Contagem de células somáticas e liberação de bactérias de quartos mamários de vacas com mastites subclínicas

Abstract

Results of 2007 show the importance of the milk productive chain in Brazil. In spite of this fact, recent publications indicate the poor quality of milk from a significant number of herds. Considering the global economy, the low quality of milk configures an obstacle for the consolidation of the Country as a milk exporter. In order to reverse this situation, two governmental initiatives deserve consideration. The deployment of the Brazilian Milk Quality Control Lab Net and the adoption of raw milk quality indicators: somatic cell counting (SCC) and total bacterial counting (TBC). The SCC signs the levels of mastitis in herds, reflecting the inflammatory response to the invasion of mammary gland. The TBC indicates the microbiological quality of milk, demonstrates the care of milking and the conservation of milk in the farms. Milk can be contaminated by three main bacterial sources: skin of the teats, surface of the equipment and the inner side of the glands. Mastitis is the inflammatory state of mammary glands, generally caused by infection. It is observed in clinical form, with modified milk properties and local symptoms, or in sub-clinical form, with total absence of signals. However, this last one is most relevant for its highly prevalence (from 15 to 40 times more than the clinical form), reduction of secretion, increase of bacteria and SCC in milk. The inflammatory response to mastite classifies its pathogens as principal, for great SCC (S. aureus, S. agalactiae, coliforms and Strepotococcus spp. that not S. agalatiae) increase, and secondary, for less inflammatory response with small variation in the SCC (Coagulase negative staphylococci and Corynebacterium bovis). In this way, the SSC of milk can measure variation of the inflammatory response by the pathogens of the mastitis. The amount of bacteria released in milk also varies with the pathogens. In the United States and Europe, infections of the group Streptococcus spp. had caused sudden peaks while S.aureus caused small rises in the TBC of herds. The general goal of this work is to evaluate the effect of subclinic mastitis pathogens (S. aureus, Staphylococcus coagulase negativos, S. agalactiae, Streptococcus spp. that not S. agalatiae) on the variation SCC and the magnitude of bacteria shedding by the mammary quarter (BSMQ). A secondary objective is the study of relations between the results as the pathogen isolated. From 2009, June to 2009, December, three samples of 638 mammary quarters aseptically prepared had been collected for bacteriological tests, SCC and TBC. The SPSS program calculated descriptive statistics, t test and linear regression. The SCC (cell/mL) and TBC (CFU/mL) geometric means results, according to the isolated pathogens, have been respectively: without growth (52.000; 12.000), coagulase

negative staphylococci (85.000; 17.000), Staphylococcus aureus (587.000; 77.000), Streptococcus spp. not S. agalatiae (432.000; 108.000) and Streptococcus agalactiae (1.572.000; 333.000). The results suggest that the more intense is inflammatory process the grater release of bacteria by the mammary gland will be. It also suggests that SCC is a useful tool for controlling mastitis and maintaining TBC decreases.