8 November 2018

8 minute read

Background and history

Since 1985 there has been a gradual reduction in farrowing rates in many herds associated with increased repeats in sows. A survey carried out at that time indicated that up to 24% of herds may have had previously unrecognised problems with this disease.

A discharge from the vulva post-service does not automatically mean there has been a pregnancy failure, but it will in most cases indicate infection. Potential areas from which discharges could arise include the rectum, the vulva, the vagina, the cervix and the uterus. Discharges can also arise from infection of the kidneys (pyelonephritis) or the bladder (cystitis) with pus being passed in the urine.

It is important to record the time when discharges are first seen, their colour and composition and effects on the sow. Use the farrowing rate loss sheet as shown in chapter 5 to record the observations.

Clinical signs

Vulval discharges are common within 3-4 days of farrowing when a thick viscous material may be excreted. If the sow is healthy, the udder is normal and there is no mastitis, ignore it. It is common practice to inject such sows, but his is not necessary under these circumstances. Always be mindful that with a heavy smelling bloody discharge there may be a retained piglet or afterbirth.

The time in the reproductive cycle when the discharge is seen is important particularly between 14-21 days post-service. The lips of the vulva of each sow should be parted daily and any tackiness or small discharge noted. The sow should be marked and if she repeats a problem may be developing. Note also the periods when it is quite normal for the sow to show evidence of a slight discharge. (Fig.6-11). Remember discharging sows may be pregnant and always pregnancy test before culling. The types of discharge are shown in Fig.6-12.

Fig.6-13 shows the reproductive performance of 42 sows in a herd that had a discharge problem and this highlights the fact that only 28% of the sows farrowed, and 62% of them repeated. Most of the animals had 5 or more litters. It is important therefore to cull such animals because farrowing rates of only 50-60% are achieved to matings. The response to treatments is poor.

Records

The changes that take place are shown in Fig.6-14 and highlight increases in repeat matings, sows not in-pig and discharges, but a proportion of sows will discharge and remain in-pig. In these cases infection arises from either the vagina or the bladder. Doubtful or negative pregnancy tests at 30 and 40 days increase, but levels of abortions, litter size and sow health remain normal.

Diagnosis

The bacteria causing reproductive tract infections are shown in Fig.6-15. The main organisms associated with endometritis and vulval discharges are opportunist invaders. In some herds no specific organism can be identified, although bacteriological tests may show one or more bacteria predominating either in the prepuce or vagina. A precise diagnosis can be difficult.

An initial diagnosis is made from observations of vulval discharges commencing 10 days post-service and associated with a loss of pregnancy. Leptospirosis caused by Leptospira bratislava/muenchen, particularly in gilts, can cause discharges post-service, particularly if there is early embryo loss (14-25 days) and absorption. Brucellosis also causes vaginal discharges following absorption.

Examination of records can help in differentiating between infectious and non-infectious causes of infertility as shown in Fig.6-16.

Post mortem examinations on sows with heavy discharges are not particularly helpful. Post mortem examination of 47 discharging sows within seven days of the event showed only 12 with an infection actually in the womb. (Fig.6-17). This is because by the time sows can be slaughtered and the wombs examined they have come into oestrus which has the effect of resolving and removing the pus from the womb. In spite of this most sows still remain infertile

Causes

Field studies have identified the following factors that do not appear to be associated with post-mating vulval discharges and infertility and these include:

• Season.
• Breed of sow.
• Source of breeding female.
• Source of boar.
• Artificial insemination.
• Cystitis pyelonephritis.
• Discharges in lactation.
• Assistance at farrowing.
• Discharge at <5 days post-mating.

Artificial insemination does not appear to be a major part of the complex because its use in problem herds does not necessarily solve the problem. Bladder/kidney infections do not cause pregnancy loss, unless the sow is ill, when abortion or death may occur. Generally, there is no relationship between discharges seen in lactation and those seen post-service with loss of pregnancy. Likewise, assistance at farrowing does not appear to affect a post-service problem.

During the period of oestrus and whilst oestrogen levels are high it is difficult to infect the womb. However, as oestrogen levels drop and the levels of progesterone rise the womb becomes susceptible to infection.

It is likely that over a period of time in problem herds, certain opportunist bacteria gradually predominate in the preputial sac of the boar, the vagina and the environment.

If matings take place towards the end of the heat period with high levels of infection persisting at the cervix, the risk of ascending infection becomes high.

The major predisposing factors leading to the development of a vulval discharge problem include:

• Herds with high numbers of old sows.
• A short lactation length (14-21 days).
• Multiple matings. Cross mating boars.
• Handling the prepuce at mating and squeezing the prepucial sac.
• No supervision at mating.
• Matings towards the end of the oestrus period.
• Wet, dirty boar pens. Poor drainage. Continual use.
• Dirty, wet sow mating pens and continual use without cleaning.
• Small stalls where the sow adopts a dog sitting posture with heavy contamination of the vulva.
• Housing maiden gilts in stalls.
• Heavy vulval contamination, for example in maiden gilts housed on slats where slurry spills over.
• Early embryo mortality.
• Re-mating discharging sows.
• Using old boars on young sows.
• Using young boars on older sows.

Management control is carried out by changing and improving the factors considered important on the farm.

Prevention

• Monitor the vulva for evidences of discharges.
• Do not serve towards the end of the heat period.
• Do not re-serve discharging sows.
• Only mate the sow when she is totally receptive to the boar. If in doubt wait.
• Do not be eager to serve too early.
• Consider single day mating i.e. boar am AI pm.
• Consider only one service.
• Use one boar to one sow only.
• Avoid wet dirty boar and mating pens. Clean and disinfect pens regularly.
• Avoid lactation periods < 21 days.
• Increase the number of gilts available for mating.
• Serve young boars to young females only.
• Prevent heavy faeces contamination of the vulva from weaning to 14 days post-service.

Treatment

This is carried out in three phases:

1. Studying the records as outlined.
2. Make regular observations of the vulva particularly 14-21 days post mating to identify affected females.
3. Bacteriological examinations of preputial and vaginal secretions. All boars and 10 sows that have repeated should be tested. A swab is introduced into the prepuce either while the boar is eating, confined in a stall or just before dismounting after mating. Likewise in problem sows the lips of the vulva are cleaned with tissue, parted and a swab inserted to its full length. The predominating organisms in the herd can then be determined and antibiotic sensitivity tests carried out. Swabs from individual discharges are worth examining but the results are sometimes not helpful. However they will identify an organism such as klebsiella which is a primary pathogen in its own right. Fig.6-18 shows a typical laboratory result and some of the antibiotics that could be used. These results were obtained from a farm where 24% of served sows repeated and there was evidence of a tacky discharge 12-20 days post-service associated with some of the infertile sows. The bacteriological picture shows a high isolation rate of klebsiella bacteria from the prepuce of the boars (90%). The level in a normal herd would be less than 10%. Further examinations showed 30% of problem sows were carrying the same organism. Klebsiella is recognised as an opportunist pathogen and from the antibiotic sensitivity tests amoxycillin was selected as the medicine of choice for treatment. 3ml of injectable solution were deposited into the anterior vagina of all sows 6 - 24 hours after the last mating. This was carried out for a four month period and 7ml placed in the prepuce of each boar once every three weeks, on five occasions. The conception rate improved to 88%.

Treatment of the boar

You are advised to discuss aspects of treatment with your veterinarian but there are three methods, antibiotics installed into the prepuce, by injection into muscle or by mouth. (Fig.6-19). The latter can be best carried out using in-feed premixes and placing a small amount on the food daily for ten days. The boar could be injected with long-acting antibiotic preparations, but this should be avoided if possible because he can become needle-shy. If leptospirosis is suspected as an initiating factor injections of streptomycin should be given daily for 3 days and this repeated monthly for 5 occasions. Streptomycin is not available in some countries.

Treatment of the sow

The most effective method is to insert an antibiotic into the anterior vagina up to the cervix (but not actually into it). A 3ml dose of most injectable antibiotics can be used the selection being dependent upon the bacteriological examinations and sensitivities. A disposable AI catheter of small diameter, or a cattle AI catheter can be used. Shorten it by approximately 150mm. Attach a syringe with an adapter. Fill the catheter and syringe completely with the antibiotic. The catheter should then be gently inserted as far as the cervix but not into it and the antibiotic can then be deposited easily. This can be carried out 6-24 hours after the last mating. It is important however, when adopting this procedure to always monitor the results for any adverse effects over the first three weeks in respect of both discharges and return rates. An alternative method of medication is to top dress the feed of the sow from weaning to 21 days post-service. In herds with major problems it may be necessary to medicate all breeding females for a period of ten days with in-feed medication using the appropriate antibiotic.