There are many approaches to meeting the nutritional requirements of developing replacement heifers, but most programs in the southeast will be forage-based. In many cases the primary feed source will be pasture, but there will be many cases where the producer will desire to feed either a hay or silage based diet. As an example of alternative programs, I have chosen a set of ingredients and offer 10 alternative rations. The ingredients selected for this exercise and their nutrient compositions are given in Table 1. All the rations include a mineral containing an ionophore which is assumed to improve energy utilization by 5%, reducing the TDN requirement from 65 to 62%.
A well managed pasture is an excellent source of energy, protein and minerals for growing heifers. The quality of pasture is potentially high, but maintaining quality means grazing young lush forage. When there are large numbers of dead leaves, this indicates that quality is lacking. We have recently been developing heifers on studies evaluating the intake of mineral mixes containing lasalocid. One study was conducted from November to February on stockpiled fescue, while the other was conducted from April to July on fescue/bermudagrass pasture. Both set of heifers gained 1.3 lb/day, and reached desired target weights. Gains on higher quality pastures may exceed 2.0 lbs/day, especially small grains. In these very high quality situations the ionophore should not be needed. The producer will have to decide how intensively to manage pastures, and this largely depends on how much forage is present relative to the needs of the heifers. However the forage is allotted, it should be grazed in a rotational system with a maximum of 7 days spent in a given paddock.
Many producers will winter heifers on hay and grain. The hay should be as high a quality as possible, and should be tested so a balanced ration can be developed. Table 1 shows typical analysis for high quality fescue hay and average quality bermudagrass hay. In general, bermudagrass will be lower in energy than cool season forages. Because of their lower energy level, the hay-based rations will need a significant level of grain, increasing the development cost.
In some cases producers will have silage for rations, or they will be able to purchase silage cheaper than hay. A ration of corn silage and soybean meal will be higher in energy than needed, and will have to be limit fed, which may cause problems with uneven body condition scores due to competition at the feed bunk. Sorghum silage is closer to the heifer's requirements, and is often available much cheaper than corn silage. Note that mixtures of silage and litter are among the cheapest rations available. Silage programs are not that common for cow/calf producers, and are usually not economical due to equipment required for both feeding and harvesting.
Many alternative concentrate sources may be useful in heifer development rations. One that has proven very effective in our area are soybean hulls. This byproduct feed is low priced compared to its feeding value and is widely available. You can see from the rations in Table 2, soybean hulls can have a significant economic impact. Other feeds that have proven feeding value include cottonseed (limit to 15% of heifer diets), and wheat midds. In studies with dried corn gluten feed, performance has been below that predicted, so it is a risky ingredient for use in these programs.
There are many ways to feed heifers to achieve target gains. Alternative programs often improve the cost of the ration, but producers should be cautious about unproven feeds. It is apparent from this exercise that high quality pasture will be the cheapest program, followed by those using alternative feeds such as broiler litter and soybean hulls.
|Table 1. Ingredients used in the ration examples.|
|Dry Matter, %||TDN, %||CP, %||P, %||Ca, %||$/ton|
|Post-Weaning Requirement||13.5 lbs||62
|(1.25 lb/day gain)|
|High Quality Pasture||25||62-70||16||.35||.45||12.5|
|High Quality Fescue Hay||88||60||11||.3||.4||60|
|Average Bermudagrass hay||88||50||9||.3||.3||40|
|Soybean meal, 48%||90||87||54||.70||.20||275|
|Concentrate Mix, 16% CP||90||80||16||.30||.50||200|
|Table 2. Cost of balanced diets for growing heifers. All contain 1.5% mineral (fed free choice) containing an ionophore.|
|6||High quality pasture||98.5||52.0||.40|