The aim of this study was to investigate the feasibility of stimulating ovarian fol icle development in order to improve fertility in water buffalo cows by immunization against inhibin. The experiment was carried out in early summer (May) and included 24 multi-parity crossbred Murrah-Swamp buffaloes that were divided into immunized (n=11) and control (n=13) groups. Each immunized cow was administered with a 2-mL immunogen of mineral oil adjuvant containing 2 mg of recombinant inhibinα-subunit fusion protein. The controls were treated with the adjuvant only. Al animals received Ovsynch protocol treatment, starting on the day of the antigen administration, and they were artiifcial y inseminated upon behavioral estrus. As a result, al of the immunized buffaloes generated antibodies against inhibin during the experimental period and had higher plasma concentrations of fol icle-stimulating hormone (FSH), activin, and estradiol (E2) related to estrous expression. A higher proportion of immunized animals expressed estrus behavior than did the controls (72%vs. 30%, P<0.05). On aver-age, inhibin-immunized buffaloes had signiifcantly more large fol icles (≥9 mm in diameter) than the controls (mean±SEM;1.2±0.1 vs. 0.84±0.1, respectively;P<0.05) and a slightly higher mean total number of fol icles (≥2 mm;11.4±0.7 vs. 9.0±1.1, respectively;P=0.09) and smal (2–4 mm) fol icles (8.81±0.6 vs. 6.84±1.0, respectively;P=0.12). A higher percentage of cows ovulated in the immunized group than in the control group (91%(10/11) vs. 54%(7/13), respectively;P<0.05). Moreover, inhibin-immunized cows had slightly larger corpus luteum (CL) than the controls 9 days after ovulation and signiifcantly higher (P<0.01) post-ovulation peak plasma progesterone (P4) concentrations. Immunization against inhibin also mar-ginal y increased the conception rate 42 days after insemination (45.8%vs. 15.4%;P>0.05). These results demonstrate that immunization against inhibin, coupled with the treatment with the Ovsynch protocol, can constitute a
