Don’t Replace Replacements –Focus on Proper Nutrition and Profitability

Proper nutrition and management sets young females up for lifetime reproductive performance.

The beef business is high-tech these days, from genome mapping and marker-assisted selection to sexed semen and instrument grading. The cornerstone of the industry, however, is still reproduction. It is the single most important factor for profitable beef production, reminds Rick Funston of the University of Nebraska West Central Research and Extension Center in North Platte.

Replacements represent future profitabilityOn the female side, replacement heifers represent the future profitability and genetic improvement of a herd. But they also represent management and economical challenges for producers, because they won’t produce a return for more than two years.

An easy way to consider a replacement’s nutritional requirements is to divide them into four phases: weaning; weaning to breeding; breeding to calving; and calving to rebreeding. Then, for each phase, consider a heifer’s weight, her nutrient requirements, and necessary forage and feed quality.

At weaning, the young females selected as herd replacements need the same attention, including vaccinations, as calves that will be marketed. Introducing immune animals into the breeding herd lessens the risk of disease spread.

The nutrient needs of replacement heifers differ from those of mature cows because they are growing and developing. For optimum results, the younger females need to be sorted, fed, and managed separately from the herd.

During the last several decades, substantial research contributed to the guidelines of developing heifers to reach 60 to 65 percent of mature body weight pre-breeding. This was to ensure heifers reached puberty and, thus, maximized pregnancy rates, particularly by being fed high-energy diets.

Current research, however, has re-evaluated this approach based on sub-stantial changes that have occurred over time in cattle genetics and the economy. It contends that, while intensive heifer development systems may maximize pregnancy rates, they don’t necessarily optimize profit or sustainability.

More recent research, including heifer development studies conducted at the University of Nebraska (Funston and Deutscher, 2004) and the USDA Agricultural Research Service Fort Keogh Livestock and Range Research Lab, Miles City, Mont., shows that heifers can be developed to lighter than traditional target weights at breeding (around 53 to 58 percent of expected mature weight) without negatively affecting profitability or future productivity.

Researchers, including Funston, suggest that one reason reproductive performance has not been drastically impaired by feeding to lower target weights may relate to genetic changes in age of puberty.

Kansas State University and Fort Keogh studies show that young females can be grown at a slower weight gain early on and then get caught up towards the end. Or they can be grown in a stair-step fashion, gradually increasing their growth rate up until the breeding season.

The most important thing is to make sure heifers are in a positive energy balance going into breeding season, and are even picking up pounds, but are not losing weight. The goal is to get the heifer bred and settled for a live calf born early on in calving season.

To this extent, 20-plus year’s research at Fort Keogh proved that heifers that produced a calf early in the calving season continued to calve early and wean heavier calves throughout their lifetimes. The lifetime reproductive performance of heifers that produced their first calf late in the calving season was more erratic, and they did not calve every year.

Good nutrition is paramount both pre- and post-calving

Once bred, replacements still need to be managed for continued growth and development so they calve unassisted as two-year-olds. Funston says that many calving problems can be eliminated if heifers are of adequate size pre-partum.

“Their weight at first calving should be approximately 85 to 90 percent of their expected mature weight,” he advises. First-calf heifers should have a body condition of 5 to 6 at calving through re-breeding to assure optimal reproductive performance.

Balanced nutrition – protein, energy, minerals, vitamins, and water – is the key to optimizing production. And the critical times for mineral supplementation are 45 days prior to calving, through breeding season, and prior to weaning.

Nutritional demands increase greatly in late gestation and even more in early lactation. Reproduction is of very low priority when nutrient partitioning is considered, and that is why cows in thin body condition often don't rebreed.

“The plane of nutrition during the last 50 to 60 days before calving has profound effects on postpartum interval,” Funston says. “Body condition at calving is the single most important factor controlling when a beef heifer will cycle after calving.”

Pre-partum body condition score correlates with factors such as postpartum interval, services per conception, calving interval, milk production, weaning weight, calving difficulty, and calf survival.

Breeding heifers ahead of the cow herd is a worthwhile strategy, as properly developed and managed heifers generally have a 20- to 30-day longer postpartum interval versus older cows. Funston says breeding replacements this much earlier gives them additional time to return to estrus and rebreed with the mature cows the next year. But these heifers need to be managed separately after calving, or early breeding is of no benefit.

He explains, “It is important to manage these heifers separately for two reasons: earlier calving will likely mean that pastures are not available as soon, and you'll need to supply additional nutrients. Also, nutrient requirements (percentage of ration) are higher for first-calf heifers than for mature cows.”

As already stated, calving difficulty also affects the post-partum interval. Heifers encounter greater calving stress than do mature cows, and that’s one reason why low birth-weight bulls with high accuracies are a must for breeding younger females.

Calving difficulty and time of intervention research from Fort Keogh indicates that females that experience calving difficulty take longer to cycle than those that don’t. The length of time before intervention in a difficult birth also affects cyclicity. According to Ft. Keogh researchers, for every 10 minutes beyond the time period in which assistance is needed, two days more are added to the time frame in which it takes a cow to begin cycling. And that’s not to mention the affects that difficult births can have on calves.For these reasons and more, Funston encourages producers to pay strict attention to their herd’s females’ pre- and post-calving phases. “Management decisions made during these time periods will greatly influence profitability of beef cattle operations.”

He explains, cows that cycle earlier have a greater chance of getting bred during a limited breeding season. As a result, conception rates will be higher, and calves born earlier in the season are older and heavier at weaning.

“The length of breeding season will influence uniformity of your calves and, therefore, influence their value at weaning,” Funston relays. “To have a short breeding season, it is vital that cattle cycle early in the season.” Thus proper nutrition and optimum body condition are two keys to success.

Focusing on Replacement Heifer Success

For 13 years, Missouri beef producers have offered in- and out-of-state customers a trusted, quality source for herd additions through what’s known as the Missouri Show-Me-Select (SMS) Replacement Heifer Program™.

This replacement development and marketing program is a state-wide educational effort emphasizing a Total Quality Management-approach to reproduction and beef-cow management. Since its inception in 1996, the program has seen state beef producers increasingly adopt management practices that offer the potential to improve their herd’s long-term reproductive efficiency.

Says founder Dr. David Patterson, state beef Extension specialist and SMS reproductive specialist, “The original intent was focused on trying to improve management of replacement heifers to improve what happened during their first calving period and rebreeding. The marketing aspect was a spin-off of this educational intent.

”To become an ‘SMS-certified heifer’, females have to meet qualifications and requirements. All undergo a comprehensive health program, including clostridial, respiratory, and reproductive vaccinations, and must meet minimum standards for reproductive soundness, pelvic size, body condition, and weight.

Heifers are guaranteed bred to easy-calving bulls of known identification and breed, with complete EPD information. All sires used naturally or artificially meet the program’s birth weight or calving-ease EPD requirements.

Replacements that sell in an SMS-trademarked sale must weigh a minimum of 800 pounds and body condition score at least a 5. They are screened for frame, muscle, structural soundness, disposition, and general sale acceptance. The females are sorted into lots according to calving dates and body-type similarities.

Since 1996, the SMS has enrolled more than 85,000 heifers from 679 farms. Oftentimes producers in their first year of the SMS have found out that what they assumed to be adequate body condition and weight on replacement heifers, wasn’t enough.

According to Patterson, there has been an improvement, in terms of nutritional development, in heifers that are in the program. “This, and a structured health program, are the two obvious things off the bat.” Some 80 percent of producers are also using synchronization and A.I. on heifers.

Surveys show that buyers appreciate the assurances offered by SMS replacements, from their health status to lower risk for calving difficulty in general. For more information on the SMS, see http://agebb.missouri.edu/select.