Developing Replacement Heifers: Birth to
Breeding
AS-1169, April 1999
John Dhuyvetter, Area Livestock Specialist
Greg Lardy, Beef Cattle Specialist
Introduction
Preweaning Management
Selection
Target Breeding Weights
Feeding and Nutrition
Alternative Feeds
Health
Economics
Custom Heifer Development Services
About 30 percent of the heifer calves produced in North Dakota
are retained and developed for cow herd replacements. Costs
associated with heifer development represent a significant
up-front investment. Furthermore, management of the heifer during
the development period can significantly affect her lifetime
productivity.
Research indicates that heifers that calve early in their
first calving season continue to calve early in subsequent
calving seasons and wean heavier calves throughout their lifetime
compared to heifers that calve later in their first calving
season. Therefore, it is very important that heifers are managed
to control costs and enhance productivity.
The period from the time the heifer calf is weaned to the time
she is bred is critically important in replacement heifer
development. As a producer, your goals should include getting
heifers bred early, minimizing calving difficulties, weaning
acceptable calves, and having the heifer stay in the herd for a
long, productive life.
During the preweaning time period, the replacement heifer is
largely dependent on the dam to provide nourishment and care.
However, there are some management practices which can impact the
future productivity of heifers during this period. If possible,
heifers should be individually identified to allow producers to
base selection upon actual records of birth weight and weaning
weight.
Implanting
The following guidelines should be followed when implanting
replacement heifers:
- Heifers should not be implanted at birth or within the
first month of birth.
- Implanting at two to three months of age appears to have
very little adverse effect on subsequent reproductive
performance.
- Use of multiple implants (once at two to three months of
age and again at weaning) appears to have some negative
impact on subsequent reproductive performance.
- If replacement heifers can be identified early (two to
three months of age) it is probably best not to implant
them. If they cannot be identified at this time,
implanting once will have little effect on subsequent
reproductive performance.
Creep feeding
Data regarding creep feeding replacement heifers is
controversial. In some instances, creep feeding replacement
heifers can result in reduced performance when those heifers
enter the cow herd. The problem is more prevalent when the cows
are good milkers and creep feed is consumed at a rate of 3 to 6
pounds per day. Apparently, excess fat can be deposited in the
mammary tissue, resulting in lower milk production potential and
lower productivity when heifers enter the cow herd.
In contrast, an extensive survey conducted by the American
Simmental Association and Montana State University indicated no
reduction in subsequent performance when creep fed heifers were
compared to non-creep fed heifers.
Traditionally, the biggest heifers at weaning have been
retained for replacements. This method is simple and
straightforward. This selection method is not necessarily bad,
since older heifers from earlier calving, heavier milking dams
with good growth potential would be selected. However, there are
problems with this method. Some of the heaviest heifers may be
overly fat, leading to reduced milk production, or may have some
endocrine imbalance leading to reduced fertility. This method may
also result in the gradual increase in mature cow size, which at
some point leads to herd production inefficiencies.
A rigorous selection process should be developed to select
replacement heifers. This process should use available weight and
performance records as well as visual appraisal. Select heifers
from sires that transmit desired milk production and mature size
and have demonstrated early sexual maturity. From this pool keep
those heifers of desired body type and frame size which are most
likely to breed early, calve without difficulty, and remain sound
with minimal inputs.
Age at puberty
In order for a heifer to calve at 22 to 24 months of age, she
must reach puberty by 12 to 14 months of age. Table 1 shows the
breed group averages for age and weight at puberty based on data
from the US Meat Animal Research Center.
Table 1. Breed group averages for
age and weight at puberty.1
-----------------------------------
Weight at Age at
Breed Group Puberty Puberty
-----------------------------------
(lbs) (days)
Jersey-x 518 308
Hereford-Angus-x 622 357
Red Poll-x 580 337
South Devon-x 639 350
Tarentaise-x 622 349
Pinzgauer-x 611 334
Saihwal-x 642 414
Brahman-x 712 429
Brown Swiss-x 615 332
Gelbvieh-x 626 326
Simmental-x 666 358
Maine-Anjou-x 672 357
Limousin-x 679 384
Charolais-x 703 384
Chianina-x 699 384
-----------------------------------
1 From Beef Research Report No. 2:
Roman L. Hruska, U.S. Meat Animal
Research Center and University
of Nebraska College of Agriculture.
Breeds vary with respect to age at puberty. In addition, sire
selection within a breed also plays a role in determining age and
weight at puberty. Age and weight at puberty are moderately to
highly heritable traits. This means that producers can use
selection to improve these traits within a given herd.
An easy method of selection for age at puberty in replacement
heifers is to select daughters of bulls with large scrotal
circumference. In general, bulls with larger scrotal
circumferences have daughters that reach puberty earlier.
Impact of bull exposure on age at puberty
University of Nebraska research indicates that exposing
heifers (from weaning to breeding) to surgically altered (gomer)
bulls can reduce age at puberty by 40 days and increase the
number of heifers bred during the first 21 days of the breeding
season.
Impact of ionophores and anthelmintics on age at puberty
Research also indicates that the addition of an ionophore or a
combination of an ionophore and an anthelmintic wormer can reduce
age and weight at puberty. Ionophores generally improve gain and
feed efficiency by 10 to 15 percent in forage based growing
rations.
Use of MGA and other progestins
Melengestrol acetate (MGA) is a feed additive commonly used by
the feedlot industry to suppress estrus in heifers being fed for
slaughter. It can also be used to induce cyclicity in some
pre-puberal heifers that are close to, but have not reached,
sexual maturity (possibly due to insufficient weight or age). MGA
can also be used as part of an estrous synchronization program.
Synchromate B implants are another progestin which can be used to
synchronize estrous.
Target Breeding Weights
Heifers that breed and calve early their first year have been
shown to have an advantage in lifetime production. For early
breeding to occur, heifers must be cycling at the start of the
breeding season. Furthermore, conception is greatly improved by
breeding after several heat cycles compared to the first puberal
estrus. Therefore, heifers should be cycling 60 days prior to
breeding or by about 12 months of age.
The level of nutrition the heifer receives the first winter
following weaning will influence her rate of development, weight
gain, and the age and weight at which she reaches puberty.
Heifers fed for a higher rate of gain will be heavier and younger
at puberty. Low rates of gain will delay puberty, but heifers
will reach puberty at a lower weight. The fact that weight has
such an important impact on sexual development allows use of a
simple nutritional management concept known as target weight. A
heifer's target weight is the minimum weight she should achieve
by the time she is exposed for breeding.
Current target weight recommendations call for heifers to
weigh 65 percent of their estimated mature weight at the time of
breeding. Mature weight of heifers can be estimated from frame
scores determined by measuring height at the hip or from weights
of similar cows in the herd. Average mature weight in a
particular cow herd can also be estimated based on weight of cows
culled from the herd and sold through an auction barn.
Once target weight has been determined for heifers, an
appropriate rate of gain can be targeted by dividing the total
pounds of gain needed to reach target weight by days in the
feeding period until breeding. Table 2 provides an example
worksheet for calculating required weight gains for heifer
development. Where there is wide variation in weights and target
gains, it is good management to sort light and heavy heifers in
groups so they can be fed according to their different needs.
Table 2. Example worksheet for calculating required heifer gains.
----------------------------------------------------------
NDSU Example Your Herd
----------------------------------------------------------
Mature cow size 1300 pounds ____________
Target weight at breeding
(65% of mature weight) 845 pounds ____________
Current weight 550 pounds ____________
Current date October 15 ____________
Start of breeding season June 1 ____________
Feeding period 225 days ____________
Total gain needed 295 pounds ____________
ADG needed 1.3 lbs/day ____________
----------------------------------------------------------
In addition to greater feed costs, overfeeding heifers may also
contribute to decreased productivity. The period from about three
to nine months of age is critical to mammary growth in heifers.
Both inadequate nutrition and overfeeding in this period have
been shown to result in reduced milk production.
Target gains will vary depending on weaning weights, frame
size, breed type, and length of the backgrounding feeding period.
Typical gain targets from weaning to breeding are 1.25 to 1.5 lbs
per day for British breed type heifers and 1.5 to 1.75 lbs per
day for Continental breed types.
Research suggests that the rate of gain in the development
period does not need to be constant as long as the target weight
is reached. In fact, some NDSU research identifies advantages to
developing heifers in stages of reduced energy and gain followed
by periods of compensatory growth. A slight reduction in feed
expenses has been shown for heifers developed at fairly slow
rates of gain early followed by a period of accelerated growth
just prior to breeding.
It is relatively easy to feed heifers from weaning to breeding
to accomplish targeted moderate rates of gain with fairly simple
rations. Table 3 provides minimum nutrient requirements which
serve as a guide in formulating rations. Replacement heifers have
nutrient requirements which differ from the rest of the cow herd;
consequently, they should be fed and managed separately.
Table 3. Nutrient requirements for medium and large frame heifer
calves.
Adapted from NRC (1984).
----------------------------------------------------------------------
Estimated
Nutrient Ration Minimum Daily
Heifer Requirements Specifications Dry Matter
Weight (per animal per day) (dry matter basis) Feed Intake
----------------------------------------------------------------------
ADG TDN Protein Ca P TDN Protein Ca Phos.
----------------------------------------------------------------------
(lbs) (%) (lbs) (g) (g) (%) (%) (%) (%) (lbs)
----------------------------------------------------------------------
MEDIUM FRAME
400
1.0 6.1 1.01 16 9 62.0 10.2 0.36 0.20 9.9
1.5 7.0 1.17 21 11 68.5 11.4 0.45 0.24 10.2
2.0 7.7 1.29 26 13 77.0 12.9 0.57 0.29 10.0
500
1.0 7.3 1.11 16 11 62.0 9.4 0.30 0.21 11.8
1.5 8.3 1.25 21 12 68.5 10.3 0.38 0.22 12.1
2.0 9.1 1.35 24 13 77.0 11.4 0.45 0.24 11.8
600
1.0 8.4 1.19 17 12 62.0 8.8 0.28 0.20 13.5
1.5 9.5 1.32 20 13 68.5 9.5 0.32 0.21 13.8
2.0 10.4 1.41 23 14 77.0 10.4 0.38 0.23 13.5
700
1.0 9.4 1.28 17 13 62.0 8.4 0.25 0.19 15.1
1.5 10.6 1.39 20 14 68.5 9.0 0.28 0.20 15.5
2.0 11.7 1.46 22 15 77.0 9.6 0.32 0.22 15.2
800
1.0 10.4 1.36 17 14 62.0 8.1 0.22 0.18 16.7
1.5 11.8 1.46 19 15 68.5 8.5 0.24 0.19 17.2
2.0 12.9 1.51 21 15 77.0 9.0 0.28 0.20 16.8
----------------------------------------------------------------------
LARGE FRAME
500
1.0 7.3 1.17 17 11 59.0 9.4 0.30 0.20 12.4
1.5 8.3 1.33 22 12 64.0 10.3 0.38 0.20 12.9
2.0 9.1 1.47 26 14 69.5 11.2 0.44 0.24 13.1
600
1.0 8.3 1.25 18 12 59.0 8.9 0.28 0.19 14.1
1.5 9.5 1.42 22 13 64.0 9.6 0.33 0.19 14.8
2.0 10.4 1.55 26 15 69.5 10.3 0.38 0.22 15.0
700
1.0 9.4 1.35 18 13 59.0 8.5 0.25 0.18 15.9
1.5 10.6 1.49 22 14 64.0 9.0 0.29 0.19 16.6
2.0 11.7 1.61 25 15 69.5 9.6 0.33 0.20 16.8
800
1.0 10.4 1.44 19 14 59.0 8.2 0.24 0.18 17.6
1.5 11.7 1.57 21 15 64.0 8.6 0.25 0.18 18.3
2.0 12.9 1.67 24 16 69.5 9.0 0.28 0.19 18.6
900
1.0 11.3 1.52 19 16 59.0 7.9 0.22 0.18 19.2
1.5 12.8 1.64 21 16 64.0 8.2 0.23 0.18 20.0
2.0 14.1 1.74 24 17 69.5 8.6 0.26 0.18 20.3
----------------------------------------------------------------------
Energy Requirement - Listed requirements are for cattle under
thermoneutral conditions. Increasing listed requirement for TDN
by 1% for each 1 degree drop below 10�F for cattle in winter hair
should be sufficient in adjusting for cold temperatures. Under
dry cold conditions to -10�F intake may increase to compensate.
Protein Requirements - Listed requirements should be adequate in
50% of cases. Increasing listed requirement by 15% should be
sufficient in 85% of cases. Increasing listed requirement by 30%
should be sufficient in 100% of cases.
Mineral Requirements - In addition to listed calcium and
phosphorous requirements, the following are suggested minimum
requirements for trace minerals: sodium chloride .08%,
potassium .65%, magnesium .10%, sulfur .10%, cobalt 10 ppm,
iodine .5 ppm, iron 50 ppm, manganese 40 ppm, selenium .20 ppm,
zinc 30 ppm.
Vitamin Requirements - Suggested requirements for growing heifers
per pound of dry ration are 1000 IU/Vit A, 125 IU/Vit D, and 5-25
IU/Vit E.
Heifers are commonly developed most economically on high forage
rations supplemented with grains and grain by-products, protein
concentrates, and minerals as needed to meet their needs and gain
target. Modest levels of gain can be achieved solely on high
quality roughage fed to appetite. Table 4 gives example rations
based on varying forage quality, heifer weight, and gain target.
Table 4. Example rations for developing replacement heifers.
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Hay Quality
----------------------
Heifer Weight Low Average High
--------------------------------------------------
MEDIUM FRAME - 1.5 TARGET ADG
400 lbs
Hay, lbs 9.0 11.0 12.5
Grain, lbs 5.0 3.5 2.0
Protein supplement, lbs .5 .1 —
Mineral supplement, lbs .2 .1 —
600 lbs
Hay, lbs 13.0 15.0 18.0
Grain, lbs 7.0 5.0 2.0
Mineral supplement, lbs .1 — —
800 lbs
Hay, lbs 16.0 18.5 21.5
Grains, lbs 8.5 6.0 3.0
--------------------------------------------------
LARGE FRAME - 1.75 TARGET ADG
500 lbs
Hay, lbs 10.5 13.0 15.0
Grain, lbs 6.5 4.5 2.5
Protein supplement, lbs .5 .1 —
Mineral supplement, lbs .3 .1 —
700 lbs
Hay, lbs 13.5 16.5 20.0
Grain, lbs 8.5 6.0 2.5
Mineral supplement, lbs .2 — —
900 lbs
Hay, lbs 17.0 19.5 23.5
Grains, lbs 10.0 7.5 3.5
Mineral supplement, lbs .2 — —
--------------------------------------------------
Low quality hay = 52% TDN, 7% CP;
average quality hay = 56% TDN, 9.5% CP;
high quality hay = 60% TDN, 12% CP.
Grain = 84% TDN, 13% CP (barley);
mineral = 12% P, 12% Ca, 12% salt.
In addition, it is important to understand the composition and
quality of feeds to be fed. Forages, in particular, vary
considerably in level of protein and energy and should be
analyzed in order to accurately balance rations. High quality
hays are those with over 12 percent crude protein and 58 percent
TDN. Hays with crude protein values between 8 and 11 percent and
TDN in the mid 50s would be considered average quality hays. Hay
with less than 8 percent crude protein and 52 percent TDN would
be considered low quality forage.
Insufficient energy intake which results in poor growth can
have devastating effects on breeding performance of heifers as
yearlings and on their subsequent performance in the cowherd.
Table 5 shows the results of research which examined the effect
of winter nutrition level on heifer development, reproductive
performance and calf production.
Table 5. Effect of winter nutrition level during heifer
development on subsequent performance of replacement heifers.1
---------------------------------------------------------
Pounds of Grain
per Head per Day
--------------------
0 2.7 5.4
---------------------------------------------------------
Number of heifers 112 113 112
Initial weight (lbs) 496 502 493
ADG, wintering period, lbs 0.07 0.50 0.80
Breeding weight (lbs) 506 577 613
% bred as yearlings (60 days) 69.2 73.9 83.5
Subsequent Production
% rebred after first calf 67.3 75.4 87.1
Weaning weight of first calf (lbs) 405 433 443
---------------------------------------------------------
1Adapted from Lemenager et al., 1980.
If large groups of heifers will be developed, producers should
consider splitting the heifers into two or more feeding groups
(based on weight). This will allow more precise feeding of each
group based on necessary target breeding weights and daily gains.
Consequences of nutritional mismanagement
- increased age at puberty
- Lower conception rates
- Greater degree of calving difficulty
- Increased calf morbidity and mortality
- Calves born later in the calving season
- Lighter weaning weights
- First calf heifers with poor reproductive performance
during rebreeding
- Later rebreeding of first calf heifers
- Reductions in lifetime productivity
- Increased rate of culling
Weaning and first appearance of the heifer into the growing
lot is a critical period. Calves which have not been creep fed
must be trained to eat harvested forage and grain from a bunk. It
is important that first feeds are highly palatable, safe, and
high in nutrients. Complete commercial starter feeds are
convenient choices in instances where starting calves in the lot
has been a problem.
Forages harvested as silage or haylage can be very good feeds
for growing heifers. Properly harvested and stored small grain
silage is generally a high quality forage. Corn silage typically
is higher in energy than most forages but only moderate in
protein and will produce adequate heifer growing gains with
little or no grain feeding if protein levels are balanced.
There is limited opportunity for use of crop residues such as
straw or corn stover in the growing heifer's diet, since these
products are generally low in energy, protein, vitamins, and
minerals. Gains of about 1 to 1.5 pounds per day might be
anticipated by heifer calves grazing corn stalks in late fall and
early winter when supplemented with protein, vitamins, and
minerals. Small grain straw and chaff are generally too low in
nutrients to be used to any great extent in heifer rations.
However, ammoniation can be used to increase crude protein and
digestibility to acceptable levels.
Increasingly in North Dakota, byproducts of the grain milling
and oil seed processing industries are available to cattle
producers. These feeds are generally moderate to high in energy
and protein. Byproducts and remnants from grain milling make
useful feeds for growing rations, typically having energy values
intermediate to common feed grains and forages with fairly high
concentrations of protein and minerals. In many instances, they
can be economically fed as a replacement for grain and protein
supplements. Oilseed meals remaining after solvent or expeller
crushing of oilseeds are generally good sources of protein. These
oilseed meals are useful as a ration ingredient for supplementing
low protein forages.
At times, some minor alternative crops become priced
competitively for consideration as feed stuffs. In particular,
field peas are high in protein and TDN and make an excellent
concentrate feed for use in high roughage growing rations.
As in all calf growing programs, sickness and death loss risks
are of concern in the growing of heifers for replacement
purposes. The health status of heifers is enhanced by minimizing
stress, providing adequate nutrition, and by a proper vaccination
program. Please refer to NDSU Extension Circulars AS-1154,
"Respiratory Illnesses," or AS-1160,
"Preconditioning Programs: Vaccination, Nutrition, and
Management," for more information regarding health programs.
A four year study of heifer development and associated costs
at the Dickinson Research Extension Center documents the greatest
single cost in developing heifers from weaning to entering the
cowherd as bred heifers the following fall is for feed in the
growing/backgrounding period. Drylot feed costs averaged $113 per
heifer for heifers developed at a rate of 1.67 pounds per day
gain and represented over 40 percent of total costs over the year
period. The second greatest expense was yardage at $36 per heifer
during this drylot period to cover costs associated with labor,
equipment, facilities, utilities, fuel, repairs, and management.
Custom Heifer Development Services
A growing number of companies or individuals will develop
replacement heifers for individual producers. The biggest
advantage these services offer is that a professional who
develops heifers for a living will be managing your heifers and
may be able to devote more management expertise to your heifers
than you could. Additional advantages may include not needing
additional facilities, feed, and labor required to develop
heifers on your ranch or farm. Most commercial development
facilities will also offer synchronization and artificial
insemination programs for your heifers as well. Disadvantages may
include increased costs associated with fees for yardage,
breeding, and other expenses which may not be cash expenses in
your operation.
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