Reproduction remains one of the most important factors affecting the success of cow-calf operations.
The Beef Cattle Research Council’s (BCRC) recent webinar on Preventing Reproductive Wrecks served as an important reminder that the reproductive capacity of beef herds remains paramount to economic prosperity in cow-calf herds. In the words of Dr. Dan Posey, Texas A and M University, “Reproductive efficiency expressed in economic terms is 10 times more important than weaning weight, and 20 times more important economically than carcass attributes.”
The math is quite simple: a herd that produces more calves per exposed female increases revenues by selling more calves. The average cow herd in Western Canada goes into fall with 93 per cent of the cows pregnant (seven per cent open), loses between four and seven per cent of calves born alive in the spring with an average weaning percentage of 85 per cent (calves weaned versus cows exposed the previous breeding season). Maximizing herd reproductive efficiency should be the primary goal of all beef producers.
In a nutshell, four critically important management practices that improve reproductive efficiency include:
- Breeding soundness evaluations on all bulls every year.
- Pregnancy examination and removal of all non-producers.
- Maintenance of moderate body condition scores at calving.
- The hidden values of vaccinations against reproductive diseases (IBR, BVD and campylobacter or vibrio).
A major study involving 205 herds and 33,000 beef cows from the beginning of the breeding season in 2001 through pregnancy testing in 2002 from across Western Canada identified herd management and cow characteristics associated with the reproductive success of participating cow-calf herds. The study team measured breeding management and cow-level risk factors such as age, body condition score (BCS) and previous reproductive history.
A second study, championed by the Western Beef Development Centre (WBDC) between 2014 and 2015 involved approximately 400 herds and with the information gathered established production benchmarks capable of being used by producers to measure individual herd performance against industry averages. The WBDC study also examined linkages between production and profit by examining factors like cow herd costs, pounds of calf weaned, conception rates, open rates, percent of calves born in the first 21 days, length of calving season, calving rate and calf death losses.
Observations made from the two studies include:
- About 60 per cent of producers pregnancy check cows; approximately 66 per cent check heifers.
- Approximately 64 per cent of producers conduct bull semen evaluations.
- 11 per cent of producers utilize estrus synchronization and 18 per cent artificial insemination in reproductive management schemes.
- Failure to conceive and early pregnancy failure were the primary causes for reduction in net calf crop.
- Commonly employed herd management practices include controlling the length of the breeding season, minimizing biosecurity risks, vaccination, and optimal nutrition.
- Shorter breeding seasons have been associated with decreased costs and improved productivity.
- The use of community pastures during the breeding season is a common challenge to biosecurity in many herds and can be linked to reduced reproductive performance because of increased exposure to disease (IBR, BVDV, trichomoniasis, vibrio).
- Vaccines can be used to help manage biosecurity risks for some pathogens. In experimental studies, vaccines against bovine viral diarrhea virus (BVDV) and infectious bovine rhinotracheitis (IBR) have been shown to protect against abortion and fetal infection.
- The most commonly used measure of nutritional management is body condition score (BCS).
- Dystocia and the degree and timing of assistance at calving have been associated with increased interval from calving to estrus and decreased conception rate in cows.
- Body condition scores less than 2.5 before calving, together with a subsequent decrease in BCS before breeding, explained the third-highest amount of variation in pregnancy status. The highest predicted probability of non-pregnancy was observed in cows that were thin before calving and lost condition afterward.
- Herds commingled during summer grazing have been shown to have higher calf mortality rates.
- Adequate body condition at calving and controlled weight loss immediately after calving are critical to optimize fall pregnancy rates.
- Blood samples indicate that up to 46 per cent of cows in Western Canada may be copper deficient. Cows with blood copper levels below 0.4 ppm prior to breeding are at increased risk of not becoming pregnant, particularly young cows less than four years of age. This suggests a need for field research on the use and effectiveness of trace mineral supplementation programs to improve fertility of beef cows.
- Nutrition is probably the most important factor that influences cow fertility. Cows deficient in energy (indicated by body condition) or trace minerals preferentially partition these nutrients to maintenance rather than reproduction.
- An optimal cow body condition score (2.5 out of five) encourages calving ease, produces higher-quality colostrum; sustains adequate milk production, and ensures relatively prompt rebreeding.
- The majority of beef herds in Canada continue to use bulls to breed females, and are therefore susceptible to sexually transmitted diseases. The most commonly reported venereal diseases of cattle include trich and vibrio. Although both diseases occur infrequently, results of infection can be quite devastating.
- As the first step toward improving reproductive efficiency, make sure to use a fertile bull. Though a fertile bull is important, he is of little use to a cow that is not cycling. The 90:90 rule of thumb assumes that 90 per cent of all cows calve and 90 per cent of these calves wean, so the average producer can expect a weaned calf crop of 81 per cent. If the weaned calf crop were to be reduced by another six per cent because the bull was not fertility tested, the producer now has a 75 per cent weaned calf crop. Using a bull that has been examined for breeding soundness could add six per cent to the average weaned calf crop of 81 per cent, resulting in a weaning percentage of approximately 87 per cent, or an estimated return of $20 for every $1 spent on semen evaluation.