Replacement heifers: target breeding weight and timing
By the RanchOS Global editorial team · Updated
Read the transcript
The classic target is about 65% of mature cow weight at breeding; newer research suggests lighter targets can work with good management (University of Wisconsin Extension). Example with made-up numbers: if your mature cows weigh 1,200 lb, the target is about 780 lb. Calve heifers at about 2 years old, a few weeks before the cows, so first-calvers have extra time to rebreed. Before the season, ask your vet for reproductive tract scores: weight, body condition and tract score together tell you who is ready.
In short: breed replacement heifers at about 65% of mature weight (lighter can work with good management), calve them at about 2 years and a few weeks ahead of the cows, and have your vet tract-score them before the season.
Target weight
The classic target is about 65% of mature cow weight at breeding. University of Wisconsin Extension notes newer research where lighter targets, about 50 to 57%, did not hurt reproduction in well-managed heifers.
Example (made-up numbers): mature cows average 1,200 lb. 1,200 × 0.65 = 780 lb target at breeding.
Weigh heifers at weaning and again 60 to 90 days before breeding, so you know how much gain per day they need to hit the target.
Timing
Heifers should calve at about 2 years old (22 to 26 months), which means breeding at about 14 to 15 months. Calving them a few weeks ahead of the cows gives first-calvers extra time to recover and rebreed. Use the gestation calculator to set the heifer turnout date from the calving date you want.
Check before the season
Ask your veterinarian for reproductive tract scores (1 to 5). Scores of 4 or 5 mean the heifer has reached puberty. Weight, body condition and tract score together tell you which heifers are ready.
General guidance. Your veterinarian and local extension office know your herd best.
See also Body condition score for beef cows.
Common questions
How much should a replacement heifer weigh at breeding?
The classic target is about 65% of her expected mature weight. University of Wisconsin Extension notes newer research suggesting lighter targets, around 50 to 57%, can work without hurting reproduction when heifers are well managed.
How do I work out a heifer's target breeding weight?
Multiply your mature cows' average weight by the target share. For example, with 1,200 lb cows and a 65% target, 1,200 × 0.65 = 780 lb.
When should heifers calve?
At about 2 years old (22 to 26 months), and ideally a few weeks ahead of the mature cows. That means breeding at about 14 to 15 months and gives first-calf heifers extra time to rebreed.
What is a reproductive tract score?
A 1 to 5 score your veterinarian assigns by palpation or ultrasound, based on the size of the uterus and ovaries and the structures present. Scores of 4 or 5 indicate the heifer has reached puberty.