久しぶりにJournal of Dairy Scienceの論文を読んだ。乳牛における分娩後膿性腟粘液にPGF2αが有効かどうかを検討したランダム化比較試験だ(10.3168/jds.2018-14765)。ドイツの大学からの研究だ。
分娩後における膿性腟粘液（Purulent vaginal discharge, PVD）の牛に対してPGF2α投与が広く行われているが、その効果に対しては議論がある。研究の目的は、PVDが受胎性に及ぼす影響を調ることと、PVDの牛に対するPGF2αの効果を評価すること。
The objectives of this study were (1) to assess the effect of purulent vaginal discharge (PVD) on reproductive performance using a 4-point vaginal discharge score (VDS) and (2) to evaluate the effect of PGF2α treatment in cows with PVD on reproductive performance.
一酪農場のホルスタイン種2473頭に対して、分娩後32日前後で腟粘液スコア（Vaginal discharge score, VDS）、BCS、卵巣を評価。VDS-2以上をPVDとした。PVDの牛に対してランダムでPGF2αを14日間隔で2回投与した。繁殖成績を評価項目として、初回授精受胎率、初回授精日数、空胎日数を用いた。
Holstein cows (n = 2,473) from 1 commercial dairy farm had their vaginal discharge scored at 32 ± 3 d in milk (DIM) using a 4-point scale. Cows were also scored for body condition score and had their ovaries examined using transrectal ultrasound. A VDS-2 or greater was used to define PVD. Cows with PVD were assigned to receive 2 doses of 500 µg of PGF2α analogue (n = 277; Cloprostenol; PGF Veyx forte, Veyx Pharma Ltd., Schwarzenborn, Germany) 14 d apart (odd ear tag number) or remained untreated (n = 272; even ear tag number). All cows not detected in estrus at 90 ± 3 DIM were enrolled into a timed artificial insemination (AI) protocol. The effect of VDS and the effect of PGF2α in cows with PVD on reproductive performance were evaluated separately. First service conception risk (FSCR), time to first AI, and time to pregnancy were used as indicators for reproductive performance. Data were analyzed with Cox’s regression and mixed logistic models.
初産牛に対しては、PVDは初回授精受胎率と空胎日数に影響を及ぼしていなかった。2産以上の牛に対してはVDS-1~3は初回授精受胎率または200日までの妊娠に悪影響を及ぼしていた（図3, 4）。
一方、黄体の認められなかった初産牛に対するPGF2α投与は初回授精受胎率を減少させた（図5）。黄体の有無に関わらず、初産牛に対するPGF2α投与は200日までの妊娠のリスクを減少させた（図6）。2産以上の牛に対するPGF2α投与は、初回授精受胎率を上昇させたものの、200日までの妊娠のリスクに影響は無かった（図6）。
The prevalence of PVD was 22.2% (548/2,473). We detected an interaction of parity and VDS for FSCR and time to pregnancy. In primiparous cows, VDS had no effect on FSCR and time to pregnancy. In multiparous cows, VDS had an effect on FSCR and time to pregnancy. Multiparous cows having a VDS-2 or a VDS-3 had decreased odds of pregnancy at first AI compared with cows having a VDS-0. Multiparous cows with VDS-1 or VDS-3 had a decreased hazard of conceiving within 200 DIM. The treatment effect of PGF2α was conditional on parity. In primiparous animals with PVD without a corpus luteum present at 32 DIM, treatment with PGF2α reduced FSCR. Irrespective of the presence of a corpus luteum, treatment with PGF2α decreased the hazard of conceiving within 200 DIM in primiparous cows. Although multiparous cows with PVD treated with PGF2α had increased odds of pregnancy at first AI, no treatment effect was observed on the hazard of conceiving within 200 DIM.
実験の結果は、PVDの乳牛に対するPGF2αのブランケット投与を肯定するものではなかった。
Our results do not support the blanket use of PGF2α as a treatment option in postpartum dairy cows having PVD.
初産と2産以上で大きな違いがあるから、初産のPVDは無視しても良いのかもしれない。初産の場合は、産道裂傷等による腟由来のPVDが多いのかな？
確かに盲目的にPVDに対してはPGF2αを打っていたので少し改めてみよう。