The results can improve heifer development return on investment plus increase ranch productivity by improving conception rates, pounds weaned per exposed female and cow longevity.
We all know cow longevity has great economic importance. When we are doing DNA testing, we are not just looking at that cow, we are also assessing traits she will pass on to her young.
The aim is to raise cows that last for many years. We call this genomic trait stayability – the probability a heifer will reproduce successfully past an age when her returns exceed her breakeven cost.
A common yardstick to remember is: Heifers must reach maturity and wean a calf five to six times to be profitable. So how soon can you predict this information? And how does that help you as an operator?
Enhancing sorting strategies
Advancing genomics give you the ability to make these selections as early as the birth of your calves. It’s also practical to think about collecting DNA at other early stages, like branding or calf processing, and to sort heifers while they’re still nursing at the side of their mother.
Taking DNA samples in the spring gives you a head start on using the results. You can pre-sort replacement heifer candidates, so you can be more focused on input decisions like nutritional supplements, vaccinations, grazing groups and so on.
With special treatment for heifers inching up to around $300 to $400 per head, plus the lost opportunity cost of keeping her rather than selling her, it’s efficient to focus development inputs and labor only on your best prospects.
Plus, if you have DNA profile results prior to turnout, you can achieve other time and money savings by assigning cow-calf pairs into replacement and feeder groups.
For example, you can group high-scoring replacement heifer calves alongside their maternally superior mother cows, then mate the cows to sires that will take your genetics in desired maternal directions. This can save you a year or two on genetic gains toward better stayability and longevity.
Simultaneously, you can graze lower-scoring heifers and their mother cows in pastures with a battery of terminal sires. Likewise, this sorting strategy allows you to devise fitting plans for implants, vaccination certifications, nutritional efficiency, grazing plans and marketing with the steers.
Improving stayability
Cows are removed from the herd for many reasons including death, failure to rebreed, loss of a calf, health and growth of calves, udder or teat problems, lameness, temperament, teeth and body condition.
A study in Tennessee on two well-managed herds showed that 78 percent of replacement heifers which successfully calved for their first time were rebred and had a second calf. However, only 38 percent of these animals had their fifth calf, 20 percent had their eighth, and 10 percent had their eleventh calf. Cow longevity ranged from 23 to 196 months and average 65 months.
Almost all (greater than 90 percent) of culling was due to a failure to rebreed. The remaining causes were disease, accidental deaths and selection decisions. One-third of the cows only had one calf, while the upper third stayed in the herd long enough to have five calves.
Managing for longevity
Replacing cull cows with retained or purchased heifers is an investment risk directly related to a ranch’s profitability. Greater longevity allows for development of fewer replacement heifers, lowering overall expenses.
The sooner you use DNA tests to pre-sort replacement candidates, the earlier you can make strategic investment and management decisions.
For example, while DNA will help reveal your top heifers, their growing environment and post-weaning management can limit the potential they will express as brood cows. But you can DNA your best heifers for development and be thrifty post-weaning too.
A paper in the 2015 Range Beef Cow Symposium discussed management alternatives for heifers post-weaning. It compared feedlot-developed heifers with the lower-cost approach of range-developed heifers.
During winter, the range heifers received no hay but were fed 3 pounds of protein cake daily. At breeding time, the range-developed heifers were lighter (averaging 771 pounds in July) than feedlot-developed heifers (averaging 879 pounds).
However, first-service conception rates were similar: 60.9 percent for range-developed heifers versus 61.6 percent for feedlot-developed heifers. Extending winter grazing decreased bodyweight without reducing reproductive performance.
A South Dakota State University trial found an advantage for raising heifers on grass. Heifers that were grazed before A.I. gained more weight and had a higher pregnancy percentage than heifers which did not have the experience of grazing before A.I.
An implication is: Heifers that had feed brought to them will need to re-learn how to graze when they are turned out. This learning period can depress their rate of development.
These researchers concluded that learned grazing behavior prior to breeding was important for reproductive success. This is a good reminder that inadequate growth rates due to poor nutrition and disease can compromise predicted development, reducing future production potential.
Making genetic gain
Great cow longevity does increase generation interval, slowing genetic gain due to less frequent replacement of “old” genetics with better “new” genetics.
With DNA testing, you can pick out heifers that will increase stayability potential and simultaneously select for other positive traits for your herd. Whether it’s birthweight, fertility, docility, gain, marbling or tenderness, you can balance trends toward longevity and genetic gain for these valuable traits.
Think about the potential of sorting heifers with high to low fertility and, at the same time, you have reliable data about feed conversion and carcass traits they will pass on to their offspring.
There are many ways you can enhance returns by developing heifers with high fertility potential while sorting out and marketing heifers with the lowest rankings for fertility or other shortcomings.
By using genomics to pre-sort heifers when they are young, you gain more options to enhance returns and more time to execute your plan. 
PHOTO: By using genomics to pre-sort heifers when they are young, you gain more options to enhance returns and more time to execute your plan. Photo provided by John Paterson.
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John Paterson
- Beef Geneticist
- Neogen GeneSeek
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