Effect of voluntary waiting period on metabolism of dairy cows in different stages of lactation

During the transition around calving, dairy cows have an increased risk for diseases. Anextended calving interval by extending the voluntary waiting period for first inseminationafter calving (VWP) reduces the frequency of these transitions. An extended VWP could beassociated with altered metabolism, due to delayed gestation and more time in latelactation with lower milk production. Low milk production end lactation could beassociated with increased body condition end lactation, which could increase the risk fordiseases during the subsequent transition around calving. Thisstudy evaluated metabolism for individual cows with different VWP during different stagesof lactation and during the subsequent transition around calving. Moreover, relationsbetween cow characteristics before insemination and lactation performance wereanalyzed, to identify cows with lower risk for low milk production and increased bodycondition end lactation. Holstein-Friesian cows (N=153) were blocked and randomlyassigned to a VWP of 50, 125, or 200 days (VWP50, VWP125, or VWP200), and followedfrom calving until 6 wk after subsequent calving. Weekly, from wk -2 until wk 6around both calvings, serum samples were analyzed for non-esterified fatty acids (NEFA),β-hydroxybutyrate, glucose, insulin and insulin-like growth factor (IGF-1). During lactation,serum samples were analyzed for insulin and IGF-1 every 2 wk. Fat-and-protein-correctedmilk (FPCM) and body weight (BW) gain were calculated weekly. Cows were divided in twoparity classes (primiparous and multiparous). During gestation, multiparous cows inVWP200 had greater plasma insulin and IGF-1 concentration and lower FPCM comparedwith cows in VWP50 or VWP125, and greater BW gain compared with cows in VWP50 (3.6vs 2.5 kg/wk). During gestation, primiparous cows in VWP125 had greater plasma insulinconcentration compared with cows in VWP50, but the VWP did not affect body conditionor FPCM. During the first 6 wk of the subsequent lactation, multiparous cows in VWP200had greater plasma NEFA concentration compared with cows in VWP125 or VWP50 (0.41vs 0.30 or 0.26 mmol/L). For primiparous cows, the VWP did not affect the metabolism,BW, or FPCM during the subsequent lactation. Independent of VWP, higher milkproduction and lower body condition before insemination was associated withhigher FPCM and lower body condition end lactation. Variation in thesecharacteristics among cows could call for an individual approach for extended VWP.