Extension by Scott Lake

Treat Those Heifers Right
By Scott Lake, UW Extension Livestock Specialist
    Heifers represent the future and the best genetics in your cowherd, therefore, it is important to manage them so they will have the best opportunity to remain in the herd and work for you.
    Discussions of heifer development and management strategies often come with strong opinions. While many operations develop heifers by feeding a medium to high-energy diet in a feedlot, just as many operations develop heifers on a low plane of nutrition with winter forage, prairie hay and supplement. There is no one right or wrong answer, as there is scientific data to suggest that either method can be successful. However, it is important to choose the strategy that will allow heifers the best possible chance to meet the goal of an individual operation at the lowest cost.This article is not intended to tell you how you should grow your heifers, rather it is our intention to outline some key year-long management steps that will hopefully make a difference to your operation.  
Buy versus sell
    Any discussion on raising heifers would not be complete without a brief discussion on raising your own versus buying replacement heifers. From an economic standpoint, there is a lot of merit to utilizing terminal cross bulls with additional growth potential on mature cows and not worrying about selecting for desirable future female replacement traits. Focusing predominantly on performance and carcass traits would allow the operation to increase weaning weights and post-weaning performance.
    Obviously, in this type of system a strong relationship must be developed with the heifer “supplier” to ensure the genetics and management strategies are in line with the overall goals of your cowherd. There is a strong resistance to this type of system from traditional cow/calf producers. Many producers get a strong sense of accomplishment or enjoyment out of improving the genetics of their herd. This must also be factored into a decision to buy or sell heifers. However, if profitability is the primary goal, all aspects of the ranch enterprises should be evaluated. There are several good tools, such as calculators (ansci.colostate.edu/beef), to help make sound economic decisions.  
Age, target weight at breeding, calving
    Evaluations have demonstrated that the most economical heifers should breed as yearlings and calve as two-year-olds. Research out of Oklahoma State University concluded that heifers that calve as two-year-olds produced 330 more pounds of calf throughout their lifetime compared to heifers that calved for the first time as three-year-olds.
    The three primary factors associated with attainment of puberty in heifers are weight, age and breed. The average age to reach puberty for heifers is between 12 and 14 months of age, depending on breed. To enable a heifer to reach puberty by 12 to 14 months of age, a proper nutritional management plan needs to be put in place. Traditional research data suggests that heifers should be fed to achieve 65 percent of their mature body weight prior to breeding. This type of management system will require that heifers are fed a moderately high-energy diet to achieve the 1.75 to 2.0 pounds per day required.
    More recent literature from the University of Nebraska would suggest that heifers could be fed to 55 percent of their mature body weight without sacrificing overall conception rate in a breeding season 15 days longer. This system has heifers on low-quality winter forage receiving a protein supplement. In a low-input range-based system that uses natural service on heifers, a lower target weight is likely acceptable. Managing heifers to lower pre-breeding weights may also serve as a herd fertility selection tool. Heifers that cycle and conceive at lighter weights, with fewer inputs, may hold their condition and consistently breed back as mature cows. Again, there is not a right or wrong system. However, if your operation utilizes a synchronization protocol and AI’s heifers, greater results will likely be obtained by feeding heifers to 60 to 62 percent of their mature body weight, simply because a larger percentage of heifers will have obtained puberty prior to the breeding season and will respond to the synchronization protocol. Regardless of system, it is important to have those heifers at 85 percent of their mature body weight by calving season to insure they are large enough to have a calf.  
Post-weaning rate of gain
    In a classical scientific study, Clanton et al., 1983, reported that when targeting 65 percent of mature body weight, there was no difference in attainment of puberty, conception rate or subsequent calf performance regardless of pre-breeding growth rate. In this particular study, the researchers grew heifers in three different diets: consistent gain, slow growth followed by rapid growth and a rapid growth followed by slow growth. The important conclusion from that data is that as long as the heifers get to their target weight, it does not matter how they got there.
    However, growing heifers consistently could have some advantages. In the northern regions of the U.S., winters can be harsh. If the plan is to grow heifers slow and catch up prior to breeding and a harsh winter or spring sets in, it may be difficult to achieve the rapid weight gain needed prior to breeding. The same principle holds true for percentage of body weight. By targeting a heavier percentage of body (62 percent) than some data suggests is needed, it can act as an insurance policy. If a harsh winter or spring sets in, the heifers will have a built in cushion to achieve their weight. In years where feed costs are high, lower targeted breeding weights may look more economical, but the added risks of poor breed-up may offset the economic benefits.
Breeding
    It is important to remember that first-calf heifers have additional nutrient requirements. They will calve for the first time, lactate for the first time and still be growing. They need extra time after calving to allow every opportunity to resume estrous and breed back as a two-year-old. To achieve this, heifers should be bred at least 14 to 21 days earlier than the mature cowherd. This will build in an extra cycle after they calve to get back in shape.  
Post-breeding
    One of the most overlooked aspects of raising and breeding heifers is nutritional management immediately post-breeding. This really applies to heifers that are developed with higher levels of nutrition prior to breeding. The typical protocol observed is for producers to breed their heifers in a dry lot, followed by turn out on pasture with bulls for clean up.
    With hay supplies running low and spring grass starting to green up, cattle are turned out, immediately chasing new growth. During early growth, grass is often washy and mostly water. This represents a large decline in nutritional plane during an extremely important period of time when her body is trying to recognize and maintain a pregnancy. The combination of rapid diet change, increased activity and a reduction in nutrients consumed all contribute to a potential reduction in conception rates. Research from Purdue University and the University of Wyoming reported almost a 20 percent decrease in conception rate when plane of nutrition was decreased immediately after breeding. Post-AI nutritional impacts will vary depending on feeds used, environment, etc. After spending time and money on developing these heifers, it is a wise investment to make sure their nutritional plane does not decrease immediately after breeding.  
Vaccinations
    As with the other cows/bulls in the herd, it is extremely important to follow a sound herd health program where heifers vaccinated and boostered at the proper time. Work with a local veterinarian to set up a protocol that will maximize protection in your area.  
Conclusion
    Successful heifer development programs not only focus on achieving targeted gains while managing input costs, it also means setting goals for breeding, conception and overall pregnancy rates. It takes two years worth of investment in time, labor, feed, fuel and interest to get a heifer to the point of calving. With such a large amount invested, including the future of your cowherd, management decisions should not be made to cut costs, rather heifers should be managed to give her and your ranching enterprise the optimal chance for long-term success and profitability.