Location: Food and Feed Safety Research
Title: Ovarian reaction and estrus manifestation in delayed puberty gilts after treatment with equine chorionic gonadotropin Authors
Submitted to: Reproductive Biology and Endocrinology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 30, 2012
Publication Date: August 22, 2012
Citation: Stancic, I.B., Bosnjak, D.V., Radovic, I.B., Stancic, B.L., Harvey, R.B., Anderson, R.C. 2012. Ovarian reaction and estrus manifestation in delayed puberty gilts after treatment with equine chorionic gonadotropin. Reproductive Biology and Endocrinology. 10:61. doi: 10.1186/1477-7827-10-61. Interpretive Summary: Sometimes in young breeding female swine (gilts), signs of breeding receptiveness are not obvious. This could be due to delayed puberty or to a lack of behavioral signs of estrus. It is important to determine which of these two conditions is present, because delayed puberty can affect the breeding potential of gilts, reduce reproductive performance, and cause them to be culled from the herd, thus creating economic problems for the swine industry. In the present study, hormones were injected into gilts to determine sexual maturity. By the use of this tool, improvement in fertility was realized. This is an important finding because increases in fertility can improve profitability for the swine industry.
Technical Abstract: Prolonged pre-insemination anestrus (estrus not detected until 8 mo of age, i.e. delayed puberty) is the major reason for culling about 30% of the total number of gilts selected for reproduction at the large breeding farm units in Vojvodina (Republic of Serbia). It is important to determine whether these gilts are truly acyclic (prepubertal) or cyclic, but fail to exhibit behavioural estrus before their culling from the reproductive herd. Recent investigations demonstrate that treatment with eCG increases diestrous phase duration in spontaneous sexually mature gilts. Based on these finding, the aim of the present studies was to determine the physiological reproductive status of delayed puberty gilts according to their ovarian reaction and estrus manifestation after treatment with a single eCG injection. Two experiments were conducted on a swine breeding farm in Vojvodina (Republic of Serbia). 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 hCG (acyclic gilts) 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, one group of gilts (n=60) culled from breeding herd due to prolonged anestrus (estrus not detected until 8 month of age, avg. 258 days) was slaughtered for their physiological reproductive status determination according to functional ovarian structures presence. The second group of such gilts (n=60) was treated with a single 1000 IU eCG injection to determine their reproductive status, according to the interval from eCG to estrus detection duration after eCG injection. The data were analyzed by descriptive statistics, t-test, analysis of variance and Duncan’s test in the software package Statistics 10th. Ovulations were induced in 90% of acyclic and, on average, 93.3% of cyclic gilts after the eCG injection. On average, 4 days after the eCG injection, estrus was detected in 85% of the treated acyclic gilts and in 95% (19/20) of the sexually mature gilts, treated with eCG on day 17 after spontaneous estrus detection. This interval was prolonged (avg. 25 days) in 95% (19/20) of the sexually mature gilts treated with eCG on day 5 and in 90% (18/20) gilts treated on day 11 after spontaneous estrus detection (Exp. 1). Forty prolonged anestrous gilts (61.1% of the total 60 studied gilts, avg. 258 days of age) reached cyclic pubertal ovarian activity before post mortem examination of their ovaries. Estrus manifestation was detected in 56 gilts (93.3% of the total 60 treated prolonged anestrous gilts, avg. 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–estrus interval (avg. 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). Present results demonstrate that treatment with eCG injection may be a useful practical method for determination of physiological reproductive status (spontaneous cyclic or acyclic) in prolonged anestrous gilts before their culling from the reproductive herd.