MICHELLE RANCK
Lancaster Farming Staff
HONEY BROOK (Chester Co.) To address the specific
topic of dairy reproduction, extension services in southeast
ern Pennsylvania organized several meetings to educate
producers.
Two meetings in Berks County, one in Chester County,
and one in the Montgomery/Bucks area gave dairy farmers
critical information on important facets of their business.
Dr. Michael O’Connor, reproduction specialist and pro
fessor of dairy science at Penn State, spread the word about
new breeding management techniques and encouraged pro
ducers to have a carefully-planned, instead of random, ap
proach to reproduction.
O’Connor also attempted to show “how effective and la
bor-saving these systems can be,” he said. Reproduction
management is not just injecting a cow but putting a system
into place and working with the cow, he said.
O’Connor began his presentation by teaching about nutri
tion and its effect on reproduction. O’Connor also covered
several methods of reproduction used on dairy farms.
Nutrition concerns for optimal reproduction was first on
the speaker’s agenda. “Energy intake and energy balance
are the most important factors in reproduction,” he said.
Since energy levels are so integral to successful breeding,
how does a producer see what the herd’s status is on the
amount of energy?
Evaluate body condition, said O’Connor. “A cow should
not exceed one body condition score loss between the time
she calves and the time you want to breed her for the first
time.”
A minor loss would .5 or lower during the first five weeks
of lactation. Consequently, keeping a cow in good condition
and cycling properly as soon as feasible has direct impact on
breeding efficiency.
Researchers in a Michigan study found that health prob
lems were less associated with conception failure than a
change in body conditioning score. Cows ate less, produced
less milk, and took more energy reserves to produce milk
than cows with earlier ovulations.
The cycle perpetuates itself as cows with lower energy
reserves use the energy off their body flesh, further inhibit
ing ovulation. Adequate feed bunk space, frequent feeding,
and a clean feed bunk will encourage dry matter intake.
The other side of the coin, overconditioning, may also be
detrimental to reproduction. Heifers just coming fresh are
often overconditioned, said O’Connor. Typicaly, an over
conditioned animal has poor uterus muscle tone, leading to
difficult births or a retained placenta. Consequently the cow
is more susceptible to uterine infection. Overconditioned
diy cows are also two-and-a-half times more likely to de
velop cystic ovaries.
Ammonia
Low ammonia levels are also important to reproductive
Dairy Reproduction Troubleshooting
Focus Of Extension Meeting
Nutrition’s Impact
On Reproduction
Holsteins
Oley, Berks
cluster between the fence and pond in
County. Photo by Michelle Ranck
health. High levels of ammonia, said O’Connor, produce a
transformation to urea. High urea levels may alter the com
position of the uterus, reduce the acid level, or have an effect
on the sperm cells.
European researchers studying crossbred heifers found
that ammonia has an adverse effect on the growth of eggs.
In addition, energy is taken from the cow to detoxify the
ammonia from the urea, taxing an animal with low levels of
necessary energy.
“If you have an animal and it already has a negative
energy balance and you feed it a high ammonia diet, it’s
really magnifying the postpartum energy deficit. You’re
asking them to expend energy to detoxify the ammonia.”
Not getting enough water may also increase the high am
monia problem, as water helps to dilute the urea. Addition
ally heat stress may compound the problem. Milk Urea
Nitrogen (MUN) is a good diagnostic tool for the protein
status of a herd, said O’Connor.
“When a group of cows have 19-20 mg percent MUN, the
reproduction percentage can be compromised. I wouldn’t
get concerned about one cow, but when a group shows high
levels, I’m suspicious of the way the ration has been man
aged from a protein standpoint.”
A certain level of starch in the diet is beneficial for the
rumen microbes to manufacture protein, which in turn gen
erates milk production.
Dairy producers, said O’Connor, have to look in the
mirror and decide if their own breeding system and tech
niques are “up to snuff before they get too excited about
MUN numbers and saying, ‘that’s my problem.’”
He said, “Please, don’t go out and risk lowering your milk
production by lowering your protein today.” O’Connor en
couraged instead testing and working on a DHIA program.
O’Connor also addressed minerals and their effect on
dairy reproduction. “So often people say, ‘My herd has re
tained placentas, so I must have low selenium levels,”’ said
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