Changing immunity in piglets prior to birth
Could low-dose LPS stimulation during gestation alter response after birth?
By Nicole Burdick Sanchez, Ty Mitchell, Rand Broadway, Amy Petry, Jerrad Legako, and Jeff Carroll
Over time, pigs have become more susceptible to pathogens that cause disease. A contributing factor is likely the increased focus on selection for lean tissue growth, which has redistributed energy towards growth and away from the immune system. This has led to more significant disease outbreaks, ultimately negatively impacting pig health and growth performance. Thus, methods that can be used to boost the immunity of pigs are needed.
One alternative method may be to change the immune system of pigs prior to birth. Maternal immunizations allow the dam to build up immunoglobulins against a pathogen and pass these immunoglobulins to piglets at birth through colostrum ingestion. However, some vaccines are not very effective in passing immune protection on to piglets.
Previous work in the Livestock Issues Research Unit studied whether administering a low-dose immune stimulant (lipopolysaccharide; LPS) to pregnant cows would affect the immune response of their offspring after birth. This prior work revealed greater weaning weights in heifer and steer calves, and an altered immune response to subsequent LPS exposure.
The latest study was designed to investigate whether a similar method of low-dose LPS stimulation during gestation could alter the response of piglets to subsequent LPS stimulation after birth. The study used 14 Pregnant Camborough sows (parity 2.6 ± 1.4) assigned to one of two treatments: 1.) Prenatal immune stimulation (Prenatal LPS; n = 7): administered 2.5 µg/kg body weight LPS from E. coli O111:B4 (Sigma Aldrich, St. Louis, Missouri) intramuscularly in the shoulder at d 78 ± 1.8 of gestation and 2.) Control (CON; n = 7): administered a similar volume of saline intramuscularly in the shoulder.
Sow gestation was allowed to proceed normally according to farm standard operating procedures. At weaning, 17 CON and 17 Prenatal LPS barrows, balanced by sow and body weight, were selected for subsequent LPS stimulation.
Barrows were housed in individual pens in an environmentally controlled room where they had free access to water and a standard nursery diet. After a 7-day acclimation period, barrows were fitted with subcutaneous temperature loggers that measured temperature at 5-minute intervals, and jugular vein catheters for serial blood sample collection. The following day, barrows were administered 10 µg/kg body weight LPS intravenously, and blood samples were collected and evaluated for various immune parameters.
Barrows exposed to LPS during gestation responded quicker to the subsequent LPS challenge after weaning with an earlier rise in body temperature (Figure 1). As leukocytes decreased following LPS administration, a typical response, there was a tendency for less change in total white blood cells and eosinophils in barrows exposed to LPS during gestation. Further, concentrations of pro-inflammatory cytokines tended to be reduced in barrows exposed to LPS during gestation.
This is one of the first studies where LPS has been administered to pregnant sows in the last third of gestation and recorded the effects of subsequent LPS administration on piglets after birth. While there are many theories for the mechanisms associated with the differences observed, including passive transfer of protective antibodies or secondary metabolic effects, this study demonstrates that prenatal exposure to an antigen may be used to positively affect postnatal health of offspring. Undoubtedly, any metabolic changes induced by such a model have the possibility of positively or negatively affecting offspring. Although these secondary effects are unknown at this time, this work provides a foundation to study all aspects of neonatal growth performance, health and resiliency in the future.
In summary, prenatal exposure to LPS altered the postnatal response to LPS in weaned barrows. This resulted in a quicker temperature response as well as a reduction in the inflammatory immune response. Exposure of piglets to immune stimulants during gestation may influence their response after birth, which may serve as a method to positively influence pig health and growth performance.
AcknowledgementsMention of trade names or commercial products in this article is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the USDA. USDA is an equal opportunity provider and employer.
Burdick Sanchez, Broadway and Carroll are scientists with USDA-ARS Livestock Issues Research Unit. Mitchell is an undergraduate student and Legako is an associate professor at Texas Tech University. Petry is a former assistant professor at Texas Tech University and currently an assistant professor at the University of Missouri.
