Breeding season for spring calving beef cows and heifers is just around the corner. Nutritional management between now and the start of the breeding season will be critical for breeding success, especially for heifers.
Research has shown that heifers developed to 65% of mature weight had greater pregnancy rates during the first 45 days of the breeding season than heifers developed to 55% of mature weight. Heifers developed to a lighter percentage of mature weight may also have a longer post-partum interval. Studies have also shown heifers fed 85% maintenance requirements of energy and protein had reduced embryo development on day 3 and day 8 after breeding than heifers fed 100% of maintenance. Be sure heifers are heavy enough and carrying enough body condition at breeding to help improve odds of breeding success.
Heifers calving in the first 21 days of the calving season have shown increased longevity in the cow herd compared to later calving heifers. Researchers from USDA-Meat Animal Research Center at Clay Center, NE analyzed data from 3,700 calves and found for each day of age after the beginning of the breeding season that a calf is born, 2.4 pounds of weaning weight is lost.
Nutritional management after breeding is critical to successful AI breeding programs. Heifers developed in dry-lot and moved to range pasture had 15% lower AI pregnancy rates 42 days after insemination than dry-lot heifers moved to range pasture and receiving 5 pounds of dried distiller’s grains per head per day.
Additional research indicates reducing feed intake for 6 days following AI decreases embryo quality and delayed embryo development. Therefore, it is important to carefully manage the nutritional change from winter hay feeding to grazing spring pasture.
If cows and heifers are to be moved to a new location after AI breeding, this should be done between days 1 and 4 following insemination. Shipping heifers or cows between day 5 and day 42 after AI breeding should be avoided since the newly developing embryo is at greatest risk for loss during these times.
While many of these research results were reported for AI breeding systems, the same principles should hold true for natural service breeding systems.
Developing heifers to correct age and weight at breeding, and reducing nutritional stress around the time of breeding are keys to successful breeding programs.
Don’t lose sight of the impact of short-term supplementation after turning cattle out to grass. Using the above research results as examples, 5 pounds of distiller’s grains will currently cost about $0.60 per day or just over $25 per head for 42 days. This level of supplementation for this length of time may not be necessary in all situations, but the point is don’t just turn the heifers and cows out to pasture and forget about them or neglect their nutritional needs. Losing one 21-day calving interval will reduce calf weaning weight by about 40 pounds, may delay breeding next year, and these losses in lifetime productivity may never be recovered.
Feed supplies are tight and expensive. Pasture growth is likely being slowed by lingering drought conditions. Being in a rush to get cattle to grass may result in long term reductions in cow and heifer productivity if body condition and nutritional management at the start of the breeding season are ignored. Targeted supplementation may be the key to getting through this situation.
If you have questions on these topics, contact me at schmitze@missouri.edu or call the Pettis County Extension Center at 660-827-0591.
