Over recent years, both litter size at birth and pre-weaning mortality (PWM) have increased significantly in US commercial swine herds. Data from PigCHAMP (2018) suggest that over the last decade the total number of piglets born and pre-weaning mortality have increased by approximately 2 piglets per litter and 2 percentage units, respectively. Increases in litter size are associated with a decrease in average piglet birth weight and, particularly, an increase in the number of low birth weight piglets (i.e., piglets weighing less than ~2.2lb at birth). Surveys of PWM on commercial units have suggested that two major predisposing factors are low birth weight and low body temperatures in the early period after birth. These two factors are related; low birth weight piglets exhibit the greatest temperature decline early after birth and have the highest level of PWM. This research project was carried out to develop an understanding of the effect of piglet birth weight on changes in rectal temperature after birth, and to evaluate practical approaches (namely drying, warming, or oxygenation) that could be applied at birth to mitigate this risk and increase piglet survival under commercial conditions. Six studies were carried out under typical farrowing house conditions involving a total of 1,032 sows and 13,208 piglets.
All piglets in these studies experienced a decline in body temperature immediately after birth, irrespective of birth weight or of any of the interventions that were evaluated. However, the decrease was much greater in magnitude in Light (<2.2lb) compared to Medium (2.2 to 3.3lb) and Heavy (>3.3lb) birth weight piglets. For example, in one of the studies rectal temperature of Light piglets that were left undried in the farrowing pen after birth declined by 10.1oF on average between birth and 60 minutes after birth compared to declines of 4.9 and 3.6oF in Medium and Heavy birth weight piglets, respectively.
Drying piglets at birth by either coating them in a commercially-available desiccant or rubbing with paper towels reduced the magnitude of the body temperature decline in piglets after birth. However, drying with paper towels was more laborious and time consuming than using a desiccant and, consequently, drying with a desiccant was the approach used in subsequent studies. Drying piglets at birth with a desiccant or warming them in a warming box (at 96 to 100oF) for 30 minutes were equally effective at minimizing the magnitude of piglet body temperature decline after birth. However, the combination of drying and warming of piglets at birth was more effective in this regard than using either approach independently.
All of the approaches to drying and/or warming of piglets at birth were relatively more effective in light than in heavier birth weight piglets. For example, compared to untreated piglets, those that were dried and warmed had rectal temperatures at 60 minutes that were 7.9, 4.3, and 3.6oF higher for Light, Medium, and Heavy piglets, respectively.
Placing piglets in an oxygen enriched chamber (40% oxygen concentration) for 20 minutes after birth was effective at increasing blood oxygen saturation but did not positively impact piglet rectal temperatures. In fact, piglets that were placed in the chamber had a lower temperature (by 0.5 to 0.7oF) on removal from the chamber than those that remained in the farrowing pen during this period. However, this effect appeared to be the result of the chamber rather than oxygen exposure, as it also occurred in piglets that were placed in chambers that were at ambient oxygen concentrations.
Plasma immunoglobulin immunocrit values at 24 hours after birth, an index of colostrum intake, were similar for piglets on all of the treatments evaluated in this project (i.e., drying, warming, or oxygenation) and for all birth weights. This suggests that colostrum intake was not impacted by either any of the intervention treatments evaluated or by piglet birth weight.
The final study evaluated the impact of drying and warming piglets at birth on pre-weaning mortality under commercial conditions. Piglets were either dried (with desiccant) and warmed (in warming box for 30 minutes) or left undried in the farrowing pen from birth onwards. A total of 800 litters and more than 10,000 piglets were involved in the study. Pre-weaning mortality levels were relatively similar for piglets that were dried and warmed compared to those that were not dried (15.7 and 16.3%, respectively). In addition, pre-weaning mortality levels for the two treatments were similar for the Light (43.7 and 45.5%, respectively), Medium (15.3 and 16.6%, respectively), and Heavy (8.0 and 8.5%, respectively) piglets.
In conclusion, this research has confirmed that all piglets experience a significant decrease in body temperature after birth and that this decrease is greater in magnitude for lighter than heavier birth weight piglets. Drying and/or warming of piglets at birth were highly effective at reducing the magnitude of post-natal body temperature decreases, particularly in piglets of low birth weight, with the combination of these two being the more effective than using either approach independently. However, drying and warming of piglets at birth had no effect on pre-weaning mortality levels in piglets of any birth weight.