The coventional wisdom is that if a pre-fresh period of 21 days is good enough for mature cows, it should be plenty long for first-calf heifers as well.
Keep in mind that heifers are facing pregnancy and calving for their very first time, says Pat Hoffman, a heifer specialist with VitaPlus. Everything is new to them, and they face a whole host of challenges that mature cows simply don’t have. That 21-day pre-fresh period for heifers may only be 11 effective days when you take these other factors into account.
For starters, gestation length is affected by genetics, calf gender, twinning, age of dam and season of year. The average gestations length for a Holstein heifer is assumed to be 278 days plus or minus 5 days. (Mature cows’ gestation length is 279 days.) But heifers bred with sexed semen tend to calve 1.7 days sooner. Heat stress can shorten gestation length by 3 to 4 days, and genetic predicted transmitting abilities (PTAs) can shorten gestation length by as much as 3 days. Calving ease sires, also typically used with heifers, can further shorten gestation length by another two days.
If you add all of these up, that can shorten the gestation length by 10 days. “Pretty soon, that 21-day pre-fresh period becomes 11 days,” he says.
In addition, it may take heifers three to five days simply to learn where to find feed and water after a she is moved into the transition pen. And it may take up to a week for her to find her place in the social pecking order of the pen. Then, if you mix first-calf heifers with older, more mature cows, the heifers will be socially disrupted each time there is a pen move and another older cow is added to the group, says Hoffman.
“If we shorten the pre-fresh period [with all these biological factors] and have pen moves, the heifer doesn’t have time to ‘learn’ the pen,” says Hoffman. Consequently, she will likely not be eating as well as she needs to or even getting enough water.
All of these factors can affect her transition from late pregnancy through calving and early lactation. It’s little wonder some heifers struggle after calving. And problems can be compounded if heifers are then grouped with older, mature cows right after calving.
Hoffman recommends that farmers consider moving first-calf heifers into the pre-fresh group at least 28 days prior to their expected calving. If possible, heifers should have their own pre-fresh group so that they are not constantly being socially disrupted with the addition of older, mature cows. After calving, heifers also should not be grouped with older cows.
Hoffman also recommends that pre- and post-fresh diets be adequately supplemented with antioxidants to reduce oxidative stress on the cellular level. Reducing oxidative stress reduces inflammation, and allows the animal to function normally and digest feed properly. That, in turn, allows her to convert feed into milk as she was bred to do.
You can view Pat Hoffman’s Powerpoint presentation on heifers here.