|If cows come into the dry period over-conditioned, they're already preconditioned to breeding delays in their next lactation.
It's been well documented that today's dairy cow, averaging 20,000 lb. per lactation, has a much harder time becoming pregnant than her great-great-grandmother.
One reason is that increased milk production. It requires greater blood flow through the liver, which dilutes the hormones in the bloodstream that cause the cow to cycle.
But modern management plays a role as well, says Ricardo Chebel, a veterinarian with the University of California, Davis. So there are things you can do to help cows cycle sooner and get pregnant faster.
"Managing body condition score [BCS] during the dry period is really important,” he says. If cows come into the dry period overconditioned, which is likely if they took longer to get pregnant, they're already preconditioned to breeding delays in their next lactation.
Cows with a high BCS three weeks prior to calving have lower dry matter intake during those weeks and drop much lower a day than cows with a BCS less than 3.5.
"At calving, high body–conditioned cows eat 50% less feed compared to a 30% drop for less obese cows,” Chebel says. At calving and on into early lactation, these fat cows are more prone to problems because they must mobilize even more energy reserves from their bodies.
The fatter cows are coming into the dry period, the more likely they are to lose condition. In fact, 75% of cows with a BCS of 4 or greater will lose condition during the dry period.
These cows are more likely to require treatment for retained placentas or metritis. As a result, days open are 10 days longer for cows that lose BCS during the dry period, Chebel says.
To prevent loss of body condition during the dry period, Chebel recommends the following steps:
- Feed and manage late-lactation cows so they don't enter the dry period overconditioned.
- Consider having an early dry-off if cows are becoming overconditioned, placing them on a lower-energy dry cow diet.
- If cows are dried off early, change them to a more energy-dense diet three weeks prior to calving.
- In the dry pens, minimize over-crowding and pen movements.
- If possible, house first-calf heifers and older cows separately.
- Ensure that cows have adequate bunk space, access to water and comfortable beds or lying space.
- After calving, offer the best-quality feed available, consistently formulated, to maximize feed intake.
The sooner cows return to positive energy balance, the sooner they will cycle and conceive.
Causes of reproductive failure in lactating dairy cattle