Effects of extended voluntary waiting period from calving until first insemination on body condition, milk yield, and lactation persistency

摘要

A 1-yr calving interval (CInt) is usually associatedwith maximized milk output, due to the calving-relatedpeak in milk yield. Extending CInt could benefit cowhealth and production efficiency due to fewer transitionperiods per unit of time. Extending CInt can affect lactationperformance by fewer days dry per year, delayedpregnancy effect on milk yield, and greater milk solidyield in late lactation. This study first investigated theeffects of 3 different voluntary waiting periods (VWP)from calving until first insemination on body weight,body condition, milk yield, and lactation persistency.Second, individual cow characteristics in early lactationwere identified that contributed to milk yield and persistencyof cows with different VWP. Holstein-Friesiandairy cows (n = 154) within 1 herd were blocked forparity, calving season, and expected milk yield. Cowswere randomly assigned within the blocks to 1 of 3 VWP(50, 125, or 200 d: VWP50, VWP125, or VWP200,respectively) and monitored through 1 complete lactationand the first 6 wk of the subsequent lactation, oruntil culling. Minimum and mean CInt (384 vs. 452 vs.501 d for VWP50 vs. VWP125 vs. VWP200) increasedwith increasing VWP, but maximum CInt was equalfor the 3 VWP. Fat- and protein-corrected milk yield(FPCM) was analyzed weekly. Milk yield and FPCMwere also expressed per day of CInt, to compare yieldsof cows with different VWP. Persistency was determinedbetween d 100 and d 200 of the lactation, aswell as between d 100 and dry-off. Values are presentedas least squares means ± standard error of the mean.During the first 44 wk of lactation, VWP did not affectFPCM yield in both primiparous and multiparouscows. The VWP did not affect milk yield per day ofCInt. The VWP did not affect FPCM yield per dayof calving interval for primiparous cows. Multiparouscows in VWP125 had FPCM yield per day of CInt similarto that of VWP50. Multiparous cows in VWP200had lower FPCM yield per day of CInt compared withVWP50 (27.2 vs. 30.4 kg/d). During the last 6 wk beforedry-off, cows in VWP125 had lower yield comparedwith cows in VWP50, which could benefit their udderhealth in the dry period and after calving. Persistencywas better for cows in VWP200 compared with cowsin VWP50 (−0.05 vs. −0.07 kg/d). Body weight wasnot different among VWP groups. Multiparous cowsin VWP200 had a higher body condition score in thelast 3 mo before dry-off and the first 6 wk of the nextlactation, compared with multiparous cows in VWP125and VWP50. The VWP could be extended from 50 dto 125 d without an effect on daily yield per day ofcalving interval. Extending VWP until 200 d for primiparouscows did not affect their daily milk yield, butmultiparous cows with a 200-d VWP had a reducedmilk yield per day of calving interval and an increasedbody condition in late lactation and the subsequentlactation, compared with multiparous cows with a 50-dVWP.