Proper management of replacement heifers begins at conception, according to SDSU specialist
Developing replacement heifers can start as early as conception, according to a South Dakota State University Extension cow/calf field specialist. Taylor Grussing tells producers the point when heifer development starts can vary by a producer’s goals and if they are raising or buying replacements.
“For some producers, it starts at birth when we notice that she’s a nice heifer and will hopefully make a good replacement,” she explains.
For other producers, she comments, it is careful genetic selection at breeding to produce heifer replacement prospects.
“If we buy replacements, it could start at weaning or when we are buying bred heifers,” she says.
“What is important to realize is that we develop heifers with a system that matches our environment, our goals and our wallet,” Grussing explains. “When talking about maximum versus optimum heifer development, it comes down to economics.”
“We want to get as many heifers in the herd bred as possible, but it comes down to doing that in the most economical way,” she says.
Top development
In a maximum development scenario, Grussing tells producers the heifers would be fed ad Librium, consuming as many nutrients as they want and growing to their optimum potential. Every heifer in the pen would be bred, the bulls would be left in for 60 or more days, pregnancy checking would be later, and open heifers would be rolled into a fall program to give them another opportunity to breed.
In an optimum scenario, replacement heifers would be limit-fed to reach a targeted weight while providing them with a supply of feed so they could grow efficiently. Only the oldest heifers would be bred, and the breeding season would be limited to 30 to 45 days.
“It is one of the best ways to put selection pressure on fertility, and it gives the females that breed early a competitive and economic advantage. Producers would also have the option of pregnancy checking the females early, and marketing the ones that are open,” she says.
“Which scenario a producer chooses depends upon their goals,” she continues. “If we sell replacement heifers, our goal is to get as many bred as possible. If we want to raise our own replacements, we will want to select ones that will stay in the herd longest because of development costs.”
Selection
With either option, Grussing says it is important to recognize the importance of selecting the right heifers to meet those goals.
She recommends keeping the oldest heifers and culling the late-born ones. She doesn’t recommend selecting the largest size for replacements.
“Larger-frame heifers may be the hard-doing ones later on. It could also increase the cow size of our herd. I would eliminate the small ones, the tall ones, the poor doers or heifers born to cows that have bad udders and feet,” she notes.
Many producers select replacement heifers from dams with proven performance.
“A fertile heifer will be a fertile cow,” she says. “Age is directly correlated to puberty. Puberty is a factor we can try and select for by physically monitoring the heifers to see which ones are mounting or riding one another.”
Most likely, producers should notice activity about 30 to 60 days prior to breeding.
“If we aren’t seeing estrus activity at that point, we may want to consult a veterinarian,” Grussing says.
Size at puberty can be influenced by age, preweaning growth and expected mature weight.
“It is an interaction of growth genetics, mothering ability, forage availability, and milk production,” she says. “Heifers given high energy rations will reach puberty at an earlier age.”
Some heifers fed a high energy ration too early in life may stall when it comes to puberty. Precocious puberty, which means they stop growing puberty, can occur at four to eight months.
“It can also be caused by underdeveloped frame and pelvic area, and they may stop cycling. These heifers may need help to start resuming their cycle later” she says.
Pre-breeding exams
Grussing recommends contacting a veterinarian to help analyze heifers prior to breeding. A reproductive soundness exam can help producers get an idea of how successful the heifer will be in terms of growth 35 to 45 days pre-breeding.
During this exam, the veterinarian pelvic measures the heifer and also calculates a reproductive tract score.
Producers can also calculate a body condition score, which is a great indicator of energy reserves the heifer has available. If a scale is available, they may also want to calculate body weight, evaluate frame score and make a functional soundness exam.
When the veterinarian calculates a reproductive tract score, it is scored from one to five, with four and five being the best scores. Grussing recommends culling any heifers that score one or two. Heifers that score a three may need more development time, she says.
“It gives us an idea on fertility, which has life-long impacts,” she says.
Heifers scoring below 145 centimeters pelvic measurement should also be culled.
“The veterinarian is measuring the width and height of the pelvis to see how big of a calf the heifer can have,” she explains.
Developing heifers
When developing heifers, Grussing says it is important to cull the right ones.
“Any with a small pelvic area, infantile reproductive tract, disposition, hard fleshing and soundness issues should all be culled. If we are custom developing heifers and selling them, we may also want to select heifers that are all uniform in color, and cull any with short ears or tails,” Grussing says.
She also recommends considering hybrid vigor.
“Research shows that heifers conceiving within the first 21 days of the breeding season stay in the herd the longest and raise the equivalent of an extra calf in their lifetime,” she says.
If the earliest born heifers calve early, 90 percent of them will calve within 15 to 20 days on either side of that when they are a cow, research shows.
Gayle Smith is a correspondent for the Wyoming Livestock Roundup. Send comments on this article to roundup@wylr.net.
