Mediation analysis to estimate direct and indirect milk losses due to clinical mastitis in dairy cattle

摘要: Abstract Milk losses associated with mastitis can be attributed to either effects of pathogens per se (i.e., direct losses) or the immune response triggered by intramammary infection (indirect losses). The distinction is important in terms prevention and treatment. Regardless, number often unknown (particularly field studies), making it difficult estimate losses, whereas indirect approximated measuring association between increased somatic cell count (SCC) milk production. An alternative perform a mediation analysis which changes yield are allocated into their components. We applied this method on data for clinical mastitis, SCC test-day recordings, results bacteriological cultures (Escherichia coli, Staphylococcus aureus, Streptococcus uberis, coagulase-negative staphylococci, dysgalactiae, streptococci other than Strep. dysgalactiae uberis), cow characteristics. Following diagnosis was treated (increase decrease) production before after were interpreted counterfactually. On daily basis, changes, mediated increase, significantly different from zero all bacterial species, decrease (ranging among species 4 33 g an increase 1000 SCC/mL/day) 2 12 g detection. Direct not SCC, only staphylococci (72 g day). concluded that mixed structural equation models useful presence yield.