Despite the livestock industry has made great improvements in feeding, breeding, and herd management, proper prevention and treatment of calf diseases are still remained as a challenge (Kim et al, 2021). Globally, calves' morbidity and mortality rates due to several diseases have been reported to be about 35% and 7%, respectively (Mee, 2013;Windeyer et al, 2014;Abuelo et al, 2019). Among several diseases of calves, calf diarrhea is a disease of the digestive system with watery feces and more frequent intestine movements, and has been a major cause of economic loss to the cattle farms due to cost of treatment, retarded growth, and death of calves (Lee et al, 2020). Of note, it has been reported that diarrhea is the main disease with the highest morbidity from newborns less than 1 month old to the preweaned calves; in accordance with published articles in Korea, 97.6% of calves had diarrhea during the suckling period and diarrhea was the cause of death in 53.4% of dairy calf deaths (Kim et al, 1990;Hur et al, 2013;Choe et al, 2017;Kim et al, 2021). The diarrheic calf presents several symptoms including dehydration by the loss of water, acidosis owing to electrolyte loss and imbalance, depression, lethargy, decrease of the suck reflex, and more severity such as recumbence, coma, and death

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.