　ホルスタイン種去勢肥育牛の肥育中期に発生した第四胃変位4症例（第四胃左方変位3頭，第四胃右方変位1頭）に対し，傍正中切開法で整復手術を実施することで，その後の発育や肥育成績に対する有効性を検討した。症例牛は手術前の臨床症状，手術時の第四胃所見および術後の経過を記録した。さらに肥育期間中の乾物摂取量(DMI)，4週間ごとの体重，日増体量(DG)の推移，および枝肉成績を正常牛と比較した。初診時の症例牛はいずれも強度の食欲不振を呈し，叩打聴診では特徴的な金属性反響音を認めた。第四胃左方変位2頭の第四胃には著しいガス体と水様物の貯留を，残りの第四胃左方および右方変位の各1頭には第四胃の弛緩・拡張が認められた。術後は，いずれの症例牛も早期にDMIが増加し，体重も順調に増加した。また，枝肉成績では枝肉重量や胸最長筋面積が小さい傾向が認められたが歩留は良好で，発育不良を示す所見は認められなかった。

　以上の結果から，ホルスタイン種肥育牛の第四胃変位に対する傍正中切開法による整復手術は，術後の発育が良好で枝肉成績への悪影響も無く，有効な治療法であると考えられた。

　We examined the therapeutic gain of ventrotomy for abomasal displacement in four Holstain steers that had gotten sick to middle term of fattening. The method of operations were paramedian incision. Three cases were left displaced abomasum(LDA) and another case was　right displaced abomasum(RDA). The clinical signs and surgical findings were recorded for treatment period. And dry matter intake(DMI) were measured every day，body weight and dairy gain(DG) were measured every four weeks. At the physical examination, all cases were heavy inappitance. And percussion of the abdominal area was detected on the left or right side. At　the operation, 2 LDA were distention of abomasum, and a LDA and a RDA were relaxation of abomasum. After the operarion, the clinical conditions were improved, therefore, DMI and body weights has increased. As the results of　carcasses judjing, carcasses weight and rib eye areas were little small, but yield criterias were excellent. From these results, the ventrotomy by paramedian incision were effective to the abomasal displacement of Holstain beef cattle.　