Livestock: April 2001

Spring is in the air, and hopefully green-up on native and introduced pasture is occurring and your winter forage is adequate until summer pastures are ready to graze. From a forage quality standpoint, your cattle should be in good shape for the next couple of months, assuming forage quantity is not limiting. However, there are a few spring-cleaning issues that you may want to consider for your livestock operation. For you spring-calving producers, breeding season is rapidly approaching, which means bull turnout is right around the corner. The length of the turnout is primarily based on the desired calving-season length and is usually between forty-five and ninety days.

Typically, a bull is judged by how many females (at least 90 percent) were bred within the specific breeding season. Is this a true indication of a job well done, or could he do better and should you ask more of him? Only individual recordkeeping can indicate a good or poor job. Although grading a bull on conception rate is very important, it is not the final justification for a passing grade. The specific time (early versus late) conception occurred is also important.

Females that conceive early calve early, and these calves will be older and potentially heavier at weaning. Furthermore, cows that breed early return to estrus earlier in subsequent breeding seasons. Extension publications from Oklahoma State and Texas A&M Universities indicate that calves born early can be 50 to 75 pounds heavier. Regardless of your herd size, if you implement a defined breeding season, this concept is important because it requires little additional management or cost. Primary concerns are the nutrition and health of the breeding herd and all animals' physical readiness for the breeding season.

It is important to monitor nutritional needs throughout the year. Recovering lost body condition just before the breeding season is costly. Poor nutrition hinders rebreeding efficiency; therefore, an ounce of prevention is worth a pound of cure. In addition, observing your animals for structural and reproductive correctness can prove beneficial even a few months before the breeding season.

One area of importance is a breeding soundness exam on all bulls before turnout. Besides detecting obvious physical defects such as in the eyes and legs, the exam evaluates your bull(s) for reproductive tract (such as testes and penis) defects and semen quality. A thorough examination by a trained veterinarian will increase the probability that your exposed females in good condition will conceive not only within the breeding season but also earlier in it, which could mean greater returns at weaning.

Figure 1 and table 1 depict the calving seasons of two ninety-day breeding programs for a fifty-head herd, assuming weaning occurs seven months after calving begins. Example 1 (figure 1) represents no breeding problems caused by nutrition, health, weather, or physical impairment. Example 2 (figure 1) reflects a defect or deficiency early in the breeding program, and a subsequent compensation. Both examples assume 100 percent conception within the specified breeding season. So has our bull done his job?

Figure 1.
Calving distribution for two fifty-head herds with different conception rates in a ninety-day breeding season (click figure for larger version.)

Example 1 (figure 1) represents a typical conception pattern. Sixty, twenty, and ten percent of the exposed cows were bred within the first, second, and third twenty-one days of the breeding season, respectively, which was broken into twenty-one-day intervals to match a cow's estrous cycle. In example two (figure 1), 10, 20, and 60 percent of the exposed cows were bred within the first three twenty-one-day intervals. Which example is better? Both are good because all the females were bred; however, calves in example 1 have heavier weaning weights (table 1) and could arguably be the more profitable, depending on the price structure at marketing. Heavier calves are typically worth less on a dollars-per-pound basis, but calves in example 2 would require approximately 12 percent more return (e.g., $0.90 versus $0.80 per pound) at weaning. The ten-year average (1990 through 1999) price for 400- to 500- and 500- to 600-pound no. 1 medium-frame steer calves at Oklahoma City was $90.39 and $82.50 per hundredweight, respectively, or about 9 percent higher. Using these figures and the average weaning weights in examples 1 and 2 (518 and 462 pounds per head, respectively), we can calculate the profit, which is approximately $10 more per head in example 1 ($427.40 versus $417.60 per head), or $500 over the entire herd.

Many factors can cause low conception rates early in the breeding season and therefore younger or lighter calves at weaning. Some are beyond a producer's control. However, implementing a high-quality health and nutrition program, managing body condition, and ensuring that the breeding herd is physically sound before the breeding season can be part of a yearly management plan. These practices can increase your returns at weaning and warrant consideration.