Effect of subclinical mastitis detected in the first month of lactation on somatic cell count linear scores, milk yield, fertility, and culling of dairy cows in certified organic herds

It is well established that subclinical mastitis (SCM), characterized by somatic cell count (SCC) >200,000 cells/mL, has a negative effect on the productivity, reproductive performance, and survivability of cows from conventional dairy herds. However, in organic herds, where use antimicrobial drugs restricted for treatment control intramammary infections (IMI) cows, little known about SCM performance survivability. The objective this study was to evaluate whether diagnosed during first month lactation associated with SCC linear score dynamics, milk production, fertility, culling USDA-certified We collected data 2 herds New Mexico Texas. A total 1,511 calved between June 2018 May 2019 were included followed until 10 current lactation. Cows cells/mL considered have SCM. used mixed regression models accounting repeated measures assess monthly production scores. Cox proportional hazards risk pregnancy culling. parity, farm, previous gestation length, stillbirth, twinning, dystocia, 2- 3-way interactions as potential confounders. produced less than without had elevated scores their throughout subsequent months compared more pronounced multiparous primiparous cows. Subclinical did not affect likelihood 300 d milk. likely die or be culled observed detrimental effects yield USDA but it performance. demonstrated continued entire lactation, carried over