Managing reproduction starts with selecting replacement heifers. For a long time, I thought that a combination of performance records and visual appraisal would allow me to tell the good heifers from the poor ones. I have now learned different.
For a couple of years, we had a group of graduate students come to the ranch around weaning time to weigh, measure and evaluate our heifer calves. We were expanding our cow numbers and needed all the replacements we could get. The calves were weighed and scored for body condition and muscle. Measurements were taken for hip height and heart girth. The calves were scored visually for soundness and other possible qualities.
The heifers were then followed through three breeding seasons and the weaning of their first two calves. Any heifers that failed to breed in any year or that failed to wean a calf were sold. They were evaluated on their breeding success and the weaning weights of their calves.
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Nothing we evaluated, however, either by itself or in combination, could explain even 15% of the variation in the outcomes. We decided that we couldn’t predict outcomes to select the best heifers with the information we had. Since then, I’ve been very willing to let the bull and Mother Nature select replacement heifers, and have been very satisfied with the results.
Some might wonder why I seem to forego the power of genetic selection. I’ve come to believe that we get the most genetic improvement through the bulls we use, and then only slowly. While I’ve seen rapid genetic change in cattle herds, I’d hesitate to call a lot of it “improvement.”
I’ve seen a lot of herds that changed growth rates of calves very quickly, but they also ended up with bigger cows, lower pregnancy rates, fewer cows run and/or significantly higher feed costs. Using the method that follows, it’s possible to achieve very efficient cows that get pregnant. Proper bull selection can then move you slowly toward your market-related goals.
Mother Nature gets first shot
I give Mother Nature or the environment the first chance, but I do remove a few poor-doing and ugly calves at weaning (don’t we all have at least a few of those?). We then aim for the remainder to achieve 55-60% of their expected mature weight by the start of breeding season. If the calves weigh 450 lbs. at weaning and are expected to become 1,200-lb. cows, they need to gain about 1.25 lbs./day from weaning (at 6-7 months of age) until breeding season.
Calves can do that on grazing and reasonable supplementation if the grazing is available. If quality grazing isn't available the entire time, lower-quality feedstuffs like grass hay can be used. If the hay is less than about 12% protein, a little alfalfa or other protein supplement could be added.
I don’t pamper these calves in any way. I prefer to push the edge on minimizing feeding and force them to graze. Remember, if you are calving just before or after the start of green grass, the heifer will have two or more months on green grass before breeding. The heifers can gain very rapidly and compensate for a slower winter gain. (However, I would not change from feedlot development of heifer calves to this minimal input approach in one year.) The environment is now beginning to select those heifers that can, and can’t, do what we want.
Prior to breeding the heifers, we booster their weaning vaccinations and administer the initial shots for lepto and vibrio. We also would cut a few more heifers – those that had wintered poorly or been doctored, some poor dispositions and a few “too tall-too narrow” females.
Now is when the bull or the artificial insemination (AI) technician joins forces with the environment to help in the selection process. If using bulls, I like to expose the heifers for no longer than 30 days. In my experience across several ranches, we’ve had pregnancy rates from 65% to 85%, but they get better with time, and your ability to predict them gets quite good after two years.
If you start with 150 heifers, a pregnancy rate of 67% will result in 100 pregnant heifers. If your pregnancy rate is 80%, you can start with 125 heifers and get 100 pregnant. Remember, in most situations, the open heifers are a nice profit center.
Some ranchers like to use AI on first-calf heifers. I know of one large ranch that heat detects and uses AI for five days, then gives a shot of Lutalyse®to the heifers that have not been inseminated and continues to heat detect and AI for another five days. That’s the breeding season – no cleanup bulls. They’ve been achieving pregnancy rates in the low 60% range, which gives them all the replacement heifers they need.
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I know of another ranch that is considering putting bulls with heifers for five days, giving a shot of Lutalyse®, pulling the bulls, and then heat detecting and inseminating for five days.
Neither of these ranches want all the cattle handling required by the more sophisticated synchronization programs.
There are three key steps to selecting replacements in an effective reproduction management program. The formula includes:
- A low-cost wintering program with minimal gain.
- Expose significantly more heifers than needed.
- A breeding season of 30 days or less. With 30 days of breeding, you will have some calves as much as 10 days early and still be calving 40 days later. At that point, you can induce the rest and get done quickly.
By eliminating the “poor doers,” the poor dispositions, the doctored, the unsound and the ugly ones at weaning and pre-breeding (This is not a big number – only a few) and then those that fail to conceive, you have a real nice set of bred heifers that were bred in your environment with low cost.
Burke Teichert, consultant on strategic planning for ranches, is retired as vice president and general manager of Deseret. He can be reached at firstname.lastname@example.org.