Dept. of Animal Sciences, University of Illinois, 232 A.S.L., 1207 W. Gregory Dr., Urbana, IL 61801 U.S.A.

Once a heifer calf is weaned, options or strategies available to dairy farmers include:

• Heifers can "rough" it with low feed costs.
• Heifers can be fed lower quality forage.
• Heifers can be over fed.

These options will not produce heifers that will enter the milk string at 23 to 25 months of age, weighing 570 kg (after calving), body condition score 3, and standing 135 centimeters at the withers. To achieve these growth targets the dairy manager must have clearly defined goals for raising replacement heifers.

Several groups of heifers are needed to optimize growth, management, and costs. The seven groups of growing heifers listed in Table 1 are based on nutrient and dry matter intake differences, competition and size differences, need to observe heifers for AI breeding, and gestation needs.

 Age guidelines in each group can be modified depending on number of heifers, facilities, and age at breeding. However, facility limitations should not be an excuse to reduce group numbers.

A minimum of three heifer rations should be developed and delivered to growing heifers. Nutrient guidelines are listed in Table 2.

The following guidelines can be considered when building heifer rations.

• Limit the amount of silage, (> 60 percent moisture), and pasture to heifers less than 6 months of age.
• Groups 1 and 2 need supplemental grain (1 to 3 kg) for energy and a protein supplement (0.2 to 0.5 kg). #9;
• Groups 3 and 4 need supplemental grain (0.5 to 2 kg) depending on forage quality.
• Groups 5 and 6 may not need additional grain or protein supplement beyond forage sources.
• Group 7 ration can be similar to that of groups 5 and 6, but supplemented with higher levels of trace minerals, vitamins, and nutrients for the unborn calf.
• ALL heifers should be force fed a balanced mineral and vitamin pack (not free choice) mixed with forage or grain.
• ALL heifers should be fed an ionophore.
• Trace mineral salt and mineral can be offered separately on a free choice basis (does not replace force fed minerals).

Research has demonstrated that high energy rations with marginal protein intake results in over-conditioned heifers with decreased mammary secretory development and milk production (1, 11). The critical time is during the pre-pubertal development phase (4 to 10 months of age) when the mammary gland, secretory ducts, and parenchyme cells develop (7). However, New York researchers have reported that if nutrient levels are balanced and body condition scores are within acceptable ranges, mammary development (measured by milk yield) is not compromised (12) by high energy intake.

Environmental factors can increase energy requirements beyond normal needs (Table 3). For example, a 275 kg heifer requires 4.14 kg of TDN per day. If the heifer is housed in open housing in winter, add .14 kg TDN. If she has heavy body mud coverage, add .17 kg of TDN. If both conditions occur, the heifer would need an additional .35 kg of grain or the heifer reduces her growth (10).

Large breed heifers should gain 0.7 to 0.9 kg per day after weaning while small breed heifers should gain 0.5 to 0.6 kg per day. Body condition scores should remain under 3 until heifers are bred to avoid fattening (7). Table 4 lists growth guideline for different breeds and ages of heifers.

 Once heifers have achieved the proper size, they should be bred. Gestation is a fixed period which will delay return on investment. Large breed heifers should weigh over 565 kg (82 percent of mature body for the herd) after calving with a body condition score of 3 to 3.25 (12). If large breed heifers grow more than five centimeters during the first lactation, these cows direct nutrients from milk production to growth (8). One hundred kilograms of growth during the first lactation can reduce milk yield by 600 kilograms (8). Poor quality forages will not allow for accelerated growth programs to succeed. If heifers calve three months earlier (27 vs 24 months of age), heifer costs decrease by $130 and require fewer replacement heifers to maintain current herd size (2).

As dairy farms increase in size, dairy managers may raise heifers for other operations or contract to have some one raise their heifers. Wisconsin workers (6) summarized the cost to raise heifers depending on starting weight (Table 5). These prices provide returns to labour, management, and capital. A signed contract or agreement must be completed by both parties outlining rate of gain, monthly payment schedule, payment based on gain or daily charge, responsibilities for death loss, breeding program, veterinarian charges, duration of the contract, and management practices (such as dehorning, parasite control, disease control, over crowding, identification, and foot care).