2. 青铜峡市恒源林牧有限公司，青铜峡 751600
2. Heng Yuan Lin Farming & Animal Husbandry Ltd., Qingtongxia 751600, China
繁殖效率是确保奶牛场盈利的关键因素[1]。近几十年奶牛的选育一直侧重于产奶量，然而奶牛的产奶量与繁殖效率呈负相关[2]。同时，泌乳期奶牛的发情表现差且发情检出率较低[3]，这些因素都会直接降低奶牛繁殖效率。
人工授精(artificial insemination，AI)是牛群加速扩繁和遗传改良的重要方法[4]。然而，由于奶牛的发情鉴定需要花大量的人力和时间，并且部分奶牛存在隐性发情、夜间发情[5]或乏情等情况而导致发情鉴定效果不佳，故在牛群中大规模单独使用AI并不能切实提高奶牛繁殖力[6]。为进一步提高奶牛繁殖效率，降低奶牛空怀天数，研究者开发了效果更好的奶牛同期发情-定时输精技术(estrous synchronization-fixed-timed artificial insemination，ES-TAI)，以提高奶牛的繁殖效率和遗传价值，这是一种通过外源激素控制奶牛发情并定时输精(fixed-timed artificial insemination，TAI)的技术[7]。
奶牛同期发情-定时输精技术基于Pursley等[8]发明的GnRH+PG+GnRH技术(GPG)，经过20多年的不断探索，其使用范围逐渐扩大且效果也得到显著提高[9]。该技术利用外源激素控制牛的发情，其核心是利用外源激素人为控制卵泡更替和黄体消退[10]。这既能减少牛隐性发情造成的漏配[11]和病理条件下产生的负面影响[12]，也能在省去发情监测的同时确保妊娠率不降[13]，还能提高对优良奶牛遗传资源的利用[14]。
同期发情-定时输精技术作为奶牛繁殖技术的重大突破和革新，将同期发情和AI的优势相结合，既提高了奶牛参配率和繁殖效率也降低了经济成本和劳动时间。本文就同期发情-定时输精技术的研究进展进行归纳总结，重点阐述同期发情-定时输精技术原理、处理流程、临床应用效果，并分析比较各种技术的优缺点以及综合效益，以期为进一步研发更为高效的同期发情-定时输精技术和牧场繁殖管理提供一定参考。
1 同期发情-定时输精技术原理和优点 1.1 同期发情-定时输精技术原理同期发情-定时输精是通过外源激素控制奶牛发情并定时输精的繁殖技术。最初Pursley等[8]发明了GPG(GnRH-PG-GnRH)，也称Ovsynch56(ovulation synchronization，Ovsynch，图 1)。该技术共使用3次外源激素处理以达到人为控制奶牛卵巢功能的目的[8]，通常在奶牛产后50~55 d实施。第一剂促性腺激素释放激素(gonadotropin-releasing hormone，GnRH)通过肌肉注射，诱导黄体生成素(luteinizing hormone，LH)激增，从而促使发育成熟的卵泡排卵以及启动新一轮卵泡波发育[15]，排卵也会诱发附属黄体，进而增加排卵期卵泡波发育过程中的循环孕酮(progesterone，P4)浓度；随后前列腺素F2α(prostaglandin F2α，PGF2α)在GnRH给药7 d后诱导黄体(corpus luteum，CL)溶解，进而降低P4浓度，为发情的同步做准备；第二剂GnRH(下文简称为GnRH2)于注射PGF2α后56 h给药以同步排卵，并在GnRH注射后16~18 h后进行TAI，以便在排出卵泡的最佳时间进行人工授精，从而提高妊娠率。
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图 1 奶牛同期发情-定时输精技术(Ovsynch56)原理 Fig. 1 Diagram of primary ES-TAI technology (Ovsynch56) in dairy cows |
受发情检测的制约，发情检测不良或不足是导致牛群参配率和繁殖效率低下的主要原因[16]。同期发情-定时输精技术可省去发情鉴定，提高奶牛的参配率和受胎率。再者，使用ES-TAI可提高奶牛优良基因的遗传利用率[14]。此外，ES-TAI程序中前期所使用的激素为后期授精提供了更好的条件，如PG即对囊性卵巢疾病有良好的治疗效果[17]，又有助于奶牛产后子宫复旧[18]。
2 奶牛同期发情-定时输精技术 2.1 同期发情-定时输精技术(ES-TAI)奶牛ES-TAI最初只是基于GnRH的技术，并与PG配合使用。若PG处理时奶牛的黄体(corpus luteum，CL)仍处于早期，则不能溶解黄体[19]。而经PG处理后约有12%~21% 的奶牛存在黄体不完全消退现象[20]，黄体的不完全消退会引发第2剂GnRH注射后P4浓度升高[21]，而高浓度P4导致子宫内膜变薄，最终降低奶牛的繁殖力[22]。
为了确保第2剂GnRH注射之前黄体完全消退，研究者采用调整Ovsynch方案中PG使用剂量和PG与第2剂GnRH注射之间时长两种方法(图 2)。Tippenhauer等[21]通过改变PG剂量，发现两次注射PG(即GPPG技术，也称二次PG法)的方法进一步提高奶牛黄体完全消退的占比，而单次加倍注射PG(即GDPG技术)却不能提高人工受精后妊娠率(Pregnancy per artificial insemination，P/AI)，并经Lauber等[23]验证二次PG法的G2-16效果更佳(G2-16∶G2-24=50%∶44%)。随后，Heidari等[24]发现延长PGF2α至第2剂GnRH注射之间的时间间隔可降低黄体不完全消退奶牛的比例。Ovsynch48相较于Ovsynch56操作更加简单且节省时间，但P/AI却稍低(Ovsynch48∶Ovsynch56=25.2%∶39%)。另外，Hill等[25]发现改变第2剂GnRH注射到TAI的时长也能影响奶牛P/AI，并通过延迟发情不明显奶牛的授精时间成功提高了奶牛的P/AI。这是因为卵泡大小与卵母细胞成熟和母牛的生育能力有关[26]。Perry等[27]发现，排卵卵泡直径大小可以显著影响随后奶牛的P/AI。排卵前卵泡直径小的奶牛有较低的P/AI，尽管推迟排卵前较小卵泡(< 11 mm)奶牛的TAI时间可以提高其P/AI，但仍低于排卵前具有较大卵泡直径的奶牛[28]。
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(1)Ovsynch48、(2)Ovsynch56、(3)GPPG、(4)G2-16和(5)GDPG的激素剂量：GnRH 100 μg，PG 500 μg；(6)Heatsynch的激素剂量：GnRH 100 μg，PG 500 μg，环戊丙酸雌二醇(estradiol cypionate，ECP) 1 mg Hormone doses for (1) Ovsynch48, (2) Ovsynch56, (3) GPPG, (4) G2-16, and (5) GDPG: GnRH 100 μg, PG 500 μg; Hormone doses for (6) Heatsynch: GnRH 100 μg, PG 500 μg, ECP 1 mg 图 2 不同类型的Ovsynch技术处理流程图 Fig. 2 Flowchart of different Ovsynch technologies |
随后，在Ovsynch的基础上又出现激素替换的新技术。Thatcher等[29]提出将第2次GnRH注射替换成雌激素的Heatsynch技术(图 2)，并经Bartolome等[30]研究证明该技术更适合发情后期的经产牛(Ovsynch48的27 d受胎率∶间情期∶发情后期∶发情前期∶卵巢囊肿=30.2%∶15.4%∶19.2%∶30.0%；Heatsynch的27 d受胎率∶间情期∶发情后期∶发情前期∶卵巢囊肿=24.1%∶52.2%∶24.1%∶5.0%)，但其整体效果与Ovsynch无显著差异(Ovsynch48∶Hestsynch的27 d受胎率=25.2%∶25.8%)。
另外，高产奶牛自身孕激素(P4)分泌稍低[31]，而排卵卵泡在低P4浓度(< 2 ng·mL-1)环境下生长会导致后续奶牛的胚胎质量受损并降低P/AI[32]。Pereira等[33]研究表明在实施Ovsynch时，PG处理时高浓度P4可以提高泌乳奶牛的繁殖力。为提高PG处理时奶牛P4浓度，由此衍生出使用孕酮阴道栓(CIDR/PRID)的同期发情-定时输精技术[34] (图 3)，它依赖含有P4的CIDR/PRID以抑制GnRH和LH分泌[35]。另外，在该技术开始实施时注射一定剂量雌激素，并在撤除CIDR/PRID时注射PG，可以加速黄体溶解，缩短黄体期，进而在给药后约4 d诱导新的卵泡波募集，最终能够提高孕激素处理后卵泡发育的同期率[36]。随后，Stevenson等[37]在Ovsynch56方案中添加CIDR，以提高PG处理时低P4奶牛的P/AI。
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(1)7D2PGF的激素剂量：GnRH用量100 μg，PG用量25 mg，PRID插入物含1.55 g孕酮；(2)2PGG的激素剂量：GnRH用量100 μg，CIDR插入物含1.38 g孕酮，PG用量25 mg；(3)5-day Cosynch的激素剂量：GnRH用量100 μg，CIDR插入物含1.38 g孕酮，PG用量25 mg；(4)CIDR5的激素剂量：CIDR插入物含1.38 g孕酮，PG 25 mg，GnRH 100 μg；(5)CIDR-7的激素剂量：GnRH 100 μg，CIDR插入物含1.38 g孕酮，PG用量25 mg (1) Hormone dosage for 7D2PGF: GnRH dosage 100 μg, PG dosage 25 mg, PRID containing 1.55 g progesterone; (2) Hormonal dose for 2PGG: GnRH 100 μg, CIDR containing 1.38 g progesterone, PG 25 mg; (3) Hormonal dosage for 5-day Cosynch: GnRH 100 μg, CIDR containning 1.38 g progesterone, PG dosage 25 mg; (4) Hormone dosage for CIDR5: CIDR containing 1.38 g progesterone, PG 25 mg, GnRH 100 μg; (5) Hormone dose for CIDR-7: GnRH 100 μg, CIDR containing 1.38 g progesterone, PG dosage 25 mg 图 3 添加孕酮的不同类型ES-AI流程图 Fig. 3 Flowchart of different types of ES-AI with progesterone |
此外，从节省成本的角度出发，研究者在进行AI时注射GnRH，即Cosynch技术[38]，这种技术通过改善卵母细胞成熟或黄体功能，对奶牛的排卵和P/AI产生积极作用[39]。然而，Pancarci等[40]发现，在5 d CIDR-Cosynch实施时给予GnRH并没有影响奶牛的P/AI。另外，置入5 d CIDR奶牛的P/AI要好于置入7 d的P/AI[41]，并且CIDR5方案和CIDR7方案的成本相近[42]。尽管CIDR的放置时长最好是5 d，且方案开始时使用的GnRH可以省去，但其P/AI低于其他Ovsynch技术。目前，不同的ES-TAI技术在牧场实际应用中的效果已经证实，不同的同期发情-定时输精后P/AI相差较大，以Ovsynch+CIDR的方案效果最好(表 1)。
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表 1 不同ES-TAI技术的应用效果 Table 1 Application effects of different ES-TAI technologies |
另外，马绒毛膜促性腺激素(equine chorionic gonadotropin，eCG)是一种具有促性腺激素样活性的糖蛋白，可促进卵泡发育，但对闭锁卵泡无效[46]。因为它具有改善排卵的同步性并有益于胚胎发育和存活，目前已被用于同期发情-定时人工授精[47]。研究表明，在CIDR移除当天注射eCG，可以促进无发情的初产或低BCS奶牛的卵泡生长，并提高排卵率[48]。另外，有研究发现将eCG注射剂量从400 IU降低至300 IU时不会改变P/AI[49]。此外，在AI后注射其他激素也能提高P/AI。Shabankareh等[50]证明, AI后5 d注射人绒毛膜促性腺激素(human chorionic gonadotrophin，hCG)可以显著提高Heatsynch方案实施后奶牛的妊娠率。此外，Zheng等[51]证实, AI后使用促黄体激素释放激素(luteinizing hormone-releasing hormone A3，LRH-A3)和hCG均能提高奶牛妊娠率。
2.2 预同期发情-定时输精技术(presynchronization estrous synchronization-fixed-timed artificial insemination，PES-TAI)预同期发情-定时输精技术的核心是预处理(presynchronization)，可确保后续实施繁育方案时奶牛具备发情的3个必备事件(卵泡波出现、黄体消退和排卵)[52]。在对奶牛实施繁育方案之前进行预处理，可以将奶牛提前同步到最佳的发情阶段，从而增加同步排卵奶牛的比例[53]。GnRH和PG在预处理过程中发挥重要作用。GnRH能够诱导促黄体素(LH)的释放，进而促使不排卵或不发情的经产奶牛排卵[54]，而PG能够促进功能性黄体溶解，促进奶牛发情。
对产后不发情奶牛不能仅靠PG进行预处理，还需配合使用GnRH。在预处理过程中给予GnRH能够增加后续ES-TAI实施时具有功能性黄体奶牛的比率，进而提高奶牛情期受胎率[24]。PO(presynch ovsynch)技术的预处理是先通过GnRH促进卵泡发育，并利用PG消除卵巢囊肿等疾病的负面影响，以同步繁育技术处理时奶牛的生理状态[55]。PES-TAI相较于ES-TAI可以改善卵泡生长波的同步性，增加同步发情率，从而提高奶牛的繁殖力。因此，为提高ES-TAI处理的P/AI，可在ES-TAI技术实施前进行预处理[56]。近些年，研究者已经开发了不同的PES-TAI技术(图 4)，并且实施后获得了不同的奶牛情期受胎率(表 2)。
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(1)PSOv的激素剂量：GnRH用量100 μg；PG用量25 mg。(2)PG7G的激素剂量：GnRH用量100 μg；PG用量25 mg。(3)PO的激素剂量：GnRH用量100 μg；PG用量25 mg。(4)G6G的激素剂量：GnRH用量100 μg；PG用量25 mg。(5)PRE54的激素剂量：GnRH用量100 μg；CIDR含1.38 g孕酮；PG用量25 mg；(6)DO的激素剂量：GnRH 100 μg；PG 25 mg (1) Hormone dose for PSOv: GnRH dosage 100 μg; PG dosage 25 mg.(2) Hormone dosage for PG7G: GnRH dosage 100 μg; PG dosage 25 mg.(3) Hormone dosage for PO(presynch ovsynch): GnRH dosage 100 μg; PG dosage 25 mg.(4) Hormone dosage for G6G: GnRH dosage 100 μg; PG dosage 25 mg.(5) Hormone dosage for PRE54: GnRH dosage 100 μg; CIDR containing 1.38 g progesterone; PG dosage 25 mg.(6) Hormone dosage for DO (double ovsynch): GnRH 100 μg; PG 25 mg 图 4 不同的PES-TAI技术流程图 Fig. 4 Flowchart of different PES-TAI technologies |
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表 2 不同的PES-TAI技术的应用效果 Table 2 Application effects of different PES-TAI technologies |
预处理即能增加有CL奶牛的占比，也能提高奶牛的排卵率[57]。PSOv技术是通过两次PGF2α预处理，并在12 d后再实施Ovsynch56[58]。Giordano等[59]通过将预处理与同期技术之间的时间由12 d延长至14 d来简化管理，但该方案依旧对无排卵奶牛没有效果，并不能提高奶牛的繁殖性能。这是因为该技术仅使用PG进行预处理，而PG并不具备类似GnRH促进黄体和优势卵泡发育的作用，对无CL的奶牛无效。为此，针对没有CL的奶牛，研究者又开发了Presynch-GnRH-Ovsynch(PGO)技术，该技术利用了PGF2α只对功能性黄体有效，将GnRH整合到非周期奶牛卵泡发育中，促使黄体发育成功能性黄体，进而提高奶牛受胎率[60]。随后，Martins等[61]也验证了PGO相较于PSOv更有效(PGO∶PSOv=40.2%∶33.6%)。然而，预处理时间较长会降低规模化牧场奶牛繁殖管理效率。
为进一步缩短预处理时间，Bello等[62]通过开发一系列的同期技术，最终确定G6G效果最好(G4G∶G5G∶G6G的P/AI=24%∶39%∶50%，对照组Ovsynch的P/AI=27%)。另外，Dirandeh等[3]证明在开始G6G或G7G前14 d使用PG，能够明显提高经产荷斯坦奶牛的晚期胚胎/早期胎儿存活率。
此外，Souza等[64]提出将两个Ovsynch56(间隔7 d)结合起来形成一种新的PES-TAI技术，也称为双同期(double ovsynch，DO)技术。DO比PSOv处理的效果更好，这可能是因为在第二个同期GnRH注射时具有功能性黄体奶牛的比例更高[68]。随后，Astiz和Fargas[69]证明DO方案是最适合初产奶牛的同期方法，DO处理显著降低了无排卵和无发情奶牛的比例。同时，Dirandeh等[56]也证实了DO相较于PO和PGO技术，可以更有效地诱导无CL奶牛的同期发情排卵。
另外，Cabrera等[65]采用人绒毛膜促性腺激素(2 500 UI hCG)代替DO方案中首次注射用的GnRH，尽管提高了奶牛的排卵率，但却降低了奶牛的情期受胎率。同时，Allahyari等[70]通过将DO技术中首次GnRH注射替换成雌激素成功提高了奶牛的P/AI。夏季奶牛常有的热应激会损害卵巢卵泡发育，降低奶牛繁殖效率[71]，但DO技术对热应激具有较好的抗性，Dirandeh等[56]证实在夏季高湿热的热应激环境下，DO方案的P/AI最高(DO∶PGO∶PO=23.2%∶16.7%∶12.4%)。此外，为了降低成本，提高牧场经济效益，可根据奶牛的胎次和自愿等待期(voluntary waiting period，VWP)[72]，对初产奶牛选用VWP较短的DO60技术[66]，而对经产牛选用VWP较长的DO88技术[67]。此外，PES-TAI方案中以DO技术和G6G应用较多，并且DO技术不仅能够使奶牛产生高的繁殖效率和好的热应激抗性，更适合初产牛(初产P/AI∶经产P/AI=44.3%±11.4%∶31.4%±8.2%)，而在经产牛中实施G6G技术后的奶牛P/AI高于实施DO技术的奶牛[69]。
3 小结与展望不同的ES-TAI技术被广泛应用到奶牛产后繁殖管理当中，相较于ES-TAI技术，PES-TAI不仅适用范围广泛，还能提高奶牛的P/AI。然而，预处理过程耗时约7~26 d，倘若预先知晓奶牛的生理状况，并针对性的选取更适合的PES-TAI，这将会更好的提高奶牛的繁殖效率[73]。因此，牧场管理者需要结合牧场自身条件并及时评估产后奶牛生理状况，选择适合自己牧场的奶牛同期发情-定时输精方案，这样既能提高奶牛繁殖率，还能增加牧场的综合经济效益。
另外，在追求提高奶牛繁殖效率的同时，还应保护消费者的健康免受激素残留物的侵害[74]。国际上已经有部分地区限制使用特定的激素，如：欧盟限制雌二醇及其衍生物的使用[60]，美国不允许使用eCG[75]。因此，开发更加绿色且能够代替传统激素的新型可用于奶牛同期发情-定时输精的蛋白化合物是将来研究的新方向。此外，传统的给药方式有其弊端，如肌肉注射会影响注射部位肉的品质，阴道栓可能会增加母畜生殖道炎症的发病率[76]。如何更好的解决上述问题也是科学家将来需要研究的方向。
此外，目前不同激素、不同同期发情-定时输精技术的效果还不稳定，同一种技术的处理效果也会因地、因时、因牛而异。因此，研发更加高效、稳定的同期发情-定时输精技术也是将来亟待解决的问题。
| [1] |
BANDAI K, KUSAKA H, MIURA H, et al. A simple and practical short-term timed artificial insemination protocol using estradiol benzoate with prostaglandin F2α in lactating dairy cows[J]. Theriogenology, 2020, 141: 197-201. DOI:10.1016/j.theriogenology.2019.09.024 |
| [2] |
PEREIRA M H C, WILTBANK M C, GUIDA T G, et al. Evaluation of presynchronization and addition of GnRH at the beginning of an estradiol/progesterone protocol on circulating progesterone and fertility of lactating dairy cows[J]. Theriogenology, 2020, 147: 124-134. DOI:10.1016/j.theriogenology.2019.11.025 |
| [3] |
DIRANDEH E, ROODBARI A R, GHOLIZADEH M, et al. Administration of prostaglandin F2α 14 d before initiating a G6G or a G7G timed artificial insemination protocol increased circulating progesterone prior to artificial insemination and reduced pregnancy loss in multiparous Holstein cows[J]. J Dairy Sci, 2015, 98(8): 5414-5421. DOI:10.3168/jds.2015-9417 |
| [4] |
FERRAZ JUNIOR M V C, PIRES A V, BIEHL M V, et al. Comparison of two timed artificial insemination system schemes to synchronize estrus and ovulation in Nellore cattle[J]. Theriogenology, 2016, 86(8): 1939-1943. DOI:10.1016/j.theriogenology.2016.06.012 |
| [5] |
田宏志, 陈晓丽, 李欣, 等. 同期排卵处理母牛体温和活动量变化规律及效果分析[J]. 畜牧兽医学报, 2020, 51(7): 1619-1627. TIAN H Z, CHEN X L, LI X, et al. Study on the body temperature and physical activity alteration of cow treated with ovulation synchronization and effect analysis[J]. Acta Veterinaria et Zootechnica Sinica, 2020, 51(7): 1619-1627. (in Chinese) |
| [6] |
SARTORI R, BARROS C M. Reproductive cycles in Bos indicus cattle[J]. Anim Reprod Sci, 2011, 124(3-4): 244-250. DOI:10.1016/j.anireprosci.2011.02.006 |
| [7] |
SANTOS V G, CARVALHO P D, MAIA C, et al. Adding a second prostaglandin F2α treatment to but not reducing the duration of a PRID-Synch protocol increases fertility after resynchronization of ovulation in lactating Holstein cows[J]. J Dairy Sci, 2016, 99(5): 3869-3879. DOI:10.3168/jds.2015-10557 |
| [8] |
PURSLEY J R, MEE M O, WILTBANK M C. Synchronization of ovulation in dairy cows using PGF2α and GnRH[J]. Theriogenology, 1995, 44(7): 915-923. DOI:10.1016/0093-691X(95)00279-H |
| [9] |
EL-TARABANY M S, AL-MARAKBY K M. Effect of synchronization protocols on reproductive indices, progesterone profile and fertility under subtropical environmental conditions in repeat breeder Holstein cows[J]. Reprod Domest Anim, 2019, 54(2): 234-242. DOI:10.1111/rda.13342 |
| [10] |
GENTRY G T JR, WALKER R S, GENTRY L R. Impacts of incorporation of follicle stimulating hormone into an estrous synchronization protocol for timed artificial insemination of crossbred beef cattle[J]. Anim Reprod Sci, 2016, 168: 19-25. DOI:10.1016/j.anireprosci.2016.02.021 |
| [11] |
周正义, 田莉, 田宏志, 等. 母牛安静发情鉴定技术概况及影响因素分析[J]. 畜牧兽医学报, 2021, 52(4): 862-871. ZHOU Z Y, TIAN L, TIAN H Z, et al. Analysis of identification technology and influence factors on silent estrus of cows[J]. Acta Veterinaria et Zootechnica Sinica, 2021, 52(4): 862-871. (in Chinese) |
| [12] |
BARUSELLI P S, FERREIRA R M, COLLI M H A, et al. Timed artificial insemination: current challenges and recent advances in reproductive efficiency in beef and dairy herds in Brazil[J]. Anim Reprod, 2017, 14(3): 558-571. DOI:10.21451/1984-3143-AR999 |
| [13] |
GUNER B, ERTURK M, DURSUN M, et al. Effect of oestrous expression prior to timed artificial insemination with sexed semen on pregnancy rate in dairy cows[J]. Reprod Domest Anim, 2023, 58(2): 342-348. DOI:10.1111/rda.14293 |
| [14] |
BÓ G A, DE LA MATA J J, BARUSELLI P S, et al. Alternative programs for synchronizing and resynchronizing ovulation in beef cattle[J]. Theriogenology, 2016, 86(1): 388-396. DOI:10.1016/j.theriogenology.2016.04.053 |
| [15] |
GINTHER O J, WILTBANK M C, FRICKE P M, et al. Selection of the dominant follicle in cattle[J]. Biol Reprod, 1996, 55(6): 1187-1194. DOI:10.1095/biolreprod55.6.1187 |
| [16] |
COLAZO M G, MAPLETOFT R J. A review of current timed-AI (TAI) programs for beef and dairy cattle[J]. Can Vet J, 2014, 55(8): 772-780. |
| [17] |
ABDALLA H, DE MESTRE A M, SALEM S E. Efficacy of ovulation synchronization with timed artificial insemination in treatment of follicular cysts in dairy cows[J]. Theriogenology, 2020, 154: 171-180. DOI:10.1016/j.theriogenology.2020.05.029 |
| [18] |
马子明, 郭星汝, 戴天姝, 等. 牛子宫复旧调控机制及促进子宫复旧方法的研究进展[J]. 畜牧兽医学报, 2023, 54(1): 58-68. MA Z M, GUO X R, DAI T S, et al. Research progress on regulatory mechanism of cattle uterine involution and methods of promoting uterine involution[J]. Acta Veterinaria et Zootechnica Sinica, 2023, 54(1): 58-68. (in Chinese) |
| [19] |
LÓPEZ-GATIUS F. Ovarian response to prostaglandin F2α in lactating dairy cows: a clinical update[J]. J Reprod Dev, 2022, 68(2): 104-109. DOI:10.1262/jrd.2021-119 |
| [20] |
CARVALHO P D, FUENZALIDA M J, RICCI A, et al. Modifications to ovsynch improve fertility during resynchronization: evaluation of presynchronization with gonadotropin-releasing hormone 6 d before initiation of ovsynch and addition of a second prostaglandin F2α treatment[J]. J Dairy Sci, 2015, 98(12): 8741-8752. DOI:10.3168/jds.2015-9719 |
| [21] |
TIPPENHAUER C M, STEINMETZ I, HEUWIESER W, et al. Effect of dose and timing of prostaglandin F2α treatments during a 7-d ovsynch protocol on progesterone concentration at the end of the protocol and pregnancy outcomes in lactating Holstein cows[J]. Theriogenology, 2021, 162: 49-58. DOI:10.1016/j.theriogenology.2020.12.020 |
| [22] |
SOUZA A H, SILVA E P B, CUNHA A P, et al. Ultrasonographic evaluation of endometrial thickness near timed AI as a predictor of fertility in high-producing dairy cows[J]. Theriogenology, 2011, 75(4): 722-733. DOI:10.1016/j.theriogenology.2010.10.013 |
| [23] |
LAUBER M R, MCMULLEN B, PARRISH J J, et al. Short communication: effect of timing of induction of ovulation relative to timed artificial insemination using sexed semen on pregnancy outcomes in primiparous Holstein cows[J]. J Dairy Sci, 2020, 103(11): 10856-10861. DOI:10.3168/jds.2020-18836 |
| [24] |
HEIDARI F, DIRANDEH E, ANSARI PIRSARAEI Z, et al. Modifications of the G6G timed-AI protocol improved pregnancy per AI and reduced pregnancy loss in lactating dairy cows[J]. Animal, 2017, 11(11): 2002-2009. DOI:10.1017/S1751731117000520 |
| [25] |
HILL S L, GRIEGER D M, OLSON K C, et al. Using estrus detection patches to optimally time insemination improved pregnancy risk in suckled beef cows enrolled in a fixed-time artificial insemination program12[J]. J Anim Sci, 2016, 94(9): 3703-3710. DOI:10.2527/jas.2016-0469 |
| [26] |
OOSTHUIZEN N, CANAL L B, FONTES P L P, et al. Prostaglandin F2α 7 d prior to initiation of the 7-d CO-synch+CIDR protocol failed to enhance estrus response and pregnancy rates in beef heifers[J]. J Anim Sci, 2018, 96(4): 1466-1473. DOI:10.1093/jas/sky058 |
| [27] |
PERRY G A, SMITH M F, ROBERTS A J, et al. Relationship between size of the ovulatory follicle and pregnancy success in beef heifers[J]. J Anim Sci, 2007, 85(3): 684-689. DOI:10.2527/jas.2006-519 |
| [28] |
PFEIFER L F M, GASPERIN B G, CESTARO J P, et al. Postponing TAI in beef cows with small preovulatory follicles[J]. Anim Reprod Sci, 2022, 242: 107006. DOI:10.1016/j.anireprosci.2022.107006 |
| [29] |
THATCHER W W, MOREIRA F, PANCARCI S M, et al. Strategies to optimize reproductive efficiency by regulation of ovarian function[J]. Domest Anim Endocrinol, 2002, 23(1/2): 243-254. |
| [30] |
BARTOLOME J A, SILVESTRE F T, KAMIMURA S, et al. Resynchronization of ovulation and timed insemination in lactating dairy cows: I: use of the ovsynch and heatsynch protocols after non-pregnancy diagnosis by ultrasonography[J]. Theriogenology, 2005, 63(6): 1617-1627. DOI:10.1016/j.theriogenology.2004.07.016 |
| [31] |
COLAZO M G, DOUREY A, RAJAMAHENDRAN R, et al. Progesterone supplementation before timed AI increased ovulation synchrony and pregnancy per AI, and supplementation after timed AI reduced pregnancy losses in lactating dairy cows[J]. Theriogenology, 2013, 79(5): 833-841. DOI:10.1016/j.theriogenology.2012.12.011 |
| [32] |
CERRI R L A, RUTIGLIANO H M, CHEBEL R C, et al. Period of dominance of the ovulatory follicle influences embryo quality in lactating dairy cows[J]. Reproduction, 2009, 137(5): 813-823. DOI:10.1530/REP-08-0242 |
| [33] |
PEREIRA M H C, WILTBANK M C, GUIDA T G, et al. Comparison of 2 protocols to increase circulating progesterone concentration before timed artificial insemination in lactating dairy cows with or without elevated body temperature[J]. J Dairy Sci, 2017, 100(10): 8455-8470. DOI:10.3168/jds.2016-12145 |
| [34] |
PEREIRA M H C, SANCHES C P, GUIDA T G, et al. Comparison of fertility following use of one versus two intravaginal progesterone inserts in dairy cows without a CL during a synchronization protocol before timed AI or timed embryo transfer[J]. Theriogenology, 2017, 89: 72-78. DOI:10.1016/j.theriogenology.2016.10.006 |
| [35] |
OOSTHUIZEN N, FONTES P L P, SANFORD C D, et al. Estrus synchronization and fixed-time artificial insemination alter calving distribution in Bos indicus influenced beef heifers[J]. Theriogenology, 2018, 106: 210-213. DOI:10.1016/j.theriogenology.2017.10.028 |
| [36] |
BO G A, ADAMS G P, PIERSON R A, et al. Effect of progestogen plus estradiol-17β treatment on superovulatory response in beef cattle[J]. Theriogenology, 1996, 45(5): 897-910. DOI:10.1016/0093-691X(96)00020-9 |
| [37] |
STEVENSON J S, PURSLEY J R, GARVERICK H A, et al. Treatment of cycling and noncycling lactating dairy cows with progesterone during ovsynch[J]. J Dairy Sci, 2006, 89(7): 2567-2578. DOI:10.3168/jds.S0022-0302(06)72333-5 |
| [38] |
SHEPHARD R W, MORTON J M, NORMAN S T. Effects of administration of gonadotropin-releasing hormone at artificial insemination on conception rates in dairy cows[J]. Anim Reprod Sci, 2014, 144(1/2): 14-21. |
| [39] |
RODRIGUES W B, SILVA A S, SILVA J C B, et al. Timed artificial insemination plus heat II: gonadorelin injection in cows with low estrus expression scores increased pregnancy in progesterone/estradiol-based protocol[J]. Animal, 2019, 13(10): 2313-2318. DOI:10.1017/S1751731119000454 |
| [40] |
PANCARCI S M, GÜNGÖR Ö, HARPUT O, et al. Effect of one-day delaying CIDR administration in 5-day cosynch protocol in dairy heifers[J]. Animals (Basel), 2021, 11(5): 1402. |
| [41] |
LÓPEZ-GATIUS F, LÓPEZ-HELGUERA I, DE RENSIS F, et al. Effects of different five-day progesterone-based synchronization protocols on the estrous response and follicular/luteal dynamics in dairy cows[J]. J Reprod Dev, 2015, 61(5): 465-471. DOI:10.1262/jrd.2015-053 |
| [42] |
LOPES G, JOHNSON C R, MENDONÇA L G D, et al. Evaluation of reproductive and economic outcomes of dairy heifers inseminated at induced estrus or at fixed time after a 5-day or 7-day progesterone insert-based ovulation synchronization protocol[J]. J Dairy Sci, 2013, 96(3): 1612-1622. DOI:10.3168/jds.2012-5971 |
| [43] |
BRUNO R G S, MORAES J G N, HERNÁNDEZ-RIVERA J A H, et al. Effect of an Ovsynch56 protocol initiated at different intervals after insemination with or without a presynchronizing injection of gonadotropin-releasing hormone on fertility in lactating dairy cows[J]. J Dairy Sci, 2014, 97(1): 185-194. DOI:10.3168/jds.2013-6827 |
| [44] |
BARLETTA R V, CARVALHO P D, SANTOS V G, et al. Effect of dose and timing of prostaglandin F2α treatments during a Resynch protocol on luteal regression and fertility to timed artificial insemination in lactating Holstein cows[J]. J Dairy Sci, 2018, 101(2): 1730-1736. DOI:10.3168/jds.2017-13628 |
| [45] |
SPENCER J A, CARNAHAN K, SHAFII B, et al. Pregnancy outcomes are not improved by administering gonadotropin-releasing hormone at initiation of a 5-day CIDR-Cosynch resynchronization protocol for lactating dairy cows[J]. J Dairy Sci, 2018, 101(9): 8524-8531. DOI:10.3168/jds.2017-13491 |
| [46] |
DE RENSIS F, LÓPEZ-GATIUS F. Use of equine chorionic gonadotropin to control reproduction of the dairy cow: a review[J]. Reprod Domest Anim, 2014, 49(2): 177-182. DOI:10.1111/rda.12268 |
| [47] |
NASSER L F, REIS E L, OLIVEIRA M A, et al. Comparison of four synchronization protocols for fixed-time bovine embryo transfer in Bos indicus×Bos taurus recipients[J]. Theriogenology, 2004, 62(9): 1577-1584. DOI:10.1016/j.theriogenology.2004.03.013 |
| [48] |
BOTTINO M P, SIMÕES L M S, SILVA L A C L, et al. Effects of eCG and FSH in timed artificial insemination treatment regimens on estrous expression and pregnancy rates in primiparous and multiparous Bos indicus cows[J]. Anim Reprod Sci, 2021, 228: 106751. DOI:10.1016/j.anireprosci.2021.106751 |
| [49] |
PESSOA G A, MARTINI A P, CARLOTO G W, et al. Different doses of equine chorionic gonadotropin on ovarian follicular growth and pregnancy rate of suckled Bos taurus beef cows subjected to timed artificial insemination protocol[J]. Theriogenology, 2016, 85(5): 792-799. DOI:10.1016/j.theriogenology.2015.09.057 |
| [50] |
SHABANKAREH H K, ZANDI M, GANJALI M. First service pregnancy rates following post-AI use of HCG in ovsynch and Heatsynch programmes in lactating dairy cows[J]. Reprod Domest Anim, 2010, 45(4): 711-716. |
| [51] |
ZHENG P, HUANG H, LI X Y, et al. LRH-A3 and HCG increase pregnancy rate during timed artificial insemination in dairy cows[J]. Anim Sci J, 2021, 92(1): e13549. DOI:10.1111/asj.13549 |
| [52] |
KIM I H, JEONG J K, KANG H G. Reproductive performance following a modified presynch-ovsynch, double-ovsynch, or conventional reproductive management program in Korean dairy herds[J]. Theriogenology, 2020, 156: 27-35. DOI:10.1016/j.theriogenology.2020.06.019 |
| [53] |
CHEBEL R C, SCANAVEZ A A, SILVA P R B, et al. Evaluation of presynchronized resynchronization protocols for lactating dairy cows[J]. J Dairy Sci, 2013, 96(2): 1009-1020. DOI:10.3168/jds.2012-5892 |
| [54] |
MENDONÇA L G D, ROCHA L S, VOELZ B E, et al. Presynchronization strategy using prostaglandin F2α, gonadotropin-releasing hormone, and detection of estrus to improve fertility in a resynchronization program for dairy cows[J]. Theriogenology, 2019, 124: 39-47. DOI:10.1016/j.theriogenology.2018.09.027 |
| [55] |
ABDALLA H, MAKAU D N, SALEM S E. Treatment of cows that fail to respond to pre-synchronization treatments with a CIDR-ovsynch regimen improves the overall pregnancy percentage after a double ovsynch treatment regimen[J]. Anim Reprod Sci, 2020, 216: 106356. DOI:10.1016/j.anireprosci.2020.106356 |
| [56] |
DIRANDEH E, ROODBARI A R, COLAZO M G. Double-ovsynch, compared with presynch with or without GnRH, improves fertility in heat-stressed lactating dairy cows[J]. Theriogenology, 2015, 83(3): 438-443. DOI:10.1016/j.theriogenology.2014.10.011 |
| [57] |
SIMÕES L M S, ORLANDI R E, MASSONETO J P M, et al. Exposure to progesterone previous to the protocol of ovulation synchronization increases the follicular diameter and the fertility of suckled Bos indicus cows[J]. Theriogenology, 2018, 116: 28-33. DOI:10.1016/j.theriogenology.2018.04.031 |
| [58] |
MOREIRA F, ORLANDI C, RISCO C A, et al. Effects of presynchronization and bovine somatotropin on pregnancy rates to a timed artificial insemination protocol in lactating dairy cows[J]. J Dairy Sci, 2001, 84(7): 1646-1659. DOI:10.3168/jds.S0022-0302(01)74600-0 |
| [59] |
GIORDANO J O, THOMAS M J, CATUCUAMBA G, et al. Effect of extending the interval from presynch to initiation of ovsynch in a presynch-ovsynch protocol on fertility of timed artificial insemination services in lactating dairy cows[J]. J Dairy Sci, 2016, 99(1): 746-757. DOI:10.3168/jds.2015-10083 |
| [60] |
LANE E A, AUSTIN E J, CROWE M A. Oestrous synchronisation in cattle—current options following the EU regulations restricting use of oestrogenic compounds in food-producing animals: a review[J]. Anim Reprod Sci, 2008, 109(1/4): 1-16. |
| [61] |
MARTINS J P N, CUNHA T O, MARTINEZ W, et al. Presynchronization with prostaglandin F2α and gonadotropin-releasing hormone simultaneously improved first-service pregnancy per artificial insemination in lactating Holstein cows compared with Presynch-14 when combined with detection of estrus[J]. J Dairy Sci, 2023, 106(7): 5115-5126. DOI:10.3168/jds.2022-22651 |
| [62] |
BELLO N M, STEIBEL J P, PURSLEY J R. Optimizing ovulation to first GnRH improved outcomes to each hormonal injection of ovsynch in lactating dairy cows[J]. J Dairy Sci, 2006, 89(9): 3413-3424. DOI:10.3168/jds.S0022-0302(06)72378-5 |
| [63] |
OOSTHUIZEN N, FONTES P L P, OLIVEIRA FILHO R V, et al. Pre-synchronization of ovulation timing and delayed fixed-time artificial insemination increases pregnancy rates when sex-sorted semen is used for insemination of heifers[J]. Anim Reprod Sci, 2021, 226: 106699. DOI:10.1016/j.anireprosci.2021.106699 |
| [64] |
SOUZA A H, AYRES H, FERREIRA R M, et al. A new presynchronization system (double-ovsynch) increases fertility at first postpartum timed AI in lactating dairy cows[J]. Theriogenology, 2008, 70(2): 208-215. DOI:10.1016/j.theriogenology.2008.03.014 |
| [65] |
CABRERA E M, LAUBER M R, VALDES-ARCINIEGA T, et al. Replacing the first gonadotropin-releasing hormone treatment in an ovsynch protocol with human chorionic gonadotropin decreased pregnancies per artificial insemination in lactating dairy cows[J]. J Dairy Sci, 2021, 104(7): 8290-8300. DOI:10.3168/jds.2021-20274 |
| [66] |
STANGAFERRO M L, WIJMA R, MASELLO M, et al. Reproductive performance and herd exit dynamics of lactating dairy cows managed for first service with the presynch-ovsynch or double-ovsynch protocol and different duration of the voluntary waiting period[J]. J Dairy Sci, 2018, 101(2): 1673-1686. DOI:10.3168/jds.2017-13425 |
| [67] |
STANGAFERRO M L, WIJMA R W, GIORDANO J O. Profitability of dairy cows submitted to the first service with the presynch-ovsynch or double-ovsynch protocol and different duration of the voluntary waiting period[J]. J Dairy Sci, 2019, 102(5): 4546-4562. DOI:10.3168/jds.2018-15567 |
| [68] |
GIORDANO J O, WILTBANK M C, GUENTHER J N, et al. Increased fertility in lactating dairy cows resynchronized with double-ovsynch compared with Ovsynch initiated 32 d after timed artificial insemination[J]. J Dairy Sci, 2012, 95(2): 639-653. DOI:10.3168/jds.2011-4418 |
| [69] |
ASTIZ S, FARGAS O. Pregnancy per AI differences between primiparous and multiparous high-yield dairy cows after using double ovsynch or G6G synchronization protocols[J]. Theriogenology, 2013, 79(7): 1065-1070. DOI:10.1016/j.theriogenology.2013.01.026 |
| [70] |
ALLAHYARI I, GHARAGOZLOU F, VOJGANI M, et al. Replacement of the first GnRH by estradiol in the breeding ovsynch of double ovsynch protocol could improve fertility in Holstein dairy cows[J]. Anim Reprod Sci, 2023, 252: 107228. DOI:10.1016/j.anireprosci.2023.107228 |
| [71] |
DIRANDEH E. Starting ovsynch protocol on day 6 of first postpartum estrous cycle increased fertility in dairy cows by affecting ovarian response during heat stress[J]. Anim Reprod Sci, 2014, 149(3/4): 135-140. |
| [72] |
KIM I H, JEONG J K, KANG H G. Factors affecting reproductive outcomes in lactating dairy cows that undergo presynchronization-ovsynch and successive resynchronization programs[J]. Theriogenology, 2022, 187: 9-18. DOI:10.1016/j.theriogenology.2022.04.017 |
| [73] |
RICCI A, CARVALHO P D, AMUNDSON M C, et al. Characterization of luteal dynamics in lactating Holstein cows for 32 days after synchronization of ovulation and timed artificial insemination[J]. J Dairy Sci, 2017, 100(12): 9851-9860. DOI:10.3168/jds.2017-13293 |
| [74] |
MOUSSA F, DOUMIATI S, BERNABÒ N, et al. Hormones residues in bovine animals: sampling, analysis and health risk assessment[J]. Steroids, 2022, 181: 108994. DOI:10.1016/j.steroids.2022.108994 |
| [75] |
RANDI F, KELLY A K, PARR M H, et al. Effect of ovulation synchronization program and season on pregnancy to timed artificial insemination in suckled beef cows[J]. Theriogenology, 2021, 172: 223-229. DOI:10.1016/j.theriogenology.2021.06.021 |
| [76] |
KAJAYSRI J, CHUMCHOUNG C, WUTTHIWITTHAYAPHONG S, et al. Comparison of estrus synchronization by controlled internal drug release device (CIDR) and adhesive transdermal progestin patch in postpartum beef cows[J]. Theriogenology, 2017, 100: 66-71. DOI:10.1016/j.theriogenology.2017.06.006 |
(编辑 郭云雁)