The optimal time of artificial insemination (AI) was determined from data for 2661 AI in 17 herds utilizing a radiotelemetric system for estrus detection that has the potential for continuous 24-h surveillance to monitor behavioral events associated with estrus. The system consisted of pressure-sensitive radio frequency transmitters affixed over the sacrum region of cows. The activation of the sensor sent a radiotelemetric signal to a microcomputer via a fixed antenna. Cow identification, date, time, and duration of each standing event were recorded in the software program provided with the system. Each farm selected a 3-h interval to AI for cows that were identified in estrus during the previous 24 h. Pregnancy status was determined from data for return to estrus and palpation of the uterus 35 to 75 d following AI. Standing events during estrus averaged (+/- SD) 8.5 +/- 6.6 per cow, and the number of events per estrus across herds averaged from 6.2 +/- 5.1 to 12.8 +/- 9.9 per cow. The duration of estrus ranged from 5.1 +/- 3.8 to 10.6 +/- 6.8 h across herds; the mean was 7.1 +/- 5.4 h. The interval from the first standing event to AI affected the probability of pregnancy; the highest conception rates for AI occurred between 4 and 12 h after the onset of standing activity. The probability of pregnancy was higher for cows > 100 d in milk, exhibiting > 2 standing events during estrus, and inseminated during March, April or May.

Study objectives were to determine the efficacy of 4 methods (intramammary amoxicillin, frequent milk-out, a combined intramammary amoxicillin and frequent milk-out, and no treatment) of managing mild to moderate clinical mastitis in a university dairy herd. Clinical and microbiological cures, milk production, disease progression, and California Mastitis Tests scores were evaluated. Cows meeting the study criteria were assigned to one of four treatment options based on a systematic randomization scheme (blocked by stage of lactation). Treatments were initiated prior to knowledge of culture results. Cows were observed and evaluated on d 1 to 8, 15, 22, 29, and 36. Overall, treatments were not significantly different than controls. However, when efficacy was evaluated by pathogen group, differences were observed. Intramammary amoxicillin appeared to be the most efficacious treatment for environmental streptococci. Frequent milk-out appeared to be detrimental for environmental streptococci. Treatment method appeared to have little effect on Escherichia coli mastitis, as nearly all cases recovered within a short time frame. None of the treatments were satisfactory for cases of Klebsiella mastitis. When obtained in a timely manner, treatment selection for clinical mastitis should be based on culture results.

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