RADIOTELEMETRY TEMPERATURE RESPONSES OF MAMMARY-GLAND AND BODY TO INTRAMAMMARY INJECTION OF ESCHERICHIA-COLI ENDOTOXIN OR STREPTOCOCCUS-AGALACTIAE IN LACTATING DAIRY-COWS

To investigate the feasibility of using changes in body or mammary tem perature to detect mastitis, radiotransmitters were implanted midway b etween rear udder quarters and in the peritoneal cavity of 5 Holstein cows (1 to 3 months in lactation) housed in an environmental chamber ( 16 +/- 2 C; lights on 7:00 AM to 11:00 PM). After a 6-week control per iod, Escherichia coli endotoxin (0.5 mg) was injected after the mornin g milking into left rear teat cisterns via the teat canal. Wisconsin m astitis test score and somatic cell count in all quarters increased si gnificantly (P < 0.01) by the next milking. Effects were greatest in t he endotoxin-exposed quarters. Milk yields for all quarters decreased significantly (P < 0.01) by the first milking after endotoxin injectio n, Udder and body temperatures at milkings were similar and were not a ffected by treatment. When temperatures were averaged for the 5 cows f or each of 120 time points/d, average temperatures, relative to time o f injection of endotoxin, were increased by 0.5 C above baseline at 2. 75 hours, peaked at + 2.9 C at 6.50 hours, and remained high through 9 .25 hours after injection. Power spectra calculated for individual cow s on a daily basis universally indicated an increase in power at low f requencies on the day of injection. Subsequently, Streptococcus agalac tiae (200 colony-forming units) was injected into right rear teat cist erns. Wisconsin mastitis test score increased at the second milking af ter injection. Cell count and quarter milk yield decreased by the thir d milking. As with endotoxin, injection of S agalactiae could not be d etected via a change in temperature at milkings. Of the 5 cows, 3 had a peak in temperature after injection of S agalactiae. Average tempera tures for these 3 cows relative to time of injection, were increased b y 0.5 C above baseline at 24.25 hours, peaked at + 1.4 C at 26.25 hour s, and remained high through 28.75 hours after injection. Power spectr a calculated for the day in which a temperature peak was detected for these 3 cows indicated an increase in power at low frequencies, compar ed with spectra for all other days. Similar increases in power were al so detected for the 2 cows that did not have temperature peaks. When c linical signs of mastitis are obvious at milking, there is little adva ntage of using body temperature for detection of infection. When clini cal signs are not obvious, body temperature is often only minimally in creased. Thus, monitoring body temperature at milkings adds little to the ability to detect mastitis. Of more interest is the ability to det ect transient temperature increases that often develop in association with less-severe infections. Also, as early treatment increases the li kelihood of successful treatment, detection of the onset of temperatur e increases would be advantageous for treatment of severe infections. Detection of a transient temperature peak requires taking temperature readings every 2 hours. To detect mastitis when a temperature peak doe s not occur requires measurement every 15 minutes to calculate power s pectra. The ability to detect the onset of acute clinical infections a nd subclinical infections, using frequent temperature readings, indica tes that development of a practical radiotelemetry system for use on f arms may be warranted, depending on cost. The added potential of using body temperature to monitor general health and to detect estrus enhan ces the economic feasibility of developing such a system.