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Friday, 17 July 2015





First of All…

In order to know how to react in situations concerning abnormal calving of a cow, it is best to first understand the normal processes that a cow goes through during uncomplicated parturition.
The first point to make is that the impact of level of assistance and subsequent breeding performance is often overlooked – the following table illustrates the assistance given and the later breeding performances…



As shown by this table, cattle assisted by stockmen/stockwomen show the least successful breeding rates for the following seasons. Therefore it is of upmost importance to understand how to hygienically, safely and successfully assist a cow during parturition.

As the stockperson, there are 3 key factors to keep in mind that can be applied to all calving situations:
1.      Patience: much damage can be caused by interfering too soon in the birth process. Disturbing the cow during the first stage of labour can delay dilation of the cervix. A cow can be safely left alone for an hour after the water bag has ruptured and in the case of a heifer this period can be extended to 3 – 4 hours. There is no need to jump in at the first sign of action; early and unnecessary ‘help’ can actually be hindering rather than helping the dam.
2.      Hygiene: not only must the maternity accommodation be clean and well bedded, the equipment to be used should also be clean and well maintained. The category of ‘equipment’ includes anything that will come into contact with the cow, calf or bedding that the cow will use. Taking time out to disinfect everything beforehand will save time and money treating infections or non-cycling cows post-calving. It is also important that person assisting has clean hands or wears gloves.
3.      Lubrication: adequate lubrication is necessary to help in the delivery of the calf. Veterinary grade obstetrical lubricant is the best option to use if possible. This will aid the passage of the calf through the birth canal. Do not use any kind of liquid soap as a lubricant as this will break down the natural lubricant of the cow.

Normal Gestation

Pregnancy in cows is around 283 days but is influenced by single or twin calves, and the sire (bull/paternal parent). Gestation length and calf birth weight are calculated for many sires used in AI programmes. These estimated breeding values (EBVs) are a very important method to reducing calving difficulties and can be incorporated into beef herd programmes using AI.

Normal Calving

Imminent parturition is indicated by separation from other cows in the group for up to 24 hours before calving, udder development and accumulation of colostrum (collectively and colloquially known as ‘bagging up’) and slackening of the sacro-iliac ligaments (the ligaments either side of the tail at the tail head, which give the tail head a depreciated stature i.e. ‘sunken in’).
When these signs are observed it is best that the cow/heifer is brought in from pasture and kept in a calving pen (i.e. a small area, bedded down well that can easily be disinfected and bedded, with ease of access and close to where the cow can be checked on regularly). Calving out in the field, especially under pour weather conditions, can increase chance of bacterial contact with the calf and increase chances of mastitis and metritis.

1. First Stage Labour:

The first stage labour is represented by dilation of the cervix (neck of the womb) which may take 3 – 6 hours.
The cow will typically continue to separate herself from the herd-mates into a corner of the field, or will reside in the corner of the calving pen, away from the entrance. Often the cow will alternate between lying/standing behaviour. A thick string of mucus is commonly observed hanging from the vulva. Bouts of abdominal straining occur more frequently, usually every 2 – 3 minutes, towards the end of first stage labour.
In a case of uncomplicated anterior parturition, this increased activity coincides with extension of the calf’s forelimbs.

2. Second Stage Labour:

Second stage labour is represented by expulsion of the calf (or calves) and takes from 5 minutes to several hours. There is rupture of the allanto-chorion (water bag) with a sudden rush of fluid – this fluid helps to lubricate the birth canal. The amniotic sac appears at the vulva and ruptures at this stage. Powerful reflex and voluntary contractions of the abdominal muscle and diaphragm (“straining”) serve to expel the calf. Occasionally, the amniotic sac may not rupture and results in death of the calf by asphyxiation (suffocation). This scenario is more common in twin births.

3. Third Stage Labour:

Third stage labour is completed by expulsion of foetal membranes (afterbirth or cleansing) which usually occurs within 2 – 8 hours after birth of the calf.
However, it is not uncommon for this process to take much, much longer. Generally speaking all cows will expel the afterbirth at 10 days from calving. After 8 hours have passed since calving, if the membranes are still retained, the stockman should take note and monitor the cow closely. Antibiotic treatment and anti-pyretic drugs may be needed to ensure the health of the cow. 
Incorrect cleansing expulsion can lead to disease and unhealthy cycling patterns. For more information on cleansing, see my specific blog post aiming to address the treatments and causes for cleansing problems in cows… *insert link here*

Facilities To Aid Calving…

The safety of everyone present is very important with excitable and potentially aggressive beef cows and some heifers. Many farmers routinely calve all cows in cattle stocks/crushes which are not ideal for several reasons but may be the best compromise with an aggressive cow and limited staff.

Advantages of stocks –
·         Restraint of aggressive cow
·         Prevents sideways movement of the cow

Disadvantages of stocks –
·         Cow unable to lie down and strain, to help expel the calf
·         Cow may become cast and unable to rise
·         Cow may fall down during delivery of the calf, causing injury to the calf
·         Stocks increase the stress of the cow which can impact on calving success

Calving Pens…

Several factors conspire to result in conflicting advice regarding calving accommodation. Ideally, the calving pen should be cleaned and disinfected between every occupant to prevent disease transmission. The diseases most readily spread from the dam to offspring and subsequent pen occupants are: paratuberculosis (Johne’s disease) and Salmonella Dublin.

Good hygiene in the calving pen will also reduce navel infections, joint ill and subsequent episodes of calf scour. Mastitis and metritis (womb infections) in the cow may also be reduced.
A compromise of the time and effort required to re-bed each pen after each calving is to add large amounts of clean dry straw between cows with the pen mucked out and disinfected after 3 – 5 calvings.
An ideal calving pen would be fitted with a light and power source, a water bowl and facilities to milk the cow in case she is not in a fit condition to move out after having gave birth.

Equipment…

Ropes
Most vets and stockmen use calving ropes rather than chains to apply traction to the legs of the calf; calving chains are much more readily disinfected. Two short ropes, preferably different colours, can be used for the legs, and a longer rope as a snare to correct the head, should it be in an incorrect position.



Almost without exception, calving ropes are not adequately cleaned and disinfected between calvings. Typically, they are left hanging on a hook in the bulk tank room or over the calving aid next to the cattle stocks. Calving ropes must be cleaned and disinfected thoroughly of all gross debris after use and left in a veterinary grade disinfectant for at least 10 minutes, then dried and stored in a clean dry bag until they are needed again.

Traction and Calving Aids…

With the calf presented in anterior presentation (coming forwards), reasonable traction will deliver the calf when two people pulling can extend both front legs such that the fetlock joints (the joint above the hoof) protrudes one hand’s breadth beyond the vulva within 10 minutes’ traction. Such movement of the calf’s forelegs represents extension of both elbow joints into the cow’s pelvis.
Veterinary assistance is necessary if greater traction is applied without obvious progress and the elbows are not extended easily.
With the calf presented in posterior condition (coming backwards) two strong people pulling on the calving ropes should be able to extend both hock joints of the calf more than one hand’s breadth beyond the cow’s vulva. The calf’s hindquarters now fully within the pelvic inlet) within 10 minutes. Further traction will safely deliver the calf.


There are two commonly used calving aids. The more simple ‘T’ shaped aid, which is more suitable for dairy breeds, has the advantage of applying traction to the calf’s legs alternately. The new design aid fits over the pelvis of the cow and, because of the more rounded rear end of the beef breeds, is more suitable for use in these breeds. Both generate friction forces in excess of four strong men – they must be used with great care to ensure they do not cause nerve paralysis and hip lock.
Calving aids must also be regularly and thoroughly disinfected and cleaned.

Calving Positions, Presentations and Postures…  

  Presentation – defined as the relation between the long axis of the calf and the maternal birth canal. It includes anterior and posterior longitudinal (i.e. backwards of forwards) presentations and ventral or dorsal transverse (i.e. facing the sky or facing the floor) presentations.
    
  Position – defined as the surface of the maternal birth canal to which the calf’s vertebral column (i.e. back) is applied. It includes dorsal, ventral and left, right.
   
   Posture – refers to the disposition of the moveable appendages (limbs) of the calf and involves flexion or extension of the cervical and limb joints e.g. bilateral hock flexion posture (both back legs bent at the joints).


General Guidelines for Uncomplicated Situations:

When the calf is in anterior presentation (i.e. head first), as the legs start to emerge from the vulva, the distance between the fetlock/pastern (first joint above the hoof) and the vulva must be at least a hand’s breadth after a maximum period of 10 minutes traction (two people) to safely proceed.



If the calf is ‘stuck’ and will not move any further without any further more skilled action, then further assistance is required. For more information on this situation visit my specific blog post aiming to address abnormal calving procedures… *insert link here*


When the calf is in posterior presentation (i.e. back legs first), as the legs start to emerge from the vulva, two strong people pulling on calving ropes should be able to extend the hocks more than one hand’s breadth within 10 minutes of pulling.



When faced with a calving situation the following process is advisable to undertake:
Ask yourself 4 questions (in order):
1.     

Has the cervix dilated? I.e. has the neck of the uterus where the foetus is held sufficiently ‘opened up’ to allow passage of the calf? – You should be able to tell if the cervix is dilated by sliding your palm along the vaginal wall toward the uterus. There should be no cervical ridge or form of ‘blockage’; it should be smooth and continuous. Think that, if you cannot fit your hand through, how will the calf be able to get through!? Assisting prior to cervical dilation can damage the cow and injure the calf.


2.     




Is the water sac/bag broken? I.e. has there been a rush of yellow-orange fluid from the vulva and is there a visible water filled bag in sight? -  Once the water bag has broken it is important to make good progress. Firstly because as time goes on, the water is leaving the birth canal and so is decreasing the amount of lubrication available. Secondly, the calf’s intrinsic reaction to take its first breath is triggered soon after the water bag is broken. If the calf has tried to begin breathing, you will see a frothy appearance of the mouth and nostrils. Premature breathing can lead to suffocation within the birth canal.





3.      Is the calf in proper position? I.e. is the calf facing forwards, with its two front legs outstretched and its head between them or is it backwards with its two back legs outstretched? If it is anything but these two presentations, it is an abnormal position. – If the position of the foetus is abnormal, using your best judgement and manoeuvring the calf into a better position can be successful, however if in doubt, call a vet to assist. In some situations not even a vet will be able to manually correct the position, so do not feel that your skills are inadequate if you have failed to do so.

4.      Can the calf pass through the pelvis? I.e. is there enough room physically for the calf to exit the womb and pass through the birth canal? – Assess the size of the calf relative to the birth canal. Forcing a large calf through a small pelvic opening can result in injury and/or death of the cow and calf.

Other points to make note of are:
-          Any chains or ropes used should be attached to the calf, below the dew claw and above the hoof.
-          Pull alternatively on each leg to ‘walk’ the shoulders out. The shoulders are the widest part of the calf’s body and will prove the most difficult to pass through the birth canal.
-          Once the shoulders are free, rotate the calf 90 degrees to aid passage of the hips. Apply traction downwards and outwards
-          It is best for the cow to lie on her left side, so that the rumen lies under and not on top of the calf.

The general time scale of events is:
Preparatory (2 – 6 hours)
Calf rotates to upright position in the womb, uterine contractions begin, water sac is expelled.
Delivery (1 hour or less)
Cow usually lying down, foetus enters birth canal, front feet and head protrude first, calf delivery complete
Cleaning (2 – 8 hours)
Button attachments on placenta relax, uterine contractions expel membranes.



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