Management practices to increase reproductivity in younger females
Though genetics play an important role in reproductive success, there are a variety of management practices producers can implement in order to improve the fertility of their heifer herd.
First and foremost, a focus on nutrition can have an impact on heifer fertility. Heifers fed for controlled weight gain will achieve reproductive puberty at the correct time.
However, heifers that fail to receive adequate nutrition are slower to reach puberty. For all females, a low body condition score inhibits their pregnancy success throughout their lifespan.
Additionally, research indicates heifers that reach proper body weight by the start of their first breeding season, have more reproductive success.
“A target weight from 55 to 65 percent of the heifer’s expected mature weight is a range that you might use to determine whether they’re on an adequate plane of nutrition,” Eldon Cole, University of Missouri Extension livestock field specialist, said.
Determining the heifer’s reproductive readiness through reproductive tract scores assists in improving conception rates.
Reproductive tract scoring systems range from a score of one (pre-pubertal, infantile tract) to five (pubertal, corpus luteum present).
“A target weight from 55 to 65 percent of the heifer’s expected mature weight is a range that you might use to determine whether they’re on an adequate plane of nutrition,”
– Eldon Cole,
University of Missouri Extension livestock field specialist
Typically, four to six weeks prior to a heifer’s first breeding is the right time to assess her reproductive tract score.
“Cull heifers that have an infantile reproductive tract score of one,” Cole stated.
“Heifers with a two-score are estimated to be over 30 days from reaching puberty and may need to be culled.”
The implementation of an estrous synchronization program can help improve fertility in some heifers. The progestins used induce peripubertal heifers to start the hormonal changes associated with achieving puberty. “Starting heifers on an estrous synchronization program will spur some two and three scoring heifers to cycle,” Cole explained. “Ideally, we want 50 percent of the heifers to be tract scores four and five when scored before the synch program begins.”
Livestock producers who utilize a synchronization program reap an additional benefit for their operation. If the heifer herd is synched, all heifers will be inseminated early in the breeding season. Come calving season, first-calf heifers will all be delivering their calves during a similar timeframe.
Taking a close look at the heifer’s genetics will help producers get an idea of her fertility potential. Most breeds will reflect heifer fertility in the Heifer Pregnancy EPD. The Heifer Pregnancy EPD determines the probability or chance of a sire’s daughters becoming pregnant during a typical breeding season.
Cole suggested if producers are concerned about a sire’s daughters’ differences in getting bred early in the breeding season, they should look closely at their EPDs.
“The top 5 percent of Angus EPDs are at 15.8 percent, while the poorest 5 percent have an EPD of 5.6 percent or below, so you can be justified in spending some time looking at Heifer Pregnancy if your breed has that EPD available,” Cole explained.
In the Ozarks, where fescue fills many fields, cattle producers need to keep in mind fescue toxicity can also create problems getting heifers developed for high fertility. If producers suspect this is the case for their heifer herd, they should consider moving the heifers to an alternate non-toxic fescue pasture. There are also supplements available that will dilute the fescue toxin levels.
Keep an eye on the physiological makeup of the heifer as well. Heifers that are late or slow hair shedders will likely have elevated body temperatures, resulting n lost pregnancies. Making sure the heifers have plenty of shade will help them keep their body temperatures regulated.
