Non-Invasive Measurement of Thyroid Hormones in Domestic Rabbits

Thyroid hormone concentrations in female baboons: Metabolic consequences of living in a highly seasonal environment

How female mammals adapt metabolically in response to environmental variation remains understudied in the wild, because direct measures of metabolic activity are difficult to obtain in wild populations. However, recent advances in the non-invasive measurement of fecal thyroid hormones, triiodothyronine (T3), an important regulator of metabolism, provide an opportunity to understand how female baboons living in the harsh Amboseli ecosystem in southern Kenya adapt to environmental variability and escape strict reproductive seasonality. Specifically, we assessed how a female's activity budget, diet, and concentrations of fecal T3 metabolites (mT3) changed over the course of the year and between years. We then tested which of several environmental variables (season, rainfall, and temperature) and behavioral variables (female activity budget and diet) best predicted mT3 concentrations. Finally, we determined if two important reproductive events - onset of ovarian cycling and conception of an offspring - were preceded by changes in female mT3 concentrations. We found female baboons' mT3 concentrations varied markedly across the year and between years as a function of environmental conditions. Further, changes in a female's behavior and diet only partially mediated the metabolic response to the environment. Finally, mT3 concentrations increased in the weeks prior to menarche and cycling resumption, regardless of the month or season in which cycling started. This pattern indicates that metabolic activation may be an indicator of reproductive readiness in female baboons as their energy balance is restored.

The Impact of Transportation on the Cortisol Level of Dwarf Rabbits Bred to Animal-Assisted Interventions

(1) Background: the popularity of rabbits has increased during the last decade and become the third most common companion animal in the EU. Rabbits' participation in Animal-Assisted Interventions (AAIs) is growing. It is highly important to ensure the well-being of the animals in AAIs. Whereas the needs and the advantages of people involved in AAI are becoming more and more evident, the needs of animals are not clearly defined, therefore, it is a great field of inquiry. Animals who are used for AAI need to be transported regularly, which itself might be a source of stress. (2) Methods: the stress of rabbits-caused by transportation-was measured in a non-invasive way: cortisol levels were determined from feces, based on their breakdown products. Eighteen animals were involved in the study. Rabbits experienced a 30 min transportation every second day for two weeks (altogether six times) while 126 samples were collected. (3) Results: rabbits could handle the transportation procedure the first time but subsequently the stress hormone metabolites in feces samples increased regardless of the offered treatments (hay, carrot and apple) during the carriage. (4) Conclusions: those owners who use rabbits for Animal-Assisted Interventions need to take into account that transportation itself is a stressful experience for the animals.

Non-invasive Assay for Measurement of Fecal Triiodothyronine (T3) Metabolite Levels in European Mouflon (Ovis aries musimon)

Thyroid hormones (THs) are important indicators of metabolism and animal health. Traditionally, they have been determined from blood or urine samples. However, as their collection may be stressful and requires ethical approval, alternative non-invasive matrices are preferred when dealing with wild animals. Triiodothyronine (T3) is the active form of THs in blood and the major metabolite excreted in feces. This creates the ideal conditions for its assay in fecal samples. Fecal sampling eliminates the stress of the animals and the need to physically capture them. However, in wild species it is rare to find species-specific kits for the hormone assay. So, the objective of this work was to validate a method for the quantification of T3 metabolite (FTM) levels in feces of European mouflon by using an economic and easily available ELISA kit designed to quantify T3 in human plasma. Analytical and biological validations were performed in feces collected from 10 mouflons (5 ewes and 5 rams). An efficient liquid-extraction method was optimized. Precision, dilution linearity, parallelism, recovery and stability of T3 in fecal samples were calculated. Obtained data were considered acceptable according to international guidelines. The reliability of the results was verified comparing human plasma and mouflon fecal samples fortified with the same T3 standard solutions. The biological validation showed higher FTM levels in March compared to June, and no differences between mouflon ewes and rams. The validation of the present method provides a non-invasive and affordable tool for the quantification of FTM in European mouflon.