だいさく　NOSAI獣医日記

強みをみつけ、チャレンジを与えられる獣医でありたい

発情周期のステージ推測④　超音波検査を用いて黄体の変化を診る

繁殖 研究

昨日に引き続き、’’超音波検査’’を用いた発情周期のステージ予測における考え方について説明します。

昨日は、①卵胞ウェーブと子宮所見から診る発情ステージの推測法、についてでしたが、今日は、②黄体から診る発情ステージの推測法について勉強していきたいと思います。

卵胞ウェーブ同様に、黄体も発情周期の中で変化を続けます。変化のチェック項目を、黄体の硬さ、大きさ、輝度、内腔、と自分はしています。

硬さは重要な所見で、発情周期の区画①や②は軟らかく、③や④では弾力性があり、⑤は硬めです41）。黄体の大きさは、排卵後徐々に大きくなり、day5でほとんどの牛は20 mmを超え32）、day11～15くらいで最大の大きさに成長し、その後退行します6）。

黄体の超音波検査所見において説明します。排卵後形成されてまもない黄体はやや黒みがあります。形成中に徐々に白みが増すことで灰色が強くなり、実質との境界が明瞭な機能性黄体に発育を続けます（図6：day11）。退行黄体は白色が増し卵巣実質と境界が不明瞭になってきます（図7）。

図6　開花期黄体

図6　形成初期黄体と退行黄体の違い。　左は形成初期黄体で実質よりもやや黒みが強く、実質との境界が明瞭。右は退行黄体で白色が強く、実質との境界が不明瞭な部分がある。

なぜ、黄体は黒い状態から白い状態に移っていくのかについて少し説明します。排卵後は血流が豊富のため水分が多いですが、その後徐々に減少しトリグリセリドが増加していきます42）。脂肪は白く、水分は黒く描出されるMRI検査においても、黄体の輝度は排卵後徐々に強くなる傾向がみえ、輝度の強さは結合組織やトリグリセリドの増加と関係していることが報告されています43）。超音波検査では水分が多いほど低輝度に描出されるので、排卵後の黄体は黒く、そこから徐々に白みが増していくと考えられます。また、day16～18の黄体退行開始時には一時的に黄体血流が増加するため、超音波検査で黒く描出されることがあります45）。区画⑤において、黄体退行によるプロジェステロン濃度低下に比べ黄体サイズの縮小は緩やかなため、発情時でも黄体サイズがまだ十分なサイズを残している牛もいるので、黄体サイズに加え、黄体のエコー輝度は周期ステージ推測の判断材料として有用です。

黄体内腔については、排卵後間もない形成期は42.1％の牛で内腔が観察され、経過とともに内腔を持つ牛の割合が徐々に減少する41)。

次回はこのシリーズの最後になりますが、発情周期のステージ推測についての考え方の’’まとめ’’を述べたいと思います。

 

参考文献（前回前々回含む）

  1. 安藤寿、大脇茂雄 : 超音波診断装置を用いた直腸検査における発情日予測の効果とその検証, 北海道獣医師会雑誌, 59, 81(2015)
  2. 古山敬祐、小山毅、松井義貴 ： ホルスタイン種経産牛における発情後出血の見られる時期及び人工授精後の受胎率との関連, 繁殖技術, 33, 67-69(2014)
  3. Sumiyoshi T, Tanaka T, Kamomae H : Relationships Between the Appearances and Changes of Estrous Signs and the Estradiol-17β Peak, Luteinizing Hormone Surge and Ovulation During the Periovulatory Period in Lactating Dairy Cows Kept in Tie-stalls, J Reprod Dev, 60, 106-114(2014)
  4. Hartigan PJ. Bovine Medicine: Diseases and Husbandry of Cattle, Andrews AH et al. eds, 2nd ed, 471-505, Blackwell Science Ltd., Oxford, UK(2004)
  5. Forde N, Beltman ME, Lonergan P et al. : Oestrous cycles in Bos taurus cattle, Anim Reprod Sci, 124, 163–169(2011)
  6. Brun-Lafleur L, Cutullic E, Faverdin P et al. : An individual reproduction model sensitive to milk yield and body condition in Holstein dairy cows, Animal, 7, 1332–1343(2013)
  7. Ricci A, Carvalho PD, Amundson MC et al. : Characterization of luteal dynamics in lactating Holstein cows for 32 days after synchronization of ovulation and timed artificial insemination, J Dairy Sci, 100, 9851–9860(2017)
  8. Remnant JG, Green MJ, Huxley JN et al. : Variation in the interservice intervals of dairy cows in the United Kingdom, J Dairy Sci, 98, 889–897(2015)
  9. Townson DH, Tsang PC, Butler WR et al. : Relationship of fertility to ovarian follicular waves before breeding in dairy cows, J Anim Sci, 80, 1053–1058(2002)
  10. Sartori R, Haughian JM, Shaver RD et al. : Comparison of ovarian function and circulating steroids in estrous cycles of Holstein heifers and lactating cows, J Dairy Sci, 87, 905–920(2004)
  11. Jaiswal RS, Singh J, Marshall L et al. : Repeatability of 2-wave and 3-wave patterns of ovarian follicular development during the bovine estrous cycle, Theriogenology, 72, 81-90(2009)
  12. Sugiura T, Akiyoshi S, Inoue F et al. : Relationship between bovine endometrial thickness and plasma progesterone and estradiol concentrations in natural and induced estrus, J Reprod Dev, 64, 135–143(2018)
  13. Silva LA, Ginther OJ : Local effect of the conceptus on uterine vascular perfusion during early pregnancy in heifers, Reproduction, 139, 453-463(2010)
  14. Cengiz M, Colak A, Hayirli A et al. : Optical density changes in ultrasonographic images of the endometrium and corpus luteum in pregnant and cyclic cows, Turk J Vet Anim Sci, 41, 18-24(2017)
  15. Souza AH, Silva EPB, Cunha AP et al. : Ultrasonographic evaluation of endometrial thickness near timed AI as a predictor of fertility in high-producing dairy cows, Theriogenology, 75, 722–733(2011)
  16. Pierson RA, Ginther OJ : Ultrasonic imaging of the ovaries and uterus in cattle, Theriogenology, 29, 21-37(1988)
  17. Adams GP, Matteri RL, Kastelic JP et al. : Association between surges of follicle-stimulating hormone and the emergence of follicular waves in heifers, J Reprod Fert, 94, 177-188(1992)
  18. Hendriksen PJM, Gadella BM, Vos PLAM et al. : Follicular Dynamics Around the Recruitment of the First Follicular Wave in the Cow, Biol Reprod, 69, 2036-2044(2003)
  19. Baldrighi JM, Siddiqui MAR, Ginther OJ : Temporal relationships between minor, preovulatory, or periovulatory FSH surges and the emergence and development of 2 mm follicles ofwave 1 in Bos taurus heifers, Domest Anim Endocrinol, 57, 80-84(2016)
  20. Jaiswal RS, Singh J, Adams GP : Developmental Pattern of Small Antral Follicles in the Bovine Ovary, Biol Reprod, 71, 1244-1251(2004)
  21. Acosta TJ, Beg MA, Ginther OJ : Effects of modified FSH surges on follicle selection and codominance in heifers, Anim Reprod, 2, 28-40(2005)
  22. 金子浩之 : ウシにおける卵胞刺激ホルモン分泌調節機構に関する研究, J Reprod Dev, 41, 113-120(1995)
  23. Ginther OJ, Pinaffi FL, Khan FA et al. : Follicular-phase concentrations of progesterone, estradiol-17beta, LH, FSH, and a PGF2alpha metabolite and daily clustering of prolactin pulses, based on hourly blood sampling and hourly detection of ovulation in heifers, Theriogenology, 79, 918–928(2013)
  24. Kulick LJ, Bergfelt DR, Kot K et al. : Follicle Selection in Cattle: Follicle Deviation and Codominance Within Sequential Waves, Biol Reprod, 65, 839–846(2001)
  25. Adams GP, Jaiswal R, Singh J et al. : Progress in understanding ovarian follicular dynamics in cattle, Theriogenology, 69, 72–80(2008)
  26. Torres-Lechuga ME, González-Maldonado J : Ultrasonography and physiological description of essential events for reproductive management in dairy cattle, Review, Rev Mex Cienc Pecu, 13, 452-472(2022)
  27. Ginther OJ, Siddiqui MAR, Baldrighi JM et al. : Differences between follicular waves 1 and 2 in patterns of emergence of 2 mm follicles, associated FSH surges, and ovarian vascular perfusion in heifers, Theriogenology, 84, 853–861(2015)
  28. Sartori R, Haughian JM, Shaver RD et al. : Comparison of Ovarian Function and Circulating Steroids in Estrous Cycles of Holstein Heifers and Lactating Cows, J. Dairy Sci, 87, 905–920(2004)
  29. Beg MA, Bergfelt DR, Kot K et al. : Follicular-fluid factors and granulosa-cell gene expression associated with follicle deviation in cattle, Biol Reprod, 64, 432–441(2001)
  30. Fortune JE, Rivera GM, Evans ACO et al. : Differentiation of dominant versus subordinate follicles in cattle, Biol Reprod, 65, 648–654(2001)
  31. Lucy MC, Savio JD, Badinga L et al. : Factors that affect ovarian follicular dynamics in cattle, J Anim Sci, 70, 3615-3626(1992)
  32. Miura R, Matsumoto N, Haneda S et al. : Double ovulation rate of the first follicular wave follicles is higher in the first follicular wave dominant follicle in the ovary contralateral to the corpus luteum treated with human chorionic gonadotropin five days after estrus in lactating dairy cows, J Vet Med Sci, 81, 1685-1687(2019)
  33. Beg MA, Bergfelt DR, Kot K et al. : Follicular-fluid factors and granulosa-cell gene expression associated with follicle deviation in cattle, Biol Reprod, 64, 432–441(2001)
  34. Mihm M, Baker PJ, Ireland JLH et al. : Molecular evidence that growth of dominant follicles involves a reduction in follicle-stimulating hormone dependence and an increase in luteinizing hormone dependence in cattle, Biol Reprod, 74, 1051–1059(2006)
  35. Nogueira MFG, Buratini J, Price CA et al. : Expression of LH receptor mRNA splice variants in bovine granulosa cells: Changes with follicle size and regulation by FSH in vitro, Mol Reprod Dev, 74, 680–686(2007)
  36. 三浦亮太朗 : 牛卵巣内での卵胞の発育動態に着目した受胎性評価と繁殖成績改善の可能性, MPアグロ ジャーナル, 7, 22(2017)
  37. Acosta TJ, Beg MA, Ginther OJ : Effects of modified FSH surges on follicle selection and codominance in heifers, Anim Reprod, 2, 28-40(2005)
  38. Taylor C, Rajamahendran R : Foltcular dynamics, corpus luteum growth and regression in lactating dairy cattle, Can J Anim Sci, 7l, 61-68(1991)
  39. Acosta TJ, Hayashi K, Matsui M et al. : Changes in follicular vascularity during the first follicular wave in lactating cows, J Reprod Dev, 51, 273-280(2005)
  40. Singh J, Adams GP : Histomorphometry of dominant and subordinate bovine ovarian follicles, Anat Rec, 258, 58-70(2005)
  41. Okuda K, kito S, Sumi N et al. : Study on the central cavity in the bovine corpus luteum, Vet Rec, 123, 180-183(1988)
  42. Singh J, Pierson RA, Adams GP : Ultrasound image attributes of the bovine corpus luteum: structural and functional correlates, J Reprod Fertil 109, 35-44(1997)
  43. Hilton JL, Baerwald AR, Sarty GE et al. : Magnetic resonance image attributes of the bovine corpus luteum during development and regression, Anat Rec A Discov Mol Cell Evol Biol, 272, 454-459(2003)
  44. Tom JW, Pierson RA, Adams GP : Quantitative echotexture analysis of bovine corpora lutea, Theriogenology, 49, 1345-1352(1998)