CORTISOL CONCENTRATIONS IN HAIR, BLOOD AND MILK OF HOLSTEIN AND BUSHA CATTLE

Abstract

Cortisol levels were measured in hair, blood and milk in two different cattle breeds, kept under different breeding conditions and with different genetic merit for milk production. Cows and heifers of Holstein and Busha breeds were selected for the study. Cortisol concentration was determined by immunoassays. Cortisol accumulation was determined in proximal (close to the skin) and distal (far from the skin) segments of the hair shaft. The influence of hair colour and washing prior to extraction and analysis was also examined in order to establish additional factors that may have an impact on hair cortisol concentrations. Concentrations of cortisol determined in the proximal and distal segments of the shaft were significantly higher in Holstein than Busha cows and heifers (P<0.05 and P<0.01, respectively). In Holstein cows, no significant difference was found between concentrations in black and white hair. In hair washed with isopropanol, cortisol concentration was significantly lower compared to unwashed hair (P<0.01). Thus, cortisol concentration in hair varies with the technique of hair processing (washing), but not with colour in Holstein cows. Blood serum cortisol concentrations in Holstein cows and heifers were significantly higher than in Busha cows and heifers, (P<0.01 and P<0.05, respectively). Milk cortisol in Holstein cows was significantly higher than in Busha cows (P<0.05). The higher cortisol concentrations in Holstein cows are assumed to be the result of intensive breeding and physiological adaptation to high milk production. Key words: cattle; cortisol; hair; blood; milk KONCENTRACIJA KORTIZOLA V DLAKI, KRVI IN MLEKU KRAV ČRNO-BELE PASME IN PASME BUŠA Izvleček: Ugotavljali smo koncentracijo kortizola v dlaki, krvi in mleku pri govedu dveh pasem, ki se razlikujeta po mlečnosti in pogojih reje. Raziskavo smo izvedli na kravah in telicah črno-bele pasme in pasme buša. Koncentracijo kortizola smo ugotavljali z imunoencimskimi metodami. Akumulacijo kortizola smo določili v proksimalnem (bliže koži) in distalnem (dlje od kože) delu dlake. Obenem smo ugotavljali vpliv barve in pranja dlake na koncentracijo kortizola. Tako v proksimalnem kot v distalnem delu dlake je bila koncentracija kortizola pri kravah črno-bele pasme v primerjavi s kravami pasme buša statistično značilno višja (P<0,01 in P<0,05). Pri primerjavi koncentracije kortizola med črno in belo dlako črno-belih krav nismo ugotovili statistično značilnih razlik. V dlaki, ki smo jo pred izvedbo določanja koncentracije kortizola oprali z izopropanolom, smo v primerjavi z neoprano dlako ugotovili statistično značilno nižjo vrednost kortizola (P<0,01). Rezultati torej kažejo, da je koncentracija kortizola v dlaki odvisna od načina priprave vzorca (pranje dlake), barva dlake pri črnobeli pasmi pa ne vpliva na koncentracijo kortizola.. V krvnem serumu krav in telic črno-bele pasme je bila koncentracija kortizola statistično značilno višja (P<0,01 in P<0,05) kot pri kravah in telicah pasme buša. Tudi v mleku krav črno-bele pasme je bila koncentracija kortizola statistično značilno višja (P<0,05) kot pri kravah pasme buša. Predvidevamo, da je višji nivo kortizola pri črno-beli pasmi rezultat intenzivne reje in fiziološke prilagoditve na visoko mlečnost. Ključne besede: govedo; kortizol; dlaka; kri; mleko