By Dan Larson
The dollars associated with developing the heifer are one of the largest costs she will accrue in her lifetime. Many of us learned at some point that a heifer should reach 65% of her mature weight by the first breeding season. In many cases, we meet this target, but often we exceed it and increase development cost.
It is not uncommon for heifers to be developed in the same lot as feeder cattle. While this system is quite convenient, it is not ideal for developing high-quality replacements. Rather, a well-designed nutrition and management program is essential for appropriate replacement development.
Providing inadequate nutrients to the developing heifer may reduce her reproductive performance, but overfeeding will limit her lifetime productivity. Heifers developed to greater than 65% to 70% of mature weight deposit fat in the udder, leading to reduced milk production. Fat heifers are also more prone to calving difficulty and may be more difficult to rebreed after their first calf.
Research studies conducted in the last 10 years show that developing heifers to 65% of mature weight is not optimal. Rather, 85% to 90% of heifers developed to as little as 55% of mature weight at breeding became pregnant. More importantly, these heifers were developed using inexpensive feed sources such as cornstalks and dormant winter grass. By moving heifer development out of the drylot in favor of standing forage, cost was reduced by $45 per pregnant heifer.
Drylot disadvantages. Heifers developed in the drylot are often fed diets including corn-processing coproducts, which are excellent sources of energy and protein for the growing heifer calf. However, the protein level in distillers’ grain or corn gluten feed may exceed the energy requirements of the heifer. Providing excess protein in the diet prior to breeding has the potential to reduce fertility in the subsequent cycle at which the heifer is bred. Diets with too great a protein concentration during the breeding season may lead to embryonic death and lower pregnancy rates.
It is important to monitor protein levels in heifer development diets in order to meet requirements without exceeding needs. Appropriate mineral nutrition is also an integral part of heifer development. Mineral nutrition is often overlooked and expensive; however, it is often the deciding factor in the success or failure of the breeding season.
Dairy nutrition research has taught us the value of trace minerals such as zinc and manganese. Macro minerals, such as phosphorus, calcium, salt and magnesium, are also important. The National Research Council recommendation of 40 parts per million of manganese in the diet is most likely low. A more appropriate target is 50 to 60 ppm. Likewise, zinc should be nearly equal in concentration to manganese and copper should be at a 3:1 ratio to zinc. Most likely, if heifers are being fed corn coproducts, their phosphorus need is being met. The only macro minerals which require supplementation are calcium, magnesium and salt.
Estrous synchronization is an essential component of heifer development. But regardless of the system, appropriate nutrition is essential to produce a heifer that will stay in the herd and be productive. Without a balanced strategy for nutrition and management, money spent on reproductive technology may be wasted.
DAN LARSON is a ruminant nutritionistat Great Plains Livestock Consulting,Inc. His experience in both cow–calf and feedlot cattle operations offers a unique perspective on the beef industry.