Tips for Replacement Heifer Management

It is almost spring, and after a challenging winter, we are ready for some warmer weather in South Georgia.   As grass begins to grow, many producers will be looking to build or restock their herds after fall and winter culling.  With cattle prices trending upward over the last year, the demand for quality females should be high heading into spring sale season.  That being said, we wanted to take an opportunity to remind everyone of a few tips to keep those heifers in top shape, whether purchasing replacements or developing your own.

Tip 1. Consider a controlled calving season. Regardless of breed or breed influences, it is safe to say that the same basic expectation exists for replacement heifers across the South:  We expect each cow to give birth to a live calf every 12 month.  Some producers have controlled calving seasons and some do not.  UGA Extension encourages everyone to manage their herds with a defined calving season for a long list of reasons, but even if you don’t, each cow should calve once within a 12-month period.  Cows that calve every 14 months, as opposed to yearly lose at least one calf over their productive lifetime or $750-$800 in today’s market.  This type of cow is more easily detected and removed from a herd that uses a defined calving season.  No matter where you go to build or rebuild your herd, make your purchases in such a way as to achieve a first calf by two years of age from a heifer.

Tip 2. Focus on BCS. Perhaps the most important factor in the reproductive success of the cow herd is body condition.  This is a simple assessment of the animal’s nutritional status using only the producer’s eye and a stratified scoring system.  The UGA Beef Team currently have guidelines for BCS published on ugabeef.com, but a hard copy of this publication may be found with your county agent. Try to maintain cows and heifers at a BCS 5 or 6.  Research from the University of Florida and Texas A&M University indicate that producers see 30% increase in pregnancy rate in cattle that are a BCS 5 compared to those that are BCS 4. This is equal to approximately 3% more body fat but represents a major step in the animal’s ability to cycle normally and consequently get pregnant.  Female that are maintained at a BCS of 5 or greater also produce healthier, heartier calves.

Tip 3. Nutritional development should be gradual. The trick, as always, is balance.  Heifers should be developed in a regimented fashion.  While thin females will not cycle with predictability, over-conditioned heifers, also face challenges during breeding season.  Fat accumulation around the reproductive tract can be a detrimental factor for artificial insemination programs.  Also, hormones secreted by adipose tissue can influence reproductive hormones as well.  Post-weaning management should target an average daily gain of 1.5 to 2.0 pounds per day.  Rate of gain should be managed to ensure that BCS remains between 5 and 7 as heifers increase body weight.  Breeding should take place when a female reaches 65% of her predicted mature body weight.  After breeding, females should continue to gain weight at the same rate in an environment that minimizes stress.

Tip 4.  Don’t forgive open females. The success of a beef cow herd and the profitability of individual cows is dictated by the combination of genetics and their environment.  Both must be optimal to have a calf every 12 month.  Good nutritional management and a herd health program primarily control the environmental portion.  In general, cows will perform as expected if their genetics are suited to the environment. (i.e. available nutrition, health program, and climate).  Yet, there are some females that may not do well regardless of management.  This may be a genetic component that is undetectable during visual selection.  These are the females that we hope to eliminate through the culling of open heifers so that we don’t incur the unnecessary cost of developing unproductive females.

Tip 5. Consider Reproductive Tract Maturity Scoring. Reproductive traits are often lowly heritable, yet they have the most economic impact in cow-calf herds.  One method for evaluating heifers as potential replacements is reproductive tract maturity scoring.  This is typically determined one month before breeding.  A bovine veterinary practitioner rectally palpates a 12 to 14 month heifer to assess the status of the reproductive tract of each individual heifer.  Then scores ranging from 1 to 5 (Table 1) are assigned.  Those heifers that have not cycled by this age and have no palpable follicles are scored a “1”.  These heifers can be selected against, and conversely those that have cycled and show more reproductive tract maturity can be retained or purchased with more confidence as to their lifetime productivity assuming no additional abnormalities exist.

Table 1. Summary of reproductive tract maturity score (RTMS) criteria for beef heifers
RTMS Uterine Horns Ovary Length Ovary Height Ovary Width Ovarian Structures
1 Immature <20 mm diameter, no tone 15 10 8 No palpable follicles
2 20-25 mm diameter, no tone 18 12 10 8 mm follicles
3 25-30 mm diameter, slight tone 22 15 10 8-10 mm follicles
4 30 mm diameter, good tone 30 16 12 >10 mm follicles
5 30 mm diameter, good tone, erect >32 20 15 >10 mm follicles, corpus luteum present

 

Table 1 shows a pattern of larger anatomical structures as you go down each column.  In addition, the uterus has more firmness to the touch (tone) as scores rise from 1 to 5.  Heifers with higher a RTMS are understood to be earlier to their first estrus and the hope is that these heifers will also tend to have shorter rebreeding intervals upon future parturitions.  Over the last two decades, it has been generally accepted that heifers receiving a score of 2 or higher should perform better than those receiving a 1 with regard to their initial breeding and consecutive years if proper nutrition is available to meet their individual needs.

These five tips are a few of the ways that heifer development can be improved in many operations. We wish everyone a happy spring, the best of luck in your operations.

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