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Bull to female ratios important to calving season

Mark Z. Johnson, Oklahoma State University Extension beef cattle breeding specialist

March 21, 2025

Breeding season is approaching, and bull turnout is only weeks away for herds that plan to start calving next January.  

The first goal of breeding season is to get cows bred early in breeding season resulting in more calves born earlier in calving season, shorter breeding/calving seasons, older calves at weaning and ultimately, more pay weight at weaning due to calf age. The typical beef calf gains about 2 lbs./day up until weaning, accordingly a calf born one heat cycle (21 days) earlier will wean off about 40 lbs. heavier. How do we get this accomplished?  By having an adequate number of bulls to get cows serviced. The following shows a conservative expectation of the number of cows we should expect bulls to cover in a defined breeding season.

12 – 15-month-old bulls = 10 – 12 females

15 – 18-month-old bulls = 12 – 18 females

18 – 24-month-old females = 18 – 25 females

24 mo. & older = 25 – 35 females

2 – 6-year-old bulls = 25 – 35 females

 Rule of Thumb: One female per month of age at turnout (after passing yearling Breeding Soundness Exam). For example: If I have 60 heifers to breed and plan to turn out 15-month-old bulls, I will need four bulls.

 What is the typical life expectancy of a breeding bull? Typically, up to the age of six is “prime of life” for breeding bulls. This isn’t to say that all bulls will break down at this age but it is more likely to happen after age six. Often when an older bull goes bad, it isn’t discovered until after breeding season when we are doing pregnancy checks.

Southern Livestock

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