Gentry G T, Gentry L R, Godke R A
School of Animal Sciences, Louisiana State University Agricultural Center, 105 J.B. Francioni Hall, Louisiana State University, Baton Rouge, LA 70803, USA.
Department of Agricultural Sciences, Louisiana Tech University, 102 Reese Hall, Ruston, LA 71272, USA.
Anim Reprod Sci. 2013 Apr;138(1-2):49-54. doi: 10.1016/j.anireprosci.2013.01.018. Epub 2013 Feb 9.
In this study, 53 crossbred beef heifers were used to test the hypotheses that administration of exogenous FSH 2 days following CIDR insertion and administration of estradiol would increase the pregnancy rate in heifers synchronized for FTAI and that plasma leptin concentrations in beef heifers would be higher for heifers that became pregnant to FTAI. The heifers used in this study had a median age of 440 days, an average weight of 324 kg, an average body condition score of 5.1 and a mean reproductive tract score of 3.1. Heifers were stratified by weight and BCS into two groups and then treatments were randomly allotted to each group: (1) control (n=28) or (2) FSH (n=27). Both groups were administered 200mg estradiol benzoate (EB) and received an intravaginal controlled internal drug-releasing device (CIDR) on day 0. On day 2, females in the FSH treatment group were administered 20 mg of FSH, while the control group received 1 ml of saline. On day 7 all females were administered 25 μg PGF2α and the CIDR was removed. Then 24h following CIDR removal all females were administered 1mg EB and 24h later were subjected to FTAI. Pregnancy diagnosis was performed via transrectal ultrasonography 43 days following insemination. Blood samples were collected via jugular venipuncture on days 2, 6-10, 13 and 52 and plasma leptin concentrations were determined by radioimmunoassay. Pregnancy rates were higher (P=0.01) for FSH-treated females (60%) compared with females not receiving FSH (25%). Circulating plasma leptin concentrations were higher (P=0.0051) for pregnant females compared with females that did not become pregnant following FTAI during the experiment. Mean plasma leptin concentration was also higher (P=0.04) from day 2 to day 9 during the synchronization protocol in heifers that became pregnant compared with heifers that did not become pregnant from FTAI. There was no difference (P=0.38) in reproductive tract scores for heifers that became pregnant compared with heifers that did not become pregnant from FTAI. Circulating leptin concentrations were not different (P=0.11) for females receiving FSH compared with females in the non FSH-treated group. Circulating leptin concentrations were affected by sampling day (P<0.0001). However, there was no interaction between sampling day and pregnancy status (P=0.80), treatment and pregnancy status (P=0.14) or treatment and sampling day (P=0.12). These results indicate that the administration of FSH on day 2 of the synchronization protocol may increase pregnancy rates in beef heifers and that increased circulating concentrations of plasma leptin during the synchronization protocol may be indicative of subsequent pregnancy outcome.
在本研究中，53头杂交肉牛小母牛被用于检验以下假设：在插入阴道孕酮释放装置（CIDR）并给予雌二醇2天后给予外源性促卵泡素（FSH），会提高经定时人工授精（FTAI）同步发情的小母牛的妊娠率，且成功通过FTAI受孕的肉牛小母牛的血浆瘦素浓度会更高。本研究中使用的小母牛中位年龄为440天，平均体重324千克，平均体况评分为5.1，平均生殖道评分为3.1。小母牛按体重和体况评分分为两组，然后将处理随机分配到每组：（1）对照组（n = 28）或（2）FSH组（n = 27）。两组均在第0天给予200毫克苯甲酸雌二醇（EB），并置入阴道内可控缓释装置（CIDR）。在第2天，FSH处理组的雌性小母牛给予20毫克FSH，而对照组给予1毫升生理盐水。在第7天，所有雌性小母牛均给予25微克前列腺素F2α（PGF2α）并取出CIDR。然后在取出CIDR后24小时，所有雌性小母牛均给予1毫克EB，24小时后进行FTAI。在输精后43天通过直肠超声进行妊娠诊断。在第2天、第6 - 10天、第13天和第52天通过颈静脉穿刺采集血样，并用放射免疫测定法测定血浆瘦素浓度。与未接受FSH的雌性小母牛（25%）相比，接受FSH处理的雌性小母牛的妊娠率更高（P = 0.01）（60%）。与在实验期间经FTAI未受孕的雌性小母牛相比，怀孕雌性的循环血浆瘦素浓度更高（P = 0.0051）。在同步发情方案期间，从第2天到第9天，成功受孕的小母牛的平均血浆瘦素浓度也高于经FTAI未受孕的小母牛（P = 0.04）。与经FTAI未受孕的小母牛相比，成功受孕的小母牛的生殖道评分没有差异（P = 0.38）。与未接受FSH处理组的雌性小母牛相比，接受FSH的雌性小母牛的循环瘦素浓度没有差异（P = 0.11）。循环瘦素浓度受采样日影响（P < 0.0001）。然而，采样日与妊娠状态之间（P = 0.80）、处理与妊娠状态之间（P = 0.14）或处理与采样日之间（P = 0.12）没有交互作用。这些结果表明，在同步发情方案第2天给予FSH可能会提高肉牛小母牛的妊娠率，且在同步发情方案期间循环血浆瘦素浓度升高可能预示着随后是否妊娠。
