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Management of Calving on Large Dairy Farms Proceedings 2
nd
Florida Dairy Road Show (2005)
42
Management of Calving on Large Dairy Farms

Maarten Drost, DVM
College of Veterinary Medicine
University of Florida, Gainesville, FL



Calving management has traditionally been approached in a passive manner.
Calving problems are common, particularly in first-calf heifers. The most frequent cause
of calving difficulty is simply a disproportion between the size of the calf and the dam, a
calf that is too large to pass through the birth canal, or a birth canal that is too small for
the calf.


On virtually all large dairy farms, calving assistance is given by herdsmen and
farm employees with varying and, at times, limited experience. This first line of defense
is important because early intervention not only prevents calf losses but also protects
subsequent fertility. However, too often the first reaction when a cow is in labor is to
immediately hook onto the calf and start pulling, frequently with a calf puller. The
person assisting must be clean and should follow some simple guidelines to determine
whether a calf can be pulled with reasonable force, or whether the delivery will require
more drastic measures such use of a calf puller, fetotomy or cesarean section.


A secondary problem is that calving difficulty rarely occurs at a predictable or
convenient time, when there is enough help. Unfortunately, both haste and delays lead
to injuries to the calf or the dam, or to both.


The solution on large dairy farms is to develop a calving management program.
This requires designated facilities and trained farm personnel. The latter should know
what to look for and how to assess what level of assistance might be required.


Calving Facilities


Ideally cows should calve on grass in a clean pasture which is free from standing
water and which has shade. The pasture should also be close enough to permit regular
and easy supervision. It must further be easy to take the cow or heifer to a calving
stanchion for close examination and assistance. This working area should provide
protection from the weather and must have running water and a cabinet for instruments
and supplies. A maternity barn with well-bedded individual pens is a good alternative to
a calving pasture, but the pens must be cleaned thoroughly between each use.
Restraint is very important but must not consist of a standard squeeze chute since most
cows go down during the actual delivery. A head gate with hinged side panels which
swing away from the back end of the cow are excellent. There must be room for the
cow to lie down plus room for the assistants to work behind the cow.
Proceedings 2
nd
Florida Dairy Road Show (2005)
43

A regular chute can be used to catch the animal and put on a halter which is then
tied low and long to the front of the chute. After this, the cow is released through the
head gate leaving her tied. This arrangement requires lots of working space in front of
the chute.


Signs of Calving


Progressive udder development is one of the earliest signs of the approach of
calving. Early enlargement occurs in heifers during the fourth month of pregnancy. In
cows, enlargement of the udder may not become apparent until 2 to 3 weeks before
calving. Just prior to the onset of calving, the udder secretion changes from a sticky
serum-like substance to colostrum, a thick yellowish-opaque secretion. It is common to
see udder edema in heifers that are ready to calve. The edema is nothing more than
tissue fluid which accumulates in front of the udder around the navel, and at the rear
attachment of the udder. Finally, the teats become turgid and lose their wrinkles. The
lips of the vulva also become larger and softer, and lose their wrinkles.


At the same time the ligaments, which connect the various bones of the pelvis,
begin to relax, giving the cow a somewhat unsteady gait. As the pelvic ligaments relax,
the tailhead appears to become slightly raised. The onset of progressive relaxation of
the ligaments coincides with the onset of softening and dilation of the cervix. Complete
relaxation of the posterior border of the pelvic ligaments, the so-called bands, is
generally followed by delivery within 12 hours.


Signs of discomfort and restlessness do not usually appear until the cervix has
dilated sufficiently to admit a hand. Slight arching of the back is apparent at this time,
but definite straining (the abdominal press) does not begin until the first water bag
(chorioallantois) nears the vulva. Hydrostatic pressure by the fetal fluids contained
within the intact membranes assists in complete dilation of the cervix. Stretching of the
vagina causes reflex contractions of the abdominal muscles, and during one of these
contractions the first water bag ruptures. Following rupture of this membrane, there is a
temporary weakening or cessation of straining, which resumes as the second water bag
(amnion) nears the vulva. The thick, slippery, slimy fluid contained in this bag provides
lubrication for the delivery once it ruptures. The average interval between rupture of the
first and the second water bag is about 1 hour.


Once the amniotic sac has burst, regular intermittent straining begins after a brief
rest period. As a labor progresses, there is a gradual increase in the frequency and
duration of the abdominal contractions, and straining sometimes becomes nearly
continuous during the last few minutes before calving. The presence of the legs also
contributes to reflex straining during this stage of labor. The greatest delay in expulsion
of the calf occurs when the head reaches the vulva. At this stage little outward
progression takes place during each series of contractions, and the calf frequently slips
back into the vagina between bouts. This feature is most obvious in heifers, in which
stretching of the vulva takes more time. Once the head of the calf has passed through Proceedings 2
nd
Florida Dairy Road Show (2005)
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the vulva, the rest of the body follows rapidly. During hot and humid weather, cows can
become easily exhausted and frequently give up. These heifers and cows require early
assistance while the birth canal is fully dilated.


Calving Assistance


The minimum supplies needed to provide assistance at the time of calving are, a
ready supply of clean water, two buckets, soap, lubricant, two obstetrical chains plus
handles, oxytocin, and 7 percent tincture of iodine. In addition it is helpful to have
available a curry comb, a supply of frozen colostrum, a nipple bottle, an esophageal
feeder and at times a calf puller. When there has been no visible progress for 2 hours
after the appearance of the membranes, the cow should be examined to determine the
cause for the delay as well as the type of assistance she may need. Heifers are slower
to dilate and should be given more time than cows. However, there should be evidence
of progress. The calf will often live for 8 to 10 hours in the uterus after the beginning of
true labor which begins with the rupture of the first water bag.


The golden rules of obstetrics are CLEANLINESS and LUBRICATION. Before
the cow is examined internally the tail should be tied to her neck, and the anus, vulva
and the pinbones should be washed thoroughly with soap and water. Next the hands
and arms of the person assisting should be washed with soap and water, and
lubricated. Soap or detergents must not be used as lubricants because they de-fat and
remove the natural lubrication from the walls of the birth canal. Mineral oil and vaseline
make very good, lasting lubricants, as does Crisco. They should be frequently
reapplied to the arms and hands during repeated entries into the birth canal.


It takes from 2 to 6 hours for the cervix to completely dilate in the average cow,
and from 4 to 10 hours in the average heifer. The actual expulsion of the calf takes
from 1 to 4 hours in the cow and from 2 to 6 hours in the heifer. The fetal membranes
(afterbirth) are normally delivered in 1 to 8 hours. They are considered retained if not
delivered within 12 hours.

The Plan


It is very important to not start to pull, by trial and error, on the first exposed part
of the calf. Figure 1 represents a flowchart of the sequence of events and what to do at
each step.







Proceedings 2
nd
Florida Dairy Road Show (2005)
45
Figure 1. Plan for determining how to deliver a calf (Adapted from Schuijt and Ball,
1980).






Examination


The first step is to thoroughly wash the cow as well as the hands and arms of the
operator with soap and water; the next step, to use ample lubrication. The internal
examination is aimed at determining whether the calf is presented head first (cranial
presentation) or tail first (caudal presentation) and whether the head and neck and both
limbs are present and fully extended. At the same time it is decided whether or not the
calf is alive. If the head is accessible, a swallowing or gagging reflex can be stimula