Replacement Dairy Heifers
Jennifer L. Garrett, Ph.D.,
Technical Services Nutritionist,
Protiva - Northeast Region
Over the last several years, numerous dairy nutrition experts have expounded the value of proper feedbunk management for optimizing milk production and profitability in the lactating herd. As commonly stated, the basics of feedbunk management are:
"Provide the RIGHT feed to the RIGHT cows at the RIGHT time in the RIGHT place at the RIGHT price." The same considerations should be made for managing replacement heifers, whether housed and fed on pasture or in confinement.
Economics. In a typical cow's life, with three lactations beyond 24 months of age, 49% of her life is spent NON-LACTATING. Of these non-lactating days, 54% of the days are spent from birth to breeding, 32% breeding to freshening, and 14% dry. Non-lactating cows are not contributing to current cash flow! The 1996 National Animal Health Monitoring Systems (NAHMS) dairy survey indicated an average age at first calving of 25.8 months. Although the average was 25.8 months, 47.5% of the respondents indicated average age at first calving to be greater than 26 months (Not contributing to cash flow!). Only 9.3% of the operations reported calving heifers at less than 24 months of age (Contributing to cash flow more quickly!).
How Fast Should Heifers Grow?
By 13 months of age (breeding age), Holstein heifers should weigh 750 to 800 lb and measure 50 inches in height. By 24 months of age (at calving), Holstein heifers should weigh 1250 lb post-calving and measure 53-55 inches in height. Average daily gains of 1.7
- 1.8 lb per day is an achievable goal. Overconditioning during the prepubertal period (< 550 lb) should be avoided to minimize replacement of mammary secretory cells (milk producing cells) with adipose (fat) tissue. To help reach a high peak in milk production, the cow needs a maximum number of functioning mammary secretory cells and should weigh at least 1200 lb post-calving.
What are the Key Considerations for Proper Feedbunk Management of Heifers? The Right Feed?
Cornell University researchers recommend ration guidelines slightly above NRC (see Table 1). Under ambient conditions, a 600 lb heifer should consume 14.3 lb DM containing 9.1 lb TDN to sustain a 1.7 lb/day gain. How much is 14.3 lb DM? Depending on the feed sources, it could be described as the following (as-fed) amounts:
26 lb of a total mixed ration (55% DM).
32.7 lb of corn silage (35% DM) and 3.1 lb concentrate.
13 lb of good-quality hay (88% DM) and 3.1 lb of concentrate.
76.3 lb of pasture (15% DM, lush, immature) and 3.1 lb of concentrate.
Most dairy producers (51.4% of NAHMS survey producers) house weaned heifers on pasture. A key point to consider is pastures can vary greatly in nutrient content. Obtaining proper quantity and quality requires pasture management, more than heifer management. Proper fertilization, adequate moisture (rainfall), and control of plant maturity (through grazing, clipping, or harvesting for hay) are essential for proper nutrition and housing on pasture. The leafier the pasture, the greater the intake, the less amount of supplement needed (< 0.5% BW), the higher the rate of gain (> 1.8 lb/day).
Pasture quality and quantity varies greatly by season. In general, a cool-season grass/legume pasture height of three to four inches is needed for adequate quantity per bite by the animal. Once the cool-season grass exceeds eight inches in height, quality declines rapidly, resulting in compromised forage intake and animal performance. Lower quality forage may increase needed amounts of purchased supplement (0.5
- 1.0% BW). If pasture is taller than eight inches (spring) or shorter than four inches (summer), adjustments in size of pasture area, or number of head grazing, or amount of supplement fed, must be made to sustain adequate heifer growth.
Smaller animals may be frequently intimidated by larger animals if individual animal weight within the group of heifers varies by more than 125 lb. Consequently, intake is compromised and growth rates slowed, regardless of feed quality. Typically, heifers greater than 400 lb perform best on pasture or other high-moisture forages. At weights less than 400 lb, it is often difficult for heifers to consume adequate quantities of high-moisture forages to meet nutrient needs. However, some producers have been successful at feeding excellent quality, high-moisture forages to smaller animals, provided bunk space or pasture area is maximized.
Consistent delivery, timing of the delivery, and time allowed for eating directly impacts dry matter intake. In a study at Cornell University, eight-week- old heifers fed for a 1.32 lb average daily gain, ate 5.5 lb of DM in 60-90 minutes. Heifers fed for a 1.8 lb average daily gain took two to three hours to consume all of the feed under similar stocking density and feedbunk conditions. How long do heifers have access to feed, and how long is the feed accessible to the heifers? If using a rotational grazing system, how long are heifers on one pasture before moving to the next one--too long? If using a self-feeder, is it ever empty? Is the self-limiting agent included in the right amount, or is growth being compromised because supplements are not checked daily?
Environmental conditions can cause swings in dry matter intake by 10% to 20%. Whether housed on pasture or in confinement, the environmental conditions (wind, temperature, mud) directly influence energy requirements. If heifers do not have a wind break, are housed in mud greater than three inches deep, or face extreme temperatures, adjustments to the ration energy density should be made.
Researchers from Wisconsin and New York have developed adjustment factors to account for variations in the environment (see Table 2). These energy adjustments are important on pasture, especially during wet, spring and cool, fall weather. As an example, a 600 lb heifer consuming 14.3 lb DM containing 9.1 lb TDN in ambient conditions would require a ration change for winter conditions. During winter conditions with open housing, an additional 0.3 lb TDN would be required for maintaining body temperature and health.
The "right price" to pay for nutrition and housing
varies from farm to farm. Assistance in calculating these costs can be found
through your feed company, local extension office, or veterinarian. High-quality
pasture can be an economical means of providing proper nutrition and housing, but
it comes with the "price" of pasture management--seasonality, weather
conditions, species selection, fertilization, fencing, water systems, controlled
grazing, and/or hay cutting. On the other hand, the "price" of feeding
heifers in confinement includes the cost of the facility, one to two feet of feedbunk
space per head, labor, equipment, waterers, mixing and delivering feed, and possibly
mud. Often in confinement, feed intake is easier to control, costs of production are
easier to calculate, and higher rates of gain may be easier to attain. The highest
"price" to pay for either system is lack of attention to details. Attention
to details--feedbunk management--pays big returns in subsequent milk production with
growthy, healthy heifers!