Whether breeding will be by natural service or AI, the season, and duration of the breeding period are important decisions. Artificial insemination requires planning for facilities, animal management, labor, and sire selection. Sire records can be used to predict offspring performance to attain production goals for either AI or natural service breeding. Sire selection based entirely on visual appraisal decreases the probability of goal attainment. Minimum scrotal circumference in yearling breeding bulls should exceed 33 cm.
A 60-day breeding season is considered maximum. Estrous synchronization can shorten the breeding season to 45 days using one AI and two subsequent natural service breedings. Synchronization of estrus with progestogen prostaglandin combinations or intravaginal devices can be used for either AI or natural service breeding. If natural service is used in synchronized herds, a bull ratio of 1:15 is adequate, whereas a ratio of 1:30 is adequate for nonsynchronized herds. Bull ratios of 2:80 cows in natural service have given high pregnancy rates. Some synchronization protocols involve 48-hour calf removal, requiring management of calves during this period. Early weaning terminates suckling effects and lactation nutrient demands, and stimulates occurrence of estrus in females. This practice can be used in adverse feeding conditions (e.g., drought), but requires management of the early-weaned calf.
Season of breeding (spring or fall) must be evaluated for forage availability and supplemental feeding requirements. Combining spring and fall breeding seasons can perpetuate poor reproductive performance if cows that do not conceive in one breeding season are moved to the later breeding period and given another chance for conception. Season consideration must include when and where marketing will occur as well as evaluation of retained ownership.
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