BackgroundProlonged pre-insemination anestrus (i.e. delayed puberty) is a major contributing factor for culling up to 30% of the replacement gilts at large breeding farm units in Vojvodina. It is imperative to determine if these gilts are acyclic (prepubertal) or cyclic, but just fail to exhibit behavioural estrus. Recent investigations demonstrate that treatment with equine chorionic gonadotropin (eCG) can increase the diestrous phase duration in sexually mature gilts. Based on these finding, the aim of the present studies was to determine the reproductive status of delayed puberty gilts following injection with eCG.MethodsTwo experiments were conducted on a swine breeding farm in Vojvodina. In Exp. 1, 20 prepubertal (acyclic) gilts, and 120 sexually mature (cyclic) gilts were injected with a single injection of 400 IU eCG + 200 IU human chorionic gonadotropin (hCG) or with 1000 IU eCG (cyclic gilts), at d5, d11 or d17 after spontaneous estrus detection, to determine their ovarian reaction and induced estrus manifestation. In Exp. 2, sixty delayed puberty gilts (estrus not detected until 8 month of age, av. 258 days) were culled from breeding herd and slaughtered to determine their reproductive status based on ovarian anatomical features. The second group of gilts (n = 60) was treated with a single 1000 IU eCG injection to determine their reproductive status, based on the interval between eCG injection to estrus detection and duration. The data were analyzed by descriptive statistics, t-test, analysis of variance and Duncan’s test in the software package Statistics 10th.ResultsOvulations were induced in 90% of acyclic (sexually immature) and, on average, 93.3% of cyclic (sexually mature) gilts after the eCG injection. On average, 4 days after the eCG injection, estrus was detected in 85% of the treated acyclic (sexually immature) gilts and in 95% (19/20) of the cyclic (sexually mature) gilts, treated with eCG on day 17 after spontaneous estrus detection. The interval from eCG to induced estrus detection was prolonged (av. 25 days) in 95% (19/20) of the sexually mature gilts treated with eCG on day 5 and in 90% (18/20) of gilts treated on day 11 after spontaneous estrus detection (Exp. 1). Forty anestrous gilts reached cyclic pubertal ovarian activity. Estrus manifestation was detected in 56 gilts (93.3% of the total 60 treated prolonged anestrous gilts, av. 259 days of age), after a single 1000 IU eCG injection. Thirty-four gilts (60.7% of the total gilts in estrus) with prolonged eCG to estrus interval (av. 24.7 days) were considered spontaneously cyclic (sexually mature), but behaviourally anestrous before treatment. The remaining 22 (39.3% of the total gilts in estrus) were considered truly sexually immature (acyclic) before the treatment or were eCG injected in the late luteal or proestrous phase of spontaneous estrous cycle (Exp. 2).ConclusionsIn 66.7% of the delayed puberty gilts, pre-ovulatory follicles (PoF), corpora hemorrhagica (CH), corpora lutea (CL), or corpora albicantia (CA) were found on the ovar...

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In this study different hormonal protocols were used, in order to determine their effectiveness in ovulation value rated postmortem by the inspection of the ovaries of treated gilts. The total of 48 prepubertal Swedish Landrace gilts were used in the study, aged 150 to 160 days, 30 sexually mature gilts, aged 180 to 210 days, with a pre-established one spontaneous estrus (first pubertal), 30 gilts aged 210 to 240 days, with a determined two spontaneous (first and second pubertal) estrus, and 40 long-term anestric gilts, aged 280 to 290 days. The following hormone protocols were conducted: 400 I.U. eCGone-time; 750 I.U. ECG -one time; 1000 IU eCG-one-time; 1500 IU eCGone-time; 250 ηg PGF2α-one time; 20 mg Altrenogest and the combination of 20 mg Altrenogest and 1,000 I.U. eCG at the end of treatment with altrenogest. An overview of the reproductive organs of slaughtered gilts was carried out in the Laboratory for Reproduction of Domestic Animals at the Faculty of Agriculture, Novi Sad. It was found that the ovulation value of the treated gilts depends primarily on the dose of ECG and reproductive status of gilts at the moment of initiation of hormone treatment.