It’s that time of year: Pastures have hardened off, leaves are off the trees, and many calves are coming off the cows and into the yard. Decisions about whether to sell directly off the cow or background until midwinter likely have been made. However, a clear-cut plan for development may not be in place for heifers.
If all calves are being backgrounded, the heifers that will be kept as replacements might be in the same pen with the steers. Target gains for backgrounding calves vary, but typically, the goal is a gain of 2.25 to 2.5 pounds per day.
The question at this point becomes what impact would this growth rate have on the heifers that will be kept as replacements. To answer this question, you need to review the factors that dictate appropriate weight gain, along with different strategies for heifer development.
Determining Target Growth Rates
The weight of the heifers at the start of the developmental period is a critical consideration when planning the ensuing feeding strategy. In addition to weight at the initiation of feeding, we must have a good handle on the mature cow weight anticipated for a group of heifers. If a blanket 1,200-pound body weight is used for all cows, we could be making a critical error.
The most accurate way to determine average cow weight in a herd would be with the use of a scale. In many instances, however, a scale is not present. Other places to look that may give an indication of mature cow weight would be sales barn receipts from cull cows.
Use caution with sales barn receipts if cows were culled because they were not pregnant and they were not pregnant because of poor body condition. The cow weight used for the following calculations will be close to the average for this part of the country: 1,350 pounds.
To make the calculation for the number of days on feed, use the date at the start of the developmental period and the target breeding date. For example, a March calving herd with a heifer breeding date of June 1 would have an interval of 190 days to reach the target breeding date if the herd started development on Nov 23 (when the kids were home to wean during Thanksgiving).
Traditionally, the target breeding weight of heifers has been cited as 65 percent of mature body weight. However, target breeding weights of 58 and 53 percent of mature body weights have been evaluated and may be appropriate in certain situations. Subtracting the current body weight from the target breeding weight will give a body weight gain that must be achieved during development.
The total weight gain needed to reach target breeding weight then is divided by the number of days of the development phase to give a predicted average daily gain needed to reach target breeding weights. Examples of calculations for 500-pound heifers are as follows:
Strategies of Development
Several strategies are available to reach target breeding weights. In the example above, a 1.5-pound gain each day of the development stage would place a heifer at 58 percent of mature weight at the end of a 190-day development period. This relatively consistent gain throughout the development period can be achieved by having a good handle on the nutrient content of feedstuffs, the heifer’s intake and changes in body weight during development.
Heifers that were backgrounded in pens with steers until midwinter likely had a more rapid growth early in the feeding period and will need a less nutrient-dense diet after the steers are marketed. Heifers that gained 2.25 to 2.5 pounds per day until early February may need to be held to 1 pound per day until breeding to not exceed target breeding weights.
Another alternative strategy would be to restrict the growth of heifers until a midpoint in the development period and increase gain thereafter. Heifers could be maintained at ½ pound of gain for the first half of development and then put on diets to reach their target weight by the time the breeding season starts.
Several research projects have evaluated the different heifer development strategies and found no real differences in reproductive performance among heifers developed using the three strategies. However, before making a final decision regarding the strategy appropriate for your operation, you must consider two items:
- If a strategy of delayed gain is used, we need to be sure the heifers will gain appropriately in the latter half of the development phase. In situations where heifers fail to achieve target gains, a greater proportion of heifers likely will be cyclic at the time the breeding season starts.
- The major difference among the systems of development is the total amount of feed that will be required using each of the respective strategies. In terms of cattle nutrition, maintenance energy (NEm) is used to describe the energy an animal uses to maintain bodily function while neither gaining nor losing weight. The amount of feed an animal needs to meet its NEm requirement is based on body weight. The three strategies of development will result in very different patterns of feed utilization.
The earlier in the feeding period heifers put on weight, the longer they are being fed more feed to satisfy NEm requirements. Hay-based diets (65 percent total digestible nutrients) were used to compare NEm intake during the course of each of the three development strategies.
During the course of the feeding period, heifers that were maintained with low gains early in the feeding period consumed 0.56 dry matter pound per day (106 pounds during the feeding period) less hay, compared with heifers that gained at a steady rate. The latter heifers consumed 0.61 dry matter pound per day (116 pounds during the feeding period) less than heifers that were developed to put on greater gains early in the feeding period.
The differences in cost of the systems with hay priced at $150 per ton would be around $10 for each interval, with a total of $20 per heifer cheaper for the heifers gaining a majority of weight late in the developmental phase, compared with heifers gaining early. Whether this price difference is great enough to warrant consideration of a different strategy is up to the individual operation.
The winter feeding period is an exciting time to select and evaluate replacement heifers remaining in a herd. Taking the time to evaluate target breeding weights and feeding management scenarios may highlight areas for improvement or uncover strategies that may work in your operation. Regardless of the strategies chosen, I wish you the best of luck in raising your operation’s future cows!
Source: Carl Dahlen, NDSU Extension Beef Cattle Specialist