Longevity is a key determinant of economic efficiency and sustainability in dairy cattle production. The study evaluated longevity and lifetime productivity traits in red breed (RB) and Holstein breed (HB) dairy cows in Latvia and assessed the effects of birth year, age at first calving (AFC), and farm size. Data from 279,818 culled and living cows born between 2010 and 2019 were analyzed. The aim of the study was to investigate biological and farm-level factors affecting dairy cow longevity in RB and HB populations. RB and HB cows born between 2010 and 2013 had significantly longer (p < 0.05) total lifespan (LS) and productive life (PL) than cows born in later years; however, they showed lower life day (MPD) and productive life day (MPPD) milk productivity. AFC significantly affected MPD and MPPD. The highest life day productivity in RB cows was observed at AFC of 22.1–24 months, while in HB cows it was observed at <24 months. Significantly longer LS and PL were recorded on farms with fewer than 20 cows, whereas the highest MPD was observed on farms with 101–500 cows in RB and 101–200 cows in HB.
Cielava et al. (Fri,) studied this question.