By Mike Boersma
Extension Educator, Pipestone and Murray Counties
Proper management of replacement heifers is one aspect of cow/calf production that is easy to overlook. But, research shows that heifers calving early in their first calving season will generally continue calving earlier in subsequent breeding seasons. This will result in cows that wean heavier calves when compared to their later-calving counterparts.
There are differing opinions regarding pre-weaning management and how these factors affect heifers later in life. Many experts believe that heifers receiving one growth-promoting implant at 2-3 months of age will not be negatively affected as cows. However, heifers receiving high potency implants or multiple implants tend to experience poorer reproductive performance later in life. So, if replacement heifers can be selected at a young age, it may be best to not implant heifers that will be used for replacement. If heifers are implanted, aggressive implant strategies should be avoided.
Creep-feeding of potential replacement heifers is another subject that tends to stir up debate among beef producers. In general, avoid feeding large amounts of grain-based creep feeds to potential replacements as these calves will tend to store excess fat in their udders. This excess udder fat has been shown to negatively affect future milk production. On the other hand, feeding smaller amounts of a low-starch creep feed can benefit calves by increasing weaning weight and training calves to eat from a bunk prior to weaning. The key is to monitor body condition of the calves and avoid adding excess body fat at an early age.
A good rule of thumb is to ensure that replacement heifers weigh 60-65% of their mature body weight by their first breeding and 80-85% of their mature body weight by their first calving. So, a heifer that will weigh 1300 pounds when mature should weigh 780-845 pounds at her first breeding and between 1040-1105 pounds when she has her first calf. Proper management and planning are important to ensure that heifers gain weight steadily during this time and are not rapidly gaining or losing weight just prior to or during breeding season as that negatively affects pregnancy rates. Likewise, rapid weight gain or weight loss between breeding and calving can result in unhealthy calves, calving difficulty, and other complications.
Keeping these basic heifer development principles in mind should result in heifers becoming pregnant earlier in the breeding season. This will result in earlier calving in the first calving season, earlier re-breeding, and heavier weaning weights over the life of the cow. Given the climate of today's marketplace, properly managed replacements can be a very valuable asset. On the other hand, mismanaged replacements are more costly to an operation than ever before.
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Michael Boersma is an agricultural production systems educator with University of Minnesota Extension.