November and December is the season in which a majority of beef producers make culling decisions. But culling is not an easy task. Often culling decisions revolve around which cow raised a calf to weaning and was rebred within a justifiable time period. There are additional considerations however. As cows age their productivity begins to decline. Just because a cow is producing a calf doesn't mean she is doing it efficiently. When an older cow requires as many or more inputs as a young cow but produces significantly fewer pounds to sell, it is probably time to replace that cow with a more efficient animal.

At what age do cows usually start to become less productive? There is great variability in the longevity of beef cows. Breed may have some influence. Region of the country and soil type may affect how long the teeth remain sound and allow the cow to consume roughage.

Records kept by the Desert Ranches of Florida in the 1980s and published in the 33rd Annual Proceedings of the Beef Cattle Short Course by the University of Florida Animal Science Department show how productivity changes over the life of the beef cows. These large data sets, (19,500 cows, and 14,000 cows in two separate years) are plotted in the chart. They indicate the average percentage of cows determined to be pregnant based on their age in years.

This data would indicate that cows are consistent in the rebreeding performance through about 8 years of age. A small decline was noted in 1983 as cows aged from 8 to 10 years of age. However the most consistent decline in reproductive performance was noted after cows were 10 years of age. A steeper decline in reproductive performance was noted as they became 12 years of age. This data, collected in Florida on cows with some Brahman influence, represents one of, if not the largest, data set on this subject.

Source: Genho, 1984 Proceedings of the Beef Cattle Short Course. Animal Science Department, University of Florida.