Cortisol and testosterone concentrations in boar bristles in relation to season and sperm viability

Boar welfare is a key factor in swine semen production and laboratory use. Hair analysis has been proposed as a minimally-invasive technique able of providing information on the stress response over the medium- to long-term period. Hormonal fluctuation in bristle could be a valid tool to study pig stress and metabolic responses. The aim of the present work was to determine cortisol (CORT) and testosterone (TEST) concentrations in hair, in relation to temperature and sperm viability. Two Italian Large White boars, of proven fertility, aged 6 and 9 years were used for the study; they were housed in 6m2 wide boxes, under artificial illumination and with controlled air temperature. Hair was collected monthly, semen was collected once every two weeks, environmental temperature was determined 6 times a day and mean temperature (Tmed), maximum temperature (Tmax) and minimum temperature (Tmin) were recorded every two weeks. CORT and TEST hair concentrations were measured, after one water and two isopropanol washings and methanol extraction from the matrix, by a validated RIA technique; sperm viability was determined by fluorescent probes (Propidium iodide to stain dead cells’ nucleus in red and Sybr green 14 to stain live cells’ nucleus in green). An ANOVA for repeated measures was used to analyze CORT, TEST and sperm viability changes during the different months; Pearson’s correlation test was used to evidence correlation between CORT, TEST, viability and temperature. There is no difference in CORT, TEST and sperm viability during the different months of the year; CORT is negatively correlated to Tmin (R=-0.33, p<0.05), while only a tendency to negative correlation could be registered with Tmed and Tmax. No other significant correlation was registered. For the first time we showed the applicability of RIA for hair CORT and TEST determination in boar; the technique could be useful for large scale assessment in semen production farms as it is not invasive, relatively easy and fast. The controlled environmental condition in which the animals are kept may be the main reason of the low variation in CORT and TEST. The negative correlation between CORT and Tmin, is not surprising and could be due to the activation of endogenous heat-production systems at low environmental temperatures. On the contrary, the environmental control of high T has been quite effective in avoiding negative stressful effects on boar. In conclusion we gave some insights on new parameters that could be studied on a larger scale and could furnish some information on boar welfare and/or stress in production farms in which the environment is not as strictly controlled as in our stable.