Fertility and milk production on commercial dairy farms with customized lactation lengths

Drying-off, calving, and start of lactation are critical transition events for a dairy cow. As consequence, most animal health issues occur during these periods. By extending the voluntary waiting period first insemination after calving interval (CInt) can be extended, with possible positive effects fertility health. Some cows might better suited an extended CInt than others, due to differences in milk yield level, persistency, or status, which would justify customized based on individual cow characteristics. This study aims investigate 13 farms CInt, respect service (CFSI), accomplished services per conception (SC), rate at artificial (CR1AI), peak yield, 305-d effective yield. In total, 4,858 complete lactations Holstein Friesian between 2014 2019 from were grouped by parity (1 2+) CFSI (CFSI class; CFSI-1 < 84; 84 ? CFSI-2 140; 140 CFSI-3 196; 196 CFSI-4 252, CFSI-5 ? 252 d) (CInt CInt-1 364; 364 CInt-2 420; 420 CInt-3 476; 476 CInt-4 532, CInt-5 532 d). Cow inseminations, available 11 out (3,597 lactations), class class. The production characteristics analyzed generalized general linear mixed models. was not associated SC, but increased SC (CInt-1–5; 1.11–3.70 SC). More 50% <84 d ended up longer expected (>364 d), showing that able conceive desired CInt. classes 3 higher had earlier before successful 1; <196 consisted both failed insemination(s). On farms, persistency greatest 1 (<364 probably related low this When shortest excluded, farms. Although majority greater d, 531 especially multiparous cows. Based results study, days seems optimal production, when high-yielding selected.