Get the Young Ones Bred
A focus on nutrition and managment is essential to get young females bred. Here, experts share strategies.
With breeding season looming, will your replacement females and two-year-olds be cycling and ready to breed? Cattle reproduction experts agree that these young females can present a challenge at breeding time, and thus require extra attention – and effort – to ensure high conception and pregnancy rates.
The goal is to ensure these females are cycling, says Twig Marston, who points out, “Non-cycling females don’t have a chance of breeding.” Marston is a former Kansas State beef specialist and is currently director of the University of Nebraska-Lincoln’s Northeast Research and Extension Center at Norfolk.
Here, he and other specialists share their strategies for successfully preparing replacement and two-year-old females for the breeding season:
Strategy 1: Monitor body weight.
Replacement females need to reach puberty and be cycling prior to the start of the breeding season. Research indicates that developing females to reach a target weight of 55 to 65% of their mature weight should accomplish that, reports Marston.
Bob Larson, professor of production medicine at Kansas State University concurs, saying, “Some heifers will reach puberty at a lighter percentage (55%) of their mature body weight than other heifers but, to be on the safe side, I recommend aiming to have heifers weigh 60% of their expected mature weight by 12 months of age.
”Therefore, if heifers mature at 1,100 pounds (lbs.), they’ll need to weigh 660 lbs. as a yearling; if they mature at 1,400 lbs., they’ll need to weigh 840 lbs.
Larson notes that post-weaning nutrition is critical to help heifers reach their target weight. Some supplemental grain or byproduct feeds may be necessary to help achieve the targeted weight gains, particularly if heifers are grazing dormant forage and if winter weather is severe.
On the flip side, Marston and Larson caution against getting heifers excessively heavy. Larson says research has indicated that heifers in a body condition score (BCS) 5.5-6 have the highest fertility, while those with either less or greater amounts of fat cover have reduced fertility.
“Heifers that are a BCS 7 or higher have a higher feed bill than properly developed heifers and may be less likely to become pregnant early in their first breeding season,” Larson reports.
Strategy 2: Provide nutrition to minimize post-partum interval for first-calf heifers.
As replacements have their first calf and make the transition to “two-year-olds,” monitoring body condition continues to be an important factor to ensure rebreeding success. Tom Geary, with the USDA Agricultural Research Service (ARS) in Miles City, Mont., explains, “We are trying to rebreed a cow that has not yet reached her mature weight and is often faced with the task of consuming enough energy to satisfy needs for growth, lactation, and maintenance.
”On top of all that, the young cow is typically required to do this when gener-ally only poor quality forage is available. And, that’s when problems can occur.
“Poor body condition score prior to and immediately after calving will postpone the return to estrus and reduce fertility for cows,” says Marston. He adds, “Difficult birthing and extreme birthing stress has also been shown to delay the return to cycling and lengthen the post-partum interval (PPI).
”Geary notes that some producers breed heifers three weeks before the mature cow herd to allow the younger females a longer PPI for recovery. But this can often stretch out the calving season and, afterward, these heifers may have an even longer wait for green grass and the necessary nutrition for breed-back.
Rather, Geary suggests that it is important for heifers to have sufficient energy stores before calving. “It’s very difficult, if not impossible, to make those up afterward.
”He adds that prepartum nutrition – especially during the 50-60 days before calving – is the primary controller of PPI length. His rule of thumb is for heifers to be in a BCS of 5 to 6 at calving.
Marston adds, “Feeding cows properly during the last trimester has been shown in numerous research projects to greatly enhance early-season pregnancy rates. Body condition score is primarily controlled by energy consumption. Producers need to also consider protein, vitamin, and mineral nutrition as well.”
Strategy 3: Utilize technology and have a plan.
Advancements in artificial insemination (AI) genetics as well as synchronization products and protocols can all be useful tools in ensuring rebreeding success, suggest these experts. As examples, administering a progestin-containing product or synchronization program to initiate estrous cycles can increase the number of cycling females and help get them bred earlier.
Likewise, selecting genetics for calving ease can help minimize calving difficulty and related breed-back issues. Moreover, research has shown feeding ionophores can help heifers reach puberty at a lower percentage of their mature weight and help shorten the PPI in cows.
A solid herd-health protocol that includes regular vaccination and deworming schedules is also beneficial in optimizing herd reproductive performance. Also worth mentioning is pregnancy checking, by traditional palpation or ultrasound, to help detect reproductive problems in preparation for the next breeding season.
Marston says, “The bottomline is to control the length of the breeding season and, whether you are using AI or natural service, have a plan for success.
”Geary adds, “Controlling the length of the breeding season is critical. It is even more important in heifers than it is for the rest of the cow herd because it sets them up to be successful within that operation.
”Marston concludes, “Know your cows and know your conditions. Have the flexibility in your management plan to meet the challenges of weather, forage production, and genetic potentials.”