Raising dairy replacement heifers to reach the desired body size and condition at calving can be challenging. Heifers should have well-developed mammary glands capable of producing to the animal's genetic potential. Nutritionally, the goal is to feed heifers economically for maximum production potential without compromising health or welfare. One very important factor in reaching this nutritional goal is the 'feed delivery method.' Following are some research notes that may help your heifer raising operation:
"Nutrient requirements for replacements stated in the NRC (National Research Council guidelines) assumes perfect environmental conditions" (Pat Hoffman, Wis.). We know that animals on the farm do not live in perfect weather conditions in perfect housing with perfect space provided with perfect convenience to feed and water. In balancing a dairy heifer ration, it is important to make adjustments for the difference of reality on your farm versus what research is recommending in ideal conditions.
Hugh Chester-Jones, Minn., states, "The key for a balanced ration for heifers is to have sufficient protein and energy so you get good gains but do not compromise mammary development." Feeding a high energy ration but low in protein to heifers before they reach puberty can cause fat infiltration of the mammary gland, which inhibits development of mammary secretory tissue and thus impairs future milk production capability (Hopkins and Whitlow, North Carolina State).
Feeding a TMR – Delivering feed using a TMR should result in heifers consuming a balanced ration more closely to what was designed for them. A TMR can minimize feed sorting, and lessen feed bunk competition (Greter et al., 2010). Without a TMR, heifers will prefer consuming the grain concentrate before consuming the hay or forage (DeVries and von Keyserlingk, 2009). The point is, a TMR fed to heifers from a young age maximizes the opportunity for all heifers to consume a balanced diet and improve growth rates. Growth should be monitored on at least 10% of the heifers and results compared to tables of recommended weights and heights (VandeHaar, Michigan State, 2011).
Competition at the bunk – Dairy heifers fed in groups tend to feed and rest at the same times. As a result, if there is not enough space for all animals to eat at once it may result in high levels of competition for feed (see table). Research has found that variation in live weight gains increases significantly as feed bunk length decreases. Longenbach et al. (1999) reported that heifers of highest social rank increased their total eating time when the feeding space became limited. DeVries et al. (2004) found that dominant heifers consume excess dry matter, thereby reducing the amount of feed available to subordinate animals. Any sorting of the diet by the dominate animals can reduce the nutritive quality of the feed available to those subordinate animals that must wait to feed (DeVries et al., 2005; Hosseinkhani et al., 2008). A study by DeVries and von Keyserlingk (2009) found that competition for feed at the bunk tended to increase the day-to-day variation in feeding time; heifers ate fewer but larger meals, and they ate faster throughout the day."