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Pre-Breeding Exams For Replacement Heifer Selection Equals Higher Pregnancy Rate, More Profitability
WEST PLAINS, MO.
Producers should also strive to have cows that are productive in the herd for many years. According to Elizabeth Picking, field specialist in livestock with University of Missouri Extension, for cow-calf producers, it is ideal to have one healthy calf on the ground per cow per year.
“On average, a cow has to stay in the herd for six years for the producer to break even on that cow's initial investment along with yearly maintenance costs. With this in mind, proper selection of replacement heifers is key to have cows that produce a calf every year for many years,” said Picking.
To set that heifer up for life-long success, heifers need to reach puberty by 15 months to potentially calve at 24 months. However, 35 percent of heifers have not reached puberty at 15 months of age.
“Identifying these later maturing heifers can be done by having a pre-breeding exam done. Pre-breeding exams are performed by veterinarians and include a reproductive tract score as well as a pelvic measurement,” said Picking.
The reproductive tract is scored from 1 to 5 in relation to the heifer's puberty status.
A tract score 1 is given to heifers with an infantile or underdeveloped tract. A tract score 2 is given to heifers that are not close to cycling but not as underdeveloped as a score 1. A tract score 3 is assigned to heifers that are near puberty but not yet cycling. A tract score 4 is for heifers that have reached puberty and are cycling in the first phase of the estrous cycle where follicles are developing but an oocyte (egg) has not ovulated. A tract score 5 is assessed by a heifer who is cycling and is in the second phase of the estrous cycle during which an oocyte has ovulated and a structure termed corpus luteum (CL) is present on the ovary.
“As the reproductive tract score increases, the likelihood of that heifer becoming pregnant increases. This occurs because the heifers with a tract score 4 or 5 are already cycling and will have more opportunities to achieve pregnancy when out with a bull than a heifer who is a tract score 1 or 2 and may not be cycling when the bull is turned out,” said Picking.
Pregnancy rates are lower on a heifer's first cycle, so it is best to have a heifer already through her first cycle when she is artificially inseminated or turned out with the bull. Heifers with higher scoring tracts will achieve their first pregnancy earlier in life, and subsequently, calve earlier in the calving season.
“This trend generally continues throughout that female's life, allowing her to produce more calves in her lifetime and be more profitable,” said Picking.
Along with the reproductive tract score, a veterinarian can measure the pelvic height and width. By multiplying the height and width, the pelvic area can be determined.
Heifers with smaller pelvic areas are more likely to have difficult births because the calf has a smaller birth canal to get through. This smaller pelvic area leads to more work for producers who may have to pull those calves and it increases the likelihood of calf sickness or death.
“By selecting for larger pelvic areas, producers can decrease the number of difficult births and death loss, improving their bottom line,” said Picking.
A pre-breeding exam is required for the Show-Me-Select heifer program. This University of Missouri Extension Program was developed to help producers to improve their replacement heifer selection and give them an outlet to market quality replacements.
In this program, heifers undergo a reproductive tract score as well as a pelvic measurement to reduce the incidence of difficult births. To qualify as a show-me-select heifer, heifers must have a pelvic area of at least 150cm as well as meet several other criteria ensuring that the heifers sold in show-me-select heifer sales are high quality, bred replacement females. ∆
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