Effects of extending lactation for dairy cows on health, development and production of their calves

Extending the voluntary waiting period for insemination (VWP) in dairy cows is of interest to reduce the frequency of calving events and inseminate at a moment with less fertility problems. Little is known about the impact of extension of the dam’s VWP on the calf. The aim of this study was to evaluate the effect of extending VWP of dams on growth, metabolites, and production performance of their offspring. Holstein-Friesian heifer calves (N = 62) from cows with different VWP 50, 125, or 200 days were monitored from birth until 100 days in milk (DIM) after their first calving and regrouped based on their dam’s calving interval (CInt) into 3 groups: CInt_1: < 409 days; CInt_2: 409-468 days; CInt_3: > 468 days. Birth weight did not differ among heifer calves of the 3 CInt groups (P = 0.34). During the rearing phase, heifer calves from CInt_1 tended to have a higher plasma glucose concentration than CInt_3 (P = 0.06). However, BW did not differ among CInt groups (P = 0.52) . During the first 100 DIM, heifers born to primiparous dams with CInt_2 had a lower FPCM compared with heifers in the other 2 groups (both P = 0.02); heifers born to primiparous dams with CInt_3 had a higher BW compared with heifers in the other 2 groups (both P < 0.01). In conclusion, extending VWP of dams did not affect growth of heifer calves during the rearing phase, but affected body condition and milk performance of heifers during the start of their first lactation, especially those from primiparous dams.