Holstein heifers should calve at 1300 pounds (591 kg) standing at least 55 inches (140 cm) at the withers at 22 months of age. Height is correlated with frame size and dry matter intake and should be evaluated in addition to weight. From weaning to breeding, Holstein heifers should grow at a rate over 2 pounds (0.91 kg)/day. This gain should primarily be in the form of muscle and bone rather than fat. This requires an adequate supply of crude protein, undegradable protein, and individual amino acids. Ionophores increase heifer growth rate by changing the rumen microbial population. Higher growth rates are due to increased microbial protein synthesis, reduced protein wastage, increased feed digestibility, and greater energy retention. From breeding to three weeks before calving, nutrients can be supplied primarily with forages. Bred heifers can produce more quality microbial amino acids and have less need for undegradable protein. Adequate crude protein must be supplied.

From weaning until calving day, heifers should be putting on muscle and bone. Many dairy farmers and their consultants simply look over the fence at heifers and if they “look good” then the heifer feeding and management program is fine in their eyes. As dairy production becomes more competitive, dairy producers must carefully evaluate their heifer enterprises. That means monitoring heifer growth and costs. A good goal for Holsteins is to calve heifers at 1300 pounds (591 kg) standing at least 55 inches (140 cm) at the withers at 22 months (see Heifer Growth Charts). It is important to emphasize that heifers need to grow in height not just weight because height is correlated with their frame size and how much dry matter they will be able to consume in a day. Dairy producers do not want to be growing fat animals that look like Angus beef cattle ready for slaughter!

Heifers grown with optimum nutrition and management will be able to eat large quantities of dry matter. They will also milk well (over 100 pounds (45.5 kg) /day at peak for a Holstein). Because these heifers have almost reached mature size by the day of their first calf is born, they will not suffer “sophomore slump”, as fatter heifers with less frame size are known to do. They will remain healthy and not lose excess condition throughout their first lactation, calve again, and produce well for their second lactation.

A number of factors must go into meeting this goal of having 1300-pound (591 kg), 55-inch (140 cm), heifers by 22 months of age. Heifers must get off to a good start as calves. That means good colostrum management and disease control. Calves must also develop their rumens as soon as possible. Calves must quickly begin eating a quality, palatable calf starter and have access to fresh water. Calves should be weaned after they have consumed two pounds (0.91 kg) of grain/day for three consecutive days. (see Calves)

Weaning to Breeding

After weaning, group heifers by weight not by age. Monitor weights, heights and body condition scores. Weights obtained with a body weight tape around the heart girth are reasonably accurate. A body condition score of 3.0 is ideal. Heifers at this age and size should not have a lot of extra flesh around the rump area. They should display “dairy character” and have about the same body condition as a healthy Holstein cow producing 100 pounds (45.5 kg) of milk. A good rate of growth from weaning to breeding is over 2 pounds (0.91 kg) /day.

Just after weaning, it is usually best to feed free-choice high-quality second or third cutting mixed hay that is fine-stemmed and mold-free. Hay, in addition to 5-6 pounds (2.3-2.7 kg) of grain per day, is usually easiest to keep fresh and stimulates appetite. Silage and pasture have generally not been recommended for calves less than 400 pounds (182 kg) because it has been thought that the calf cannot consume enough dry matter in the form of wet forage. However, in a study at Michigan State, young dairy steers were fed either alfalfa hay or silage and no differences in dry matter intake were observed. All steers gained an average of 2 pounds (0.91 kg) per day. It was concluded that management and forage quality are probably more important in maximizing forage intake than the moisture content of the forage. Feeding silage before 400 pounds (182 kg) requires a higher level of management to stimulate intake than does feeding hay, but it can be done.


High quality forages can provide a significant amount of the energy needed by the young heifer. Grasses containing 14-16% CP and no more than 60% NDF can make up a significant part of the heifer’s diet so long as the NDF is fairly digestible. Corn silage can also make up a portion of the heifer’s diet. Feed refusals from the milking cows are usually unpalatable, low in energy, and not recommended. Refused feed may also increase the risk for Johne’s disease since manure can often contaminate the scraped up feed. For simplicity, some farmers feed the high-cow ration to young heifers. This ration, although usually excellent in protein quality, is not recommended because it usually contains more energy than the heifer needs.

Crude Protein

The young heifer (weaning to breeding) is not capable of consuming and fermenting large quantities of feed and forage and therefore, does not produce large amounts of rumen microbial protein. On many commercial dairy farms, protein is the nutrient that limits growth. In the Northeastern U.S. corn silage is commonly a major ration ingredient for heifers and it is complemented with a 16% protein “heifer” feed. This diet meets the young heifer’s energy requirements but not the protein requirements and especially not the amino acid requirements. This diet produces heifers that carry more condition than they need and do not grow muscle and bone as they should. A research study compared heifers fed a diet with either 14% CP or 16.5% CP from five to eleven months of age. Heifers fed the higher protein diet had a 17% higher average daily gain and a 9% higher growth rate (Westway Trading Corporation).

Amino Acids

In reality, heifers do not grow based on the percent crude protein in their diets. Their bodies need the amino acids that make up the protein absorbed from their intestine. Protein is defined as a chain of fifty or more amino acids. For the heifer to make her body protein (muscle and bone), there must be an adequate supply of each of the 10 essential amino acids (lysine, methionine, arginine, valine, isoleucine, leucine, histidine, threonine, tryptophane, and phenylalanine) needed for body protein synthesis. The heifer must also be able to manufacture the 10 non-essential amino acids. Muscle production is limited by the amino acid that is in the shortest supply in relation to the heifer’s requirement. That amino acid is called the “first-limiting” amino acid in the diet. Often, the first-limiting amino acid is lysine or methionine.

Feed proteins are rated for protein quality based upon the profile of amino acids that they contain versus the profile of amino acids required by the animal. If just one amino acid is deficient in the blend of amino acids absorbed from the heifer’s intestine, it will limit muscle growth in the animal. So, heifers, especially young heifers with a small rumen, will respond with muscle growth when they are fed a blend of high-quality protein sources.

A young heifer should be fed a bypass amino acid package similar to that needed to feed a high-producing lactating cow. For a 400-pound (182 kg) heifer this would mean a 17% CP of which 35-40% is UIP. The bypass protein should be a blend of processed soybeans, corn proteins, and animal proteins. Individual bypass amino acids can also be helpful. If you consider that the rumen microbes likely supply about 60% of the amino acids needed by the young heifer and the rumen microbes have a ratio of lysine:methionine of 2.86:1, then a bypass protein package with a ratio of lysine:methionine of 3.4:1 should supply a total lysine:methionine ratio of 3:1. This ratio is similar to that of the muscle that the heifer is trying to produce.

It should be noted that because of the young heifer’s small rumen size and high bypass protein needs, large amounts of high protein grasses or legumes containing a lot of soluble protein (SIP) are not recommended. The heifer will not utilize all of this protein. It will be wasted and growth rates will not be optimal.

Will Growth Rate Affect Milk Production?

Puberty is associated with the weight of the heifer rather than her age. It usually occurs between 550 and 650 pounds (250-295 kg). The development of the udder occurs in two stages, pre- and post-pubertal. The growth rate of the mammary system before puberty is allometric, meaning that it is much faster than the growth rate of the body. The size of the fat pad and the ducts going into the fat pad increase at this time. Work at Michigan State indicated that the rate of mammary growth before puberty was 3.5 times the rate of body growth. These workers also found that excessive energy intake during the pre-pubertal period had a negative effect on the mammary system and decreased subsequent milk production. Unfortunately, the Michigan researchers grew fat heifers rather than focusing on muscle and bone development.

Work at Cornell University has shown that it is the balance of protein and energy absorbed from the intestine which is important rather than simply the amount of energy metabolized. Heifers were fed diets balanced for the carbohydrate and protein fractions and groups of animals gained 1.6, 1.9, or 2.1 pounds/day (0.73, 0.86, and 0.95 kg/day) during the pre-pubertal period with age of calving at 24, 22, and 21 months, respectively. Mammary development as evidenced by first lactation milk yield was not compromised by accelerated growth during the pre-pubertal period.


Rumensin® (Monensin) and Bovatec® (Lasolocid) are two commercially available ionophores that increase heifer growth rate because of their impact on the rumen microbes.

Ionophores change the movement of certain ions into and out of the microbial cells. (An ion is a charged particle like sodium (Na+) or potassium (K+) formed by the loss or addition of electrons by a neutral atom.) The result of this ion exchange is that the affected microbes don’t have as much energy to grow and reproduce. A type of bacteria called Gram-positive bacteria is primarily inhibited by ionophores. Included in the Gram-positive category are: bacteria that produce a lot of lactic acid and drive down rumen pH creating acidosis, bacteria that digest and waste a large amount of dietary protein, and bacteria that produce hydrogen ions which must be converted to methane and are wasted by the animal. Thus, feeding ionophores results in higher growth rates due to increased microbial protein production, reduced wastage of dietary protein, and increased feed digestibility. Also, more energy is diverted from methane production to propionate production leading to more energy retention and growth of the animal.

Because ionophores act in the rumen to enhance average daily gain and because they improve absorption of nutrients by inhibiting the growth of coccidia in calves, ionophores can reduce the time it takes a heifer to reach calving weight by about three weeks. Their cost is usually fairly easy to justify, so most successful heifer growers feed ionophores.

Rumensin® versus Bovatec®

In the last five years, new research has shown Rumensin® to be a more effective growth promotant than Bovatec®. Research in the laboratory at Cornell University showed that Bovatec® binds more tightly to the rumen microbes as well as to feed particles. Of course, an ionophore isn’t doing its job if it is bound to a feed particle. Other research in the same lab showed that Rumensin® was 3.75 times more effective than Bovatec® at making potassium ions move out of the rumen microbe.

Two growth studies were conducted in 1998. Heifers were fed 100 mg/day of either Bovatec® or Rumensin® from 200 to 400 pounds (91 –182 kg) and then 150 mg/day of either Bovatec® or Rumensin® from 400 to 550 pounds (182 – 250 kg). In the New York trial with 120 Holstein heifers, those fed Bovatec® gained 2.71 pounds (1.2 kg)/day. Heifers fed Rumensin® gained 0.16 pounds (0.07 kg) more per day with an average daily gain of 2.87 pounds (1.3 kg)/day. In the Kansas study with 90 heifers, those fed Bovatec® gained 1.97 pounds (0.90 kg)/day. Heifers fed Rumensin® gained 0.13 pounds (0.06 kg) more per day with an average daily gain of 2.10 pounds (0.95 kg)/day. In the Kansas study, intakes were measured and it was found that heifers fed Rumensin® consumed 0.12 pounds (0.05 kg)more dry matter per day (10.07 pounds (4.6 kg) versus 9.95 pounds (4.5 kg) for the Bovatec® animals).

Breeding to Calving

Holstein heifers should be bred at 750 pounds (340 kg). From breeding to three weeks before calving, heifers are capable of consuming larger quantities of forage that they ferment to provide a large proportion of their energy and protein needs. Bred heifers produce a lot of microbial protein from the rumen degradable nitrogen and protein in their diets. They do not need to be supplemented with much high-quality bypass protein but it is important to make sure that their crude protein needs are met. It is desirable to maintain a high growth rate (1.6 - 1.8 lbs (0.73-0.82 kg) gain/day, large breeds) without excessive body conditioning during this time.

If refusals from the lactating cows are being fed to the heifers, estimate their nutrient content and supplement accordingly. Remember that the nutrient analysis of the refusals will not be the same as that which was offered because cows tend to leave the fibrous components (i.e. corn cobs) of the ration and pick out the grain. Feeding refusals from cows to heifers could increase the spread of Johne’s disease through contaminated feed.

Bred heifers sometimes have little shelter. Environmental conditions affect maintenance requirements. Since this requirement is variable and difficult to predict, it is important to watch body condition and adjust the ration accordingly, especially at times of heat or cold stress and muddy conditions.

Pre-Fresh Heifer

Heifers should be fed a pre-fresh diet 3-4 weeks prior to calving. This diet is even more important for the heifer than for the older cow. Most first-calf heifers have smaller rumens and therefore, consume less feed. They also tend to be less aggressive at the bunk. A more nutrient-dense ration containing some long hay and some of the same silage fed to the lactating cows should help to adjust the rumen and help the heifer to be at maximum dry matter intake soon after calving.

Nutrient Recommends for Replacement Heifers

300# 400# 600# 800# 1000# 1200#
3 months 5 months 9 months 12 months 16 months 20 months
DMI (lbs/d)
9 11 16 21 24 28
DMI (% BW)
3 2.75 2.67 2.6 2.4 2.33
CP (%)
18 17 16 15 15 15
CP (lbs) 
1.87 2.56 3.15 3.6 4.2
25-30 28-32 30-35 30-38 32-40 32-40
58-62 60-65 60-65 65-70 70-75 70-75
38-42 35-40 35-40 30-35 25-30 25-30
NSC (%)
35-40 32-38 30-35 26-32 26-32 26-32
Rumen Available FAT (%)
<5 <5 <5 <5 <5 <5
<7 <7 <7 <7 <7 <7
>21 >25 >32 >32 >32 >32
1.89 2.75 5.12 6.72 7.68 8.96
NEl (Mcal/lb)
0.74 0.72 0.68 0.64 0.62 0.60
NEl (Mcal)
6.66 7.92 10.88  13.44 14.88 16.80
0.7 0.6 0.55 0.45 0.4 0.4
0.37 0.35 0.35 0.3 0.3 0.3
0.22 0.22 0.2 0.2 0.2 0.2
0.9 0.8 0.8 0.8 0.7 0.7
0.1 0.1 0.1 0.1 0.1 0.1
0.2 0.2 0.2 0.2 0.2 0.2
0.25 0.25 0.25 0.25 0.25 0.25
IRON (ppm)
100 100 100 100 100 100
COBALT (ppm)
0.2 0.2 0.2 0.2 0.2 0.2
COPPER (ppm)
12 12 12  12 12 12
44 44 44 44 44 44
ZINC (ppm)
65 65 65 65 65 65
SELENIUM (ppm) 0.3 0.3 0.3 0.3 0.3 0.3
VITAMIN A (IU/lb) 3500 3500 3500 3500 3500 3500
VITAMIN D (IU/lb) 750 750 750 750 750 750
VITAMIN E (IU/lb) 25 25 25 25 25 25
Methionine (%UIP) 1.25 1.25 1.25 1.25 1.25 1.25
Lysine (%UIP) 4.25 4.25 4.25 4.25 4.25 4.25


Arndt, Jr. F.M. and A.L. Skidmore. 1993. Effect of alfalfa hay and alfalfa silage based diets on average daily gain and dry matter intake on male Holstein calves after weaning. J. Dairy Sci. 76:275 (Suppl 1).

Cady, R.A. and G. Willett. 1996. Case study of contract raising. Presented at the NRAES Conference on Calves, Heifers, and Dairy Profitability: Facilities, Nutrition, and Health. January 11, 1996.

Russell, J.B. 1997. Mechanisms of action of ionophores. In: Proceedings of the 1997 Cornell Nutrition Conference for Feed Manufacturers, Rochester, NY, p.88.

Sejrsen, K., J.T. Huber, H.A. Tucker, and R.M. Akers. 1982. Influence of nutrition on mammary development in pre- and post pubertal heifers. J. Dairy Sci. 65:793.

Van Amburgh, M., D. Galton, D. Fox, and C. Holtz. 1993. Predicting the most profitable heifer feeding program. Northeast Winter Dairy Management Schools - Extension Recommends, Cornell University. p. West-M-1.

Van Amburgh, M.E., D.M. Galton, D.G. Fox, D.E. Bauman, L.E. Chase, H.N. Erb, and R.W. Everett. 1994. Effect of pre-pubertal growth rate in Holstein heifers on first lactation milk yield. J. Dairy Sci. 77:712 (Suppl 1).

Related Links:

Management of Dairy Heifers
Penn State University
Article provides general guidelines for ration options for feeding heifers.

Penn State University
Comprehensive discussion of many aspects of feeding management for growing heifers. Provides good guidelines for rations.

Biosecurity and Vaccinations for Heifers, Pfizer Animal Health
Details biosecurity measures important to implement to optimize the health and productivity of growing heifers. A commerical article, so has product biases.

Feeding the Dairy Herd, In: Feeding the Dairy Herd, North Central Regional Extension Publication
J.G. Linn et al.


Mary Beth de Ondarza

Mary Beth de Ondarza
45 articles

Nutritional consultant for the dairy feed industry at Paradox Nutrition, LLC.

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Dr. de Ondarza received her Ph. D. from Michigan State University and her Masters Degree from Cornell University, both in the field of Dairy Nutrition.

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Paradox Nutrition

Paradox Nutrition

Paradox Nutrition, LLC is a nutritional consultation business for the dairy feed industry. Mary Beth de Ondarza, Ph.D. is the sole proprietor.

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