Reduced rumen pH and its fluctuation during the day are considered to be the main factors influencing the development of subacute rumen acidosis (SARA), which negatively affects the general health status, feed intake and the quantity and quality of milk produced. The risk of SARA is highest in high-producing dairy cows at the peak of lactation. The aim of the study was to mitigate the risk of SARA by adding a calcareous seaweed (Lithotamium calcareum) buffer to the optimized total mixed ration (TMR). 34 Holstein dairy
cows at the peak of lactation were included in the experiment. 2 groups were created from them. The dairy cows were housed in a barn with automatic feed weighing troughs and were fed a typical, well-balanced ration that theoretically should not induce acidosis. In the first experimental period, one group of cows received TMR with buffer, the other without buffer. After 21 days, the addition of buffer was switched in the groups. Data from sensors in the milking parlour, from tensometric feed troughs and neck collars were evaluated. Samples of milk, rumen fluid and faeces were also analyzed. The inclusion of a calcareous seaweed buffer in a well-balanced TMR in cows at the peak of lactation had no significant impact on most performance and health parameters measured. Statistically significantly higher values were found when switching from unbuffered TMR to buffered TMR for rumination time (from 350 to 464 minutes per day).