Effects of extended voluntary waiting period from calving until first insemination on udder health in dairy cows

Traditionally, cows are managed for a 1-year calving interval. This yearly calvingmoment is associated with challenging transitions related with the process of dryingoff, calving and start of a new lactation together with a negative energy balance(NEB) and high disease incidence in early lactation. One possible solution to reducehealth disorders in peripartum dairy cows is to reduce the frequency of calving andassociated critical transitions by extending the voluntary waiting period until firstinsemination (VWP). The aim of this study was to evaluate the effect ofextended VWP on SCC, SCC elevations and clinical mastitis incidence during thecomplete lactation and the first 6 weeks of the next lactation. Holstein-Friesian dairycows (N=154) were blocked for parity, expected milk yield, calving season andbreeding value for persistency and were randomly distributed across 3 VWP (50, 125or 200 days: VWP-50, VWP-125, VWP-200). Cows were monitored from calving until6 weeks in the next lactation, or until culling. An elevation of SCC in milk was definedas SCC in milk ≥200,000 cells/mL after two previous weeks with SCC <200,000cells/mL. Over the complete lactation, extending the VWP did not affect SCCelevations and occurrence of clinical mastitis per lactation or per cow per year. Theeffect of VWP on average SCC in the complete lactation depended on parity.Multiparous cows in VWP-125 had a higher SCC over the whole lactation comparedwith multiparous cows in VWP-50, no effect of VWP was found in primiparous cows.Dry-off antibiotic usage per year was lower in VWP-200 compared with VWP-50 formultiparous cows. In the first 6 weeks of the next lactation, cows in VWP-200 had ahigher SCC compared with cows in VWP-50. In conclusion, although extending theVWP resulted in prolonged lactations, no effects were found on number of elevationsin SCC, incidence of mastitis and average SSC in primiparous cows over the wholelactation. In multiparous cows, SCC during the complete lactation was higher forcows with VWP-125, but not for cows with VWP-200. Extending the VWP maytherefore be used to reduce the frequency of transition periods and the associateduse of dry-cow antibiotics, with limited impact on udder health, and a similaroccurrence of SCC elevations and clinical mastitis per year.