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Thursday 13 August 2015

Delivering an Oversized Calf and Dealing with Hiplock

The clinical diagnosis of “oversize calf” includes “relative oversize” (in which the calf is of normal dimension but the cow’s pelvis is abnormally small) and “absolute oversize” (in which the cow’s pelvis is normal sized but the calf is abnormally large).

The key concept to understand when delivering an oversized calf is that the maternal pelvis is the limiting structure in determining whether or not the calf can be born normally. The pelvis is the bone structure surrounding the birth canal, the birth canal passes directly through the pelvis, through the pelvic inlet. It is here where the shoulders or hips of the calf are most likely to become ‘stuck’ as they may be too large, or at the wrong angle to pass through.

The question for the person assisting is whether or not the calf is deliverable by forced extraction. Forced extraction consists of manually pulling the calf out of the birth canal.

This article assumes that the calf is in normal presentation, position and posture and explains the general guidelines for extraction of a calf in such situation. (‘normal’ = frontwards facing, both fore limbs outstretched towards the vulva with head nestled between the fore limbs or backwards facing with both hind limbs extended into the birth canal).

Forwards Facing Calf Part 1…

After determining the correct position and posture of the calf, chains or ropes should be placed on both forelimbs. It is important to know the correct attachment of calving chains/ropes onto the calf to prevent bone breaks and growth plate damage.

The chains should be placed with one loop above the fetlock joint and one loop below the fetlock joint, just above the claw. This distributes the traction force across the whole joint instead of in one small area. Traction using the calving chains should only be applied when in time with the cow’s abdominal press.

At this point, you are now ready to test whether the cow can be delivered by forced extraction or not.

The principle that is being tested during this attempted extraction is whether or not the calf’s shoulders can fit through the pelvis of the cow.
In order to determine this, the cow should be lying down on her right side. This allows the frontward calf to enter the pelvis of the cow relatively straight.
Traction should be applied to one leg at a time (unilateral traction) to walk the shoulders of the calf through the pelvis of the cow. Before attempting this traction it may be helpful to line the birth canal with lube, to aid the shoulders through the pelvis.

It is preferable to start with the left leg of the calf. This usually comes through easily, so the actual test for delivery is if you can get the second shoulder past the cow’s pelvis.

When pulling the calf, you should be able to feel the shoulder move past the pelvis as you are applying traction. A suggested rule to determine if the shoulder of the calf is past the pelvis of the cow is if the calf fetlock joint is one hand’s breadth (about 10cm) outside the vulva of the cow.

Once one shoulder is through the pelvis, the extended leg should be held in place while traction is applied to the other leg. Traction of the leg should not exceed one man per leg. Excessive traction may ensure delivery of the calf, but forceful traction can lead to trauma and decreased survival chance of the calf.

Forwards Facing Calf Part 2

By this point, both shoulders should be through the pelvis. If has not been possible to bring the calf through the pelvis after a maximum of 30 minutes of trying, call veterinary assistance.

Once the shoulders are through the pelvis delivery by forced extraction is possible.

Bilateral traction (pulling on both legs simultaneously) can be exerted at this point to pull the mid-section of the calf through the pelvis. As in normal delivery, this is when the umbilical cord is compressed and the cow usually takes a break for a short period of time. At this point, the calf should start to breathe on its own. It is also the point at which rotation of the calf should occur.

This rotation is necessary to bring the widest part of the calf pelvis through the widest diameter of the cow’s pelvis. This concept is almost like removing a key from a keyhole; the key must be in the right position for it to be removed - just as the calf must be in the right position pass through the pelvis.

The first image shows the diameter of the cow’s pelvis, the second is the width of the calf’s hips; the third is the ideal fit through the pelvis.
For example on the image above, if the calf were to come out straight at the hips, the sides of the hips would get lodged within the pelvis and the calf would become ‘hiplocked’.

Rotating the calf halfway through the birth allows the rear end to be rotated so that the hips lie vertical to the pelvis, to allow passage of the calf.

Occasionally at this point the calf is lost due to failure of the calf to breathe adequately. During the break that the cow has when the calf’s shoulders pass the pelvis, pulling should stop for a short amount of time to allow the calf to breathe. Constant pulling on the calf a this point will not allow the calf to expand its chest and take in any oxygen – i.e. the calf will die.
Once traction is applied to the rotated calf, the whole calf body should be delivered without problem. In some cases, the hips still become ‘locked’ behind the pelvis. This is a problem and needs to be addressed urgently. For more information on hiplock, scroll down to the bottom of this page article for specific advice on how to deal with it.
If at any point along the way it is decide that the calf is really too big to be delivered, veterinary assistance should be sought out. Caesarean section is the most probable answer. If the calf is half-delivered (i.e. hanging out of the cow) complete or partial fetotomy may be necessary (killing the calf and removing by surgical quartering).
Backwards Facing Calf...
Just like with a forwards facing calf, it is difficult to assertain just by observation whether or not the calf is too large to fit through the pelvis of the cow. Due to this reason, you must also perform a ‘test’ to find out whether or not forced extraction is possible.
This advice assumes that the calf is in normal backwards position (i.e. coming backwards, with both hind limbs in the birth canal outstretched towards the vulva with the calf in dorsal position (right way up)).

The first thing to do is apply calving chains/ropes to the hind limbs of the calf. Once the calving traction aids have been applied, the calf can be slightly pulled at the legs but the main action here is to rotate the calf so that the legs become verticle and not horizontal. This take advantage of the widest diameter of the cow’s pelvis in order to fit the hips of the calf through the pelvic inlet. The slight pull on the calf at this point should be outwards and sligthly upwards as shown in the illustration below.

Bilateral tracton can be applied in the amount of two people (or a calving aid) and should be applied simultaneously, to both legs at the same time.

So the test for delivery is if the hips of the calf can pass through the pelvis of the cow. This is determiend in most instances by the extension of the hocks of the calf beyond the vulva.

If this is easily accomplished, possible delivery can be made. However, now that the calf is ‘halfway’ out the cow, there is very little time left to accomplish the re-rotation of the calf back to a normal verticle position in order for the chest of the calf be delivered through the cow. There is rarely more than 2-3 minutes to complete the delivery.

If the test fails in either case, call for professional assistance as surgical delivery is probably indicated. Note: do not get the calf’s hips past the pelvis and then call for delivery – once the hips are through, generally there is not enough time for a vet to arrive and save the calf, it is better to try as hard as you can to get the calf out once the hips are through.

There is a common misunderstaning, that calves need to be pulled out very rapidly otherwise they will die. One must remember that the calf’s life will not be compromised until its umbilical cord becomes trapped against the maternal pelvis – and this is when the calf will take its first breath. In practical terms, traction should be slow and controlled until such time as the calf’s tail head and anus begin to emerge from the cow’s vulva. Once this point is reached, do not rush, but do avoid delay.

As the anus and tailhead emerge from the vulva, continue the traction simultaneously on both legs until the calf is fully delivered. Check the calf is breathing on its own once it has been delivered and then return the calf to the mother to allow the mother to lick and soon the calf will start to suck the colostrum from the dam.

Dealing with Hiplock

Hiplock occurs when the hips of the calf become lodged in the pelvis of the cow. This makes delivering the calf extremely difficult and can often lead to death of the calf and damage to the cow.

Most hiplock cases are unavoidable because the hips of the calf are simply so big or the pelvis of the cow is unusually small.
The illustration above shows what most hiplock cases look like. The red mass in the centre is a cross section of the calf and the light blue bone structure is the pelvis of the cow.
In order to understand the best ways to to treat hiplock and increase the chances of a successful delivery without veterinary assitance, it is importance to understand the relative anatomical structures that play a key part in these situations.

The pelvis of a cow is widest in its verticle axis (red line) and narrowest in its horizontal width (green line).

When the calf is passing through the pelvis, if the calf is in a frontwards facing position, different parts of its body can pass through with different ease. The fore limbs pass through easy as they are long and thin. The head, if straight, will also pass through easily. When the shoulders are reached the calf’s fore limbs should be pulled alternately so that the shoulders are eased through slowly; trying to pull both shoulders through at the same time would be near impossible. The torso, which is larger in verticle axis than in width, can also pass through relatively easy. Once the torso has passed the hips approach the pelvis. The hips of the calf are larger in horizontal width than they are in vertical height.

When the hips approach the pelvis and are not rotated, there is a good chance they will simply become ‘locked’ behind the pelvis. Consequently the calf will not be able to pass any further. This can lead to compression and tension of the chest of the calf, preventing breathing if the umbilical cord has broken and often leading to brain damage or death of the calf.

Essentially this problem is similar to a moose trying to fit through a door frame

How would an intelligent moose solve this problem? Turn his head and walk right through the door. The solution for the calf is similar!

As the hips approach the pelvis, if the legs are rotated so that the legs appear verticle, rather than horizontal, the hips will rotate so that the widest part of the hips are situated in the widest part of the pelvis.

Once the hips have been rotated, traction can be applied to the legs at the same time to pull the hips through the pelvis.

Sometimes this rotation simply is not enough to fit the calf through the pelvic inlet. Other methods can be applied that can also increase the chances of the hips being passed.

The cow can be rolled onto her back, and then back onto her side again, sometimes dislodging the hips and allowing them to pass freely. This method should be done cautiously as when the cow has her legs in the air the chance of being kicked is much higher.

Sometimes the hips become so tightly and deeply lodged behind the pelvis that no measure of rotation will allow them to move. It can be helpful to attach calving ropes to the legs and head, repel the calf back inside and try again slowly, aiming to get  the hips above and through the pelvic inlet, avoiding the bottom ridge on which the hips can become ‘caught’ behind.
A method I have been told anecdotely, which is claimed to be very successful is to gently have an assistant press on the side of the cow, where the hips of the calf would be inside the birth canal, with their foot. Rhythmically pressing down as the calf is being pulled can ‘jolt’ the calves hips into the correct position which will allow the calf to be delivered.

When the cow is coming backwards the same procedure of rotation can be used but in reverse order. First the hind limbs are rotated to allow the hips to pass. Then they are rotated back to normal position so that the rest of the body can be delivered normally.

Excessive traction should never be used in order to correct this position. This will only damage the calf and cow and lead to increased likelihood of infertility and death of the calf. If using the above techniques do not work, seek veterinary assistance.


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