The frequency of bovine genital campylobacteriosis (BGC) in 157 cows from nine herds from the microregion of Varginha - Minas Gerais - Brazil was evaluated. Farmers use either artificial insemination and natural breeding after two insemination procedures or natural breeding. The diagnosis of BGC was performed by the direct fluorescent antibody test (DFAT) using vaginal mucus. All studied herds showed C. fetus infected animals and, of 157 animals, 40 (25.5%) were positive in DFAT: 7 (26.9%) from herds with natural breeding and 33 (25.1%) from herds with both artificial insemination and natural breeding after the second-to-third insemination. The high frequency of BGC found in this study shows that this disease is present among herds which have reproductive problems and the use of natural breeding after the second-to-third unsuccessful insemination could be a risk factor for the disease.

Cromatografia líqüida de alta eficiência (HPLC) foi utilizada na identificação de isoniazida (hidrazida do ácido isonicotínico) no leite de bovinos tratados com a dose de 25 mg/kg/dia em dias alternados. Também foi verificado o efeito da pasteurização sobre a concentração residual de isoniazida no leite. A excreção da droga no leite apresentou variação cíclica com picos no primeiro dia após a administração da droga, média de 1104,48µg/l, e queda dois dias após, média de 104,12µg/l. Quatro dias após a última administração da droga não foi mais possível a identificação de resíduos de isoniazida no leite. Observou-se influência do peso corporal e da produção de leite sobre a quantidade da droga excretada. A pasteurização diminuiu, em média 47,07%, a concentração de resíduo de isoniazida no leite.

The high pressure liquid chromatography (HPLC) was used for the identification of isoniazid (isonicotinic acid hydrazide) in the milk of cattle treated with a dose of 25 mg/kg/day in alternated days. The effect of milk pasteurization on the isoniazid residue concentration was also studied. The drug excretion presented a cyclic variation, with higher levels in the first day after administration (aa), a mean of 1104.48µg/l, and a decrease two days aa, with a mean of 104.12µg/l. Four days after the last administration of the drug it was not possible to identify residues of isoniazid in the milk of treated animals. Body weight and milk yield influenced the amount of the excreted drug, and pasteurization decreased (mean 47.07%) the concentration of isoniazid residue in milk.