In newborn piglets does drying versus no intervention reduce the risk of mortality pre-weaning?

a Knowledge Summary by

Nicola Blackie BSc (Hons) PhD ^1*

¹Department of Pathobiology and Population Sciences, Royal Veterinary College, Hatfield, AL9 7TA
^*Corresponding Author (nblackie@rvc.ac.uk)

Clinical scenario

Piglets are born with limited energy reserves and are not licked dry by the sow therefore risk hypothermia around the time of birth. Mortality levels pre-weaning on indoor pig farms in the UK average 11.6 % (AHDB, 2019). The practice of drying piglets is more common in the US than in the UK based on anecdotal evidence. Conversations with UK pig farmers and veterinarians revealed that there are mixed strategies for managing the newborn piglet indoors, many of which do not include a direct intervention to dry the piglet. Indirect methods of drying piglets may include lamps at the rear end of the sow or providing bedding. Drying piglets may be a way of reducing the risk of hypothermia and thus reduce the risk of mortality. Therefore, an appraisal of the evidence could be used to advise farmers on best practice.

The evidence

There are three methods of drying piglets from the literature. One is drying with stimulation such as using paper towels, cloth towels or straw, as well as drying the piglets they may also receive stimulation from the act of rubbing them. Another method included the use of drying powders and the third method was moving the piglet under a lamp. From the evidence it is clear that drying piglets can result in lower mortality however, a simpler method may be to place the piglet under a heat lamp (Andersen et al., 2009). Drying piglets with stimulation without combination of other strategies was only assessed in four studies (Christison et al., 1997; McGinnis et al., 1981; Pan, 1995; and Vasdal et al., 2011), of which one study did not record mortality (Pan, 1995), one study showed no effects on mortality and two showed an improvement in mortality where piglets were dried (Christison et al., 1997; and Vasdal et al., 2011). A further two studies included drying as part of an “advanced care” around farrowing which included a number of interventions (Dewey et al., 2008; and White et al., 1996). Dewey et al. (2008) found no impact of extra care on mortality however, they did have low mortality levels in the study overall (7–8 %). In contrast, White et al. (1996) had less mortality when farrowing was assisted and piglets were dried among other interventions.

When comparing with the average level of mortality on UK pig farms 11.6 % (AHDB, 2019); mortality was considerably higher where no intervention was made in one study of 21% (Christison et al., 1997) and similar in two studies (Andersen et al., 2009; Vasdal et al., 2011).

Summary of the evidence

Appraisal, application and reflection

When appraising the evidence on this topic it became clear that there are limited papers which can be used to address this research question. A number had to be excluded due to not being published in English (n= 6) and a large number were not directly related to the PICO question as they addressed general management practices; sow management or older piglets. A number were also related to embryo production and development. Papers which were not published in English could not be translated for this knowledge summary. We excluded them from the appraisal as only the abstract was available.

Where sows are loose housed, drying and placing piglets under a heat lamp did reduce death from crushing (Andersen et al., 2009), overall however, mortality was similar whether piglets were dried and placed under a lamp or just placed under a lamp in comparison to a control. Within this experiment there was no drying only treatment (Andersen et al., 2009). Whereas Christison et al. (1997) compared no intervention or control with drying piglets and moving piglets under a heat lamp without drying them. This was a smaller cohort of piglets than that of (Andersen et al., 2009) and the litters were standardised to just nine piglets per litter. Mortality was significantly lower in dried piglets and those placed under a heat lamp compared to control piglets (Christison et al., 1997). Dewey et al., (2008) compared level of care given to piglets at birth through to 16 days of age. Drying piglets was just one of many additional procedures undertaken on piglets considered to have had maximal care in comparison to standard levels of care. However, maximal care litters did end up heavier at 16 days with no impact on mortality between groups (Dewey et al., 2008). Another study with multiple treatments looked at the impacts of drying piglets with a paper towel, the addition of supplemental heat and two different floor temperatures on growth and thermoregulation (McGinnis et al., 1981). Within this study piglets which were dried had higher rectal temperatures at 1 hour old and higher skin temperatures at 30 minutes and 1 hour of age (McGinnis et al., 1981). The sows in the study had quite small litters of just under 10 piglets per litter, which is not as comparable to modern sows with large litters. As well as paper towels and straw utilised to dry piglets there is research into using drying powders (Goden, 2016; Kiehne, 2006; Pasca et al., 2008). However, the paper by Goden (2016) was not available in English, Kiehne (2006) was too general and Pasca et al. (2008) did not include statistics. The work of Pasca et al. (2008) also showed differences in the thermoregulation pattern when piglets were treated with drying powder, however, this paper did not look at differences in mortality between treatment groups. The development of thermoregulation is key for the piglet to adapt to environmental conditions outside the uterus (Herpin et al., 2002). Another small scale study compared drying piglets straight after birth with no intervention (Pan, 1995). This study again did not look at mortality of growth rates of piglets, they focused on skin and rectal temperatures and there were no treatment effects in this study, however, it should be noted that the ambient temperature during the study was particularly high 23–35°C compared to recommended temperatures of 18–20°C for sow comfort (Pan, 1995). A further study was undertaken by Vasdal et al. (2011) comparing six treatment groups using different methods of drying piglets. Drying piglets and placing piglets at the udder resulted in lower mortality in one but not all batches (Vasdal et al., 2011). They did find however, that litter size; birth weight; latency from birth to suckle; and rectal temperature 2 hours post birth had an impact on mortality independent of treatment (Vasdal et al., 2011). Of the three treatments in the study of Vasdal et al. (2011) which involved drying the piglets, the mortality rate was less than 10% which was positive considering the sows were loose-housed. In addition, placing the piglets close to the udder (with or without drying) reduces the latency to suckle (Vasdal et al., 2011). Rosvold et al. (2017) looked at overall management effort within 52 herds in Norway, where higher levels of management included drying piglets. Farms which dried piglets as well as supervised farrowing, practiced split suckling as well as other management practices were rewarded with lower levels of piglet mortality (Rosvold et al., 2017) although drying piglets was not an independent treatment. Another study which included drying as part of an overall enhanced management strategy at farrowing showed significant improvements in mortality (White et al., 1996). The extra interventions were estimated to take around 2 minutes of extra processing time with a reasonable amount of time waiting for piglets to be born with at least 15 minutes between piglets (mean 156 minutes per litter in total) (White et al., 1996).

A number of the excluded papers focused on general management around farrowing and its impact on mortality. Ogunbameru et al. (1991) evaluated different configurations of supplementary heat given during farrowing; their study found no benefits of treatment on piglet survival or growth, however, it was not clear what temperature the rooms were during the experiment. One issue which influences piglet performance including mortality is difficult to separate out, this is stockmanship. Self-discipline and a warm nature were positively correlated with good performance on farrowing units in Canada (Ravel et al., 1996).

More evidence is still required to determine which is the best method of drying piglets, particularly that of a peer reviewed nature with robust statistical evaluation to answer the PICO addressed through this report. There is evidence that drying piglets results in less mortality. Although there are a number of methods utilised across the studies of drying piglets which makes direct comparison difficult. There is evidence however, that drying piglets does influence thermoregulation with less of a drop post farrowing in core body temperature. There is also evidence that the temperature of the farrowing room itself has an impact on piglet mortality and sow performance. Drying of piglets would appear to be of value within the general area of farrowing management and as such is not always a standalone treatment. The consideration of creep configuration and type of heating was outside the scope of this knowledge summary. These may have an impact along with the environmental conditions as mentioned above. Farms will vary hugely in terms of creep management and as such this was considered out of the scope of this review.

Methodology Section

Search Strategy
Databases searched and dates covered:	CAB Abstracts on the OVID interface 1973 to 2018 Week 42 PubMed accessed via the NCBI website 1910–October 2018
Search strategy:	CAB Abstracts: piglets or exp piglets/ or ((newborn or birth or baby or neonatal or infant) and (pig* or swine)) (dry* or warm* or towel* or 'heat lamp') (mortal* or death or surviva* or viabil* or shiver* or chilling or chill or chills or hypothermia or thermoregulation or 'body temperature') or exp mortality/ or exp hypothermia/ or exp thermoregulation/ 1 and 2 and 3   PubMed: piglets OR ((newborn OR birth OR baby OR neonatal OR infant) and (pig OR pigs OR swine)) drying OR warming OR towel OR towelling OR heat lamp mortality OR death OR survival OR viability OR shiver OR shivering OR chilling OR hypothermia OR thermoregulation OR body temperature 1 and 2 and 3
Dates searches performed:	31/10/2018

Exclusion / Inclusion Criteria
Exclusion:	Most common reasons for exclusion was age of pigs, work focused on sows, embryos or older piglets (not PICO) Non-English papers could not be apprised fully as we could only see the abstract and therefore assessments of methods and experimental design could not be made Papers which we could not get access to were following extensive online search and following contacting the British Library (by Clare Boulton RCVS Knowledge)
Inclusion:	Peer-reviewed articles/td>

Search Outcome
Database	Number of results	Excluded – Did not answer the PICO	Excluded – Non-English	Excluded – Could not get access	Total relevant papers
CAB Abstracts	262	230	6	7	19
PubMed	35	31	0	0	4
Total relevant papers when duplicates removed					8

The author declares no conflicts of interest.

The author would like to gratefully acknowledge Clare Boulton (RCVS Knowledge) for help with the search strategy and obtaining papers that were not available.

1. (2019). Prices & Stats \ Costings & Herd Performance \ Indoor Breeding Herd.
2. Andersen, I. L., Haukvik, I. A., & Boe, K. E. (2009). Drying and warming immediately after birth may reduce piglet mortality in loose-housed sows. Animal, 3(4), 592–597. DOI: http://dx.doi.org/10.1017/S1751731108003650
3. Christison, G. I., Wenger, I. I., & Follensbee, M. E. (1997). Teat seeking success of newborn piglets after drying or warming. Canadian Journal of Animal Science, 77(2), 317–319. DOI:  https://doi.org/10.4141/A96-119
4. Dewey, C. E., Gomes, T., & Richardson, K. (2008). Field trial to determine the impact of providing additional care to litters on weaning weight of pigs. Canadian Journal of Veterinary Research, 72(5), 390–395.
5. Goden, B. (2016). How to get more piglets at weaning? Svinovodstvo (Moskva)(8), 22–23.
6. Herpin, P., Damon, M., & Le Dividich, J. (2002). Development of thermoregulation and neonatal survival in pigs. Livestock Production Science, 78(1), 25–45. DOI: https://doi.org/10.1016/S0301-6226(02)00183-5
7. Kiehne, R. (2006). Quick dry: warming up by drying piglets off conserving piglet energy. Large animal. Proceedings of the North American Veterinary Conference, Volume 20, Orlando, Florida, USA, 7-11 January, 2006, 329.
8. McGinnis, R. M., Marple, D. N., Ganjam, V. K., Prince, T. J., & Pritchett, J. F. (1981). The effects of floor temperature, supplemental heat and drying at birth on neonatal swine. Journal of Animal Science, 53(6), 1424–1431. DOI: https://doi.org/10.2527/jas1982.5361424x
9. Ogunbameru, B. O., Kornegay, E. T., & Wood, C. M. (1991). Evaluation of methods of providing supplemental heat to newborn pigs during and after farrowing. Journal of Animal Science, 69(10), 3939–3944. DOI: https://doi.org/10.2527/1991.69103939x
10. Pan, S. (1995). Effect of mop-drying on body temperature of porcine neonates. Journal of Veterinary and Animal Sciences, 26(1), 62–63.
11. Pasca, I., Pusta, D., Morar, R., Cimpean, A., Sobolu, R., Oroian, R., Dalea, I., & Bagita, C. (2008). Researches regarding piglet thermoregulation. Lucrari Stiintifice - Zootehnie si Biotehnologii, Universitatea de Stiinte Agricole si Medicina Veterinara a Banatului Timisoara, 41(2), 601–608.
12. Ravel, A., D'Allaire, S., & Bigras-Poulin, M. (1996). Influence of management, housing and personality of the stockperson on preweaning performances on independent and integrated swine farms in Quebec. Preventive Veterinary Medicine, 29(1), 37–57. DOI: http://dx.doi.org/10.1016/S0167-5877(96)01053-7
13. Rosvold, E. M., Kielland, C., Ocepek, M., Framstad, T., Fredriksen, B., Andersen-Ranberg, I., Naess, G., & Andersen, I. L. (2017). Management routines influencing piglet survival in loose-housed sow herds. Livestock Science, 196, 1–6. DOI: http://dx.doi.org/10.1016/j.livsci.2016.12.001
14. Vasdal, G., Ostensen, I., Melisova, M., Bozdechova, B., Illmann, G., & Andersen, I. L. (2011). Management routines at the time of farrowing-effects on teat success and postnatal piglet mortality from loose housed sows. Livestock Science, 136(2/3), 225–231. DOI: http://dx.doi.org/10.1016/j.livsci.2010.09.012
15. White, K. R., Anderson, D. M., & Bate, L. A. (1996). Increasing piglet survival through an improved farrowing management protocol. Canadian Journal of Animal Science, 76(4), 491–495. DOI: https://doi.org/10.4141/cjas96-075