Abstract
BackgroundInfluenza A(H1N1)pdm09 virus infection in Norwegian pigs was largely subclinical. This study tested the hypothesis that the infection causes negligible impact on pigs’ growth performance in terms of feed conversion efficiency, daily feed intake, daily growth, age on reaching 100 kg bodyweight and overall feed intake. A sample of 1955 pigs originating from 43 breeding herds was classified into five infection status groups; seronegative pigs (n = 887); seropositive pigs (n = 874); pigs positive for virus at bodyweight between 33 kg and 60 kg (n = 123); pigs positive for virus at bodyweight between 61 kg and 80 kg (n = 34) and pigs positive for virus at bodyweight between 81 kg and 100 kg (n = 37). Each pig had daily recordings of feed intake and bodyweight from 33 kg to 100 kg. Marginal effects of the virus infection on the outcomes were estimated by multi-level linear regression, which accounted for known fixed effects (breed, birthdate, average daily feed intake and growth phase) and random effects (cluster effects of pig and herd).ResultsThe seropositive and virus positive pigs had decreased (P value<0.05) growth performance compared to seronegative pigs even though feed intake was not decreased. Reduced feed conversion efficiency led to lower average daily growth, additional feed requirement and longer time needed to reach the 100 kg bodyweight. The effects were more marked (P value<0.03) in pigs infected at a younger age and lasted a longer period. Despite increased feed intake observed, their growth rates were lower and they took more time to reach 100 kg bodyweight compared to the seronegative pigs.ConclusionOur study rejected the null hypothesis that the virus infection had negligible adverse effects on growth performance of Norwegian pigs.
Highlights
Influenza A(H1N1)pdm09 virus infection in Norwegian pigs was largely subclinical
The virus positive group one (VIR1) with 123 pigs was defined as pigs tested positive for influenza A (H1N1)pdm09 virus by RT-PCR when their bodyweight was between 33 kg and 60 kg
The virus positive group three (VIR3), with 37 pigs was defined as pigs that tested positive for influenza A(H1N1) pdm09 virus by RT-PCR when their bodyweight was between 81 kg and 100 kg
Summary
Influenza A(H1N1)pdm virus infection in Norwegian pigs was largely subclinical. This study tested the hypothesis that the infection causes negligible impact on pigs’ growth performance in terms of feed conversion efficiency, daily feed intake, daily growth, age on reaching 100 kg bodyweight and overall feed intake. Marginal effects of the virus infection on the outcomes were estimated by multi-level linear regression, which accounted for known fixed effects (breed, birthdate, average daily feed intake and growth phase) and random effects (cluster effects of pig and herd). Er et al BMC Veterinary Research (2014) 10:284 by concurrent infections of other respiratory pathogens of which Porcine Reproductive and Respiratory Syndrome virus (PRRSV), Mycoplasma hyopneumoniae, Pasteurella multocida, and Actinobacillus pleuropnuemoniae are the most common. Such respiratory diseases are most frequently detected in 10- to 22-week-old pigs and are termed the porcine respiratory disease complex [1,11]. Farmers of positive herds reported mild or absence of clinical signs in their pigs [16] in Norway and in other parts of the world [7]
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