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3: Pig health of sows, reproductive failure
Veterinary Medicine

Additional Veterinary Medicine Flashcards




There are many factors which affect the health and performance of sows:

1. environmental factors

2. management factors

3. nutritional factors 

Environmental factors affecting Sows health and performance


  • - stress

    - Insufficient lying area for sows, poorly drained floors, rough floors, protrusions in pens which injure pigs.

  • -   Poor building and farrowing crate design, poor light intensity( need 12-16 hr per day to maintain pregnancy. , fluctuating light.

    - sows are on heat longer when exposed to more lights. 

    - Gilts exposed to 14-18 hours light- reach puberty earlier, are lighter weight at puberty, no difference in ovulation rate, are sexually more active. 

  • -   Fluctuating temperatures: day-by-day, week-by-week, draughts.

  • -   Temperatures - above higher critical temperature, without cooling devices or a wallow - below lower

    critical temperatures, with insufficient bedding and shelter.

  • -   Stony ground, unduly muddy, wet ground.

  • -   Poor water availability. 

Management factors affecting health and performance of sows


  • -   Poor methods of introducing sows and gilts into groups resulting in aggression.

  • -   Allowing vices to develop, e.g. vulva biting, by failure to identify causes.( with plenty of space, shouldnt have that problem) 

  • -   Poor stockmanship - no empathy with the pigs.

  • -   Failure to clean and disinfect buildings at adequate intervals.

  • -   Failure to vaccinate, worm and mange-treat sows.

  • -   Mechanically transferring infections between sows, continuous throughput of buildings.

  • -   AI/Mating management: what, when, where, how. 

Management factors affecting health and performance of sows


  • -   Poor methods of introducing sows and gilts into groups resulting in aggression.

  • -   Allowing vices to develop, e.g. vulva biting, by failure to identify causes.( with plenty of space, shouldnt have that problem) 

  • -   Poor stockmanship - no empathy with the pigs.

  • -   Failure to clean and disinfect buildings at adequate intervals.

  • -   Failure to vaccinate, worm and mange-treat sows.

  • -   Mechanically transferring infections between sows, continuous throughput of buildings.

  • -   AI/Mating management: what, when, where, how. 

Nutritional factors affecting health and performance of sows

 feeding for: growth and body condition, folllicle development, placental development, fetal growth 

  • -   Insufficient feed/energy in relation to ambient temperature conditions and body condition.

  •   - Incorrect feeding at different stages of the production cycle.

  • -   Insufficient feeder space, no provision for feeding individual sows. 

Sow disposal and wastage


  1. Factors to consider in relation to sow disposal are:

    • -   Herd culling policy - Indoor herds have an average target of 38%, outdoors 45%.

    • -   Individual sow’s reproductive performance, sow’s body condition, number of functional teats

    • -   Health problems, e.g. lameness, availability of gilts (pig flow on the unit).

    •   - Mortality rate in sows. 

What is the target for culling sows and why

6-7 parity

as there are increasing problems as the sows get older such as: 


  •   - Prolonged farrowings - increased stillbirth rate, more piglets overlain.

  • -   Variable litter size and birth weights.

  • -   Problems with lactation arising from chronic mastitis and non-functional teats.

  • -   Greater likelihood of poor fertility, lameness, endometritis, vulval discharge, cystitis/pyelonephritis. 

    if overall age of sows becomes too old, productivity is affected, a large sow cull would then be needed followed by a hugh influx of gilts which unbalances the herds age structure. 

Gestation only sustained if:

1. correct hormonal balance ( high progesterone)

2. strong immune suppression at implantation level

3. local cytokine and GF cross talk 

- uterine leucocytes

- endometrial cells

- embryonic/fetal macrophages

- chorionic cells

Reproductive performance

important indicators of reproductive performance: 


1. Reduced farrowing rate: Definition: Farrowing rate is the number of sows which farrow to the number

of services in a given period (expressed as a percentage).
2. Reduced litter size (incl number of mummies, stillborns, weak borns) 

Failure of reproductive performance can occur at:


1. Conception or implantation sows/gilts return to oestrus at 21 days
2. Post implantation
irregular returns or sows/gilts come through not in-pig

3. Maturation abortion, mummification 

Causes of reproductive failure include?


  • -   May be single or multiple problems and causes

  • -   Problems differ between indoor and outdoor units

  • -   Majority of problems are non-infectious, ie managemental and/or environmental causes are common.

  • -   Viral and/or bacterial infections may be implicated. 


Boar vs. AI

- when signs of heat 4 days before ovulation, serve 24-48 hrs later. 

- know signs of oestrus

Management and environmental factors to consider for poor reproductive performance


  1. Sow condition - level of nutrition, suitability of diet(s), feeding system.

  2. Service management - boar contact, heat detection, number / timing of services, supervision,


  3. Boar usage - frequency of use, sow:boar ratio, health of boars, supervision of young boars.

  4. AI usage - timing, operator experience, handling of semen, quality of semen.

  5. Seasonal effects -'autumn reproductive syndrome', 'winter anoestrus', adverse temperature and

    weather conditions (especially for outdoor sows)

  6. Pregnancy testing

  7. Farrowing house management and environment - hygiene, all-in all-out policy, sow comfort, farrowing

    supervision, speed of farrowing, neonatal care, suitable conditions for piglets, health.

  8. Culling policy - parity, health problems, sow deaths.

  9. Gilt replacement - genetic suitability for unit (indoor/outdoor), home-breeding, selection defects.

10.Efficiency and accuracy of data recording 

Anoestrous gilt

atleast 8 months of age without showing oestrous

- cessation of oestrus cycles in the absence of pregnancy 


Anoestrous sow

- weaned at least 10 days without showing oestrus

- cessation of oestrus cycles in the absence of pregnancy or lactation 

DDX for anoestrous in pigs


inactive ovaries, pregnancy, undetected oestrus cycles, irregular oestrus cycles due to persistent corpora lutea or cystic follicles, intersexuality, defects. 

Solving anoestrous problems


  • -   Is it true anoestrus? (examine tracts of cull sows at slaughter - no developed follicles or corpora lutea, ovaries small and flattened.

  • -   Examine above husbandry factors and correct problems.

  • -   Consider the use of hormonal therapy in truly anoestrus animals (eg PG 600 - sows and gilts should

    come into oestrus 5 days post single injection). Regular use of hormonal stimulation should not be necessary and should be discouraged or used with care. In cyclic animals it can cause cystic ovaries and long-term anoestrus. 

    - inactivity of ovaries can usually be attributed to some fault or combination of faults in housing, poor nutriton, inadequate stimulation by oar, poor genetic selection, parasitism

Cystic ovaries in Pigs


  1. Follicular or luteal cysts are seen quite commonly but their effect on fertility is uncertain as they can be seen in normal pregnant animals. Approximately 7% of sows culled as barreners have polycystic ovaries.

    Cause -High progesterone concentrations from adrenal cortex (induced by environmental stress or exogenous ACTH) inhibits positive feedback mechanism of oestrogens on the pituitary gland thus inhibiting pre-ovulatory surge of LH. Examine for causes of environmental stress. 

Regular returns to oestrus at 21 days


- failure to conceive or implant. Consider these possible problem areas:
  •   Accuracy of oestrus detection, timing of services or AI (possible incorrect timing)

-   Boar factors - possible infertility, testicular size and consistency and penile defects or injuries, sow to

boar ratio, boar usage.

  •   Quality of service, experience of AI operator; age, handling and storage of semen used for AI.
  •   Suitability of service area (floors, space, temperature)
  •   Previous reproductive diseases, vaginal discharges post service (possible endometritis) 
Irregular returns to oestrus


  1. - loss during the embryonic phase (up to 35 days) leading to resorption or the foetal stage (> 35 days) leading to abortion. Consider these possible problem areas:

    •   - Seasonal effects (August - October months associated with increased rates of resorption/abortion - 'autumn reproductive syndrome')

    • -   Overuse of boars leading to small number of embryos (foetuses resorbed at approximately 35 days)

    • -   Vaginal discharges/endometritis- poor hygeine at service, esp w. boar

    • -   Infectious reproductive diseases : PRRS, Parvo, enteroviruses etc.

    • -   Other acute illnesses - Swine influenza, erysipelas, Actinobacillus pleuropneumoniae etc.

    • -   Toxic factors - feed (eg. Mycotoxin) 

      - <5 embryos at day 10 - not enough to signal maintenance of pregnancy 



bortion occurs when pregnancy control mechanisms cease ie. luteal function ceases, ovarian progesterone production falls and premature farrowing is initiated.

In contrast, when foetuses undergo resorption or mummifications, the maternal pregnancy state usually continues. Sporadic abortions occur in most herds.

Check the abortion rate against target and action figures to assess the significance. There are many potential causes of abortion; the major factors are represented in the diagram below. 

Still births: Type I


Foetuses die before the end of gestation and are classified as pre-partum deaths. Often due to

infectious causes eg parvovirus or PRRS infection.

Stillbirths Type II


- Foetuses die during parturition (intrapartum deaths). Usually due to non-infectious causes, eg:

  • -   Duration of farrowing; high interval between piglets (13-18 minutes:low stillbirth rate; 45-55


  • -   Either small litters(<4 piglets) or very large litters.

  • -   Where parturition is 6-7 days early or late

  •   High parity sows

  • -   Position of foetus (80-85% occur in the last third of the litter); anoxia (umbilical rupture, impeded blood


  •   - Carbon monoxide (faulty gas heaters); high ambient temperature (390C) in late gestation (sow



    1. Intrapartum anoxia stimulates CNS respiratory centres and can lead to inhalation of amniotic fluid and debris. It also causes relaxation of anal sphincter with release of meconium into amniotic fluid. Piglets can be examined for these signs of foetal distress. 

Inducing parturition

injection of prostaglandin

  1. Farrowing commences 18-36 hours later. Small doses of oxytoxin (5-10iu) can be given from 20 hours post prostaglandin (or once farrowing commences naturally) in order to speed up the farrowing. Single large doses of oxytoxin are contra- indicated as this has been shown to cause dystocia. Oxytocin will not induce farrowing in sows and gilts. 

Causes of small litter sizes


Many causes. Compare figures between 'parities' to look for any particular age distribution. Consider the following causes:

  •   Genetics: maximum heterosis required to maximise litter sizes.

  •   - Management factors post weaning - ad lib feeding and boar contact recommended.

  • -   Number of services. Recommended at least 2 with 24 hour interval or 3 at 12 hour intervals. Single services - small litters

  • -   Age of gilt at first mating. Small litters when bred before 220 days (body weight important).

  • -   Young boars (<10 months old) can leave small litters; overuse of boars

  • -   Poor sow condition

  • -   Infections - endometritis, parvovirus, enteroviruses, PRRS. 

Intersexuality and other birth defects in Pigs


  1. Common in pigs, incidence approximately 1% of females, conditions have a genetic basis
    - True hermaphrodite - both ovarian and testicular tissue in gonads with female external genitalia. Vulva often upturned and clitoris prominent.
    - Male pseudohermaphrodite - testicles for gonads with female external genitalia (similar to hermaphrodites).
    - Uterine horns - hypoplastic or aplastic
    - Other tubal anomalies can occur - aplasias of vagina, cervix or uterine horns duplications of any of the tubal structures. 

Stress on repro tract
stress -> hypothalamopituitary adrenal system-> corticotrophin RH-> ACTH-> adrenal glands-> cortisol pgF2alpha progesterone-> reprotract
Signs of oestrus

swelling of vulva, redness and small amounts of mucus

- changes in vocal sounds

- standing when back pressure is applied with ears pricked

- standing when mounted by other females

- seeking contact with a boar

- nosing the flank of other females or boars

- smelling the prepuce

- permitting teh boars to mount and mate 


1. conventional articifical insemination in the cervix

2. intrauterine insemination in the uterine body

3. deep intrauterine insemination 2/3 of the way up a uterine horn 

- take your time

- during AI nose-nose contact with boar

will increase heat signs, increase uterine contractions

- apply back pressure/flank rub

- leave catheter in for 10 mins after

- hygeine

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