Impact of subclinical mastitis on cost of production and milk quality in dairy herds

Abstract

The hypothesis of this study is that the methodology of complete and individual milking per mammary quarter allows estimating production losses caused by intramammary infections caused by primary pathogens. The project will be developed by conduction of three experiments, which general objectives will be: 1) to evaluate the effects of subclinical intramammary infections caused by primary pathogens on somatic cell count, milk yield and composition of cows on mammary quarters level; 2) to evaluate production losses and changes in milk composition at herd level through CCS, and 3) to evaluate the economic impact of subclinical mastitis caused by major pathogens in dairy herds. For experiment 1, six dairy herds will be selected (approximately 600 cows), in which an estimated number of 330 lactating cows with intramammary infection caused by primary pathogens distributed in 5 groups will be selected (1: Staphylococcus aureus; 2: environmental Streptococcus; 3: Streptococcus agalactiae, 4: Escherichia coli, and 5: Klebsiella spp.). Samples will be collected by the method of complete and individual milking at mammary quarter level from selected cows, totaling 150 milk samples from healthy mammary quarters and 150 infected contralateral (control), which will be submitted for species identification by microbiological culture and determination of the composition (fat, protein, lactose, casein, total solids, nonfat dry). The bacterial isolates will be identified to the species level by MALDI/TOF-MS. The effect of intramammary infections caused by the five groups of pathogens will be assessed on the response variables (milk yield and composition) using the statistical model strip -plot. For experiment 2, the last two years data from 29,010 dairy cows distributed in 353 herds from the records of Associação Paranaense de Criadores de Gado da Raça Holandesa will be used. Thus the reduction in milk production caused by subclinical mastitis in dairy cows will be assessed through the regression of test day milk yield on log-transformed somatic cell counts. For experiment 3, we will use two data sets: data set (1) will be based on the estimated cost associated with production losses and changes in milk composition from contralateral mammary quarters; and for data set (2) 50 herds from Educampo/SEBRAE will be used, whose data will be processed using the methodology of estimating operational costs, which the cost of production and income analysis will be assessed in presence of subclinical intramammary infection caused by primary pathogens in dairy herds. By the development of present study it is expected to determine the negative effects of subclinical mastitis on these variables on mammary quarter and herd levels in order to minimize losses, both the primary chain, such as dairy products industry. (AU)