There are a number of things that producers can do that will encourage cows to return to estrus more quickly after calving and thus be more likely to conceive and calve earlier in the next calving season.
- Body condition score at calving and plane of nutrition.
Cows that are nursing a calf have the highest nutrient requirements of the year approximately 45 days after calving. These high nutrient demands are also when we want the cow to begin cycling again. Mature cows that are in a body condition score of 5 or higher at the time of calving and are maintaining or gaining weight will be more likely to return to estrus sooner than cows that are in a body condition score of 4 or less. Cows that are losing weight between calving and breeding are less likely to return to estrus and conceive.
- Early weaning of calves at 6 -7 weeks. Completely weaning calves is a more drastic practice but can be very effective. Specific information on early weaning calves is available, see futurebeef.com.au
- Use of a progesterone controlled internal drug-releasing device (CIDR) for 7 days. Research has shown that 20 days after calving, the use of a progesterone CIDR can initiate cycling earlier than may occur naturally. By initiating estrus earlier, cows are more likely to conceive earlier in the breeding season. This initial estrus induced through the use of a CIDR is fertile and cows can be bred either by artificial insemination or through natural service. Many producers associate the use of a CIDR device with estrus synchrony before artificial insemination. However, a CIDR device may also be used effectively with natural service. Natural service herds may benefit from identifying non-cycling cows that are at least 20 days post-calving and utilizing a 7-day CIDR protocol to initiate estrus that coincides with the start of the breeding season.
- Bull exposure to cows after calving. This practice has, in some circumstances been shown to decrease the time interval between parturition and return to estrus when compared to herd mates that were not exposed to a bull. Epididyectomised bulls can be used to induce estrus without cow conception until the start of the breeding season.
A cow must conceive by approximately 85 days after calving to maintain a yearly calving interval.
Calves born in the first 30 days of the calving season have many advantages over their contemporaries who are born later. Early-born calves weigh more at weaning and replacement heifers born early in the calving season are more likely to conceive early in the breeding season as a yearling.
Research has shown in a fixed-breeding season, two-year-old heifers that calve early in the calving season are more productive throughout their lives than herd mates calving later.
In a fixed-breeding season, cows that calve late in the calving season are less likely to become pregnant in the subsequent breeding season than early-calving cows. Cows calving early will have more opportunity to have multiple estrus cycles during the breeding season and therefore be more likely to conceive. The economic loss associated with later-born calves and the higher tendency of late-calving cows to not conceive in a fixed-breeding season highlights the potential benefits of inducing estrus earlier than may naturally occur for later-calving cows.