Steady weight best for reproducing cows

Cows that maintain an average body condition score year round are more likely to get pregnant, have minimal calving difficulties and produce live calves, says large animal professor and researcher Dr. Cheryl Waldner of the Western College of Veterinary Medicine (WCVM).

"Beef cows perform best when they maintain a condition score of 5 to 6 throughout the year with no dramatic losses after calving," says Waldner, referring to a nine-point body condition scoring (BCS) system commonly used in the cattle industry.

Under the system, a score of 1 is given to extremely thin cows while a score of 9 describes obese animals. These recommendations would be similar to a 2.5 to 3.0 on the comparable five-point system used in some areas.

Waldner's information is based on her analysis of data collected as part of the Western Canada Beef Productivity Study. Waldner was principal investigator for the massive study that involved more than 200 herds in Saskatchewan, Alberta and northern British Columbia.

Previous recommendations for managing BCS were based on experimental studies involving research herds with most of the work done in the U.S. "The big difference with our data is that it was collected from more than 30,000 beef cows in Western Canada," explains Waldner. "This research involved real herds under actual weather and feed conditions that we see in the West."

By visually inspecting and palpating cows to determine each animal's fat stores, veterinarians and producers can monitor a herd's nutritional status. The goal is to keep the cows at the necessary nutrition level, optimizing herd performance and profitability without overfeeding.

"We're looking for the ‘sweet spot': the best body condition score for a cow to be at during critical points in the production year to optimize her chance of getting pregnant, carrying that calf to term and delivering a healthy calf on the ground," explains Waldner.

During the western Canadian beef study, veterinarians collected a wide range of data — including BCS — from thousands of cows at three intervals in 2001 and 2002.

By analyzing all the breeding and calving records for individual cows in the study, Waldner was able to pull out the separate effects of BCS at different times of the year and determine critical cutoff points.

Here are some of Waldner's additional findings about BCS based on her data analysis:

In the fall, cows that score at least 6 are most likely to be pregnant and cows that are 5 or better are less likely to abort than cows that are thinner.

    • Cows with scores of at least 5 just before calving have the best chance of delivering live calves and becoming pregnant for the following year.

    • Contrary to what some people believe, there were fewer calving difficulties for cows with BCS of 5 or more before calving than for very thin cows. "In fact, cows that gain weight between pregnancy checking and calving seem to do better," says Waldner. "The really thin cows that score 3 or less are much more likely to have calving issues than cows that have a score of 7 or more."

    • Cows that score between 5 and 7 and do not lose weight after calving or during the breeding season are most likely to get pregnant. They will also get pregnant faster than cows that are thinner and lose weight during this critical period.

    • Thin cows with BCS less than 5 are less likely to get pregnant, take longer to get pregnant and are more likely to abort or have stillborn calves. Two- to three-year-old cows (ones with their first and second calves) and cows over 10 years of age are more likely to be thin.

Waldner adds that these findings underline the value of body condition scoring individual cows: "Paying attention to the group as a whole makes sense, but these numbers confirm that's it's worth taking the time to walk through the herd and assess the condition of individual cows."

The results also suggest caution about some common beliefs. For example, many people assume cows that are at risk because they are thin in the spring will catch up in the summer. "If there's no direct intervention, the same cows are more likely to be thin in the fall," points out Waldner. "It's worth the effort to segregate at-risk animals when possible and provide additional feed before their performance is affected."

Another common misconception is that once cows get pregnant, producers can allow their condition to drop below critical values in the fall and then increase their feed just before calving without having any adverse effects. In contrast, the data indicates that it's better to keep the animals' condition at 5 to 6 throughout the year.

If feasible, Waldner advises producers to check the body condition scores on individual cows at least three times a year: before calving, before the breeding season and during pregnancy testing.

"But if producers can only do this once, it's best to body condition score the cows right before calving so they can make changes to their feed before the next breeding season."

Waldner acknowledges that body condition scoring cows in winter is more difficult if the cows aren't going through the chute for routine processing. It's also harder to assess them from a distance because of their heavy hair coats. But visual assessment of individual animals is still valuable and can make a huge difference to those thinner cows that aren't faring so well in the cold weather.

"It's your chance to pick out the cows that need extra attention and change their feed before it's too late."
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