聚乙烯吡咯酮与促卵泡素对奶牛活体采卵效率的影响

采用4×4拉丁方设计,研究聚乙烯吡咯酮(PVP)溶解促卵泡素(FSH)一次肌肉注射对奶牛活体采卵效率和体内血清FSH含量的影响。将8头荷斯坦空怀母奶牛随机分为4组,每组2头,分别用5mgFSH 5mL15%PVP(15%PVP组)、5mgFSH 5mL30%PVP(30%PVP组)、5mgFSH 5mL生理盐水(对照组)和常规注射FSH(常规组)处理供体奶牛。试验期4个月,每月处理1次,各组均为处理后4d应用B型超声波导引采卵。结果如下:30%PVP组每头次平均可采卵泡9个,获可用卵母细胞4枚,与常规组比较差异不显著(P>0.05),但与对照组比较差异显著(P<0.05);15%PVP组每头次平均可采卵泡6个,获可用卵母细胞2.25枚,与对照组比较差异显著(P<0.05);体内血清FSH浓度,30%PVP组与常规组变化趋势相似,维持适宜FSH浓度时间较长,15%PVP组次之,而对照组注射后4~12h血清FSH浓度较高,以后急剧下降,表明PVP可延长FSH在体内存留时间,但以30%PVP效果最佳。     

不同外源促性腺激素诱导成年山羊卵泡发育及活体采卵研究

为探讨不同的外源促性腺激素FSH和PMSG对诱导山羊卵泡发育和活体采卵的影响,选择25只2~4岁断奶3个月以上成年云岭黑山羊分两组进行试验。实验结果:用FSH处理后可用卵泡数明显高于PMSG组(P<0·05),但卵母细胞回收率显著低于PMSG组(P<0·05),两组间可用卵率无显著差异;PMSG处理后直径大于5mm卵泡的比例显著高于FSH处理组,结果表明活体采卵前用FSH诱导卵泡发育可以获得稳定的效果。     

优势卵泡对供体牛超排效果的影响

利用超声波活体采卵仪,去除具有优势卵泡的荷斯坦母牛卵巢上的优势卵泡,诱发新的卵泡波进行超排处理,并进行了:(1)与发情后9d处在黄体期的母牛进行的超排效果比较;(2)与利用CIDR、孕酮、雌二醇诱发新的卵泡波进行的超排效果比较;与具有优势卵泡但没有去除而进行的超排效果进行比较,从而探讨优势卵泡对奶牛超排效果的影响。结果表明,去除优势卵泡组与CIDR组以及自然发情组的超排结果,3组间头均获卵、受精卵数、可用胚胎数差异均不显著(p>0.05)。带有优势卵泡组超排结果与其他三组相比,头均获卵、受精卵数、可用胚胎数差异极显著(p<0.01),可见超排处理时优势卵泡的存在对超排效果的影响极大。     

影响水牛活体采卵效果的因素研究

为探讨不同采卵季节、供体牛年龄和连续采卵时间3个因素对水牛活体采卵效果的影响,本实验选择3～12岁、体重400～700 kg的尼里拉菲水牛52头（其中3～7岁40头、8～12岁12头）,根据单因子完全随机试验设计进行分组,分别观察不同采卵季节、供体牛年龄、连续采卵3个月以下（包含3个月）和3～9个月时间对活体采卵效果的影响。结果表明：冬季的头均卵母细胞数、头均可用卵母细胞数均高于春季（P<0.05）和夏季（P<0.01）,且夏季的头均卵母细胞数、头均可用卵母细胞数均低于其他季节（P<0.01）;3～7岁牛的头均可用卵母细胞数比8～12岁牛的多1.78枚（P<0.05）;活体连续采卵时间在3个月以下（包含3个月）的卵母细胞可用率比连续采卵3～9个月的多8.03(P<0.01)。可见,一年四季都可进行水牛活体采卵,但秋、冬季进行活体采卵较为适宜;3～7岁年龄段牛做供体的活体采卵效果更佳;卵母细胞可用率会随着连续采卵时间延长而明显下降,建议同一批牛连续采卵不超3个月。     

促卵泡素超排效果比较试验

用宁波产促卵泡素(FSH)超排处理供体牛19头,共冲出156枚卵,每头平均8.21枚,其中可用胚胎为140枚,每头平均7.36枚,达到国内平均水平;用北京产FSH超排处理供体牛15头,共冲出98枚卵,每头平均6.53枚,其中可用胚胎为72枚,每头平均4.48枚.试验证明2个不同产地FSH的超排效果有显著差异.     

雪龙黑牛活体采卵与屠宰采卵在体外受精技术中的应用研究

利用超声波活体采卵技术(ovum pick-up,OPU)对12头纯种雪龙黑牛间隔4d采卵2次,对51头F2代遗传性能优秀的雪龙黑牛每周采卵1次,并对活体采卵与屠宰采卵及体外受精后胚胎的发育进行了对比分析.结果表明,活体采卵第2次卵泡数比第1次多82个,而获得的卵母细胞数第2次比第1次少1 2枚;屠宰采卵优秀卵母细胞率高于活体采卵,并且囊胚发育率高于活体采卵.     

促卵泡素诱导羔山羊卵泡发育及活体采卵研究

对8只131￣150日龄山羊采用5 mg FSH诱导卵泡发育后,采用手术法间隔7 d进行采卵,第1￣4次诱导卵泡发育的可用卵泡数分别为(20.1±5.6)、(15.5±3.2)、(9.3±3.7)、(8.7±2.5)个,回收可用卵母细胞数分别为(11.1±3.2)、(8.3±1.8)、(6.6±3.7)、(6.0±1.7)枚,随采卵次数增加,每只羊的可用卵泡数呈下降趋势;不同采卵次间卵泡直径、回收卵母细胞的可用率无显著性差异。26次采卵抽吸卵泡376个(14.5个/只.次),回收COCS279枚(10.7枚/只.次),回收可用COCS 219枚,每只羊每次采卵获可用卵8.4枚,卵母细胞回收率和可用率分别为74.2%和78.5%;不同个体间回收率和可用率无显著性差异。     

超排前有腔卵泡数对青年和牛体内胚胎生产效率的影响

为提高和牛体内胚胎生产效率,优化供体牛筛选标准,本实验选取68头青年黑毛和牛为供体,超排处理前使用B超检查两侧卵巢上直径为3～5 mm的有腔卵泡数,以卵泡总数10和20为临界值将其分为3组,Ⅰ、Ⅱ、Ⅲ组有腔卵泡数分别为<10、10～19、≥20个,以CIDR+FSH+PG法进行超排处理后人工授精,比较不同组间胚胎生产效率。结果表明:Ⅲ组黄体数(15.44)、回收胚胎数(13.13)及可用胚胎数(9.56)均显著高于其他2组(P<0.05),Ⅱ组黄体数、回收胚胎数及可用胚胎数显著高于Ⅰ组(P<0.05),即随着供体牛超排前有腔卵泡数增多,回收胚胎数及可用胚胎数随之增多;Ⅲ组胚胎可用率显著低于Ⅰ组,退化率显著高于Ⅰ组和Ⅱ组(P<0.05)。综上,有腔卵泡数对和牛胚胎生产效率有影响,可以作为供体牛筛选标准之一。     

奶牛活体采卵-体外受精效率的影响因素研究

为建立稳定高效的活体采卵-体外受精技术体系,提高体外胚胎生产效率,本研究先利用屠宰场采集的新鲜卵巢卵母细胞进行体外受精,通过胚胎发育潜力来筛选最佳的体外胚胎培养液;再进一步研究不同种公牛精液和供卵母牛对活体采卵-体外受精效率的影响。结果显示,CR1aa培养液和mCR1aa培养液卵裂率差异不显著（P>0.05）,但mCR1aa组的囊胚发育率显著提高（28.1% vs 20.6%,P<0.05）;选取的3头荷斯坦种公牛精液的活体采卵-体外受精胚胎的卵裂率差异不显著（P>0.05）,但1号种公牛精液体外受精后囊胚率（38.7%）显著高于2号和3号（23.8%&22.9%）（P<0.05）;随机选择的3头活体采卵供体母牛（H1、H2、H3）获得的头均可用卵母细胞数无显著差异,但H1和H2供体母牛体外受精胚胎的卵裂率和囊胚率均显著高于H3供体牛（P<0.05）,且H1供体牛体外受精囊胚率显著高于H2供体牛（P<0.05）。结果表明,mCR1aa培养液能显著提高体外受精囊胚发育率,适用于体外胚胎生产;种公牛精液和供体母牛个体差异会直接影响活体采卵-体外受精胚胎的生产效率,为奶牛活体采卵-体外受精生产技术体系的优化提供参考。     

褪黑素与卵泡刺激素对小鼠卵巢卵泡发育及其血管生成的影响

为了探讨褪黑素(Mel)与卵泡刺激素(FSH)对雌性动物卵巢卵泡发育及其血管的影响，选取40只3周龄ICR雌性小鼠随机均分为4组，即：对照组(Control组)、褪黑素组(Mel组)、卵泡刺激素组(FSH组)和卵泡刺激素+褪黑素组(FSH+Mel组),腹腔分别连续注射生理盐水、Mel、FSH和FSH+Mel后的第13天8:00采集血样及卵巢。每组采集5只小鼠的左侧卵巢进行固定，HE染色观察卵泡发育状况，免疫荧光技术观察卵泡血管状况；剩余卵巢利用Western blot测定Bax、Bcl-2的蛋白表达量。结果：与对照组相比，显著升高的有：Mel组和FSH组卵泡直径50～150μm卵泡数，FSH组和FSH+Mel组血清雌二醇、孕酮浓度，Mel组、FSH组和FSH+Mel组Bcl-2蛋白表达，Mel组>250～350μm卵泡CD34荧光强度，FSH组和FSH+Mel组>350～450μm卵泡毛细血管数和CD34荧光强度(P<0.05);显著降低的有：Mel组、FSH组和FSH+Mel组Bax蛋白和卵泡闭锁率(P<0.05);极显著升高的有：FSH组和FSH+Mel组卵...     

Effects of Ovum Pick-up Frequency and FSH Stimulation: A Retrospective Study on Seven Years of Beef Cattle In Vitro Embryo Production

The aim of this retrospective study was to compare the number of follicles, cumulus oocyte complexes (COCs) and cultured In Vitro Produced (IVP) embryos obtained from 1396 non‐stimulated Ovum Pick‐up (OPU) sessions on 81 donor animals in a twice weekly OPU scheme. Results were obtained from 640 sessions following FSH‐LH superstimulation, on 112 donors subjected to OPU once every 2 weeks. The stimulation protocol started with the insertion of an ear implant containing 3 mg norgestomet (Crestar, Intervet, Belgium) 8 days before puncture (day ?8). The dominant follicle was ablated by ultrasound‐guided follicle puncture on day ?6. On day ?3 and day ?2, cows were injected with FSH (Ovagen, ICP) twice daily (8 am to 8 pm ), i.e. a total dose of 160 μg FSH and 40 μg LG per donor per stimulation cycle. Animals were punctured 48 h after the last FSH injection (day 0). Progesterone implants were removed the next day. Stimulated donor cows were treated with this protocol at 14‐day intervals. Follicles were visualized with a Dynamic Imaging ultrasound scanner, equipped with a 6.5 MHz sectorial probe. Follicles were punctured with 55 cm long, 18 gauge needles at an aspiration pressure corresponding to a flow rate of 15 ml/min. Cumulus oocyte complexes were recovered and processed in a routine IVF set‐up. Results demonstrate that, expressed per session, FSH stimulation prior to OPU increases production efficiency with significantly more follicles punctured and oocytes retrieved. However, when overall results during comparable 2‐week periods are considered (four non‐stimulated sessions vs one stimulated), more follicles are punctured and more oocytes are retrieved using the non‐stimulated protocol. No significant differences in the number of cultured embryos could be detected, indicating that FSH/LH stimulation prior to OPU might have a positive effect on in vitro oocyte developmental competence as more embryos are cultured with less, presumably better‐quality, oocytes.     

Influence of Superovulatory Protocols on In Vitro Production of Nellore (Bos indicus) Embryos

There are indications in the literature that delaying the period between ovarian superestimulation and ovum pick up (OPU) would induce follicles to a condition of initial atresia, which could be beneficial to oocyte development. In this work, we compared three protocols for OPU and in vitro production (IVP) of embryos, in Nellore cattle. Nellore cows (n = 18) were randomly allocated in three groups: Group 1 (OPU), Group 2 [Follicle stimulating hormone (FSH) and OPU] and Group 3 (FSH deprivation and OPU). Three OPUs were performed, and the animals were switched to a different group each time (crossover), in such a way that at the end of the experiment all cows received the 3 protocols. At random stage of the oestrous cycle (D‐2), all follicles ≥ 6 mm were aspirated to induce a new follicular wave 2 days afterwards (D0). In Group 1, OPU was performed on D2 and oocytes were processed to IVP. In Group 2, starting on D0, cows were superstimulated (FSH, Folltropin^®, 30 mg administered daily, i.m., during three consecutive days, total dose = 180 mg), and 6 h after the last FSH dose, they received exogenous luteinizing hormone (LH) (12.5 mg, i.m., Lutropin^®, D3). The OPU was performed 6 h after LH administration, i.e. 12 h after the last dose of FSH. Animals in Group 3 received the same treatment as those in Group 2, except that LH was administered 42 h after the last dose of FSH, and OPU occurred 6 h later. Therefore, in this group, follicles were deprived of FSH at 48 h. Both cleavage and blastocyst rates were similar (p > 0.05, anova ) among oocytes from Groups 1, 2 and 3, respectively: 77.4% (144/185) and 42.70% (79/185); 75.54% (105/139) and 31.65% (44/139); 63.52% (101/159) and 33.33% (53/159). However, hatched blastocyst rate was higher (p < 0.01) in Group 1 (30.27%, 56/185) when compared with Group 2 (11.51%, 16/139) or 3 (15.72%, 25/159). It is concluded that, contrary to previous work on European breeds (Bos taurus), ovarian superstimulation associated with deprivation of FSH and OPU (Group 3) did not increase IVP of Nellore embryos (Bos indicus). On the contrary, the highest hatched blastocyst rates were observed in oocytes from non‐superstimulated cows.     

Follicular development after ovum pick-up and fertilizability of retrieved oocytes in postpartum dairy cattle

This study aimed to evaluate gonadotropin secretion and the developmental competence of follicular oocytes in dairy cattle during the early postpartum (PP) period. The number of follicles developed after transvaginal ultrasound-guided ovum pick-up (OPU) and fertilizability of retrieved oocytes were compared between cows in which the first dominant follicle (DF) ovulated (ovulated group, n=4) and did not ovulate (non-ovulated group, n=3), and between early PP (early PP group, n=2) and after the resumption of the estrous cycle (cyclic group, n=2). Follicular ablation was performed 2-4 days after the detection of DF in the second follicular wave PP. OPU was repeated 3-5 times at 3 or 4-day intervals from 3-4 days after the follicular ablation. At OPU, the follicles were enumerated and all those > or = 5 mm in diameter were aspirated. Recovered oocytes were subjected to in vitro maturation and fertilization. Both criteria were similar between ovulated and non-ovulated groups, and between early PP and cyclic groups. These results suggest that FSH/LH secretions required for follicle recruitment and subsequent follicular growth during the early PP period are similar to those after resumption of the estrous cycle. They also indicate that follicular oocytes during the early PP period have developmental competence.     

Effect of short-term calf removal at three stages of a follicular wave on fate of a dominant follicle in postpartum beef cows.

The hypothesis that ovulation in response to short-term (48 h) calf removal (CR) is dependent on the developmental stage of the dominant follicle was tested in two studies. The objective of Exp. 1 was to characterize the fate of a dominant follicle following 48-h CR on d 2, 4, or 8 of a postpartum follicular wave. Ovaries of 61 beef cows were examined daily by transrectal ultrasonography starting at d 20 to 21 postpartum. Treatments were no CR (n = 14) and CR on d 2 (n = 12), 4 (n = 16), or 8 (n = 10) of first detected follicular wave. Percentage of cows that ovulated a dominant follicle following treatment was not different among groups (P = 0.62). Maximum size of dominant follicles was larger in cows that ovulated (P = 0.002) than in cows that did not ovulate. The objectives of Exp. 2 were 1) to determine whether a follicular wave could be synchronized in anestrous cows following injection of 1 mg of estradiol benzoate (EB) and 200 mg of progesterone (P4; EB + P4); 2) to characterize the fate of dominant follicles following 48-h CR at three stages of a synchronized follicular wave; and 3) to determine whether estrous cycles of normal length followed ovulation in cows pretreated with EB + P4. Ovaries of 50 anestrous beef cows were examined daily as in Exp. 1. Treatments were sesame oil (SO) injected (i.m.) on d 25 postpartum and no CR (n = 9); EB + P4 and no CR (n = 9); EB + P4 and CR on 6 (n = 12), 8 (n = 9), or 12 (n = 11) d after injection. The EB and P4 injections were given on d 25 postpartum. Variability in day of emergence of subsequent follicular waves was lower in cows receiving EB + P4 than in SO-injected cows (P < 0.05). The percentage of cows that ovulated was not different (P = 0.16), but CR increased the percentage of cows that ovulated when groups that received EB + P4 were compared to the EB + P4 group that did not have CR (53.1 vs 11.1%, respectively; P < 0.05). Maximum diameter of dominant follicles was larger (P = 0.05) in ovulatory follicles. The luteal phase was longer (P < 0.03) in cows receiving EB + P4 injection (10.6 +/- 1.2 d) than in cows receiving SO (4.4 +/- 2.2 d). In summary, the maximum size of ovulatory follicles was greater than that of nonovulatory follicles, the ovulatory response of postpartum anestrous cows was maintained through d 8 of a follicular wave, synchronization of follicular waves was accomplished in postpartum cows using EB + P4, and the subsequent luteal phase length was increased in animals that were administered EB + P4.     

Effects of follicle‐stimulating hormone followed by gonadotropin‐releasing hormone on embryo production by ovum pick‐up and in vitro fertilization in the river buffalo (Bubalus bubalis)

In this study, we examined the effects of superstimulation using follicle‐stimulating hormone (FSH) followed by gonadotropin‐releasing hormone (GnRH) on buffalo embryo production by ultrasound‐guided ovum pick‐up (OPU) and in vitro fertilization (IVF). Nine Murrah buffaloes were subjected to OPU‐IVF without superstimulation (control). The morphologies of the oocytes collected were evaluated, and oocytes were then submitted to in vitro maturation (IVM). Two days after OPU, same nine buffaloes were treated with twice‐daily injections of FSH for 3 days for superstimulation followed by a GnRH injection. Oocytes were collected by OPU 23–24 hr after the GnRH injection and submitted to IVM (the superstimulated group). The total number of follicles, number of follicles with a diameter > 8 mm, and number of oocytes surrounded by multi‐layered cumulus cells were higher in the superstimulated group than in the control group (p ≤ 0.05). After IVF, the percentages of cleavage and development to blastocysts were higher in the superstimulated group than in the control group (p < 0.05). In conclusion, superstimulation improved the quality of oocytes and the embryo productivity of OPU‐IVF in river buffaloes.     

Effects of Twice-Weekly Follicular Punctures of Ovaries With or Without the Corpus Luteum on Follicular and Luteal Dynamics

We investigated the effects of twice-weekly follicular punctures of ovaries with or without corpus luteum (CL) on follicular and luteal dynamics. A cross-over design was used, with each cow (seven Japanese Black beef cows) being assigned to one of the three groups at 2-month intervals. Follicular punctures were performed twice weekly for three consecutive weeks until day 20 (oestrus = day 0). All visible follicles (diameter >3 mm) in the ovaries bearing CL (ipsilateral group) or those in the contralateral ovaries (contralateral group) were aspirated. As a control, all visible follicles in both ovaries were aspirated (bilateral group). Follicular development, CL formation and progesterone concentrations in each cow were monitored from days 0 to 30. Follicular growth profiles in the punctured ovaries during/after puncture treatment were similar, irrespective of the presence of follicles in the unpunctured ovary and the CL in the punctured or unpunctured ovaries. After puncture, two cows (28.6%) each in the ipsilateral and bilateral groups did not exhibit behavioural oestrus until day 30, whereas all cows in the contralateral group exhibited oestrus. CL growth and increase in progesterone concentrations after the last follicular puncture in the bilateral group were delayed when compared with those in the ipsilateral group. Our results indicate that the presence of follicles in the unpunctured ovary and the CL in the punctured or unpunctured ovaries does not significantly influence follicular growth in punctured ovaries during/after puncture treatment. However, follicular puncture in ovaries bearing CL may disturb or delay oestrus occurrence after treatment.     

Repeat Ovum Pick-up and In Vitro Embryo Production from Adult Ewes with and without FSH Treatment

Ovum pick-up (OPU) was performed three times on adult ewes after synchronization with (n = 4) or without (n = 4) FSH treatment to investigate the effects of FSH treatment on the number of ovarian follicles, oocytes recovered, oocyte quality and development in vitro. FSH treatment increased the number of ovarian follicles (85 vs 162) and oocytes recovered (33 vs 91), although recovery rate was similar for ewes with and without FSH (91/162, 56.2% and 33/85, 38.8% respectively). Of the oocytes recovered, those classified as grades I and II were similar between ewes with (78/91, 85.7%) and without FSH treatment (27/33, 81.8%). The number of ovarian follicles was similar after repeated OPU for ewes treated with FSH, but for ewes not treated with FSH the number of ovarian follicles decreased with repeated OPU. The number of oocytes recovered decreased for FSH-treated ewes only, while the oocyte recovery rate and proportion of oocytes classified as grades I and II were not affected by repeated OPU. Oocyte cleavage (46/78, 58.9% and 19/24, 79.2%) and blastocyst formation (35/46, 76.1% and 12/19, 63.2% respectively) were similar for ewes with and without FSH treatment. The number of ovarian follicles varied between ewes (p < 0.05) although the number of oocytes recovered and oocyte development in vitro were similar between ewes.     

Follicle-stimulating hormone isoforms and plasma concentrations of estradiol and inhibin A in dairy cows with ovulatory and non-ovulatory follicles during the first postpartum follicle wave

Following parturition, all cows display a wave of ovarian follicular growth, but a large proportion fail to generate a preovulatory rise in estradiol, and hence fail to ovulate. Follicle-stimulating hormone (FSH) exists as multiple isoforms in the circulation depending on the type and extent of glycosylation, and this has pronounced effects on its biological properties. This study examined differences in plasma FSH, estradiol, and inhibin A concentrations, and the distribution of FSH isoforms in cows with ovulatory or atretic dominant follicles during the first postpartum follicle wave. Plasma FSH isoform distribution was examined in both groups during the period of final development of the dominant follicle by liquid phase isoelectric focusing. Cows with an ovulatory follicle had higher circulating estradiol and inhibin A concentrations, and lower plasma FSH concentrations. The distribution of FSH isoforms displayed a marked shift toward the less acidic isoforms in cows with ovulatory follicles. A higher proportion of the FSH isoforms had a pI>5.0 in cows with ovulatory follicles compared to those with atretic follicles. In addition, cows with ovulatory follicles had greater dry matter intake, superior energy balance, elevated circulating concentrations of insulin and insulin-like growth factor-I, and lower plasma nonesterified fatty acids. The shift in FSH isoforms toward a greater abundance of the less acidic isoforms appears to be a key component in determining the capability for producing a preovulatory rise in estradiol, and this shift in FSH isoforms was associated with more favorable bioenergetic and metabolic status.     

Effects of low-dose follicle-stimulating hormone administration on follicular dynamics and preovulatory follicle characteristics in dairy cows during the summer

The well-documented phenomenon of reduced conception rate in dairy cows during the hot season involves impaired functioning of the ovarian follicles and their enclosed oocytes. Three experiments were performed to examine the administration of low doses of follicle-stimulating hormone (FSH) to induce turnover of follicles that are damaged upon summer thermal stress and to examine whether this FSH administration has beneficial effects on preovulatory follicles. In experiment 1, synchronized heifers were treated with 100 mg of Folltropin-V (n = 7) or 4.4 mg of Ovagen (n = 6) on day 3 of the estrous cycle. Treatment with both FSH sources resulted in greater (P < 0.05) numbers of follicles than in control animals (n = 12) on day 6 of the estrous cycle, indicating that low doses of FSH can increase the number of emerging follicles in a follicular wave. In experiment 2, milking cows were assigned to a control group (n = 4) or treated with 2.2 mg (FSH-2.2; n = 6) or 4.4 mg (FSH-4.4; n = 5) Ovagen. Follicle-stimulating hormone was administrated on day 3 or 4 and day 10 or 11 of the estrous cycle, coinciding with emergence of the first and second follicular waves, respectively. The number of follicles emerging during the first wave tended to be higher (P < 0.1) in FSH-4.4-treated cows than in controls. The second-wave dominant follicles emerged 2 d later in the treated cows and were smaller in diameter (P < 0.05) than controls, 2 d before aspiration. Despite being younger, the preovulatory follicles of FSH-4.4 cows expressed a steroidogenic capacity that was similar to controls with a tendency toward greater insulin concentrations (P < 0.09). In experiment 3, milking cows were assigned to a control group (n = 6) or treated with 4.4 mg Ovagen (FSH-4.4; n = 6). Follicle-stimulating hormone was administrated on day 3 and day 12 or 13 of the estrous cycle. The number of emerging follicles was higher (P < 0.05) in the treated vs control cows. However, the features of the preovulatory follicle developed in the subsequent cycle did not differ between groups. In summary, low doses of FSH can efficiently induce follicular turnover accompanied by a modest effect on the preovulatory follicle of the treated cycle. It appears that the administration of low doses of FSH, precisely timed to synchronize with the emergence of follicular waves, might have a beneficial effect on the preovulatory follicle and its enclosed oocyte.     

Postpartum follicular and luteal activity in Holstein-Friesian cows genetically selected for high or low mature bodyweight: Relationships with follicle stimulating hormone,insulin, insulin-like growth factor-1 and growth hormone

AIM: To investigate ovarian follicular and luteal activity during the postpartum period of cows genetically selected for high or low mature bodyweight, in relation to metabolic and reproductive endocrine parameters, to determine whether there are differences between strains that could affect fertility outcomes.

METHODS: The presence of follicles ≥5 mm diameter and luteal structures was mapped in the ovaries of 12 high (heavystrain) and 12 low (light-strain) mature bodyweight cows by daily trans-rectal ultrasonography from Day 7 postpartum until the end of their first normal oestrous cycle. Blood samples were collected daily, for measurement of concentrations of follicle stimulating hormone (FSH), progesterone, growth hormone (GH), insulin-like growth factor-1 (IGF-1), and insulin. Intervals to first ovulation were calculated from ultrasonography data.

RESULTS: Heavy-strain cows had shorter intervals than light-strain cows from calving to the emergence of the first (9.0 (SE 0.9) vs 12.4 (SE 1.3) days) and second (16.4 (SE 1.8) vs 20.6 (SE 1.6) days) dominant follicles (p<0.05). Concentrations of FSH in heavy-strain cows prior to the emergence of the second, third and fourth dominant follicles were higher than in light-strain cows (p<0.05). Heavy-strain cows were more likely to have a large (>15 mm diameter) follicle earlier than light-strain cows (p<0.01). Concentrations of insulin and IGF-1, but not those of GH, were higher in heavy- than light-strain cows during the postpartum period (p=0.01 and p=0.02, respectively), and concentrations of both on Day 6 were inversely related to the time of emergence of the first dominant follicle (p>0.01).

Concentrations of progesterone were similar in both strains of cow until Day 10 of the first oestrous cycle, but thereafter were higher in light- than heavy-strain cows until Day 16. Progesterone concentrations in heavy-strain cows declined earlier and more rapidly than in their lighter counterparts.

CONCLUSION: These results indicate that there is a rapid postpartum resumption of follicular activity in both heavy-and light-strain cows, but that there is an earlier emergence of dominant follicles and ovulation in the former. Differences in luteal function, in terms of lower dioestrus progesterone concentrations and an earlier onset of luteolysis, in heavy- than light-strain cows might be sufficient to impair the fertility of the former.