Effects Of PMSG Doses On Reproductive Performance;Preparation And Application Of Antibodies Against-PMSG In Chinese Holstein Dairy Cows

Pregnant mare serum gonadotropin (PMSG) is a glycoprotein hormone, produced by trophoblast cells of endometrial cups in pregnant mares. PMSG exhibits mainly FSH like activity but also have some LH like activity and its parenteral administration stimulates follicular growth and ovulation. PMSG is widely used in small and large ruminants industry as it is cost-effective and less labor involved.The present study was conducted to evaluate effects of different doses of PMSG on estrus induction, estrus interval, and conception rate in synchronized Chinese Holstein dairy cows and compared with heifers. Furthermore, follicular population, plasma estradiol concentrations and the interval from PMSG administration to first natural estrus were also determined. Because of prolonged half-life of PMSG we also studied the production and application of PMSG antibodies.1. Effects of PMSG Doses on Reproductive Performance in Chinese Holstein Dairy Cows(1) Effects of PMSG Doses on Reproductive Performance in Chinese Holstein Dairy CowsThe study was conducted on one hundred cyclic dairy cows. Cows were equally divided into five treatment groups. Each group (n=20) was administered with an injection of PMSG at dose rate of2,2.5,3,3.5, or4IU/kg BW, followed by an injection of PGF2α48h later. Estrus was detected every day. The cows were artificially inseminated8-12h after standing heat. On day30after artificial insemination, pregnancy rate was confirmed by transrectal ultrasonography while calving rate and multiple calvings were added up after successful parturition. There was no significant difference in estrus response among all treatment groups. Similarly, interval from PMSG administration to estrus was decreased non-significantly with the different doses of PMSG. Pregnancy rate was significantly lower in the highest treatment group (4IU/kg BW) than in low treatment groups (2and2.5IU/kg BW). Calving rate was non-significant among different regimens. The effects of PMSG dose on multiple calving was found to be statistically significant and administration of4IU/kg BW PMSG resulted in50%multiple births. The cows failed to get pregnant returned to estrus naturally. The interval from PMSG administration to first natural estrus was significantly higher in high treatment groups (>2.5IU/kg BW) than in the lowest treatment group (2IU/kg BW), however, later pregnancy rate was non-significant in all groups.(2) Influence of PMSG doses on follicular population and plasma estradiol concentrations in Chinese Holstein dairy cowsWe studied the influence of different doses of PMSG on follicular population and plasma estradiol concentrations in Chinese Holstein dairy cows. Ovarian scanning was performed by transrectal Beta-ultrasonography around estrus while plasma estradiol concentration was measured by Radioimmunoassay at the time of administration of PMSG, PGF2a, estrus and insemination. The results showed that medium follicles (5-10mm) population varied among all treatment groups with increasing trend however, there were no significant difference on large follicles (>10mm) population.(3) Effects of PMSG Doses on Reproductive Performance in Chinese Holstein Dairy heifersAccording to the results of the last experiment where higher multiple birth rate was observed in high dose group (3.5and4IU/kg BW), we selected three low PMSG doses (2,2.5and3IU/kg BW) in order to avoid abortion in first trimester. In order to compare the response of PMSG in heifers and cows we conducted this experiment under similar managemental conditions. The response was same as found in cows, where there was no significant difference in estrus response and interval from PMSG administration to estrus among all treatment groups. Pregnancy rate was significantly lower in the highest treatment group (3IU/kg BW) than in low treatment groups (2and2.5IU/kg BW) and the conception rate of heifers was lower than cows under the similar PMSG dose. Calving rate was non-significant among different regimens, and was non-significant in each PMSG group too. Multiple birth rate increased with increase in PMSG dose and was higher in low dose group (2and2.5IU/kg BWkg) heifers (25%) than in cows (0%) The interval from PMSG administration to first natural estrus increased non-significantly among different doses of PMSG. In high dose groups (2.5and3IU/kg BW), the interval in heifers was shorter than cows. 2Preparation and Application of Antibodies Against-PMSG(1) Preparation of Antibodies Against-PMSGPMSG was successful coupled with bovine serum albumin (BSA) by carbodi-imide method, and identified by ultraviolet spectrophotometry. PMSG-BSA was injected in bull for possible immunization. The results revealed high antibodies titer against-PMSG and later purified by saturated ammonium sulfate (SAS) methods.(2) Applied Research of Antibodies Against-PMSGFor this study,225cows were divided into three treatment groups (n=75). And each treatment group was further divided into five subgroups (n=15). Each subgroup was administered with an injection of PMSG at dose rate of2,2.5,3,3.5, or4IU/kg BW respectively, followed by administration of PGF2α48h later. Cows were artificially inseminated8-12h after standing heat. On day30after insemination, pregnancy rate was confirmed by transrectal beta-ultrasonography. Cows were administered with an injection of antibodies against-PMSG at the time of estrus and inseminated respectively. The third group served as control group without antibodies against-PMSG administration. The results demonstrated that antibodies against-PMSG increased the conception rate of cows in high PMSG dose groups and improved the negative impact of PMSG on consequent reproduction of cows compared with control group.