The first step in reproductive management is controlling the breeding and calving seasons. Whichever calving season (winter, spring, or fall) is chosen, the following reasons illustrate why a controlled, seasonal calving schedule is desirable.
1. The culling of cows and selection of replacements is based on production records; however, accurate comparisons in the production of cows within a herd cannot be made unless a certain degree of uniformity exists among their calves. Decisions to keep or cull cows should reflect relative performance of calves within the herd. Acceptable performance implies not only weaning weight but also that a cow produce a calf every 12 months.
2. Shortened calving seasons provide a better opportunity to offer improved management and observation of the cow herd, which should result in fewer death losses at calving (a source of reproductive failure among any herd of cows). This is vital because percent calf crop weaned is one of the major profit determining factors in a cow calf operation.
3. Shortened calving periods facilitate improvements in herd health and management. Uniformity in timing of vaccinations and routine management practices result in decreased labor requirements and enhanced efficiency. Pregnancy testing and culling of open cows, which can reduce feed expense and improve herd efficiency, cannot be accomplished with year round calving.
4. Brood cow nutrition can be improved by grouping cows according to stage of gestation and feeding each group accordingly. When cows are strung out in their expected calving dates, it is difficult to provide cows adequate nutrition in a cost effective manner.
5. Calf crops that are uniform in age and size can be marketed to better advantage and thereby exceed returns over calves that lack uniformity in either age or weight. Calves born in the first 21 days of the calving season can weigh 30 pounds more at weaning than those born during the second 21 day period. Calves born 42 days into the calving season have been found to weigh as much as 70 pounds less than those born in the first 21 days and 42 pounds less than calves born in the second 21 days. Data from Cattle Fax indicates a $7 per cwt increase in the value of 7 like calves marketed together compared to marketing a similar calf as a single.
Hence, shortening the calving season results in: $ heavier, more uniform calves at weaning $ better use of available labor $ better opportunity to select for fertility in the cow herd $ greater income potential
One management tool to shorten and manage the breeding and calving season is estrus synchronization.