-treated and 1 of 9 FCA-treated deer reproduced and reproduction was similar (P=0.13); 78% reproduction by control deer was higher than FCA deer (P<0.001), but similar to S-TDCM deer (P=0.20). Mean percent titers in blood collected 4-5 months post-treatment were higher in FCA deer (100±7) than those of S-TDCM (32±6) and control (18±2) deer (P<0.001). The S-TDCM adjuvant appeared less effective than the FCA adjuvant at preventing conception and maintaining titer levels with PZP. In spring, fecal progesterone metabolite concentrations (PdG) ranged from (0.16-17.6 μg/g dmf) and were similar for pregnant and nonpregnant deer in 1998 (P=0.13) and 1999 (P=0.84). Failure to identify pregnancy status using PdG may have been influenced by the variability in progesterone production by continually cycling and pregnant deer.