The pattern of temporal measurements of electrical conductivity obtained from electrodes that had been surgically implanted in the mucosa of the vagina or in the submucosa of the vulva in each of five dairy cows was evaluated for changes associated with the occurrence of estrus. Tissue conductivity was monitored at 6-h intervals during and around estrus by hard-ware devices operating at either 16 or 100 kHz. Blood samples were taken at time of conductivity measurement for progesterone determination and at 2-h intervals during estrus for LH determination. Vaginal and vulvar biopsies were performed during diestrus and estrus to measure tissue hydration. Conductivity increased significantly at estrus relative to a nonestrus base period in both vaginal and vulvar tissue. Both electrical frequencies were found to be satisfactory for characterizing changes in tissue conductivity associated with estrus. Peak concentrations of luteinizing hormone, increases in tissue hydration, and patterns of blood progesterone were consistent with the occurrence of estrus during the time of elevated tissue conductivity.

No abstract

The profile of milk conductivity values that were collected using an automated data acquisition system was evaluated for errant values. Conductivity values were recorded from 35 cows for three milkings. Conductivity values that were collected at 2-s intervals were extremely variable. They contained erroneously low values because of the nature of the electronic measuring system. The variability was reduced, but not eliminated, by increasing the interval to 6 s. Erroneously low values were removed by calculating a point estimate representing a mean of the 10 highest values recorded at 6-s intervals.

No abstract

Domesticated livestock have always been an important part of agricultural production. They have been utilized as scavengers to consume the production which could not otherwise be marketed at a better return. Livestock systems were typically very small holdings and were cared for in the odd time that the farmer would have from tending crops. This has been referred to as chores. The chores were done in the morning before field work and in the evening after return from the field. There was slow change in this system or in the pattern of production until after World War II. Since that time because of the shifts in population and the desire for better living conditions that could be afforded in urban areas livestock production has been systemized. Dairy production was one of the first livestock operations to be mechanized. Perhaps this is due to the milking operation being one of the most odious chores which had to be performed in livestock production. The milking machine was a very welcome addition to the farm industry.