A randomized study on the effect of an extended voluntary waiting period in primiparous dairy cows on fertility, health and culling during first and second lactation

When the voluntary waiting period (VWP), defined as days between calving and when cow is eligible to receive first insemination, extended, high-yielding dairy cows may have better opportunities regain energy balance before insemination. This study investigated effect of an extended (145–215 DIM, n = 280) or conventional (25–95 251) VWP treatment on fertility, disease incidence, culling rate in during their lactation. The were also followed through a second lactation without intervention regarding VWP, which farmers could decide they wished start inseminations. was done randomized-controlled 16 commercial herds southern Sweden containing total 531 primiparous Holstein (HOL) Red Dairy Cattle (RDC) breeds. Data from Swedish national herd recording scheme (SNDRS) collected August 2018 September 2021 used analysis, including records breed, calvings, estrus intensity, inseminations, disease, somatic cell count (SCC), date, reason. During lactation, more receiving showed strong intensity (score 4–5, 55% vs. 48%), fewer moderate 3, 35% 43%), at compared with treatment. First service conception (FSCR) higher (67% 51%) number inseminations per (NINS) lower (1.6 2.0), for For incidence expressed events cow-time study, there no differences 2 treatments any Calving interval (CFI) longer (86 74 d) VWP.In conclusion, improved reproductive functions, form FSCR, NINS, However, apparent these fertility measures following (without intervention), prevalence either Compliance planned We studied “intention-to-treat” effect, i.e results all randomized each regardless whether achieved not, identify bias arising due degree compliance. we found difference those VWP. These findings can be support management decisions length herds.