The most profitable age for first
calving is between twetjty-'fpur>
and twenty-six months. Heifers
that calve later produce slightly
more milk during their first lacta
tion. However, increased costs of
raising late-calving heifers, the
delay in recovering investment
costs, and reduced production per
day of herdlife outweigh the slight
increase in milk yield. If heifers
are managed well, they are large
enough to breed at fifteen months
and calve at twenty-four months
of age.
A heifer reaches puberty when
normal sexual behavior is exhi
bited and ovulation occurs. Onset
of puberty is more closely related
to body weight than to age. Heif
ers reach puberty when body
weight is 30% to 40% that of aver
age adult weight. Occasionally,
the first few estrous cycles occur
without behavior signs of heat.
These are called silent heats. On
the other hand, some of the first
standing heats are followed by
anovulation (no ovulation).
Frequency of silent heat and
anovulation decreases as heifers
experience more cycles. For these
reasons and because they are not
yet lirgc enough, heifers should
not be toed when they first reach
puberty. If growth is slowed down
by underfeeding, disease, or para
sites puberty is delayed.
With regard to nutrition, low
dietary energy levels can lead to
ovarian inactivity.
Inadequate protein intake and
nutritional problems leading to
anemia can cause silent or irregu
lar heats. Deficiencies of pho
sphorus, vitamin A and E may
also affect reproduction. Heifers
approaching breeding age should
be watched closely for heat to
insure that they are cycling. A vet
erinarian can examine heifers to
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ZI
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• Expanded metal floor stays cleaner and
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Dairy Heifer Reproductive Management . Seminar
determine which ones are cycling
and also determine if there are any
congenital reproductive
abnormalities.
There are numerous advantages
to artificial insemination and
dairymen should consider breed
ing their heifers to the bctlei AI
bulls. The most important advan
tage is the improved genetic merit
of the calves sired by AI bulls.
Daughters of AI sires have at least
900 pound milk production advan
tage over daughters of non-AI
sires.
A successful AI program
involves routine heat detection
and timely insemination.
Although the average interval
between heats for heifers is twenty
days there is a normal range of
eighteen to twenty-four days.
Because considerable variation
exists between animals, dairy far
mers should record all heat dates
on a chart so that they can antici
pate future heats. To monitor heats
accurately, heifers must be clearly
identified with neck chains, large
ear tags, or freeze brands.
Heifers should be checked for
heat twice a day. If heat detection
is routine and frequent, heifers
should be inseminated twelve
hours after the beginning of stand
ing heat. When the onset of heat
cannot be accurately determined,
heifers should be bred soon after
standing heat is noticed. Dairy
men who cannot^routinely check
for heat should consider using
heat synchronization and a con
centrated AI breeding program for
selected months during the year.
Heat detection aids, such as
heat mount detectors, crayon or
chalk markings, surgically altered
bulls or androgenized heifers
equipped with chin-ball markers,
can make heat detection easier and
more efficient.
When selecting AI sires to
breed heifers, primary emphasis
should be placed on production
merit. From among these bulls,
the choice should be further nar
rowed to those bulls with the least
expected calving difficulty.
Thirty-five to fifty days after inse
mination heifers should be exa-
295 Woodcorner Rd.
Lltitz. PA 17543
IMilaWoatofEphrata
Phone:7l7-735-1121
Franklin County Extension
The 1989 Executive Committee of the Franklin County (PA) Cooperative Extension
Association was selected at the recent Board of Director’s reorganizational meeting
In Chambersburg. They are (seated, I. to r.): Michael John of Waynesboro - President;
Philip Lobaugh of Chambersburg • vice President; (standing left to right): Dana Mey
ers of Chambersburg - secretary; Joel Rotz of Chambersburg - director; and Mark
Cayman of Waynesboro - director. John Hart serves as treasurer. The executive
committee, along with the Board of Directors, is responsible for funding and direct
ing the Penn State Cooperative Extension educational programs for Franklin County.
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225 Wood Comer Road, Lititi, PA 17543
Call Toll Free: In PA 1-800-2KEYAID (1-800-253-9243)
Elsewhere 1-800-4KEYAID (1 -800-453-9243)
Local calls 738-4241
Hours: Mon - Thur 7:30 A.M.-5:00 P.M. Fri 7:30 - 9:00
Saturday 7:30 A.M.-12:00 Noon (Eastern Time)
mined for pregnancy.
Accurate breeding records are
important for predicting calving
dates. Heifers close to calving
should be observed frequently.
They should be moved to the calv
ing area several clays to a week
before the anticipated calving
date.
The best calving area is a level,
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uncasnr farming, snuraay, narcn n, dmimuj
dry, easily accessible grassy pas
ture. A good alternative is a large,
dry, well bedded maternity pen.
Maternity pens should be kept
clean and reserved solely for calv
ing. Selecting sires for calving
ease, raising heifers to adequate
size and using proper calving
management practices will
minimize calving problems.
PINK-EYE
In Cattle