The pig industry has put a lot of effort into increasing litter size. However, more than 1 pig out of each litter born alive still dies before weaning. This figure is even higher when you consider that, on some units, a large proportion of pigs recorded as born dead were alive at farrowing. Perhaps we should concentrate more on keeping live born pigs alive and less on increasing litter size, which is often associated with an increased incidence of light, low viability pigs.
This paper looks at industry statistics and individual on farm factors related to pre-weaning mortality. It looks at how pre-weaning mortality is related to litter size, gives recommendations on how to increase piglet viability and describes how large litters should be managed so as to minimise piglet mortality.
What the industry statistics say
The trend in average litter size and pre-weaning mortality over the last 10 years is shown in Table 1. It can be seen that total born has increased by 0.3 of a pig. Number born alive per litter was increased by 0.2 of a pig over this period. Not a huge increase! In the same period pre-weaning mortality increased by 0.5%.
|No. born alive per litter||10.8||10.8||10.8||10.9||10.8||10.9||10.9||10.8||11.0||11.0|
|No. born dead per litter||0.70||0.75||0.74||0.76||0.74||0.76||0.76||0.75||0.76||0.78|
|Pre-weaning mortality (%)||8.9||9.1||8.8||8.8||8.6||8.7||9.0||9.1||9.0||9.4|
In 2003 average pre-weaning mortality in Ireland was 9.4%. The top 25% of producers recorded a pre-weaning mortality of 7%, while pre-weaning mortality for the bottom 25% of producers was recorded at 12.4% (Martin, 2004).
Table 2 demonstrates the savings that can be achieved per 100 sows by reducing pre-weaning mortality to levels currently being achieved by the top 25% of producers. This should be the target for every serious producer. Industry average figures take into account “the good, the bad and the ugly” and as such should never be used as a target by a serious progressive producer.
|Top 25%||Average||Bottom 25%|
|No. born per 100 sows||2500||2500||2500|
|Pre-weaning mortality (%)1||7.0||9.4||12.4|
|No. pre-weaning deaths||175||235||310|
|Cost of dead pig (€)2||45||45||45|
|Loss associated with dead pigs (€)||€7,875||€10,575||€13,950|
2, Calculated by subtracting predicted cost of feed to slaughter (€48) from the predicted sale price of the pig (€93).
3, Comparison between Top 25% and Average.
4, Comparison between Top 25% and Bottom 25%
Looking deeper at individual farm data
From the National Industry statistics (Martin, 2004) we know the average pre-weaning mortality figures. We also know that large differences in pre-weaning mortality exist between individual farms and that we need to set our targets at the best levels being achieved by our peers (Top 25% of producers).
This information is useless unless producers have their own records and as importantly that they use this information to make management decisions. For the purpose of this paper Pig Champ data was taken and summarised for the past 5 years from a 2000 sow herd (Appendix 1). What does this data say?
- Average pre-weaning mortality was 8.9% over 5 years but has increased to 9.4% in the past year.
- 55% of this mortality occurs in the first 48 hours after birth.
- The main reasons for pre-weaning mortality were Runt/unviable (47%) and Injury/Trauma (43%).
- Pre-weaning mortality was highest for parity 2 sows and sows on their 7th or greater parity. Injury/Trauma as a cause of death increased markedly for sows on their 7th or greater parity.
- Pre-weaning mortality was positively correlated with litter size.
Examining the records from any farm would probably reveal very similar findings to those in appendix 1. However, the of death relies on subjective appraisal and it is often only the terminal factor that is recorded. There may have been one or more predisposing influences leading up to death. Overlying, pig size and starvation are usually the principle causes (Varley, 1995). Appendix 1 shows that 90% of pre-weaning mortality on our 2000 sow herd was recorded under these labels. Table 3 indicates that large variations exist between farms /surveys, in the proportions of specific causes of death.
|% of total pre-weaning mortality|
|Reference||Overlying, Savaged||Small, weak, malnourished||Infection||Genetic abnormality||No Cause||Other|
|Fahmy and Bernard (1971)||19||27||18||14||16||6|
|Spicer et al. (1986)||32||9||27||5||3||24|
|Dyck and Swierstra (1987)||39||42||1||1||17||0|
|Prime et al. (1987)||45||14||7||-||-||-|
Problems with large litters
As might be expected, Appendix 1 reveals that pre-weaning mortality is highest in sows that have a high litter size. This increase in mortality is largely attributed to increased within litter variation in piglet birth weight (Marchant et al., 2000). As a consequence, some piglets out-compete their littermates causing them to starve or become crushed (Lay et al., 2001).
As litter size increases there is also an increase in the length of the parturition process. Piglets are more likely to be subjected to a state of hypoxia (lack of oxygen). This is associated with an increased incidence of stillbirths. Even live born pigs may have a reduced viability as a consequence. Such pigs are more likely to starve, be crushed or become diseased (Lay et al., 2001).
The following is a list of management interventions that may prove worthwhile in reducing the level of mortality from large litters.
1. Increase size / viability of pigs
Large litters have a high proportion of light pigs. Piglets weighing <800g at birth have only a 32% survival rate compared with 97% for piglets weighing 2kg or more (Gardner et al., 1989). Wolter et al. (2002) found that pre-weaning mortality increased from 5.2% to 9.4% for pigs that weighed 1.33kg and 1.83 kg, respectively at birth. Any means that can increase piglet birth weight is likely to increase piglet survivability.
|Weight range (kg)||Weight distribution of population (%)||Survival (%)|
Number born alive and piglet birth weight can vary greatly between breeds. Pig size at birth can vary with breed. Meishan sows have large litters of lightweight pigs. However these pigs are very vigorous. The fat content in the colostrum of the Meishan sow is higher than of the European breeds and that can provide her piglets with the energy needed to maintain body temperature (Le Dividich et al., 1991)
Litter size is usually smallest on gilt litters and rises to a maximum between the third and fifth litter and then remains constant or declines slightly with older parities. The incidence of stillbirths is usually highest in the fifth or greater parities. Average herd parity should be between 2.5 and 3.0, with over 45% of sows in parities 3 to 6 being the optimum for overall productivity (Aherne, 2002)
1.3 Gestation feeding
In late gestation the demands on the developing litter for energy and nutrients increase dramatically. Sixty per cent of foetal growth occurs in the last 30 days of gestation (Noblet et al., 1990). Cromwell et al (1989) increased sow feed intake by 1.36 kg per day between day 90 of gestation and farrowing. This increased average born alive by 3%, pigs weaned per litter by 3% and pig birth weight by 3%.
Aherne (1997) and Young (2003) recommended feeding an extra kg per day from day 100 of gestation until farrowing. Tokach, et al. (1999) recommended feeding 1 to 2kg extra feed per day in this critical period. This extra feed has been shown to prevent backfat loss in late gestation and it does not effect sow feed intake during lactation.
2. Farrowing crate
The farrowing crate has been a major success when it comes to reducing pre-weaning deaths due to crushing (one of the main causes of pre-weaning mortality) (Lay et al. 2001).
3. Supervised farrowings
Supervision of farrowings can help greatly to lower pre-weaning mortality. However excessive disturbance by the stock person can stress the sow thus prolonging the farrowing process. This prolonged farrowing can increase pre-weaning mortality. It doubles for litters whose farrowing process takes more than 6 hours (Lay et al., 2001).
Induction of sows can be a very useful technology in that it allows all farrowings to be supervised. It gives the opportunity to carry out earlier fosterings and it reduces weekend work. However, records must be perfect if it is to be carried out or else an increased incidence of abortions will occur. It also results in reduced birth weight piglets and colostrum quality is likely to be compromised as a result of its use (Teagasc, 2003). Both of these consequences are of particular concern where piglet weight is small/variable (ie. with large litters).
Sows can be induced to farrow by injecting with a prostaglandin analogue. Injected sows usually farrow about 27 hours after injection. Induce on Thursday morning of day 114 or later to farrow on Friday. This procedure is best restricted to overdue sows since litters induced to farrow prematurely usually have reduced viability. Inducing overdue sows facilitates fostering of piglets.
Temperature regulation in the farrowing house is a play off between the sow and the piglets’ temperature requirement; too high a temperature and the sows’ intake drops and too low a temperature and the piglet suffer from hypothermia. It is important to remember that birth for the piglet results in a rapid 15-200C drop in temperature between the uterine environment and the ambient temperature of the farrowing house.
The low birth weight pig is at particular risk of hypothermia, with a greater body surface to volume ratio and reduced energy stores (English and Morrison, 1984). Furthermore, newly born pigs do not increase (unlike older pigs) but rather decrease their intake of colostrum during cold exposure, exacerbating the likelihood of starvation (Le Dividich and Noblet, 1981).
The general recommendation is to turn on the heating in advance of farrowing so that piglets are born into a warm, dry, draught-free pen. An infra-red lamp and/or shredded paper should be positioned at the rear of the farrowing pen and the slatted area under the lamp should be covered with a paper bag or mat to prevent draughts from below. The house temperature should be increased to 24oC before the first piglet is born.
3.3 Supervision of the farrowing process
Pre-weaning mortality can be greatly reduced (18% improvement) and stillbirths halved due to good supervision and timely intervention around farrowing (English, 1993). This is particularly important when litter size is high as farrowing duration is usually longer and there is a greater number of small pigs.
If the interval between piglets being born exceeds 30 minutes the sow should be checked and handled, if necessary. The sow should complete farrowing within 5 hours. A suitable lubricant gel, but not soap, should be used to cover the hand and arm when handling the sows or wear an arm length disposable plastic glove.
The farrowing process may be accelerated, especially in older sows, by injecting the sow in the vulva with Oxytocin. However the sow should first be checked so that there are no blockages. Individual doses should not exceed 5 i.u. (0.5 ml). The injection may be repeated after 30 minutes provided piglets are being born.
Newborn piglets with low viability should be assisted immediately to suckle the sow to ensure that they receive colostrum and/or be given an energy booster by oral doser
4. Post-farrowing supervision
Pigs must get their allocation of colostrum as early in life as possible. Colostrum is an excellent energy source for the newborn pig. However the newborn pig also depends on early transfer of maternal antibodies from colostrum for immune protection. Colostral IgG levels drop by 50% within 6 hours of the first suckling (Lay et al., 2002).
4.1 Cross fostering
Cross fostering has been shown to reduce pre-weaning mortality by 40% (English et al., 1982). However cross fostering should be carried out as soon as possible after birth, because continuous cross-fosterings later in the suckling period can decrease overall growth (Straw et al., 1998). Small herds don’t have the same opportunities to cross foster as larger herds, however moving to batch farrowing may prove advantageous in this regard.
Standardise litter size within the first 24 hours when two or more sows farrow together, by transferring piglets between sows, ensuring that the piglets on each sow are of similar weight. Piglets which do not have a settled teat are the most obvious candidates for fostering. Smaller piglets where possible should be fostered on to gilts or on to sows with long slender teats. All piglets must get colostrum immediately or, at latest, within 6 – 12 hours of being born.
Ensure that the number of piglets on a sow does not exceed her rearing capacity i.e. the number of exposed functional teats when suckling. Limit the number of piglets suckling first litter sows to 10 where possible.
4.2 Where fostering is not an option
Cross fostering may not be an option in some cases (e.g. on small herds or with large litters born on the weekend). In such instances few litters are born at the same time making it impossible to cross foster. The following options are available
- Split suckling – This involves enclosing the heavier pigs in the creep area, injecting the sow with 5iu of oxytocin and assisting the smaller pigs to suckle. This ensures that all pigs in a large litter get adequate colostrum.
- Piglets can be given sow colostrum or colostrum replacer by oral dosing or stomach tube 3 – 4 times daily until there is a possibility to foster.
- Forward fostering – After all piglets have had their ration of colostrum forward fostering could be practised. Forward fostering is where the largest piglets in the litter are fostered onto a docile good milking sow which has farrowed one week previously. In turn the one-week-old piglets from this sow can be fostered onto a docile good milking sow weaned at the normal stage.
- Supplemental milk – Large litters left suckling the sow should be supplemented with a suitable milk replacer. It is essential that each piglet has received colostrum before this practice starts. Pigs should be fed on a little and often basis and strict hygiene is essential to prevent milk going off to reduce the incidence of enteric infection.
4.3. Minimise crushing
Regardless of temperature or heat sources within the pen (infra-red lamps, heat pads etc.) piglets prefer to huddle close to the sow and littermates during the first 3 days of life (Hrupka et al., 1998). For this reason, it is advisable, over this critical period to enclose the litter in the creep area each time before feeding the sow. When the sow has been fed, and within 1 hour of locking them in, the litter must be released (Teagasc, 2004).
5. Sows’ milking ability
Adequate and prompt intake of colostrum is crucial for the survival of the newly born piglet as its energy reserves at birth are low (half that of lambs and calves) (Lay et al., 2001). This can particularly be a problem with large litters where colostrum demand may exceed its supply. In addition herds with high born alive figures will need increased milk supply during lactation to ensure that as many as possible survive.
5.1. Gestation feeding
The importance of gestation feeding cannot be over emphasised. Having sows “fit but not fat” at farrowing is not only critical for lactation feed intake and subsequent return to oestrus but also to ensure the adequate milking ability of the sows mammary gland. Gilts with a back fat depth of 36mm at farrowing had a 60% lower milk yield than gilts with a back fat depth of 25mm (Pluske et al., 1995).
Adding fat to the sows’ diet in late gestation and during lactation can increase the milk yield and fat content in colostrum. This will increase the survival (+17%) of low birth weight pigs (<1kg) much more than larger littermates (Pettigrew, 1981). Feeding medium chained triglycerides in the sows’ diet is particularly beneficial in increasing the survival of pigs weighing <900g at birth.
5.2. Lactation feeding
Sow feed intake during lactation is widely known to influence milk yield and associated nutritional status of suckling pigs as well as re-breeding performance (Lay et al., 2001). For this reason promoting high sow feed intake must be a major priority in the farrowing house. Some practical tips that will increase sow feed intake in lactation include:
- Environmental temperature should be kept as low as possible to promote sow feed intake. Reduce the farrowing house temperature to 20°C when the youngest piglets are over 2 days old. This is likely to provide a suitable compromise between the high temperature requirements of the piglets and the low temperature requirements of the sow. Warmer farrowing houses will result in reduced sow feed intakes (Teagasc, 2004). .
- Wet fed sows will eat more than dry fed sows
- If feeding dry then pelleted feed will give higher intakes than meal.
- Use a high energy lactation sow feed.
- Feed sows 3 times daily and .
- Ensure that an adequate supply of clean water is available (nipple drinker plus leaver valve or hose)
- An effective health control programme should prevent disease stressors that can contribute to depressed feed intake.
There are indications that through decades of breeding we have unwittingly selected poor mothering characteristics in sows that contribute to crushing (Lay et al., 2001). Because farrowing crates were so successful selection pressure was put on characteristics like litter size and growth rate at the expense of the maternal traits. This should be reversed and in future breeding programmes, maternal traits and mothering ability should be selected for.
A positive effect of heterosis on piglet survival is known to exist even though it also increases litter size. An improvement of 5 to 6% in survival is found in crossbred compared with pure bred piglets (Blasco et al., 1995)
The basic selection criteria for gilts are that they are a good weight for age, have good sound legs and have a minimum of 14 functional, evenly spaced teats (English et al., 1982). This should minimise overlying and ensure that there is sufficient teat access for large litters.
Sows that cannot rear 10 pigs or have a history of overlying should be marked for culling.
The bulk of pre-weaning piglet deaths occur in the first 48 hours after birth. Therefore close supervision and providing optimum environmental conditions at this time can be very rewarding. Birth weight has a major influence on piglet survival and this can be maximised by optimising parity profile and increasing feed levels to sows in late gestation. Overlying and crushing are major contributors to pre-weaning mortality. Closing piglets into the creep area for an hour each time the sow is fed in the first 2 days of life can help. Where the rearing capacity of the sow cannot cope with excessively large litters cross fostering where possible should be carried out. Quality colostrum and a high sows’ milk yield are essential for piglet survival. Sow feeding during gestation and in lactation can influence the yield and quality of sows’ milk.
- Aherne, F.X., 1997. Feeding the lactating sow. In: Proceedings of Teagasc Pig Farmers Conferences. October 14-16. p. 19-25.
- Aherne, F.X. 2002. Improving breeding herd efficiency: An industry perspective. In: Proceedings of the 29th Annual Pig Health Society Symposium. 30-44
- Azain, M. J. 1993. Effects of adding medium-chain triglycerides to sow diets during late gestation and early lactation on litter performance. Journal of Animal Science, 71:3011-3019.
- Blasco, A.J., Bidanel, J.P., and Haley, C.S. 1995. Genetics and Neonatal survival. In: The neonatal pig: Development and survival. (Ed. M.A. Varley). CAB International, Wallingford UK, pp.1-13.
- Cromwell, G.L., Hall, D.D., Clawson, A.J., Combs, G.E., Knabe,D.A., Maxwell, C.V., Noland, P.R., Orr, D.E. Jr., and Prince, T.J. 1989. Effects of additional feed during late gestation on reproductive performance of sows: a cooperative study. Journal of Animal Science 67:3-14.
- English, P.R. 1993. Factors affecting piglet losses and management practices to minimise such losses. In:Veterinary Journal, (Eds. M.E. Raw and T.J. Parkinson). Blackwell Scientific Publications, Oxford, UK. Pp.107-119.
- English, P.R., and Morrison, V. 1984. Causes and prevention of piglet mortality. Pig News and Information. 5:369-376.
- English, P.R., Smith, W.J. and Maclean, A. 1982. Management of the lactating sow and litter. In: The Sow: Improving her efficiency. Farming Press Ltd., Ipswitch, UK. pp.186-218.
- Gardner, I.A., Hird, D.W. and Franti, C.E. 1989. Neonatal survival in swine: Effects of low birth weight and clinical disease. American Journal of Veterinary Research. 50:792-797
- Hrupka , B.J. Leibbrandt, V.D. Crenshaw, T.D. and Benevenga N.J. 1998. The effect of farrowing crate heat lamp location on sow and pig patterns of lying and pig survival. Journal of Animal Science, 76:2995-3002
- Lay Jr. D.C., Matteri, R.L., Carroll, J.A., Fangman, T.J., and Safranski, T.J. 2001. Preweaning survival in swine. Journal of Animal Science. 80(E. Suppl.1) E74-E86.
- LeDividich, J., Mormede, P., Catheline, M., and Caritez, J.C. 1991. Body composition and cold resistance of the neonatal pigfrom European (Large White) and Chinese (Meishan) breeds. Biology of the Neonate. 59:268-277.
- LeDividich, J. and Noblet, J. 1981. Colostrum intake and thermoregulation in the neonatal pig in relation to environmental temperature. Biology of the Neonate. 4:167-174.
- Marchant J.N., Rudd, A.R., Mendl, M.T., Broom, D.M., Meridith, M.J., Corning, S., amd Simmons, P.H. 2000. Timing and causes of piglet mortalityin alternative and conventional farrowing systems. Veterinary Record. 147:209-214.
- Martin, M.A. 2004. PIGSYS data analysis report. 22pp
- Noblet, J., Dourmad, J.Y. and Etienne, M. 1990. Energy utilisation in pregnant and lactating sows: modelling of energy requirements. Journal of Animal Science 68:562-572.
- Pettigrew, J.E. 1981. Supplemental dietary fat for peripartal sows: A review. Journal of Animal Science, 53:107-117.
- Straw, B.E., Burgi, E.J., Dewey, C.E., and Duran, C.O. 1998. Effects of extensive crossfostering on performance of pigs on a farm. Journal of the American Veterinary Medicine Association. 212:855-856.
- Teagasc, 2004. Pig unit Routine Manual. Teagasc Pig Service. 21pp.
- Tokach, M., Dritz, S., Goodband, B. and Nelssen, J. 1999. Nutrition for the optimal performance of the female pig. In: Proceedings of Teagasc Pig Farmers Conferences. October 18-20th. p. 96-110.
- Varley, M.A. 1995. Introduction. In: The neonatal pig: Development and survival. (Ed. M.A. Varley). CAB International, Wallingford UK, pp.1-13
- Wolter , B.F., Ellis, M., Corrigan, B.P. and DeDecker J.M. 2002. The effect of birth weight and feeding of supplemental milk replacer to piglets during lactation on preweaning and postweaning growth performance and carcass characteristics. Journal of Animal Science, 80:301-308.
- Young, M. 2003. Nutrition and management of the modern gilt. In: Proceedings of Teagasc Pig Farmers Conferences. October 20-22. p. 41-54.
|No. born alive per litter||11.0||11.3||11.5||11.5||11.2||11.3|
|No. born dead per litter||1.2||1.1||1.1||1.1||1.2||1.1|
|Pre-weaning mortality (%)||9.2||8.4||8.9||9.0||9.4||8.9|
|Cause||Time post-partum (days)|
|Runt/ Unviable (%)||39||61||50||55||47|
|Other disease (%)||1||0||5||7||2|
|Total recorded deaths (%)||55||21||16||8||100|
|% of farrowings||20.7||19.2||51.4||8.7||100|
|Runt/ Unviable (%)||53||52||43||27||47|
|Other disease (%)||3||2||2||3||2|
|% of Total Deaths||8.2||4.9||7.6||10.5||12.6||14.2||13.5||28.7|