The integration and selection of heifers in the cattle herd is essential for the establishment of a production system (cow-calves).
The replacement rate is on average between 10 to 20% and varies from one farm to another. The age of the cow, its reproduction, the quality of its calves, its temperament, its health and its breeding are the basic criteria for the choice of the breeder. The main factor remains the age of the cow in order to determine which cows to cull.
In a herd of productive cows, the choice of replacement heifers has a great impact on the profitability of the farm operation thanks to their genetic characteristics, their longevity and their future yields. The age of first calving has a major impact on lifelong productivity, it is the most important factor. Studies show that heifers calving at 24 months (at first calving) give more calves in their lifetime than heifers calving at 36 months. The heifer must be inseminated at a maximum of 15 months to calve at 24 months.
The lifetime productivity rate also depends on the calf's diet. Research has shown that an infiltration of fat into the developing udder may be due to excess energy intake. As a result, milk production decreases in the dairy cow and therefore culls faster.
The proper selection and management of heifers for breeding is critical to the progress of the herd and to the long-term profitability of the cattle operation.