Mark Johnson, Oklahoma State University Extension Beef Cattle Breeding Specialist, offers herd health advice as part of the weekly series known as the “Cow Calf Corner,” published electronically by Dr. Derrell Peel, Johnson, and Paul Beck. Today, Johnson talks about best management practices of replacement heifers.
In order to maximize profit potential it is important to have heifers calving at two years of age. Research shows heifers becoming pregnant early in their first breeding season, (specifically the first 21 days) remain in the herd longer and produce more total calf weaning weight over their lifetime in production.
How do we select and manage replacement heifers so that they are having fertile heats and ready to conceive by 14-15 months of age? Genetics, photoperiod, level of nutrition and growth rate all influence when beef heifers reach puberty; that being said, heifers that have reached 65% of their mature weight by this age should have reached puberty and be ready to breed. Obviously, age should be taken into account, (along with other selection criterion), when selecting replacements, with older heifers having an advantage. Heifers calves born earlier in the calving season, are produced by cows that conceived earlier in the breeding season.
After heifers are selected, how do we arrive at the target weight they need to gain from weaning until their first breeding season? First, we need an accurate estimate of the average mature cow weight. By using the weights taken at weaning time on the 4 to 7-year-old cows and adjusting to a Body Condition Score of 5 (Chapter 20 Beef Cattle Manual) we can calculate the average mature weight of the cowherd.
What is the best way to feed to reach that Target Weight? In a normal Oklahoma year, spring-born heifers weaned in fall are old enough to make good use of wheat pasture typically available by late November and gain 1.5 lb. per day (or better) to reach targeted weight. With wheat pasture conditions sporadic this year in Oklahoma, it is comforting to know that heifers can be grown very slowly through the winter months and fed harder for a couple of months going into breeding season in order to reach target weight by breeding season. This is the development method referred to as SLOW-FAST in Chapter 29 of the newest edition of the OSU Beef Cattle Manual. The SLOW-FAST feeding method for replacement heifers can also be a more cost-effective means of reaching the target weight than feeding for a consistent daily gain over the entire feeding period.
References
Beef Cattle Manual. Eight Edition. E-913. Oklahoma Cooperative Extension. Chapters 20 and 29.
Mark Johnson, OSU Extension beef cattle breeding specialist, discusses bull preparation for breeding season on Cow-Calf Corner segment of SunUpTV at https://www.youtube.com/watch?v=w4y5aiq5qq4
