Early calving paradoxes

Biologically, heifers can handle calving under 24 months. Are you up to the challenge?
by Paula Mohr

When weighing the pros and cons of early heifer calving, consider these three points:

• Heifers grow.
• Economics—low.
• Management—whoa!

The critters will put size on—some more, some less—depending on how you feed them. When you calve them younger, you'll put more money in your pocket. Research shows that heifer-rearing costs increase $50 to $60 per animal each month that calving is delayed. Plus, you need more herd replacements when you calve older animals.

And as you alter your management to lower calving ages, be prepared for an educational ride. Closely monitor body condition and breeding efficiency. Lead, don't just hang on. You don't want to handicap your heifers with excess weight or breeding delays.

Pat Hoffman, dairy specialist, University of Wisconsin-Marshfield, says early calving isn't achieved simply by breeding heifers sooner. "Growth rates of heifers must be accelerated to assure heifers are of adequate body size at calving," Hoffman says.

If heifers are undersized, they'll give less milk and be at higher risk for problems at calving (dystocia). Research shows increased dystocia has a direct effect on retained placenta, metritis and breeding efficiency, and ultimately herd culling.

On the flip side, fat heifers are also prone to dystocia, fat mobilization, ketosis, displaced abomasums and decreased dry matter intake. "You can't just look at one thing," Hoffman says. "There's a domino effect."

After compiling research, Hoffman came up with a chart suggesting the optimum body size of Holstein replacement heifers at calving (see table). "Producers should pay special attention to meeting skeletal measurements defined in the table because they may be more related to milk yield than body weight when heifers calve at ages less than 24 months," he says.

The ultimate goal is to accelerate heifer growth while maintaining a healthy weight. This is where biology can get touchy.

"The faster a heifer grows, the faster a heifer becomes fat," Hoffman says. Yet an animal needs to attain a certain size before she should be bred.

To increase growth without increasing body fat, some researchers have looked at adding undegraded intake protein (UIP) to heifer diets. But results have been inconsistent, either improving or having no effect on growth. Some scientists have used bovine somatotropin (BST) and seen positive results. BST increases growth and body protein accretion. Both need further research.

"Body condition scores at calving are indicative of what's going on," Hoffman says. "If they're above 3.5, heifers don't seem to do well. They aren't able to carry condition as well as cows."

To ensure heifers in good body condition, Hoffman recommends following current heifer growth guidelines, based on age and weight. "If a heifer follows the height plane fairly well, she won't be excessively conditioned," he says.

Breeding. Accelerating growth is half of the equation when lowering calving age. The other? Breeding efficiency.

"If heifers are fed to calve at 22 months and don't conceive until 15 to 16 months of age, heifers will be on feed an extra 60 to 90 days," Hoffman says. "Breeding delays can result in obese heifers, often weighing more than 1,500 lb. at calving." Review your reproductive management program with your veterinarian to get ideas on how to improve it. Breeding efficiency must be nearly perfect to avoid delayed conception, he says.

As you strive to lower the calving age in your herd, Hoffman offers the following suggestions:

Reduce the calving age slowly. Don't assume you'll jump from 25 to 22 months in a single bound. "Get comfortable with the changes as you go along," Hoffman says. "Find out where the roadblocks are."

Capitalize on the early growth of heifers in the first 12 months. "Heifers have most of their efficient bone and organ growth in their first year of life," he says. "Take advantage of that by providing a dry, clean environment. Feed ionophores. Follow all those good management practices we preach. As the animals get older, the window of opportunity for growth closes."

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