Investigations of the practical application of non-invasive continuous temperature measurement in animal reproduction

Abstract

Non-invasive continuous temperature measurement in animal reproduction

Continuous measurement of body temperature provides an extensive insight into the complex variations of body temperature within the given range of physiological and pathological temperature of animals. To reach the aims of investigations with a low degree of invasiveness, is an important objective in modern science. Within this scope, we investigated body temperature measurement exemplarily in two different animal species and two different research questions in the field of animal reproduction. In the first study, body temperature was measured by rectal measurement and vaginally under the terms of a study on the effect of the phase I Coxiella burnetii inactivated vaccine Coxevac on body temperature and milk yield in dairy cows. Q fever is a zoonotic disease caused by C. burnetii. The pathogen is prevalent in ruminants (goats, sheep and cows), which are the main sources of human infection. In the cattle industry around the world, animal and herd level prevalences of C. burnetii are high. Vaccination of ruminants against Q fever is considered important to prevent spreading of the disease and risk of infection in humans. However, published information on side effects of the Q fever vaccination under field conditions is limited for cows. In two experiments, a total of 508 cows were randomly divided into two groups to determine the effect of first vaccination on body temperature and milk yield. The first experiment took place in the teaching and research barn of the Clinic of Animal Reproduction at the Freie Universität Berlin. Temperature of 10 cows was measured vaginally with temperature data loggers housed in modified controlled internal drug release devices without progesterone (CIDR) in a crossover design. The second experiment was conducted on a commercial dairy farm. Milk yield of 498 cows was measured one week before and one week after vaccination. In a subset of 41 cows, temperature was measured rectally with digital thermometers. Body temperature increased significantly after vaccination and a significant difference was also found in body temperature between vaccinated and control cows. Thirty percent of the vaccinated animals in experiment 1 showed reversible swelling at the injection site as a reaction to the vaccination. The results indicate that vaccination against Q fever causes a transient increase of body temperature that peaks in the first 12 to 24 hours and declines after that. In experiment 2, vaccinated cows produced significantly less milk than did control cows 7 days after first vaccination. The cumulative milk loss after first vaccination was influenced by an interaction between C. burnetii serostatus and average milk yield 7 days before first vaccination. This was considered as part of the physiological immune response. In the second study, body temperature of bitches in the first 7 days after parturition was measured with ingestible temperature loggers. The first days after parturition in dogs are characterized by many claims raised by nursing the puppies, uterine involution, milk production and hormonal changes. Hence, in this period, bitches are supposed to be more susceptible to pathologic conditions. The study was performed on 20 private-owned bitches of different breeds. The bitches stayed in their common environment. The ingestible temperature loggers were programmed to measure core body temperature every 15 minutes. Seven loggers and a monitor which they were connected with were given to the owners between day 56 of pregnancy and start of parturition. Each bitch swallowed one ingestible temperature logger daily. Bitches were defined to be healthy by spontaneous parturition and leukocyte concentration. Body temperature of healthy puerperal bitches did not differ from those of healthy dogs in general, while the appearance of short episodes of febrile temperatures seems to be physiological. Body temperatures differed significantly between weight classes showing that small bitches had higher temperatures. Puerperal bitches with leucocytosis showed significant higher body temperatures. Animals did not show any signs of distress. Parallel measurements of temperature were recorded in the majority of the dogs (18/20) involved in the second study. For the statistical analysis, we paired temperature data within a time difference of ≤ 59 seconds (n = 1609) and ≤ 15 seconds time difference (n = 401), respectively. The difference of measured temperatures was 0.165⁰C ± 0.21 (mean ± SD) for the maximum 59 seconds pairs and 0.162⁰C ± 0.19 (mean ±SD) for the maximum 15 seconds pairs. From a clinical perspective, most measurements did not differ more than 0.2°C which can be considered tolerable. It still can be assumed that temperature measured by ingestible loggers might be of better reliability than a measurement in the rectum. In case of elevated temperatures or temperatures below the threshold, repeated measurements are advised for clinical decisions.