Beef cattle producers are the generators of new wealth for the beef cattle industry each time a calf is born. Therefore, reproduction and developing replacement heifers is an important and essential part of any cow-calf business. Since reproduction is among the most important management criterion, breeding heifers to calving-ease elite sires known for chart topping performance and efficiency is a valuable decision. For beef cattle producers that are small to medium size in terms of gross sales volume, accessing the merits of elite sires is out of their reach financially. Artificial insemination, however, puts access to elite sires at the cattle producer’s finger tips, because the breeding cost per pregnant artificially inseminated heifer has not appreciated much over time compared to the average herd bull cost per pregnant heifer.
As a component of a larger USDA/NIFA/Small and Medium Sized Farm grant, a voluntary survey of cattle ranchers that synchronize replacement heifers for AI was initiated with the 2021 breeding season for the purpose of establishing trends and identifying areas where future research efforts can be expended. Currently, two rancher breeding seasons (2021 and 2022) have been summarized. Without exception, environmental insult from drought, blizzards, long winter cold spells, and nutrition play a heavy role in heifer response and pregnancy rate. Drought during the 2021 breeding season and back-to-back April 2022 blizzards effected pregnancy rates. Looking ahead into 2023, brutally cold temperatures in all likelihood may have a negative effect on pregnancy rates unless nutritional energy supplementation is provided to ensure heifers are in a positive energy and gaining condition 30-days before, during, and 30-days after AI has been completed.
Ranchers that participated in the voluntary estrous synchronization systems survey used either a drylot or pasture system.
Looking at year-over-year change between heifer synchronization results from 2021 and 2022, costs increased for feed, vaccine, semen, and veterinary services, while pasture grazing system heifer pregnancy rates declined 17.0% from 74% to 57% due to stress resulting from the April back-to-back blizzards. For the most part, heifers are artificially inseminated one time and then are cleaned up with calving-ease bulls. Seedstock producers, however, repeat a second insemination of heifers that did not conceive during the initial synchronized timed-AI breeding. Those seedstock producers that repeated AI by detecting estrus the second time around also experienced a decline in repeat pregnancy rate. For seedstock producers, comparing first service pregnancy rate from 2021 to 2022 actually increased 3.0% from 56.0% to 59.0%. However, heifers that did not conceive during the first timed-AI and were detected according to estrus for repeat insemination faired poorly. Seedstock producer repeat pregnancy rate in 2021 was 47.2% whereas the 2022 seedstock producer repeat pregnancy rate declined to a 13%. Year-over-year declines of the reported magnitude clearly show the long-term environmental impact severe weather events can have on reproduction performance.
Thus, for the upcoming 2023 synchronized heifer breeding season, TMR diets with increased energy-protein content and pasture-based energy-protein supplementation will be necessary to ensure heifers affected by the recent unusually cold 2022-2023 winter are in a gaining condition before, during, and after heifers have been artificially inseminated.
Caution is advised for producers that manage heifers in drylot for AI and then turn the heifers out on spring pasture. Nutritionally, spring pasture has 70-80 water content, which declines with advancing season, as the forage matures, and becomes more lignified. Because early spring pasture is high in water content, heifers going from drylot confinement where nutritionally balanced TMR diets were fed will experience a decline in the plane of nutrition due to forage water content and exercise, and lose weight without supplementation on pasture. Providing supplementation in bunks or range-type cubes is extremely important to maintain the plane of nutrition on pasture for a 30-day period following turnout on pasture.
Supplemental fortified energy-protein feeds are available through local feed suppliers that not only manufacture, but also deliver to the ranch. In addition, supplemental ground or dry rolled supplements can be prepared on ranches that have the necessary equipment to do so. For supplement formulation assistance, call or email Douglas Landblom, Dickinson Research Extension Center, Beef Cattle and Integrated Systems Specialist, 701-690-8245 or douglas.landblom@ndsu.edu.
