Lymphocyte stimulation by phytohaemagglutinin and concanavalin A in different swine breeds

On the influence of the source of porcine colostrum in the development of early immune ontogeny in piglets

The effects on the ontogeny of serum cytokines and immune cells caused by feeding suckling piglets with sow/gilt colostrum and milk replacer was assessed in the present study. After farrowing, the piglets born were randomized into six groups: GG and SS (n = 10/group): piglets were kept with their dam; GS (n = 10): piglets were changed from gilts to sows; SG (n = 10): piglets were changed from sows to gilts; GMR (n = 6) and SMR (n = 8): piglets from either gilts or sows were isolated from the dams and were bottle-fed ad libitum with commercial formula milk replacer. The piglets remained in the groups during the first 24 h of life and were later returned to their respective mothers. Serum immunoglobulin concentration and lymphocyte proliferation from the blood, spleen, thymus, and mesenteric lymph node of the piglets were assessed at 24 h and at 28 days of age. Serum cytokine concentrations were measured through a cytokine multiplex assay at 24 h. Overall, piglets suckling on sows (SS and GS) had a higher concentration of serum immunoglobulin at 24 h, which was also associated with a rise in plasma cytokine concentration and greater ability of B and T cells from lymphatic organs and blood mononuclear cells to respond to mitogens. We suggest a bias towards Th1-, Th2-, and Th17-cell polarizing and cytokines during the suckling period, which may be influenced by maternal immunological factors in the colostrum, such as dam parity. All findings suggest sow parity having a possible role, which may contribute to exerting a modulating action on immune response development.

Health and immune traits of Basque and Large White pigs housed in a conventional or enriched environment

Since decades, production traits such as growth rate, feed efficiency or body composition have been drastically increased in pigs by genetic selection. Whether this selection impacted animal robustness is still unclear. In this study, we compared Large White (LW) pigs, a breed submitted to intense genetic selection for production traits, and Basque (B) pigs, a local rustic breed, reared in two different housing environments (conventional v. enriched). Adaptation to housing conditions among each breed was evaluated at the level of endocrine and immune traits. These are known to be impacted by housing conditions and breed; however, the interaction effects between genotype and environment are less described. Animals (20 per breed and housing environment) entered the experiment at 35 kg of live weight. Levels of cortisol, acute-phase inflammatory proteins, immunoglobulins and hydrogen peroxide, blood formula, lymphocyte proliferation and in-vitro cytokine expression were measured at ∼115 kg of live weight. Animals were checked for skin injuries during the growing period. At slaughter, at the average live weight of 145 kg, carcasses were examined for pathological conditions of the respiratory tract. The major result was that the two breeds exhibited differences in response to the housing environment. Among the 24 sanitary, endocrine or immune traits investigated, the housing conditions affected eight variables in both breeds (salivary cortisol at 0700 and 1900 h, severity of pneumonia at slaughter) or only in B pigs (severe skin lesions) or LW pigs (salivary cortisol at 1500 h, granulocyte numbers and lymphocyte/granulocyte ratio and lymphocyte proliferation). These observations strengthen the hypothesis that selection for high meat production level might be associated with an increased susceptibility of animals to environmental stressors.

Age, gender and litter-related variation in T-lymphocyte cytokine production in young pigs

The capacity of farm animals to produce cytokines could be an important determinant of robustness and health. From research in rodents and humans it appears that the production and the balance of T helper 1 (Th1) and T helper 2 (Th2)-type cytokines influences susceptibility to autoimmune and infectious diseases. It is known that pigs show a large variation in many immune response parameters. So far the extent of individual variation in the production of Th1- and Th2-type cytokines in commercial outbred pigs has not been reported. In the current experiment we determined mRNA expression, as well as protein production of cytokines in 32 pigs from eight litters. From each litter two male and two female pigs were tested at 2, 5 and 8 weeks of age. Two Th1-type cytokines, interleukin (IL)-2 and interferon (IFN)-gamma, and two Th2-type cytokines, IL-4 and IL-10, were measured after phytohaemagglutinin (PHA)-stimulation of blood mononuclear cells. Cytokine production and the Th1/Th2-ratio were highly variable. The variation in cytokine protein production was moderately consistent across ages, i.e. pigs that produced high levels of cytokine at 2 weeks of age tended to do so as well at 5 and 8 weeks of age. Cytokine production tended to increase with age, and gilts and boars differed in their IL-2/IL-4 ratio. Unexpectedly, age, gender and litter effects often differed for mRNA and protein production data. We hypothesize that cytokine production is a consistent trait in pigs, especially at the protein production level. Future investigations in more animals and across a wider age range are necessary.

Effects of housing and individual coping characteristics on immune responses of pigs

The impact of environmental factors on immune responses may be influenced by coping characteristics of the individuals under study. The behavioral response of pigs in a so-called Backtest early in life seems indicative of their coping style at a later age. The present study investigated the effects of housing, barren versus enriched, and coping style, as assessed by Backtest classification, on immune responses of pigs. Pigs were housed either without a rooting substrate (barren housing) or in identical pens enriched with deep straw bedding (enriched housing) from birth. During the suckling period, pigs were subjected to the Backtest. Each pig was restrained on its back for 1 min and the resistance (i.e., number of escape attempts) was scored. Pigs classified as 'high-' or 'low-resisting' (HR and LR, respectively) were immunized with di-nitrophenyl-conjugated keyhole limpet haemocyanin (DNP-KLH) at 9 weeks of age. Blood samples were drawn before immunization (Day 0) and weekly thereafter, until Day 35. KLH-specific lymphocyte proliferation following immunization was higher for HR pigs than for LR pigs. Housing did not affect proliferative responses. Housing and coping style interacted in their effect on KLH-specific humoral immune responses. LR pigs from barren housing showed higher KLH-specific antibody titers than LR pigs from enriched housing. Differently housed HR pigs, however, showed similar antibody titers. These findings support other research indicating that individual coping styles of pigs are reflected in their immune responses. More important, the present study demonstrates that effects of housing on humoral immune responses of pigs may differ for pigs with divergent coping styles.

Characterisation of a resource population of pigs screened for resistance to salmonellosis

The degree of resistance to Salmonella choleraesuis infection in a reference family purposely bred to map resistance genes was assessed. Aspects of the innate and specific immune system were studied to find a parameter that might predict the resistance of pigs to salmonellosis. The family was bred from commercial full-sister pairs of F1-gilts and four boars. One boar (G398) was identified as breeding susceptible offspring, and one boar (G402) as breeding resistant offspring on the basis of pyrexial responses and numbers of Salmonella in liver and spleen post mortem. The other two boars were classified as 'possible resistant' (Y2008) and 'unknown' (Y6101) respectively. Functional differences in immune cells (neutrophils and lymphocytes) between the offspring of G398 and G402 were detected. The most resistant piglets had a higher number of circulating neutrophils and better polymorphonuclear neutrophils (PMNs) function, but a lower mitogenic response of lymphocytes both pre- and post-infection and a lower antibody response. Between the offspring groups of Y2008 and Y6101 no differences were found in the number of viable Salmonella in liver and spleen at post mortem or in immune cell function, however, the survival rate of these offspring groups was clearly different. Twenty three percent of the Y2008-offspring and 33% of the Y6101-offspring reached the predetermined humane clinical endpoint before the end of the experiment. Our findings suggest a role for several inherited immunological traits, including PMN function and lecithin-induced mitogenic proliferation, which appear to influence resistance to salmonellosis.

Disease incidence and immunological traits for the selection of healthy pigs. A review

Disease is a major issue in animal production systems and society demands that the use of medicines and vaccines be reduced. This review describes the breeding approaches that could be used to improve disease resistance and focuses especially on their application to pigs. Disease reduction by genetic means has certain advantages through cumulative and permanent effects, and direct and indirect selection methods are available. Direct selection for disease incidence requires, besides a unique pig identification and disease registration system, challenge routines that are inconvenient in intensive pig production. Indirect selection for the expression of immune capacity may be an alternative but requires detailed knowledge of the different components of the immune system. There is ample opportunity for genetic improvement of the immune capacity because immune traits show substantial genetic variation between pigs. We therefore conclude that indirect selection via immune traits is very interesting, also for practical implementation, and that there is an urgent need for knowledge, within lines, about the genetic relationships between immune capacity traits and resistance to specific diseases or to disease incidence in general. Furthermore, knowledge about the relationship between immune system traits and production traits is needed as well as knowledge about the effect of selection on the epidemiology of disease at a farm/population level and on the host-pathogen interaction and coevolution.