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

PICO question 
In newborn piglets, does drying piglets, compared to no intervention, reduce the level of mortality pre-weaning (up to 28 days)? 
Clinical bottom line 
Data specifically evaluating drying piglets are limited. Many papers had multiple factors evaluated or were assessments of management in general. There is evidence that drying piglets can reduced mortality and improve thermoregulation of piglets. The cost of such interventions has not been appraised and should be considered on a case-by-case basis. Therefore, currently when advising farmers it could be suggested that the drying of piglets may form part of a number of recommendations given to reduce piglet mortality pre-weaning. 



Clinical Scenario
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

PICO question
In newborn piglets, does drying piglets, compared to no intervention, reduce the level of mortality pre-weaning (up to 28 days)?

Clinical bottom line
Data specifically evaluating drying piglets are limited. Many papers had multiple factors evaluated or were assessments of management in general. There is evidence that drying piglets can reduce mortality and improve thermoregulation of piglets. The cost of such interventions has not been appraised and should be considered on a case-by-case basis. Therefore, currently when advising farmers it could be suggested that the drying of piglets may form part of a number of recommendations given to reduce piglet mortality pre-weaning. Induced farrowing Trial conducted from 0 -21 days of age (weaning age not given) Sample size: 98 piglets (litters standardised to nine piglets/sow -additional piglets were fostered off) Intervention details: Three treatment groups -the three treatments were randomly assigned within birth order trios (first three born, second three born, final three born were trio 1-3, respectively):  Control n = 33 piglets -Piglets were not handled except to dry and colour one ear (method of drying not specified)  Dried n = 32 piglets -Piglets dried at birth with paper towel and returned to where they were born, marked on back  Heat Lamp n = 33 piglets -Piglets picked up by back legs and moved under heat lamp, one ear was dried and coloured for identification (method of drying ear not specified) Mucus was cleared from the nose and mouth for all groups. Umbilical cords were detached or shortened if required to ensure that it did not hinder their movement.

Study design: Randomised controlled trial
Outcome studied:  Teat seeking success (made up of latency to udder contact and first suckle)  Weights at various time points (2 hours, 6 hours, days 1, 3, 7, 14 and 21  Mortality

Main findings: (relevant to PICO question):
 No effect of any treatment on mean time to udder contact  No effect of any treatment on mean time to suckle  No effect of any treatment on weight at 2 hours or average daily gain at 24 hours and 21 days  Mortality higher in control piglets 7/33 (21%) compared to dried piglets 2/33 (6%) and heat lamp piglets 0% mortality

Limitations:
 Litters reduced to nine piglets which may mean that the litters were smaller than normal which may be less representative of the population as the piglets had less competition for teat access  Induced farrowing (this can make piglets less viable however, equal across treatments)  Marking process may confound results -dried piglets perhaps should have been marked on ear as well  Relatively small sample size

Limitations:
 Lot of variables changed between treatments, cannot decipher if one or more additional care factor influenced outcomes more than another  System comparison rather than treatment/control study  Drying of piglets was not an independent treatment

McGinnis et al. (1981)
Population: Litters from 33 sows (breed and parity not given) Housing -farrowing crate concrete floor Natural farrowing Room temperature 22°C Trial conducted from 0 to 5 days of age

Main findings: (relevant to PICO question):
 Overall mortality significantly lower in attended farrowing 32/318 (10.1%) compared with control 56/308 (18.2%) these data include stillbirths. Excluding stillbirths mortality was 27/318 (8.5%) and 38/308 (12.3%) for attended and unattended farrowing respectively.  Significantly more piglets were stillborn, starved and contracted e-coli in the control group  Weight of control piglets higher at birth (assumed that they had suckled before weighing)  Mean weight at 21 days higher for the attended piglets (5.33 kg) versus (5.09 kg)

Limitations:
 No drying only group, drying formed part of a number of interventions made at birth  Large range of parities however, similar between treatment groups

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.

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