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: 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. · 1.65 Impact Factor
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ABSTRACT: Porcine reproductive and respiratory syndrome (PRRS) is an infectious disease caused by a positive RNA strand arterivirus. PRRS virus (PRRSV) interacts primarily with lung macrophages. Identifying the genetic components involved in host resistance/susceptibility would represent an important step forward in the design of disease control programs. In this study, alveolar macrophages derived from five commercial pig lines were used to study the innate immune response to PRRSV infection in vitro. Analysis by flow cytometry has demonstrated that bronchial alveolar lavage fluid (BALF) preparations were almost exclusively composed of alveolar macrophages and that the pigs tested were free from infection. Macrophages from the Landrace line showed significantly reduced virus replication and poor growth of PRRSV during 30 h of infection. By 72 h, PRRSV viral load was down to 2.5 log(10) TCID(50) compared with an average of 5 log(10) TCID(50) for the other breeds tested. These observations suggest that factors intrinsic to the Landrace breed may be responsible for this reduced or delayed response to PRRSV. Preliminary investigation suggests that the PRRSV coreceptor, sialoadhesin, may not be responsible for the Landrace macrophage phenotype as its abundance and localisation were comparable in all the breeds. Strikingly, we found that the reduced or delayed growth of PRRSV was temporally associated with high levels of tumor necrosis factor-alpha (TNF-alpha) and interleukin (IL)-8 mRNA accumulation and substantial reduction of secretion of IL-8, suggesting a key contributory role for cytokine synthesis and secretion during the innate immune response to PRRSV infection.Viral Immunology 03/2007; 20(1):105-18. · 1.75 Impact Factor
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ABSTRACT: The reduction in feed intake and growth rate that occurs following weaning is of major economic consequence to the pig industry. Currently, a range of antimicrobial products can be used to minimise the impact of weaning on piglet health and subsequent performance. However, the use of these products in pig diets is subject to increasing restriction worldwide because of perceived risks to public health and to the environment. Thus, alternative methods are required to mitigate the growth check that almost invariably occurs after weaning in most production systems. Piglets produced outdoors are claimed to experience less of a growth check at weaning and to be able to thrive in relatively unsophisticated weaner accommodation. However, these claims have not been substantiated under Western Australian conditions, nor a scientific basis for these claims established. Consequently, a series of experiments was designed to test the general hypothesis for this thesis – ‘the gut structure and function, and lifetime performance of the weaned pig are affected by its pre- and post-weaning rearing environments’. Experiment 1 was conducted in two parts to quantify differences in the growth performance, health and gut structure of weaner pigs produced indoors or outdoors and reared in conventional or deep-litter pens. The weaner diet in the first part of the experiment contained 100 ppm of olaquindox and 3,000 ppm of zinc oxide (Exp1a). This experiment was repeated without using dietary antimicrobial products (Exp1b). Experiment 2 was conducted in conventional buildings to examine the effect of exposing piglets in lactation to similar substrates to those available to outdoor piglets used in Exp1a and Exp1b in the absence of other differences in the outdoor production milieu. Pre-weaning environments in Exp1a (indoor production (IP) and outdoor production (OP)) appeared to have little effect on gut structure and overall growth rate but significantly affected carcass composition, whereas post-weaning environments (conventional (C) or deep-litter (DL)) affected both overall growth rate and carcass composition. Although feed disappearance was similar, OP pigs grew faster than IP pigs in the first 47 d after weaning in Exp1a but not in Exp1b. Lifetime growth rate (GR), P2 backfat, feed disappearance and feed conversion ratio (FCR) were not significantly affected by the production environment in Exp1a whereas OP pigs grew slower with higher P2 backfat and FCR in Exp1b. Interestingly, OP pigs had heavier carcass weights and higher dressing percentages than IP pigs in both parts of the experiment. The effects of post-weaning environment were more consistent as DL pigs grew faster, were fatter, and had higher carcass weights and dressing percentages than C pigs. Villus height and crypt depth of IP and OP pigs were not different at 21 (weaning) or 28 d, but villus height decreased and crypt depth increased in the week after weaning. Pigs reared in C pens had greater faecal concentrations of volatile fatty acids than pigs in DL, indicating that the latter ingested sufficient straw to alter fermentation characteristics. In Experiment 2, there were no differences in gut structure or pre-weaning and lifetime GR of pigs offered no creep feed (NC), a commercial creep feed (CF) or an ‘outdoor’ mix (OM) comprising of 1 part straw, 5 parts sow feed and 25 parts of soil taken from paddocks in which OP pigs used in Exp1a and Exp1b were farrowed. However, NC pigs grew slower in the week after weaning than the other two treatments. Backfat and feed disappearance were similar for all treatments but pigs on the OM treatment had higher carcass weights and dressing percentages than pigs on the NC and CF treatments. Villus height and crypt depth were not different between treatments and, although the piglets were weaned at 28 d, villus height decreased and crypt depth increased in the week after weaning to an extent similar to that experienced by piglets weaned at 21 d in Experiment 1. Although all piglets received intramuscular injections of 200 mg iron (Fe) dextran when 1 to 2 days old, piglets offered the OM during lactation had higher serum iron and blood haemoglobin (Hb) levels than those offered NC or CF. Furthermore, half the piglets offered NC or CF had Hb levels indicative of chronic Fe deficiency anaemia. The average parity of sows used in this experiment was 6.3 litters, suggesting that piglets may have been born with low Fe stores, possibly because of low Fe stores in their dams due to sub-optimal mineral nutrition over successive parities. In summary, the findings from these experiments partly supported the general hypothesis for this thesis. Under the conditions of these experiments, access to outdoor substrates in lactation had little effect on gut structure and lifetime growth rate but increased both carcass weight and dressing percentage, whereas rearing in DL pens increased feed intake, FCR, growth rate, P2 backfat, carcass weight and dressing percentage.Payne, Hugh <http://researchrepository.murdoch.edu.au/view/author/Payne, Hugh.html> (2009) How Does the Pre-weaning Environment Affect Gut Structure and Function, and Lifetime Performance of the Pig? Masters by Research thesis, Murdoch University.