Identification of resilient sows in porcine reproductive and respiratory syndrome virus–infected farms1

Abstract

The identification of resilient sows can improve reproductive performance in farms exposed to multiple challenges. A common challenge is the porcine reproductive and respiratory syndrome virus (PRRSV). A key issue to deal with disease resilience is to set up a feasible phenotyping strategy. Our aim was to develop a phenotyping criterion to discriminate susceptible from resilient sows in PRRSV-infected farms. A total of 517 Landrace x Large White gilts were classified as resilient (R) or susceptible (S) to PRRSV virus, following vaccination with MLV-PRRSV at 6 to 7 wk of age, in a PRRSV negative multiplication farm. Female piglets were phenotyped as R if their serum was negative to PRRSV at 7 and 21 d postvaccination (DPV) or as S if their serum was positive at 7 and/or 21 DPV. Amongst them, 382 gilts were transferred to a PRRSV-positive production farm, where the number of piglets born alive (NBA), stillborn (NSB), mummified (NMU), lost (NLP = NSB + NMU), and total born (NTB = NBA + NLP) were recorded for almost 3 yr. Data were collected during 2 periods according to the PRRSV farm health status, which were confirmed as either PRRSV-positive stable (endemic) or inestable (epidemic). Analyses were carried out under a Bayesian approach. The heritability for the resilience criterion was estimated using a threshold model. A linear (for NTB and NBA) and a binomial model (for NSB, NMU, and NLP) on the resilience criterion by the farm health status were used to assess the difference between R and S sows. The heritability of the resilience criterion was 0.46 (SD 0.06). The probability of a piglet being lost was greater (≥0.97) in S than in R litters, regardless of whether the delivery occurred during a PRRSV outbreak (20.5% vs. 17.0%) or not (15.8% vs. 13.7%). The lower piglet mortality rate in R sows was due to NSB, in the endemic phase (13.0% vs. 15.0% of NTB, with a posterior probability of 98% of S sows showing higher NSB than R sows), and to NMU, in the epidemic phase (4.0% vs. 8.4% of NTB, with a posterior probability of >99% of S sows showing higher NMU than R sows). During a PRRSV outbreak, the S sows were twice as likely to give birth to a mummified piglet when compared with R sows. These findings provide evidence that the described phenotyping scheme has a potential use as a PRRSV resilience criterion.

Genetic Analysis of Antibody Response to Porcine Reproductive and Respiratory Syndrome Vaccination as an Indicator Trait for Reproductive Performance in Commercial Sows

“…Serão et al (2016), using the same PRRS ELISA test as in our study, reported h 2 estimates ranging from 0.28 ± 0.04 to 0.47 ± 0.06, as the proportion of seroconverted animals increased in the dataset; however, there was no confirmation on whether the replacement gilts in were PRRSV-vaccinated or PRRSV-infected or even both. More similar to our study, Abella et al (2019) estimated h 2 for S/P ratio at 42 days after PRRSV vaccination and obtained a higher h 2 estimate than we observed in our study (0.69 ± 0.10). Although they used the same ELISA test as us, the animals in their study were growing pigs at 6-7 weeks of age, and it is possible that the redirect of energy being used to growth for antibody production may have affected future performance.…”

“…Although they used the same ELISA test as us, the animals in their study were growing pigs at 6-7 weeks of age, and it is possible that the redirect of energy being used to growth for antibody production may have affected future performance. Another important point to be highlighted is that in the study by Abella et al (2019), the herds were endemic for PRRS, and, therefore, the animals were in constant health challenge during vaccination and farrowing. Therefore, our study is the first one, to the best of our knowledge, to estimate h 2 for S/P ratio in PRRS-vaccinated F1 replacement gilts.…”

“…Putz et al (2019) also reported a similar estimate of r g between S/P with NSB, of -0.73 during a PRRS outbreak but not for NBA, which was positive but very low (0.05). Abella et al (2019) also investigated the relationship between S/P ratio in vaccinated young gilts and subsequent reproductive performance in endemic herds. In contrast to our results, they found a small but positive phenotypic correlation between antibody response to PRRSV vaccination and NSB when looking at extreme phenotypes for response to PRRSV vaccination (resistant and susceptible gilts).…”

“…These authors measured S/P ratio at 42 days after vaccination and obtained an h 2 estimate of 0.69. Also, they developed a phenotyping criterion to discriminate susceptible and resilient sows based on viral load at 7 and 21 days post vaccination (Abella et al, 2019). At the phenotypic level, they reported that susceptible sows had greater antibody response to vaccination and higher NSB than those classified as resilient.…”

Genomic Analysis of IgG Antibody Response to Common Pathogens in Commercial Sows in Health-Challenged Herds

“…Infectious diseases are well known to cause productivity losses in the swine industry (Lee et al, 2012;Lewis et al, 2007), motivating the investigation of traits related to disease resilience for genetic selection. It has been shown that there is genetic variation in total antibody (Ab) response to swine pathogens, such as porcine reproductive and respiratory syndrome (PRRS) virus (PRRSV) (Serão et al, 2014;Hess et al, 2018;Abella et al, 2019). Selection of more resilient animals could decrease the losses caused by the decreased performance of animals exposed to pathogens.…”