Dinâmica da infecção intramamária em ovelhas da raça Santa Inês acompanhadas durante a lactação e seu impacto sobre a composição físico-química do leite

Abstract

This study aimed to evaluate the dynamics of the intramammary infection on different stages of lactation (beggining, middle and ending) and its impact in the physical-chemical composition of milk from Santa Inês ewes. Thirty four primiparous and multiparous Santa Inês ewes raised under semi-intensive and submitted to the same sanitary and nutritional management during all lactation period were studied. The moments of evaluation and sampling were approximately 10 days before parturition (colostrum formation phase), 15 days postpartum (dpp), 30 dpp, 60 dpp and 90 dpp (weaning), moments in which it was conducted clinical examination of the mammary gland. The bacteriological and susceptibility profile of isolates were performed at all times; and in the postpartum moments also perform the direct counting of somatic cells (SCC) and physico-chemical evaluation of milk (fat, protein and lactose contents, density, Dornic acidity, electric conductivity, pH and chloride content). Based on bacterial growth samples were characterized as being from healthy (G1) or infected mammary glands (G2) in the respective moments. Variance analysis was employed and the F statistics with its respective level of significance (p) was calculated; in the descriptive study of the variables studied it was used a frequency distribution (%).All ewes were seronegative for lentiviruses. It was observed an elevation (P<0,05) in the somatic cell count, characterizing the inflammatory process with consequent elevation, although mild, in the fat, protein and chloride contents, pH elevation and reduction in lactose content, and those alterations were more significant in the final stage of lactation. The pre-parturition phase showed a high percentage of bacterial isolation from apparently healthy mammary glands, as well as at the end of lactation. Coagulase-negative Staphylococcus was the most frequently isolated from subclinical cases, which prevailed. The value of somatic cell direct count and the percentage of bacterial isolation which characterize the intramammary infection showed elevated values insofar as it intensifies the reaction of the CMT. A high antimicrobial sensitivity to ampicilin, cefalotin and cefoxitin was verified for Gram-positive bacteria. As for Gram-negative bacteria a good sensitivity to ampicilin, cefoxitin and sulphazotrin was verified.