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1 INSTITUTE OF FOOD AND AGRICULTURAL SCIENCES
Feeding for maximum milk productionrand
Barney Harris, Jr.*
Florida Cooperative Extension Service / Institute of Food and Agricultural Sciences / University of Florida / John T. Woeste, Dean
Advances in technology and research in recent
years have had major impacts on dairy
management practices and performance of dairy
cattle. With higher levels of milk production, there
is a continuing increase in the requirements for
energy, protein, fiber, minerals and vitamins. Also,
just as important as the nutritional needs of high-
producing cows are the various management
strategies needed to achieve and maintain those
higher levels of milk production. In short, the
many scientific discoveries and advances in
technology continually taking place are exciting
and challenging to those managing today's dairy
farm. Total management becomes the objective
when striving for efficiency and profitability. This
is accomplished by understanding the different
phases of lactation and how to cope with each
phase in order to maximize performance (Figure 1).
Reproductive performance of dairy cattle is
influenced by how cows are fed during the dry
period and early stages of lactation. After
parturition, cows should be fed rations balanced to
maximize dry matter intake so that body weight
losses are minimized. This allows the cow to attain
a positive energy balance in a shorter period of
time. In addition to feeding more energy in the
early stages of lactation, perhaps more bypass
protein is needed. The new NRC (1989) publication
on nutrient requirements for dairy cattle has
suggested 60 to 65 percent degradable and 35 to 40
percent undegradable protein (bypass) in the ration
dry matter. Also, a slightly higher level of protein
has been suggested during the first few weeks of
lactation due to less dry matter intake.
*Professor, Dairy Science Department, Institute of Food and
Agricultural Sciences, University of Florida, Gainesville,
It has been suggested that feeding ratiois high
in protein (18 to 20 percent of dry matter) over long
periods may have an adverse effect on conception
rate and days open. This paper will attemptof6c
examine some of the protein studies as well as the
effect of energy and some of the minerals and
vitamins on reproductive performance.
Fertility in lactating dairy cows appears to have
a downward trend in recent years and at a time
when rapid advances were being made in milk
production. In a Cornell study (12), the lowest
conception rate was for the highest level of milk
production when herds were stratified into groups
milking less than 15,000 pounds, 15,000 to 19,000
pounds, and greater than 19,000 pounds. In
another study, Ferguson (2,3) compared cows
milking less than 20,000 pounds to those milking in
excess of 20,000 pounds. In the higher group,
conception rate was significantly lower if
inseminated before 100 days in milk. However, if
cows were inseminated after 100 days, there was no
difference in conception rate. Even so, since
fertility has been shown in a number of studies to
increase only modestly beyond 60 days postpartum,
delaying breeding beyond this time period is not
Dry cow management and body
Good body condition at calving is important
because many high- producing cows cannot con-
Table 1. Nutrient requirements during the dry period (last two
months of gestation) NRC (1989).
Weight Protein NEL TDN Ca Phos
(Ibs) (Mcal) Ibs -- -
1,000 2.16 10.3 10.0 0.07 0.04
1,200 2.47 11.8 11.5 0.08 0.05
1,400 2.78 13.2 12.9 0.10 0.06
NEL= net energy for lactation, TDN= total digestable nutrients.
sume enough feed to meet their energy needs in
early lactation, making it necessary to draw on
body reserves during this period. Since the cow is
losing weight in early lactation, she is in a negative
energy balance. Having the cow in good body
condition at the time of calving indicates that dry
cows are being fed adequately (Table 1).
The body reserves of dairy cows are evaluated by
a procedure known as body condition scoring. The
cow is scored according to the fat covering over her
rump and loin area, and given a numeric score
between 0 and 5 with half scores in between. A
desired score at the time of dry-off for cows is 3.0 to
3.5, and at calving the same or slightly higher.
Conditioning of dairy cows for subsequent
lactations should start near the end of lactation
and not to any large degree during the dry period.
The key to success is to have the cow in the right
condition at dry-off and slightly higher at calving.
Body condition at calving can affect feed intake,
milk yield, and the magnitude of negative balance
The dry period can be separated into two periods
for ease of management: the early dry period and
the prepartum period. During the early dry period,
there is a final mammary tissue involution and
0 1 2 3 4 5 6
stability. It is a period of fetal growth and a period
of tissue maintenance. The prepartum period is
characterized by accelerated fetal growth, new
mammary milk synthesis tissue growth, and
certain hormonal changes that prepare the cow for
calving and milk synthesis.
It has been shown that over-conditioned cows
consume less dry matter, produce less milk, and
have greater incidence of retained placenta,
mastitis, and cystic ovaries after calving. The
severity of over-conditioning probably determines
the impact of body condition at calving on
reproduction and health. Cows with postpartum
fatty infiltration of the liver often have reduced
Feeding dry cows
Dry cow feeding is important in attaining maxi-
mum performance after calving. The feeding of
forages and minerals is probably the most fre-
quently mismanaged component of the dry cow
feeding program. The reason is probably due to the
nutrient variation in forages and the easily
accessible mineral mixtures used for lactating cows.
Minerals of concern are usually calcium, phospho-
rus, magnesium, potassium, and salt (sodium
chloride). As an example, too much salt and
3 4 5
Body Stores Dry Period
Regained for Rumen
Next Lactation Rehabilitation
9 10 11 1I
I I I I I
7 8 9 10 11 1
Figure 1. Dry matter intake, milk yield, and body weight changes and relationship during a lactation cycle.
potassium lead to udder edema, and an imbalance
of calcium, phosphorus and magnesium is associ-
ated with milk fever.
The lack of a good source of effective fiber or
forages in the dry-cow feeding program increases
health problems such as displaced abomasum.
Suitable forages are good quality grass hay, limited
amounts of silage (20 to 25 pounds) and by-product
roughages such as cottonseed hulls. The key
criterion is to keep the cows consuming a lower
quality feed in order to maintain rumen volume
and tone, especially in the prepartum cows. Since
feedstuffs such as corn, corn silage, and alfalfa hay
tend to over-condition cows, limit their intake or
avoid these as much as possible during the
A variety of feeding programs can be used to feed
dry cows. An example ration is in Table 2.The
protein concentration in the example ration is
somewhat higher as compared to the NRC (1989)
recommendation, but would assure adequate
intake. A lower degradable protein is suggested for
prepartum cows as compared to early dry cows in
order to minimize ration changes at parturition.
Beginning about three weeks prior to parturition,
the amount of energy being fed should be increased
in order to adapt the dry cow to consuming more
feed. Continue with ample amounts of long grass
hay during the prepartum and early postpartum
period in order to avoid metabolic problems. (For
more information on dry cow feeding see Circular
The transition and early
As the dry cow enters the lactating herd, she will
be under some stress for a few days. A fresh cow
group is frequently maintained for a period of one
to two weeks, or until such time as the cow is
declared healthy. Again, adequate amounts of long
grass hay should continue to be fed to avoid prob-
lems such as displaced abomasum.
The most critical period in the cow's lactation is
from parturition until peak production (which takes
from five to eight weeks postpartum). It is during
this period that the stage is set for obtaining the
highest possible peak in production and also for the
onset of normal reproductive cycling, which may
occur as early as two to three weeks in some cows.
To be successful, strategies such as the use of high
quality feedstuffs, nutritionally balanced rations,
feeding and management practices, feed bunk
management, milking practices, and heat stress
management should be applied. In general, cows
entering the high group will be fed ad libitum for a
period of three to five months or more, depending
on their performance. Afterwards, cows should be
moved to lower-producing groups as their perfor-
Energy intake and fertility
It is common knowledge that early lactating
cows do not eat as much feed as they do at two to
three months into lactation, even though the level
of milk production may be the same (Figure 1).
Feed intake lags behind peak milk production by
about two to four weeks. This results in a negative
energy balance and, as such, body reserves are
mobilized to overcome the energy deficit, which
results in some body weight loss. Although it is
normal for high-producing cows to lose weight in
early lactation, the energy, and especially the
protein, available from body stores can supply only
a limited amount of their needs. As body fat is
mobilized to produce more milk (1 pound of fat can
provide energy to produce 7 to 8 pounds of milk),
proportionally more energy is available than
protein. Therefore, the percent of protein in the
ration during early lactation should be higher in
order to maximize the efficiency of energy utiliza-
tion and to meet the added protein needs.
Table 2. A typical dry cow ration for prepartum cows.
Ib DM CP TDN NEL Ca Phos
(Ib) (Ib) (Ib) (Mcal) (Ib) (Ib)
Bermuda Hay 12 10.7 .84 5.28 4.80 .04 .01
Sorghum silage 25 7.5 .63 4.00 4.00 .02 .01
Grain Mix 8 7.2 1.12 5.44 5.60 .06 .05
45 25.4 2.59 14.72 14.40 0.12 0.07
Requirements (1400 # BW)' 2.20 13.90 13.20 0.10 0.06
1NRC Requirements 1989; BW = body weight; 14 = 14% crude protein; DM = dry matter; CP = crude protein
Because high-producing cows lose body weight in
early lactation, a number of studies have attempted
to correlate bodyweight losses to performance.
Studies at Cornell (2, 12) showed that when cows
were regrouped on the basis of body condition score
loss during the first five weeks of lactation (<0.5
units, 0.5 to 1.0 units, > 1.0 unit), only cows losing
> 1.0 units of body condition had lower fertility
(increased days to first ovulation, estrus, and first
service, and lower first service conception rate).
Both the extent of negative energy balance and
the rate of recovery of energy balance appear to be
important. In well fed cows, the negative balances
of energy begin to improve at about week four of
lactation. Recovery in energy balance from its most
negative state may be a signal for initiation of
ovarian activity. Thus, negative energy balance
may impair fertility by delaying first estrus by
limiting the number of estrus cycles occurring
before the preferred breeding period. A number of
studies (2, 3, 12) have indicated that conception is
correlated positively with the number of ovulatory
cycles preceding insemination.
First ovulation usually occurs at 17 to 42 days
after parturition. It has been suggested that the
greater the level of milk production, the slower the
cow is to reach first ovulation. For this reason,
program strategies must be developed so that the
high-producing cow will have every opportunity to
maximize her energy intake without compromising
her needs for fiber. Concentrated sources of en-
ergy, such as whole cottonseed and ruminally inert
fats, may be beneficial in early lactation.
In a University of Florida study, Staples and
Thatcher (13) monitored 54 Holstein cows for feed
and bodyweight change (energy loss or gain) in
their second or greater lactation from parturition
through nine weeks of lactation. Cows received a
55:45 roughage (corn silage) to concentrate diet
(DM). The results are in Table 3.
Table 3. Performance of lactating Holstein cows differing in
activity the first nine weeks of lactation.
EC LC NC
Number of cows 25 14 15
Dry matter intake, Ib/day 41.4 39.0 33.5
4% FCM, Ib/day 73.6 69.9 62.8
Days to ovulation 21.9 43.1
Days to first heat 47 73 110
Percent of cows conceiving 84 93 36
EC=early cycling; LC=late cycling: NC=noncycling. Staples and
During the nine weeks, blood plasma was
measured regularly for progesterone in order to
detect day of ovulation for each cow. Based on
tests, 15 cows were anestrus for the entire nine
weeks. Twenty-five cows returned to estrus within
40 days of parturition and 14 cows between 40 and
60 days after parturition. The study shows the
importance of energy intake in early lactation. The
earlier cycling cows produced more milk, consumed
more energy, and experienced the smallest negative
Protein intake and fertility
With increasing levels of milk production,
dairymen have been encouraged to feed higher
levels of protein that contain a greater proportion of
bypass protein. The concentration of protein in the
diet of high-producing cows can be expected to
increase in the future as management technology
and genetic selection further enhance milk-
producing ability. The new 1989 NRC publication
on nutrient requirements of dairy cattle suggests
17 to 19 percent protein in the ration dry matter for
early lactating cows, as well as a requirement for
absorbed protein. The requirements for absorbed
protein is expressed as UIP (undegraded intake
protein) and DIP (degraded intake protein). The
UIP or bypass protein recommended for lactating
dairy cows varies from 32 to 35 percent for low-
producing cows and up to about 40 percent for high-
producing cows. The greatest efficiency in protein
utilization should occur in this range.
Protein that bypasses or escapes the rumen is
degraded to amino acids and absorbed from the
small intestine. The degraded protein or ammonia
not utilized by the rumen microbes is absorbed
from the rumen into the blood stream and
converted to urea by the liver. This safeguards the
animal, since ammonia is toxic but urea is not. The
urea is then excreted in the urine or recycled to the
rumen in the saliva or by passage through the
During recent years, a number of scientists have
suggested that feeding rations high in protein may
have an adverse effect on reproductive performance
of dairy cows. Production of ammonia from dietary
protein metabolism in amounts exceeding the
body's ability to detoxify or convert the ammonia to
urea may affect reproductive processes negatively.
Since urea synthesis and gluconeogenesis (the
formation of glucose from noncarbohydrate sources)
are operating near maximum at peak production,
cows receiving excess protein in their diet would
need extra energy for the conversion of ammonia to
urea, thereby creating a possible energy shortage.
In addition, a high concentration of ammonium ions
may depress gluconeogenesis.
Several researchers have attempted to define
better the effect of different levels of ration protein
on reproductive performance in dairy cattle. A
number of those studies will be reviewed in this
Carroll et al. (1) used 57 early lactating cows to
compare the effect of 13 and 20 percent protein
rations on the reproductive performance of dairy
cattle. The results are in Table 4.
Table 4. The effect of two levels of protein on certain
production and reproductive measures.
Measurements 13% 20%
Milk yield (4% FCM, Ib) 57.4 58.5
Dry matter intake, Ib 36.7 35.4
Days to first observed estrus 24.0 27.0
Days open 72.0 82.0
Conception rate, % (1st service) 64.0 56.0
Pregnancy rate, % 96.0 93.0
Services per conception 1.5 1.8
Blood urea nitrogen (mg/dl.) 8.2 20.9
Cows fed the 20 percent protein ration had
higher protein intake, higher ruminal ammonia,
and higher urea nitrogen concentration in plasma
and vagina mucus. There was no significant
difference between low- and high-protein groups in
days to first observed estrus, days to first service
(55 versus 59), days open, or services per
conception. Days to first estimated ovulation were
longer (22 versus 17) in the high- versus low-
Jordan and Swanson (8) used three levels of
protein (13, 16 and 19 percent protein) in rations
consisting of soybean meal, barley, silage and
alfalfa hay to study the effect of protein level on
reproductive performance. Rations were formu-
lated to contain a 30:70 forage-grain ratio in the
dry matter. Heats were determined by visual
observation and aided by progesterone tests.
Breeding of the 15 cows per treatment started at 45
days postpartum. The results are in Table 5.
Table 5. The effect of three levels of protein on certain
Ration Crude Protein (%)
Measurement 12.7 16.3 19.3
Days open 69a 96b 1060
Days to first observed estrus 36a 450 27b
Service/conception 1.47a 1.87a 2.47b
a,b,cValues with different superscripts in the same row are
significantly different. Jordan and Swanson, (8).
Cows receiving the 19.3 percent CP rations had
27 days to first estrus, while the 16.3 and 12.7
percent CP groups averaged 41 days. Delaying the
time of breeding to 45 days may have biased the
results for the high-protein group because of their
earlier expression of estrus.
Folman et al. (4) used three groups of 20 cows in
an experiment to study two levels of protein 16.0
and 20.0 percent while using a forage-grain ratio of
22:78. One of the low-protein rations contained
formaldehyde-treated soybean meal. Treating with
formaldehyde increased the bypass protein content
of the soybean meal. Cows were checked visually
for heats four times daily and bred only when
showing standing heats. Breeding started at 60
days postpartum. The results are in Table 6.
Table 6. The effect of formaldehyde treatment and two levels
of protein on certain reproductive parameters.
Ration Crude Protein (%)
Measurement 16.0-F 16.0 20.3
Days to first standing estrus
Conception rate (%)
Milk production (Ib)
*Three cows culled before pregnancy diagnosis were assumed
aApparent difference are not statistically significant.
Folman, Neumark, Kaim and Kaufmann, (4).
The authors reported that three cows in the 20
percent protein group were inseminated four to
seven times and then culled before confirmation of
pregnancy. These cows may have had other
problems that were not reported. However, these
cows were included in the group data. The
conception rate was the lowest for the higher
protein group. Increasing the bypass protein
content of the lower protein ration had a positive
effect on reproductive performance as well as on
increasing milk production.
In another experiment, Kaim et al. (9) included
data from 224 cows. Low-protein rations contained
soybean meal treated or untreated with
formaldehyde, whereas the high-protein ration
contained only untreated soybean meal. Breeding
commenced at 60 days. Cows not seen in heat were
excluded from the experiment. The results are in
The reason for the significance seems to be that
older cows are more affected by the high protein
than are younger cows. It was indicated that the
older cows lost an average of 80 pounds body
weight during the first nine weeks as compared
Table 7. The effect of two levels of protein on certain
Ration Crude Protein (%)
Measurement 15 to 16 19 to 20
Days to first estrus
First service conception rate
Pregnant at 126 days (%)
aValues are significantly different, mainly due to differences seen in
cows past third lactation.
Kaim, Folman, Neumark, and Kaufmann, (9).
with 55 pounds for the younger cows. Since no
difference was obtained from the formaldehyde-
treated soybean meal, the results were pooled.
Oklahoma workers (5) used 146 Holstein and
Ayrshire cows to investigate the reproductive
performance when using two levels of protein (15
or 20 percent total protein ration dry matter).
Rations contained sorghum silage and concentrate
with additional protein provided by soybean meal.
The forage-grain ratio was 45:55. Cows were
observed visually for heat twice daily. Breeding
began at 55 days postpartum. Cows with chronic
uterine infection or other severe illnesses were
eliminated from the trial. Numbers eliminated
were not related to protein level. The results are
in Table 8.
Table 8. Reproductive performance of dairy cattle fed either
moderate or high-protein diets.
Ration Crude Protein (%)
Measurement 14.5 19.4
Days open 80 80
Days to first observed estrus 41 38
Average number services/90 days
experiment breeding period
All cows 1.55 1.47
Cows conceiving 1.39 1.40
Percent pregnant on experiment 87.0 85.0
No significant differences. Howard, Aalseth, Adams and Bush, (5).
Cows were eliminated if treated for ovarian cysts.
While milk production was enhanced by the 20
percent protein diet, milk fat and milk protein
percentages were not affected by diet. Actual
decreases in body weight and condition were small.
Plasma urea nitrogen increased rapidly, with cows
on the 20 percent protein diet maintaining a 10 mg/
dl advantage after the fourth week on the experi-
ment. This study is in agreement with a review by
Huber (6), where the reproductive performance of
dairy cows fed diets with different levels of protein
were reported and concluded no relationship
between reproduction and level of ration protein.
The exact relationship of high protein to repro-
duction is not well defined. There are probably
other more important factors involved. Protein
requirements must be supplied for good reproduc-
tion. A good balance of both degradable and
undegradable protein (bypass) might support equal
production with less total protein in the ration and,
in addition, reduce high blood urea nitrogen levels
sometimes associated with reduced reproduction.
It seems apparent that the key to good reproductive
performance in dairy cattle is good nutrition in
early lactation under suitable management condi-
tions. The most critical period with regard to
nutrient balance and supply to the high- producing
cow is from the time of parturition until peak milk
Vitamins, minerals and fertility
Proper mineral and vitamin supplementation in
dairy cattle feeding programs is essential to animal
health and performance. Optimum feeding of the
animal means that the individual nutrients such as
vitamins and minerals must be supplied in the
right quantities and proportions, since interactions
between individual substances may influence their
availability and utilization.
Vitamins A, D and E have all been implicated as
having a role in maintaining normal reproduction.
Minimum requirements, reported in the NRC
(1989) in early lactation (IU/lb of dry matter
intake) are: Vitamin A 1450, Vitamin D 450 and
Vitamin E- 7. Nutritionists frequently add these at
higher levels to dairy cattle rations to assure an
Vitamin A. A deficiency of vitamin A has a
direct effect on the structure and function of the
pituitary gland, gonads and uterus. In the hy-
pophysis, it leads to irreversible cystic degenera-
tion. Further deficiencies cause keratinization of
the endometrium, thus affecting development of the
placenta. In the early stages, there is a degenera-
tion of the mucosa of the respiratory tract, mouth,
salivary glands, eyes, tear glands, intestinal tract,
urethra, kidneys, and vagina. Animals become
more susceptible to infection and colds.
The first signs of vitamin A deficiency in preg-
nant cows are shortened gestation periods, a high
incidence of retained placentas, and the birth of
dead, uncoordinated or blind calves. Blindness or
night blindness may also be the first noticeable
sign of vitamin A deficiency in growing cattle that
are being fed high-concentrate diets.
Under hot, humid, and stress conditions, the
need for vitamin A increases. We recommend the
level be increased from 1450 IU/lb (NRC, 1989) to
2500 IU/lb of ration dry matter.
Vitamin D. Vitamin D is essential for the
normal calcification of bones. Some of the first
signs of vitamin D deficiency are rickets due to
decreases in the calcium blood plasma concentra-
tions and increases in serum phosphates. These
blood changes are associated with characteristic
alterations in bones. Vitamin D is implicated in
reproductive losses through its effects on phospho-
rus and calcium utilization. The NRC (1989)
recommended level is 450 IU/lb of dry matter.
Vitamin E and selenium. Vitamin E and sele-
nium have been used successfully in combination to
reduce the incidence of retained placenta, metritis
(uterine infection), and cystic ovaries in herds
having low levels of these nutrients. Herds having
such problems are frequently injected with a
vitamin E-selenium compound containing 680 IU of
vitamin E and 50 mg of selenium as selenite about
three weeks prior to calving. Because other factors
are related to retained placenta, such as reproduc-
tive diseases and stress conditions, added vitamin
E and selenium may not always be helpful in
correcting a problem. Although it is not well
defined, the new NRC (1989) has recommended the
selenium concentration in the ration be increased
from 0.1 to 0.3 ppm and vitamin E at 7 IU/lb of dry
Copper and magnesium. Deficiencies of copper
and magnesium may be related to infertility,
anemia or suppressed immune function. In a
Louisiana State University study, 204 Holstein
cows and heifers were supplemented with copper
and magnesium or both minerals to provide up to
150 percent of NRC recommendations. The results
are shown in Table 9.
Table 9. Cows conceiving by 75, 100,125 and 150 days
postcalving by mineral supplement group.
No. Days postcalving
Supplement Ani. 75 100 125 150
Control 49 22 39 45 59
Copper 51 16 34 53 62
Magnesium 55 16 35 49 63
Copper + Magnesium 49 39b 63b 73a 84a
aDifferent from other numbers in column (P<.01).
bDifferent from other numbers in column (P<.005).
Ingraham et al. (7).
When compared with cows supplemented with
copper or magnesium alone or with neither min-
eral, cows supplemented with both copper and
magnesium improved conception rates from about
62 percent to 84 percent by 150 days postpartum.
First-service conception rates for control, copper-
supplemented, magnesium-supplemented and
copper- plus magnesium-supplemented cows were
33, 27, 38 and 57 percent, respectively. Days to
first estrus, first service and services/conception
were not affected by copper and/or magnesium
supplementation. Further research is needed to
determine why copper plus magnesium but neither
mineral alone improved conception.
Phosphorus and calcium. Phosphorus and
calcium are important major minerals when
formulating diets for dairy animals. A phosphorus
shortage is more likely to occur than a calcium
deficiency under conditions where forages are used
more abundantly, since forages tend to be good
sources of calcium and concentrates better sources
of phosphorus. A phosphorus deficiency has been
associated frequently with a reduction in appetite,
retarded growth, less efficiency in feed utilization,
decreased milk production, and impaired reproduc-
Reproductive performance is affected by how
cows are fed during the dry period and throughout
early lactation. Dry cow feeding programs should
be designed to minimize metabolic problems
associated with calving. The body condition of the
cow should be monitored. Other suggestions are
outlined as follows:
1. The dry cow feeding program should be closely
2. A desired body condition score at the time of
dry-off for cows is 3.0 to 3.5 and at calving is 3.5
3. Separate dry cows into two groups-the early
dry period and prepartum period (3 to 4 wks).
4. After calving, the feeding program should be
designed to maximize energy intake so that a
positive energy balance can be achieved early in
5. Prepartum cows and early lactating cows
should receive rations containing 35 to 40
percent bypass protein.
6. High levels of degradable protein in early
lactation increases the amount of nitrogenous
nutrients to ruminant tissues that may affect
reproduction by toxic effects of ammonia on
sperm cell, ova, and embryo viability.
7. Heat stress management programs should
include shade, sprinklers and fans to improve
8. Marginal deficiencies of certain minerals and
vitamins may lower fertility.
9. The addition of fat and certain feed additives in
early lactation may have a favorable effect on
10. Feeding higher levels of vitamin E (800 to 1000
IU/cow/day) in combination with selenium
during the prepartum period (last 3 to 5 weeks)
may be beneficial in reducing retained pla-
centa, metritis and cystic ovaries.
1. Carroll, D. J., B. A. Barton, G. W. Anderson
and R. D. Smith. 1988. Influence of Protein
Intake and Feeding Strategy on Reproductive
Performance of Dairy Cows. J. Dairy Sci.
2. Ferguson, J. D. 1988. Feeding for Reproduc-
tion. The Application of Nutrition in Dairy
Practice. American Cyanamid Company Pro-
ceedings. p. 48..
3. Ferguson, J. D., and W. Chalupa. 1985. Effects
of Protein Level and Type on Bovine Reproduc-
tion. Third Asgway Bovine Nutrition and
Health Symposium for Veterinarians (27 pp).
4. Folman, Y., H. Neumark, M. Kaim and W.
Kaufmann. 1981. Performance, Rumen and
Blood Metabolites in High-Yielding Cows Fed
Varying Protein Percents and Protected Soy-
bean. J. Dairy Sci. 64:759.
5. Howard, H. J., E. P. Aalseth, G. Adams, L. J.
Bush, R. W. McNew and L. J. Dawson. 1987.
Influence of Dietary Crude Protein on Dairy
Cow Reproductive Performance. J. Dairy Sci.
6. Huber, J.T. 1983. Michigan State Univ.
Mimeo. East Lansing.
7. Ingraham, R. H., L. C. Kappel, E. B. Morgan
and A. Srikandakumar. 1987. Correction of
Subnormal Fertility with Copper and Magne-
sium Supplementation. J. Dairy Sci. 70:167.
8. Jordan, E. R., and L. V. Swanson. 1979. Effect
of Crude Protein and Reproductive Efficiency,
Serum Total Protein, and Albumin in the High
Producing Cow. J. Dairy Sci. 62:58.
9. Kaim, M., Y. Folman and H. Neumark. 1983.
The Effect of Protein Intake and Lactation
Number on Post-Partum Body Weight Loss and
Reproductive Performance of Dairy Cows. J.
Dairy Sci. 37:229.
10. National Research Council. Nutrient Require-
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