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  • Author: C. A. Pinkert x
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C. A. Pinkert, G. B. Rampacek and R. R. Kraeling

Summary. The temporal relationships of serum prolactin, oestrogen and LH concentrations during the perioestrous period were compared in prepubertal gilts induced to ovulate by PMSG and hCG and in mature gilts. In Exp. 1, 2 sustained prolactin surges, beginning 4 days and 1 day before the preovulatory LH surge, occurred in all mature gilts. A single preovulatory prolactin surge occurred in 3 prepubertal gilts, starting just before the preovulatory LH surge, but 4 prepubertal gilts had neither a prolactin nor an LH surge. A status (prepubertal or mature) versus time interaction (P < 0·01) was detected for serum prolactin concentrations. A preovulatory oestrogen surge occurred in all gilts but was of lesser magnitude (P < 0·01) and duration (P < 0·05) in the prepubertal gilts without prolactin and LH surges compared to mature gilts and of lesser magnitude (P < 0·01) compared to prepubertal gilts with prolactin and LH surges. The relative timing of the oestrogen surge in prepubertal gilts corresponded with that of mature gilts when adjusted to the LH surge (if present) but was delayed (P < 0·01) in all prepubertal gilts if standardized to the hCG injection. In Exp. 2, mature gilts were examined to determine whether 2 perioestrous prolactin surges were characteristic of all cycling gilts. Of 9 gilts, 8 exhibited an initial prolactin surge 4–5 days before oestrus and 5/9 gilts exhibited a periovulatory prolactin surge. The presence of 2 perioestrous serum prolactin surges was not a requirement for subsequent pregnancy maintenance. The temporal relationships amongst serum oestrogen, prolactin and LH concentrations during the perioestrous period were dramatically different in prepubertal gilts induced to ovulate and mature gilts. Such differences may contribute to early pregnancy failure in the prepubertal gilt.

Keywords: prolactin; oestrogen; LH; prepubertal; pigs

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C. A. Pinkert, D. L. Kooyman, A. Baumgartner and D. H. Keisler

Summary. Ten prepubertal and 8 mature gilts were superovulated with PMSG and hCG, and inseminated with fresh boar semen. Zygotes were surgically recovered from oviducts 54–60 h after hCG. One and 2-cell zygotes were randomly allotted to Medium PL (modified BMOC-3 supplemented with 0·1 mm-EDTA and 1·5% BSA) or Medium G (Medium PL without pyruvate or lactate). Eggs were washed twice in medium, and placed in microdrops of medium overlaid with silicon oil for culture in an humidified 5% CO2, 5% O2, 90% N2 environment, then observed daily for 6 days. Development of eggs was dependent (P < 0·001) on the interactive effects of age of gilt (prepubertal versus mature) and medium type (PL versus G) used in culture. A greater proportion of eggs cultured in Medium G developed further than did eggs in Medium PL (P < 0·001). Additionally, a greater proportion of eggs from mature gilts developed further than did eggs from prepubertal gilts (P < 0·02). We suggest that these results provide evidence that zygotes resulting from superovulation regimens of prepubertal gilts do not possess the same capacity for in-vitro development as do zygotes from pubertal gilts.

Keywords: zygote; blastocyst; prepubertal; pigs