Braunvieh World Winter 2024

Impacts of Gestation Length on Cattle Performance By Mason Carter, MS, PAS, West Texas A&M University, and Tommy Perkins, Ph.D., PAS, Associate Professor of Animal Science, West Texas A&M University

For beef producers , maintaining a high pregnancy rate in their beef herd is the driving variable for sustain ability and economic viability for beef production. With the increased use of assisted reproductive technologies (ART) such as artificial insemination (AI), fixed-time AI (TAI) and Embryo Transfer (ET), along with the inclusion of conventional or sexed semen, we have seen increased genetic diversity compared to the sole use of bulls for natural service (NS). Since the introduction of AI, ARTs improvements over the previous decades have increased observed fertility efficiency. As the use of AI (more specifically TAI) has increased, many advantages such as increased sire accessibility, im proved calf uniformity, reduced exposure to reproductive disease, potential for rapid genetic improvement, earlier calving and reduced herd bull numbers (due to increas ing the cow-to-bull ratio compared to NS). Through the use of ARTs, the opportunity for increased data collec tion and information accessibility has improved producer management decisions. Implementing an AI protocol with the use of conventional and/or sexed semen in working operations allows producers to utilize previously inacces sible sires in programs. The use of sexed semen would allow producers to target calf crops of higher concentra tions of bulls or heifers. The concern with incorporating AI protocols into beef production has been due to increased costs, labor and heat-detection error compared to the upfront lower costs of NS. However, with TAI, heat detection labor is removed due to breeding cows and heifers at a set time compared to heat detection AI protocols. Use of estrus synchroniza tion protocols reportedly has resulted in pregnancy rates of 78.3 percent using a non-PGF2 and 73.7 percent with a PGF2. Implementing AI ARTs assist the beef producer with increased economic benefits such as higher con ception rates compared to only NS programs, TAI + NS (92.7 percent) vs. NS only (83.2 percent), along with the report that TAI increased pregnancy rates earlier in the breeding season. In a 40-head TAI vs. NS research trial, the herd pregnancy rate of TAI was 97.5 percent (with a calving rate of 92.5 percent and 90 percent weaned calf rate) while NS had a herd pregnancy rate of 92.5 percent (with an 80 percent calving rate and 77.5 percent wean ing rate). Research has shown a higher percentage of calves being weaned from TAI (84 percent) compared to NS (78 percent). From these findings, producers could see increased net profits of $11,110 with TAI over the use of NS. Along with adopting some form of ART, AI producers increased data recording. Additional benefits toward beef cattle improvement comes through the recording of AI date and calf date of birth (DOB), which allows for ac curate gestation length (GL) determination. By using AI instead of NS, producers know the exact date, time and bull that the dam was serviced. Again, the No. 1 goal in

Bred cows at Diamond H Ranch, Childress, Texas

beef production is getting cows and heifers bred to even tually have a live calf. Some incorporation of NS through clean-up bulls is needed to ensure this is achieved. Another important management decision that must be considered for breeding success must include an ade quate plane of nutrition, prior to and during the breeding season, whether TAI or NS is being implemented. In operations that utilize clean-up bulls following a one- or two-time AI protocol, they must utilize DNA par ent verification to guarantee calf parentage back to the AI sire (or clean-up bull). Through use of parent verification practices, producers will see increased sire EPD accura cies. Additionally, this practice validates the data being recorded for each calf, thus allowing producers to know which sires are influencing their calves’ genetics. The in troduction of AI by beef producers can improve efficiency through genetically improving their cow base, increasing pregnancy rates, increasing pounds weaned, reducing in breeding from sire selection, and overall ability to increase data collection for improved herd management decisions. As mentioned previously, adding AI protocols into a beef operation has added benefits, including increased data recording for increased knowledge to investigate the positive and negative impacts of their cow herd genetics, especially in the calf crop. Accurate recording of AI date, DOB and parent verification is needed to maximize gains from AI systems. The increased data collection allows for the calculation of calf GL, which is limited in the current breed association world. GL may be critical in influencing calf

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Braunvieh World  Winter 2024