Desempenho reprodutivo de vacas leiteiras lactantes acometidas pela mastite clínica de ocorrência espontânea ou induzida por LPS de Escherichia coli

Abstract

The high incidence of clinical mastitis in dairy herds is responsible for impairments to the dairy livestock, such as the decrease on milk production and quality, and poor reproductive efficiency of sick cows. This thesis was subdivided in three chapters. The first chapter approaches general considerations about the theme. On chapter II, the objective was to evaluate the effects of the occurrence of one or more clinical mastitis (CM) cases, associated or not with puerperal reproductive diseases (metritis and retained placenta), on reproductive parameters, as well as verify the temporal relation between CM and the nearest artificial insemination (AI) on the conception rate of Girolando and Holstein lactating cows. As a result, CM occurrence increased the number of services per conception and calving to conception interval, without altering the conception at first AI postpartum. The effects of CM on reproductive parameters were even more pronounced when cows had two or more CM cases in the same lactation. CM occurrence within 42 days before or 35 days after AI affected in the same way the conception rate. The association among CM and reproductive diseases promoted a negative addictive effect on reproductive performance of Girolando and Holstein lactating dairy cows. Objectives of the chapter III were to evaluate the effects of two intrammamary infusions of lipopolysaccharide (LPS) performed on 5 and 10 days after AI on inflammatory and reproductive parameters, and its effects on endometrial and conceptus gene expression during early pregnancy of lactating Holstein cows. From inflammatory parameters analysed, only reticular temperature and somatic cell count (SCC) were altered by LPS challenge, while milk yield and serum haptoglobin concentration showed a tendency of reduction and increase respectively, on treated group compared with control. None of the evaluated reproductive parameters, especially plasmatic progesterone concentration, were influenced by LPS intrammamary challenge. In relation to the endometrial and embryonic tissues gene expression, 13 from the 100 analysed genes were differently expressed, 11 from endometrium and 2 from conceptus. In summary, the effects due to infection and inflammation of the mammary gland are able to alter reproductive performance as well as gene expression profile of the uterus and conceptus during the first 15 days of gestation of lactating dairy cows.