LAUSR

Simple Summary Because the estrus in cattle is thought to be energy-consuming if the animals are not planned to breed, spaying in cattle has recently been applied to improve daily weight gain and meat quality. However, postoperative changes in ligation-spaying method with the silicon ring to ovaries via transvaginal methods in heifers have not been clearly identified. This retrospective study presented that heifers spayed with this method exhibited no estrus signs at the pubertal age and the ligated ovaries disappeared within a month post-surgery due to ischemic necrosis. Whereas ovarian steroid hormone levels in spayed heifers were not changed following the puberty, luteinizing hormone level at the pubertal age was higher than unspayed controls. Although carcass weight and yield were similar between groups at the pubertal age upon slaughtering, the spayed animals presented higher marbling degree than that of controls. These results may contribute to develop new management strategies for livestock. Abstract Although spaying prepubertal heifers has routinely been conducted to control cattle herd and improve meat quality, understandings of the postoperative changes following new spaying methods with the silicon ring on the ovaries via colpotomy remain limited. Therefore, as a retrospective study, 28 cases of spayed heifers were reviewed for postoperative changes after employing this method, with inclusion criteria including complete medical records for clinical observation, ultrasonography, measuring reproductive hormones, and tracking slaughter records. No mortality and heat signs at the pubertal age postoperatively occurred in spayed animals. On ultrasonography during rectal examination, the ovaries were enlarged without any folliculogenesis from one week, while massive ovarian edema appeared from two weeks, and ovaries were no longer palpable at four weeks post-surgery. In hormones, whereas estrogen and progesterone levels did not change from prepubertal to pubertal age in spayed animals, luteinizing hormone levels progressively increased during this period and reached a higher level at pubertal period than unspayed controls. Although carcass weight and yield were similar between groups upon slaughter at pubertal age, the spayed animals presented higher carcass quality (marbling degree) than that of controls. These results may contribute to develop herd management strategies, including control of estrus in cattle.