Rumen microbial community and milk quality in Holstein lactating cows fed olive oil pomace as part in a sustainable feeding strategy

•Olive oil pomace from milling agro-industry is suitable in dairy cow feeding.•Olive oil pomace in dairy cow feeding increases milk quality.•The use of olive milling by-products in animal feeding is a circular economy example.•Olive pomace as feed ingredient do not affect dairy cow performances.•Olive oil pomace from two-phase milling contains molecules useful for rumen modulation.