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Oklahoma Agricultural Experiment Station research shows body condition at the time of calving is the most important factor affecting rebreeding performance in normally managed beef cow herds. (Photo by Todd Johnson, OSU Agricultural Communications Services)

Spring-calving beef herds face nutritional challenges

Tuesday, March 12, 2019

Late winter and early spring is the most challenging time of the year relative to the nutrition of spring-calving beef cows, meaning cow-calf producers need to pay special attention to their livestock’s body condition.

“Unless cool season grasses are available, this is a season where maintaining or gaining body condition on spring calving cows is really quite difficult,” said Glenn Selk, Oklahoma State University Cooperative Extension emeritus animal scientist and editor of the university’s popular Cow-Calf Corner newsletter.

Warm season grasses have not yet begun to grow. What little is left of dormant grasses is a low-quality feed. Cows cannot – or will not – consume a large amount of standing dormant grass at this time year.

“If the only supplement is a self-fed, self-limited protein source, the cows may become very deficient in energy,” Selk said. “Consider the instructions that accompany self-fed supplements: They are to be fed along with free-choice access to adequate quality forages.”

Selk adds there is another factor that compounds the problem. A small amount of winter annual grasses may begin to grow in native pastures. These are the first tastes of green grass many cows have seen since last summer.

“The cows may try to forage these high moisture, low-energy density grasses, in lieu of hay or cubes that are more energy dense,” Selk said. “The sad result is the loss of body condition in early lactation beef cows just before the breeding season is about to begin.”

The science says...

Research conducted under the auspices of OSU’s statewide Oklahoma Agricultural Experiment Station system shows body condition at the time of calving is the most important factor affecting rebreeding performance in normally managed beef cow herds.

“Body condition changes from the time the cow calves until she begins the breeding season can play a significant role in the rebreeding success story,” Selk said. “This appears to be most important to cows that calve in the marginal body condition score range of four or five.” 

OSU animal science research conducted under principal investigator Bob Wettemann and published in the 1987 Journal of Animal Science, Supplement 1:63, illustrates the vulnerability of cows that calve in the body condition score of five.

Two groups of cows began the winter feeding period in similar body condition and calved in very similar body condition. The average body condition score was 5.3 to 5.4. However, after calving and before the breeding season began, one group was allowed to lose almost one full condition score. The other group of cows was fed adequate amounts to maintain the body condition they had prior to calving.

“The difference in rebreeding rate was dramatic, 73 percent to 94 percent,” Selk said. “Cows that calve in a body condition score of five are very vulnerable to weather and suckling intensity stresses. Cow-calf producers must use good nutritional strategies after calving to avoid disastrous rebreeding performance.”

OSU Cooperative Extension recommends...

Cows should calve in moderate-to-good body condition, scores of five or six, to ensure good rebreeding efficiency.

“Ideally, cows should be maintaining condition during mid to late pregnancy and gaining during breeding,” Selk said. “The goal of the management program should be to achieve these body conditions by making maximum use of the available forage resource.”

OSU recommends producers continue feeding a source of energy, such as moderate-to-good quality grass hay free choice or high energy cubes until the warm season grasses grow enough to provide both the energy and protein the lactating cows need.

“The price of feed may be high, but the cost of losing 21 percent of next year’s calf crop is even greater,” Selk said.

Oklahoma is the nation’s fourth-leading producer of cattle and calves, according to USDA National Agricultural Statistics Service data.

The Oklahoma Agricultural Experiment Station system and Oklahoma Cooperative Extension Service are the university’s two state agencies, administered by OSU’s Division of Agricultural Sciences and Natural Resources. Both are key elements of OSU’s state and federally mandated teaching, research and Extension land-grant mission.

By Donald Stotts

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