An evaluation of milk temperature measurement for detecting oestrus in dairy cattle. I. Factors affecting measurement of milk temperature.

The paper reports the development of an electronic system of milk temperature measurement and the results of investigations into the influence of milk yield, milk flow and ambient temperature on milk temperature. The milk and body temperatures of randomly selected multiparous Friesian cows were recorded at afternoon milkings. Temperature was measured by bead thermistors housed in perspex probes from which a digital read-out with an accuracy of +/- 0.1 degree C was obtained. Milk temperature was measured at four sites: the short milk tube (SMT), claw piece (CT), and the beginning (BLT) and end of the long milk tube (ELT) with readings being taken every 30 s from the commencement of milking. Body temperature measured with a probe in the vagina (VT) 38.85 +/- 0.02 degrees C) was significantly higher than milk temperature at any of the four sites although a significant positive correlation existed between milk and body temperature. Milk temperature measured at each site decreased with distance from the cows (SMT: 38.64 +/- 0.03 degrees C, ELT: 37.92 +/- 0.04 degrees C). The difference between body and milk temperature was greatest in cows in which milk flow rates were below average (less than 1.37 kg/min) and/or milk yields were below average (less than 7.82 kg/milking). Milk temperature sites SMT and CT were least affected by variation in milk yield or flow, and showed the closest relationship between maximum milk temperature and body temperature. Milk temperature measurement was most reliable when taken during the full flow of milk.