Comparison of serologic testing and slaughter evaluation for assessing the effects of subclinical infection on growth in pigs.
OBJECTIVE
To compare serologic testing with slaughter evaluation in assessing effects of subclinical infection on average daily weight gain (ADG) in pigs.


METHODS
Cohort study.


METHODS
18 cohorts (30 to 35 pigs/cohort) of pigs on/farms.


METHODS
Blood samples were collected, and pigs were weighed at 8, 16, and 24 weeks of age. Sera were tested for antibodies to porcine reproductive and respiratory syndrome virus (PRRSV), swine influenza virus (SIV), transmissible gastroenteritis virus (TGEV), pseudorabies virus, Mycoplasma hyopneumoniae, and Actinobacillus pleuropneumoniae. At slaughter, skin, nasal turbinates, lungs, and liver were examined. Associations between ADG and results of serologic testing and slaughter evaluation were examined by use of multiple linear regression.


RESULTS
Pathogens that had a significant effect on any given farm during any given year and the magnitude of that effect varied. However, at 16 and 24 weeks of age, a higher antibody titer was consistently associated with a lower ADG. Mean differences in ADG between seropositive and seronegative pigs were 18 g/d (0.04 lb/d) for SIV, 40 g/d (0.09 lb/d) for PRRSV, 38 g/d (0.08 lb/d) for M hyopneumoniae, and 116 g/d (0.26 lb/d) for TGEV. Of the evaluations performed at slaughter, only detection of lung lesions was consistently associated with a decrease in ADG.


CONCLUSIONS
Results suggest that subclinical infection with any of a variety of pathogens commonly found in swine herds was associated with a decrease in ADG. Serologic testing was more effective than slaughter evaluation in assessing the impact of subclinical infection on ADG in these pigs.
Regula
G
G
Department of Veterinary Pathobiology, College of Veterinary Medicine, University of Illinois, Urbana 61802, USA.
Lichtensteiger
C A
CA
Mateus-Pinilla
N E
NE
Scherba
G
G
Miller
G Y
GY
Weigel
R M
RM
D000189:Actinobacillus Infections / Q000097:blood / Q000503:physiopathology*; D016977:Actinobacillus pleuropneumoniae / Q000302:isolation & purification / Q000472:pathogenicity; D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood; D000914:Antibodies, Viral / Q000097:blood; D015331:Cohort Studies; D005260:Female; D005761:Gastroenteritis, Transmissible, of Swine / Q000097:blood / Q000503:physiopathology*; D011558:Herpesvirus 1, Suid / Q000302:isolation & purification / Q000472:pathogenicity; D009980:Influenza A virus / Q000302:isolation & purification / Q000472:pathogenicity; D008099:Liver / Q000473:pathology; D008168:Lung / Q000473:pathology; D015999:Multivariate Analysis; D009976:Orthomyxoviridae Infections / Q000097:blood / Q000503:physiopathology*; D019318:Porcine Reproductive and Respiratory Syndrome / Q000097:blood / Q000503:physiopathology*; D019316:Porcine respiratory and reproductive syndrome virus / Q000302:isolation & purification / Q000472:pathogenicity; D011557:Pseudorabies / Q000097:blood / Q000503:physiopathology*; D012044:Regression Analysis; D012867:Skin / Q000473:pathology; D013552:Swine / Q000254:growth & development*; D013553:Swine Diseases / Q000382:microbiology* / Q000821:virology; D005760:Transmissible gastroenteritis virus / Q000302:isolation & purification / Q000472:pathogenicity; D015430:Weight Gain
D000907:Antibodies, Bacterial; D000914:Antibodies, Viral