2008 Brygo Auvigne Ipvs

EVALUATION OF THE IMMUNE STATUS OF SOWS BY MEASURING SERUM IMMUNOGLOBULIN LEVELS Brygo M.3, Chito C.2, Houlbert J.2, Sallé E.1, Laval A.3, Auvigne V.4 (1) CEVA, BP 126, F-33501 Libourne, France (2) SELARL de Vétérinaires CLD et Associés, F-03420 Marcillat-en-Combraille, France (3) ENVN, BP 40706, F-44307 Nantes Cedex 03, France (4) EKIPAJ, E-28223 Pozuelo de Alarcón, Spain

Introduction Colostrum plays a fundamental role in newborn piglets, by its contribution to the energy supply and immune protection. It is characterised by a high protein and low fat and carbohydrate content, in contrast to milk. IgG is the main immunoglobulin. Contrary to IgA, which is mainly produced in the udder, IgG originates from the serum of the dam. In colostrum, they represent 80% of all Ig and in serum, 83%. Colostral IgG levels are linked to the serum levels of the pregnant sow (1). In this context, the aim of the study was: (a) to set up a field method for the evaluation of the immune status of the breeding herd, by measuring the serum IgG; and (b) to study the factors related to this status. Materials and methods The study was carried out in 9 breeding-finishing farms (100 to 2200 sows). All farms vaccinated their sows against neonatal diarrhoea (using Neocoli Por®, Porcilis Porcoli® or Gletvax®). Four out of 9 farms recorded neonatal diarrhoea in the first 24 to 48 hours after farrowing. In 15 gilts (first-litter sows) and 15 sows (3rd to 5th litter), the IgG levels were measured using radial immunodiffusion plates (Triple J Farms, Washington, USA). This test is based on the centrifugal diffusion of serum IgG on a gel plate. Precipitation of IgG with anti-IgG renders the gel opaque (2). The concentration is calculated by interpolating the results of 4 reference sera. For each farm, the average IgG concentration was calculated, one for gilts and one for multiparous sows. Surveys of the farms were based on 9 variables that, according to literature, are susceptible to have an impact on IgG levels (contamination of gilts, number of contaminant introductions in quarantine, farm size, replacement method, number of vaccine administered to the breeding animals, lysine/threonine ratio in the feed for pregnant sows, female line genetics and number of weaned piglets per productive sow per year). Results 259 sera were analysed. The overall average IgG concentration was 24.2 mg/ml in gilts and 32.2 mg/ml in multiparous sows (Fig 1). This difference is significant (Mann & Whitney test, p=0.001). The difference between gilts and multiparous sows was found in all farms, with one exception.

b e r o f s o w s N u m

G ilts 50

20

M u ltip a r o u s sows

45 40 35 30 25 15 10 5 0 11

16

21

26

31

36

41

46

Ig G

Figure 1: Distribution of IgG concentrations

51

56

Between the 3rd and 5th litter, the IgG level increases slightly but significantly (p<0.05, R2=0.09). At farm level, there is a correlation between concentrations found in gilts and in sows (p=0.05, R2=0.46). For the farm variables, only the size of the farm is linked to IgG levels: the serum IgG levels are higher in large-size farms, both for gilts and for multiparous sows (table 1). Presence of neonatal diarrhoea Contamination of gilts Nb of contaminations during quarantine Number of sows Replacement Nb of sows vaccines Lysine / Threonine ratio Genetics (number of breed lines per sow) Weaned piglets / sow / year

No Yes No Yes <2 2 or more < 300 > 300 Buying-in Self R. 2 3 or more < 1.37 > 1.37 1 ou 2 3 < 26 > 26

IgG (mg/ml) Gilts Sows 24.2 31.4 23.9 33.1 23.7 30.4 24.3 33.1 23.6 31.4 24.7 33.1 23.1 29.6 25.3* 34.4** 23.8 32.1 24.5 32.3 23.4 32.0 24.5 32.2 24.2 30.8 23.9 33.9 24.3 30.5 23.8 33.6 25.0 33.1 23.4 31.4

Table 1: Relationship between farm variables and IgG levels (Mann & Whitney test: *: p<0.1, **: p<0.05) Discussion This study confirms the large difference in immune status between gilts and multiparous sows. This corroborates the need to respect a balanced age pyramid. There was no evidence that a quarantine and acclimatisation strategy allowed a quicker achievement of immunity in gilts. However, it is worth noting that the farm where the difference between gilts and multiparous sows was not significant was the only farm without quarantine (the replacement gilts were introduced directly in the pregnant sow unit). The hypothesis proposed to explain the higher immune status in farms with over 300 sows are that the contact between animals, as well as the movement of people and animals, increases with the size of the farm. This might lead to an increase of immune stimuli and thereby a higher production of IgG in the sows. The study did not show a link between the IgG levels in sows and the presence of neonatal diarrhoea on the farms. In absence of a link between serum IgG levels and health status, it is difficult to conclude whether it is desirable or not that sows have elevated IgG levels. It would also be of interest to analyse the IgA variation, since this immunoglobulin is particularly involved in the local intestinal immunity. However, there is no commercial test method available for measuring IgA levels. References (1) VoisinF., (2005) Thèse ENVT, 3- 4040 : 94 pages. (2) Mancini G., et al. (1965),. Immunochemistry; 2: 235-254.