Heifers take longer to start cycling after having their first calf than mature cows do. This means that if heifers are bred to calve at the same time as the main cow herd they are already behind coming into their second breeding season.
“It’s just basic biological math,” says Dr. John Campbell, veterinarian, and Professor in the Department of Large Animal Clinical Sciences at the Western College of Veterinary Medicine. He points out that this is why a lot of what would be second calvers drop out of the herd – they simply don’t have enough time to start cycling and rebreed.
black bull with heifers on straw during breeding season
Photo: Stacey Domolewski
To calve at the same time the following year, cows and heifers need to be bred about three months after a calf is born. This is easier in cows as they return to estrus 50-60 days after calving, giving them plenty of time to get bred in the first cycle after bulls are turned out. It is more challenging for heifers because they take 80-100 days to return to estrus meaning they may not have even started cycling again prior to bull turn out.
Breeding heifers prior to cows does lengthen the overall calving season, but Campbell points out that this can have advantages. Heifers are more likely to have problems calving and, with less animals calving during the same time period, producers have more time to closely monitor and deal with any potential issues. If not using a strategy like the Sandhills Calving System, having heifers calve first also reduces the disease burden on these calves. Heifers are able to calve on bedding areas when they are fresh and at their cleanest.
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