Nutritional imbalances cause reproductive problems in
By George F.W. Haenlein
Extension Dairy Specialist
University of Delaware
Reproductive Problems
Can Have
Nutritional Causes
NEWARK, Del. - Several
reproductive problems in dairy
cattle result from physiological
(glandular) changes caused
primarily by nutritional im
balances, not disease organisms.
Abortion, repeat breeding,
anestrus, silent estrus, and
retained placenta can all be in
fluenced severely by nutrition. Of
course, changes in amount of
daylight and hormone implanation
or injections also affect
reproduction.
Four major nutritional
categories influence reproductive
performance: energy, protein,
minerals, and vitamins. - Fifty
years ago, scientists at the
University of Wisconsin
discovered the role and im
portance of vitamin D in bovine
diets. More recently, interest was
focused on vitamin E in relation to
reproductive problems. Currently,
beta-carotene and selenium are
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receiving much attention.
Let’s take a closer look at the
effects of certain rtutrients and
their imbalances in dairy cattle.
Energy-“ Hollow belly disease,”
poor pastures, drought, un
palatable feed (silage, hay and
concentrates), reduced feed in
take, scouring, and loss of body
weight due to heavy milking are
conditions that lower the cow’s
energy supply. The opposite
condition-so-called “flushing” or
increased supply of energy-can
stimulated ovulation and estrus.
This practice has long been used
by sheep breeders to synchronize
estrus and to increase the lamb
crop.
Energy supply is directly related
to normal reproductive function in
dairy cattle. Newborn calves that
are weak due to lack of energy in
utero have trouble surviving.
Puberty and first estrus will
sometimes be delayed several
months in calves that are fed low
levels of energy. Those becoming
fat on too much energy will ex
perience irregular estrus cycles
and delayed conception. Heifers
that have conceived but are un-
thrifty because of a lack of energy
will have problems in calving or
may even abort. Reduced milk
secretion also results.
Thus, energy shortages are
serious impediments at all stages
of reproduction, but energy supply
excesses are just as detrimental.
Overconditioning, especially when
cows or heifers are prepared for
shows or are on a show circuit, is a
frequent problem. Remember this
as the annual show season gets
under way again.
Under range conditions, shor
tages of energy supplies stunt the
growth of young pregnant heifers
and may cause so-called stress
abortions due to low blood-glucose
levels that trigger hyperactivity of
the adrenal gland.
In our dairy herd at the
University of Delaware we have
now placed all our cows, as well as
our heifers down to 6 months of
age, on electronic feeders. This
enables us to feed each individual
exactly what she needs or
deserves-no more, but also no
less-and not just energy.
Protein-A shortage, as well as
excess, of this nutrient also causes
reproductive problems, though
these are not quite as dramatic as
those caused by a lack of energy.
Protein and energy interact, so
when energy supplies are adequate
but protein is deficient, estrus,
puberty, and pregnancy are
delayed or impaired. Amino acids
are a basic part of protein needs
but the cow’s specific amino acid
needs have not been clearly
defined under normal production
circumstances. Methionine has
shown some promise in cattle
experiments.
Minerals-A phosphorus shor
tage is more likely than a calcium
deficiency under high roughage
conditions because forages are
short on phosphorus. Adequate
phosphorus supplies are critical
for normal reproductive ef
ficiency. A level of 0.4 percent
phosphorus in the total diet and a
Ca to P ratio of about 1.2 to 1.0 is
recommended.
dairy cattle
This ratio also indicates that
calcium is an essential feed
ingredient for normal reproduc
tion. But its bioavailability and
intestinal absorption vary widely,
depending on content, pH, lipids
that form insoluble soaps, car
bohydrates and vitamin D ac
tivation. Interaction with other
minerals, such as manganese, is
also critical. The large amounts of
calcium the cow loses daily in milk
must be replaced.
Selenium is of particular interest
in relation to reproductive
problems because it has been
linked to a reduction in retained
placenta. Soils in certain parts of
the U.S.-the East Coast, Great
Lakes, New England, Florida, and
the Northwest-are deficient in
selenium. In these regions, routine
supplementation in feed or by
injection is indicated. Brewer’s
grain is a good natural source of
selenium.
Salt shortages will cause
reduced feed intake, dirt chewing,
poor haircoat, and heat stress, all
of which indirectly affect
reproductive efficiency. Normally,
cows should receive 1 percent salt
in their concentrate supplement.
Salt is also a convenient carrier for
trace minerals such as zinc,
manganese, iodine, cobalt, iron,
molybdenum, copper, and sulfur,
which have a role in normal
reproductive performance. Zinc
and manganese affect the
production of eggs and sperm,
libido and the sex rations of calves.
Vitamins-Vitamin A and its
precursor, carotene, are of par
ticular importance for efficient
reproductive function. Vitamin A
is essential for normal sperm
production. It’s also important for
the normal function of mucal
membrances, including those in
the reproductive tract.
Conversion of carotene to
vitamin A may be inhibited by
nitrates in the feed from drought
stricken grasses or from corn and
small grains which were fertilized
heavily with nitrogen. It may also
be affected by phosphorus
deficiency, protein deficiency, a
high energy-low roughage diet, or
by heat stress.
Possible effects of vitamin A
shortage include the birth of dead
or weak calves, retained placentas
or even abortions. Vision ab
normalities are typical diagnostic
symptoms of vitamin A deficiency.
Fresh and dried green forages are
good sources of vitamin A, but
commercial supplements of
vitamins A, D, and E are quite
inexpensive and should be added to
commercial concentrate mixtures
at ratios of 5 to 1 to 0.01. Cattle
should receive 3,500 international
units of vitamin A equivalent per
day for every 100 pounds of
bodyweight for maintenance,
pregnancy, growth and milk
production.
Vitamin D is implicated in
reproductive losses through its
effects on phosphorus and calcium
utilization. Supplementation is
important for unthrifty animals.
It has been suggested that
Vitamin E may play a beneficial
role in reproduction, but hard
evidence is lacking. However, it is
important as a feed supplement
and antioxidant to prevent off
flavors in milk. It also has ex
cellent healing properties for in
jured tissue.
Although it is assumed that
rumen microbes produce enough
of the B vitamins to meet cow
requirements, different microbial
species have different vitamin B
producing abilities and changing
the cow’s diet will change her
rumen microbe population. For
example, corn is known to be low in
the amino acid precursors
required for some rumen B
vitamin synthesis, so if more com
is suddenly added to a cow's
ration, problems due to B vitamin
deficiencies can develop which
affect reproduction indirectly.