Associations of weight gain and food intake with leukocyte sub-sets in Large White pigs
ABSTRACT Associations between productivity and a range of immune traits were tested by multiple regression analysis on 128 Large White pigs (62 male, 66 female). Daily weight gain, daily feed intake, and efficiency (i.e. weight gain/feed intake), assessed from 14 to 24 weeks of age, were the productivity traits. Total and differential white blood cell count and leukocyte sub-sets positive for CD4, CD8, CD11R1, gamma delta T cells, B cell, and monocyte markers, all measured at 18 and 24 weeks, were the immune traits. At 24 weeks of age, higher percentages of monocytes were associated with a decrease in daily weight gain. Higher percentages of B cells were associated with a decrease in daily feed intake. Higher percentages of CD11R1 positive cells were associated with a decrease in daily weight gain and a decrease in efficiency. Relationships at the age of 18 weeks were similar, but slightly less significant. Associations between the numbers of monocytes, MIL-4 positive cells and B cells and certain performance traits were also observed at the age of 24 weeks. Overall, these results indicate an association between productivity and certain immune traits. We suggest that the observed associations between these immune traits and performance could be due to the impact of sub-clinical infections.
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ABSTRACT: There is mounting evidence that bacteria originating from pigs degrade the environment of the pig shed and adversely affect the health of the animals and the pig-shed workers. α-haemolytic cocci (AHC) occur in pig-shed environments, but are regarded as commensals. Ammonia is also a component of the pig-shed environment, and is known to damage upper respiratory tract epithelia. The aim of this study was to determine whether polluted air in pig sheds adversely affected performance indicators in pigs. Modelling revealed a direct effect of AHC on voluntary feed intake and hence AHC are not commensal. No direct effect of ammonia on the pigs was detected, but the combination of AHC and ammonia stimulated the immune system in a progressive manner, and there were direct effects of immune stimulation on food intake and growth resulting in poorer feed-conversion efficiency, even though the effects remained subclinical. The authors conclude that exposure of the respiratory epithelia of pigs to viable AHC in the presence of ammonia redirects nutrients away from production and towards the immune system, explaining the impact of poor pig-shed hygiene on production parameters.The Veterinary record. 06/2012; 171(5):123.
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ABSTRACT: Genetic selection is well established as a means of improving productivity in pigs, but the effects of continued selection for increased performance on immunity are not well understood, nor are genetic relationships between performance and immunity. This study compared differences in the levels of a range of immune traits between lines of Large White pigs divergently selected for a number of productivity traits. Selection lines compared were high v. low lean growth under restricted feeding (31 high line v. 10 control v. 38 low line pigs), high v. low lean growth under ad libitum feeding (18 high line v. 10 control v. 19 low line pigs), and high v. low food intake (24 high line v. 26 low line pigs). Immune traits measured were total white blood cell numbers (WBC), and the numbers of leukocyte subsets: neutrophils, monocytes, eosinophils, lymphocytes, CD4+ cells, CD8α+ cells, B cells, γδ T cells and CD11R1+ Natural killer (NK) cells. CD4+, γδ T cells and CD11R1+ cells were subdivided into subpopulations that were positive or negative for the CD8α marker, and conventional CD8αhigh+ cytotoxic T cells were also determined. Pigs were tested under ad libitum feeding conditions from 14 to 24 weeks, and immune traits were assessed at ages 18 and 24 weeks. Line differences were estimated using residual maximum likelihood techniques. Consistent differences in immune trait levels were evident between pigs previously selected for high and low lean growth under restricted feeding: at age 24 weeks, high line pigs had higher basal levels of WBC (39·6 v. 27·8×106 cells per ml, s.e.d. 2·09, for high v. low line pigs) mainly explained by higher levels of lymphocytes (25·5 v. 17·3×106 cells per ml, s.e.d. 1·54, for high v. low line pigs) with increased numbers of CD8α+ cells (8·19 v. 5·15×106 cells per ml, s.e.d. 0·14) and CD11R1+ cells (5·23 v. 2·46×106 cells per ml, s.e.d. 0·43), predominantly the CD11R1+ CD8α? subpopulation ((3·20 v. 1·64×106 cells per ml, s.e.d. 0·11). High line pigs also had increased numbers of monocytes (2·64 v. 1·83×106 cells per ml, s.e.d. 0·35). Similar results were obtained at age 18 weeks. There were no consistent differences between divergent lines in pigs selected for lean growth under ad libitum feeding or food intake. This is the first report to demonstrate that selection for some aspects of performance can influence WBC and leukocyte subset numbers in pigs.Animal Science. 11/2006; 82(06):867 - 876.
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ABSTRACT: Indicator traits used to select pigs for increased resistance to infection or improved health must be heritable and, preferably, be associated with improved performance. We estimated the heritability of a range of immune traits and their genetic and phenotypic correlations with growth performance. We measured immune traits on 589 pigs and performance on 1941 pigs from six farms, three of which were classified as 'high health status' (i.e. specific pathogen-free) and three were of lower health status. All pigs were apparently healthy. Immune traits were total white blood cells (WBC), and peripheral blood mononuclear leucocyte (PBML) subsets positive for CD4, CD8α, gamma delta (γδ) T cell receptor, CD11R1 (natural killer cell marker), B cell and monocyte markers at the start and the end of standard growth performance tests. At both time points, all immune traits were moderately to highly heritable except for CD8α+ cells. At end of test, heritability estimates (h2) (±s.e.) were 0.18 (±0.11) for total WBC count. For PBML subset proportions, the heritabilities were 0.52 (±0.14) for γδ TCR+ cells, 0.62 (±0.14) for CD4+ cells, 0.44 (±0.14) for CD11R1+ cells, 0.58 (±0.14) for B cells and 0.59 (±0.14) for monocytes. Farm health status affected the heritabilities for WBC, being substantially higher on lower health status farms, but did not have consistent effects on heritabilities for the PBML subsets. There were significant negative genetic correlations between numbers and proportions of various PBML subsets and performance, at both start and end of test. In particular, the proportion of PBML cells that were CD11R1+ cells, at end of test, was strongly correlated with daily gain (rg = -0.72; P < 0.01). There were also weaker but significant negative phenotypic correlations between PBML subsets measured at end of test and performance, for γδ+ T cells, CD8α+, CD11R1+ cells, B cells or monocytes. Phenotypic correlations with daily gain were generally lower at the start of test than at the end of test. These results show that most of the major pig PBML subsets are heritable, and that systemic levels of several of these PBML subsets are genetically negatively correlated with performance. This approach provides a basis for using immune trait markers when selecting boars that can produce higher-performing progeny.animal 11/2008; 2(11):1575-84. · 1.78 Impact Factor