The following is from an article by Jud Heinrichs, professor of dairy science at Penn State University, which appeared on the DAIReXNET learning network.
Q: What are we learning about precision feeding of dairy heifers?
A: Much of the recent heifer nutrition research has evaluated precision feeding of highly digestible diets to dairy heifers for improving feed efficiency and reducing manure. Feed represents the largest component of the total cost of heifer production, and it clearly represents the major way to control heifer costs. Diet type and the amount fed can be large factors that affect feed efficiency and are the major aspects that we use in precision-feeding heifers. Ration digestibility is also obviously important. The more digestible the feedstuffs used in the ration, the more efficient the heifer will be.
Based on published research for precision-fed dairy Holstein heifers, nutrient specifications as currently understood are as follows:
- Protein: Balance primarily for crude and soluble protein.
- 14% to 15% CP for pre-pubertal heifers based on DMI of 2.15% BW/day.
- 13% to 14% CP for post-pubertal heifers based on DMI of 1.65% BW/day.
- Maintain at least 30% to 35% soluble CP in the rations at all times to allow for optimal rumen microbial protein production.
- Rumen undegradable CP levels in excess of 25% to 30% of the CP are not required; use only standard feed sources based on price and availability and not feeds specifically designed for high bypass protein values.
- Soluble protein (SP) and rumen degradable protein (RDP) are efficiently utilized by dairy heifers.
- Energy: The energy requirement of the heifer will be influenced by BW, growth rate, and the environment in which the heifer is being raised. Diets can be formulated at a fixed (generally higher) energy content and precision-fed to specifically meet the heifers’ energy requirement for growth.
- Fiber: Traditionally, high levels of fiber or low-quality forage are fed to dairy heifers to control dietary energy intake; however, precision-feeding high-concentrate, low-fiber diets effectively accomplishes the same goal. Economics and the mix of forages available to a farm usually drive the forage level to feed. Research has revealed that the ratio of forage to concentrates can be extremely wide, from 95% forage to 25% forage.
- Vitamins and minerals: In precision-feeding systems, it is important to balance diets to current National Research Council (NRC) specifications for vitamins and minerals. With limited newer data, there are no indications to suggest vitamin and mineral requirements are altered when heifers are precision-fed.