The objectives of this study were (1) to determine the sensitivity (Se) and specificity (Sp) of somatic cell count (SCC) thresholds to identify subclinical mastitis in Gyr cows caused by major and minor pathogens; (2) to study the effects of month of sampling, rear or front mammary quarters, herd, intramammary infection (IMI), and bacterial species on SCC at quarter level; and (3) to describe the prevalence of IMI in Gyr cows in commercial dairy herds. In total, 221 lactating Gyr cows from 3 commercial dairy farms were selected. Milk samples were collected from individual quarters once a month for 1 yr from all lactating cows for SCC and bacteriological analysis. Mammary quarters were considered the experimental units and the SCC results were log(10)-transformed. Four SCC thresholds (100, 200, 300 and 400 × 10(3) cells/mL) were used to determine Se and Sp to identify infected mammary quarters. The overall prevalence of IMI in quarter milk samples of Gyr cows was 49.8%, and the prevalence of minor pathogens was higher (31.9%) than that of major pathogens (17.8%). Quarter samples with microbial isolation presented higher SCC compared with negative samples. Sensitivity and Sp of selected SCC thresholds varied according to the group of pathogen (major and minor) involved in the IMI definition. Sensitivity increased and Sp decreased when mammary quarters with only major pathogens isolation were considered positive. The use of a single SCC analysis to classify quarters as uninfected or infected in Gyr cows may not be a useful test for this breed because Se and Sp of SCC at the studied thresholds were low. The occurrence of IMI and the bacterial species are the main factors responsible for SCC variation in mammary quarters of Gyr cows. Milk samples with major pathogens isolation elicited higher SCC than those with minor pathogens.

RESUMOAvaliaram-se as concentrações de ocitocina e de cortisol e as produções de leite e de leite residual de

Aiming to evaluate the infrared thermography technique for early detection of subclinical mastitis in Gyr cows, 70 animals were selected in 2 nd or 3 rd lactation, with an average production of 7.2 kg / d between 90 and 200 days in milking. Images of two quarters (front and backside) of the same udder side were monthly performed during three months using a thermal camera to evaluate the surface temperature at three different heights (upper, median and lower), totalizing 420 measurements. Milk samples from each quarter were also collected to evaluate the SCC and microbiological culture. The SCC did not influence udder temperature at different heights (p>0.05). However, temperatures among the regions of the quarter were different, the upper area had higher values than the median and lower regions (p<0.05). There was no difference in udder temperatures in relation to the type of microorganisms isolated in milk (p>0.05). The use of thermal camera allowed the identification of temperature variations of skin surface at different udder regions of Gyr cows. However, this technique was not effective in the detection of subclinical mastitis.Keywords: Gyr, Subclinical mastitis, Thermal camera, Dairy cows. 252 RESUMOCom o objetivo de avaliar a técnica de termografia infravermelho para detecção precoce de mastite subclínica em vacas da raça Gir, foram selecionadas 70 vacas de 2 a ou 3 a lactação, com produção média de 7,2 kg/dia, entre 90 e 200 dias de lactação. Imagens de dois quartos colaterais (anterior e posterior) do úbere, foram realizadas mensalmente, durante três meses utilizando uma câmera termográfica para avaliação da temperatura superficial em três alturas distintas (superior, medial e inferior), totalizando 420 avaliações. Também foram colhidas amostras de leite de cada quarto para avaliação da CCS e cultura microbiana. A CCS não influenciou a temperatura do úbere nas alturas estudadas (p>0,05). Porém, entre as regiões dos quartos houve diferença de temperatura, com valores mais altos na área superior (p<0,05) do que nas regiões medial e inferior. Não houve diferença de temperaturas no úbere em relação ao tipo de microrganismo isolado no leite (p>0,05). O uso da câmera termográfica permitiu identificar as variações de temperatura superficial da pele em diferentes regiões do úbere de vacas Gir. Porém, essa técnica não foi eficiente no diagnóstico da mastite subclínica.