Take Care of those first-calf Heifers
Good nutrition and time of calving will earn you more beef
In future years the beef cattle industry will have to make some significant changes and become more businesslike in its approach to owning cattle. The move will be necessary to cope with interest rates, tight capital and a fluctuating cattle market. One of these changes will be an increased level of management in the beef cow herd.
Aside from plain frugality, there are a couple calculations cattle producers must be aware of to increase productivity. One is a simple formula: the percent net calf crop is equal to the number of calves weaned divided by the number of cows in the breeding herd times 100. Calculation of net calf crop in this manner gives a true measure of production.
Primary factors affecting percent net calf crop are:
• Failure of the female to become pregnant.
• Calf losses at or shortly after birth.
These two factors, in a survey of 12,827 calvings at Miles City, Montana Research Station, accounted for 82 percent of the net calf crop reduction.
The second formula to be aware of is pounds of calf produced per cow, calculated as the total pounds of calf weaned per year divided by the number of cows in the breeding herd. The Montana data showed one herd had the highest net calf crop but the lowest pounds of calf per cow, causing it to be the least productive. In that study, poor reproductive performance was 28 percent and calving loss at birth was 14 percent of the reduction in pounds of calf weaned per cow. Weaning weight and growth rate are important, but if you lose 42 percent of the potential calf crop along the way, it is time for an honest evaluation of your program.
Since failure of the female to become pregnant accounts for 60 percent of the total reduction in net calf crop and 28 percent of reduced pounds of calf weaned per cow, let’s have a closer look at how you can increase pregnancy rates.
Beef Digest Dec-Jan 1980
Heifers calving as two-year-olds early in the breeding season wean heavier calves and continue calving early throughout their productive life. The nearby table shows the effect of time of birth in the calving season on weaning weight with heifers that calve earlier and wean older, heavier calves.
Late-calving heifers exhibit erratic reproductive performance, producing calves sporadically and missing some years. Therefore, selection of replacement heifers based on pregnancy and especially early conception may be an excellent tool for increasing profits. A study at Miles City with 140 yearling Angus heifers was conducted to examine this possibility. Two groups were evaluated:
Miles City, Montana Experiment Station
• A control group with a 90-day breeding season and selection into the cow herd on pregnancy, adjusted weaning weight and conformation.
• The “new management” group. Heifers in this group were bred 21 days earlier, selected into the cow herd entirely on early pregnancy and had a 45-day breeding season.
Seventy-percent more heifers were exposed than were needed as replacements and estrus synchronization was used on the new management group. Table 2 shows the results with more heifers in the new management group exhibiting early estrus and pregnancy and increased weaning weight.
These data show that getting heifers cycling and settled early in the breeding season is important for early calving the first and subsequent calvings. This emphasizes the importance of heifers reaching puberty by 14 months of age. The weights needed for 50, 70 and 90 percent of the heifers to cycle for several breeds are shown below. By knowing your weaning weights and target breeding weights, rate of gain may be calculated and a management plan and nutrition program formulated.
Heifers on straight roughage usually do not have the rumen capacity to meet energy needs and can’t compete well with older cows for available feed. In addition, protein and mineral requirements are higher for heifers than for cows and often are not met. Therefore, heifers should be separated from the cows and fed to meet their needs.
Heifers in a trial at Kansas State University were divided into three groups to study the effect of energy level on cow and calf performance. Energy levels were based on the NRC requirement of 8.4 lbs. TDN and altered as shown Table 4.
As the research shows, management and nutrition of heifers are extremely important for the beef producer. Ideally, heifers should be separated from cows and fed to meet their higher nutrient requirement and increase the number cycling for early breeding.
Light-weight heifers at weaning require more grain to reach puberty by breeding season and may need to be separated from heavier heifers. They should be bred 20 to 30 days before the cows and bred at 14 months if calving as two-year-olds is desired. More heifers should be kept back for replacements and emphasis of selection into the cow herd on early conception.
You’ll never catch me claiming that ruminant nutritionists have rhythm. But we sure can bang on a drum. I’ve been banging this one a long time. In fact, I penned the bulk of what you’ve just read 30 years ago. It’s all still true. Bang, bang, bang…
Dr White is ruminant nutritionist for MFA Incorporated.
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