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Adverse effects of Influenza A(H1N1)pdm09 virus infection on growth performance of Norwegian pigs - a longitudinal study at a boar testing station.

Er C, Lium B, Tavornpanich S, Hofmo PO, Forberg H, Hauge AG, Grøntvedt CA, Framstad T, Brun E - BMC Vet. Res. (2014)

Bottom Line: 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).Reduced feed conversion efficiency led to lower average daily growth, additional feed requirement and longer time needed to reach the 100 kg bodyweight.

View Article: PubMed Central - PubMed

Affiliation: Norwegian Veterinary Institute, P.O. Box 750, 0106, Oslo, Norway. chiek.er@vetinst.no.

ABSTRACT

Background: Influenza 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).

Results: The 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.

Conclusion: Our study rejected the hypothesis that the virus infection had negligible adverse effects on growth performance of Norwegian pigs.

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Related in: MedlinePlus

Marginal plots for average daily growth (ADG) and adverse effects of influenza A(H1N1)pdm09 virus infection. Based on the model presented in Table 2, the mean ADG was predicted for each of the five infection status groups and the three growth phases (GF), while all other covariates of birthdate, feed intake and breed were fixed at the sample means. The effect of the virus infection is marked by comparing the four infected groups with the reference seronegative group on the same growth phase denoted by the line joining the groups. Comparisons between groups were made for each growth phase since ADG vary with age. As depicted in the graph, the younger pigs would hypothetically have a higher ADG because they have a better FCE (see Figure 2 and Table 3) if feed intake is fixed at the same level. The gradient of the lines joining the means of each group and the confidence intervals indicate whether there were differences between the groups. Abbreviations: INFGP = Infection status group; SEROPOS = seropositive pigs, SERONEG = seronegative pigs, VIR1 = PCR-positive pigs at bodyweight between 33 kg and 60 kg (GF1); VIR2 = PCR-positive pigs at bodyweight between 61 kg and 80 kg (GF2); VIR3 = PCR-positive pigs at bodyweight between 81 kg and 100 kg (GF3).
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Fig2: Marginal plots for average daily growth (ADG) and adverse effects of influenza A(H1N1)pdm09 virus infection. Based on the model presented in Table 2, the mean ADG was predicted for each of the five infection status groups and the three growth phases (GF), while all other covariates of birthdate, feed intake and breed were fixed at the sample means. The effect of the virus infection is marked by comparing the four infected groups with the reference seronegative group on the same growth phase denoted by the line joining the groups. Comparisons between groups were made for each growth phase since ADG vary with age. As depicted in the graph, the younger pigs would hypothetically have a higher ADG because they have a better FCE (see Figure 2 and Table 3) if feed intake is fixed at the same level. The gradient of the lines joining the means of each group and the confidence intervals indicate whether there were differences between the groups. Abbreviations: INFGP = Infection status group; SEROPOS = seropositive pigs, SERONEG = seronegative pigs, VIR1 = PCR-positive pigs at bodyweight between 33 kg and 60 kg (GF1); VIR2 = PCR-positive pigs at bodyweight between 61 kg and 80 kg (GF2); VIR3 = PCR-positive pigs at bodyweight between 81 kg and 100 kg (GF3).

Mentions: Tables 2, 3 and 4 show that with SERONEG pigs as the reference, there were statistically significant marginal adverse effects on ADG and FCE in all infected groups (SEROPOS and VIRs 1–3). The marginal plots in Figures 2 and 3 show the predicted means of ADG and FCE while the covariates of BD, ADFI and Br were kept at the sample means. Only GF and INFGP were allowed to vary so that the effect of the virus infection on ADG and INFGP could be studied in the three strata of growth phases. The differences in the predicted FCE and ADG between the five groups of pigs in each of the three growth phases can then be attributed to infection status of the pig.Table 2


Adverse effects of Influenza A(H1N1)pdm09 virus infection on growth performance of Norwegian pigs - a longitudinal study at a boar testing station.

Er C, Lium B, Tavornpanich S, Hofmo PO, Forberg H, Hauge AG, Grøntvedt CA, Framstad T, Brun E - BMC Vet. Res. (2014)

Marginal plots for average daily growth (ADG) and adverse effects of influenza A(H1N1)pdm09 virus infection. Based on the model presented in Table 2, the mean ADG was predicted for each of the five infection status groups and the three growth phases (GF), while all other covariates of birthdate, feed intake and breed were fixed at the sample means. The effect of the virus infection is marked by comparing the four infected groups with the reference seronegative group on the same growth phase denoted by the line joining the groups. Comparisons between groups were made for each growth phase since ADG vary with age. As depicted in the graph, the younger pigs would hypothetically have a higher ADG because they have a better FCE (see Figure 2 and Table 3) if feed intake is fixed at the same level. The gradient of the lines joining the means of each group and the confidence intervals indicate whether there were differences between the groups. Abbreviations: INFGP = Infection status group; SEROPOS = seropositive pigs, SERONEG = seronegative pigs, VIR1 = PCR-positive pigs at bodyweight between 33 kg and 60 kg (GF1); VIR2 = PCR-positive pigs at bodyweight between 61 kg and 80 kg (GF2); VIR3 = PCR-positive pigs at bodyweight between 81 kg and 100 kg (GF3).
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
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getmorefigures.php?uid=PMC4300606&req=5

Fig2: Marginal plots for average daily growth (ADG) and adverse effects of influenza A(H1N1)pdm09 virus infection. Based on the model presented in Table 2, the mean ADG was predicted for each of the five infection status groups and the three growth phases (GF), while all other covariates of birthdate, feed intake and breed were fixed at the sample means. The effect of the virus infection is marked by comparing the four infected groups with the reference seronegative group on the same growth phase denoted by the line joining the groups. Comparisons between groups were made for each growth phase since ADG vary with age. As depicted in the graph, the younger pigs would hypothetically have a higher ADG because they have a better FCE (see Figure 2 and Table 3) if feed intake is fixed at the same level. The gradient of the lines joining the means of each group and the confidence intervals indicate whether there were differences between the groups. Abbreviations: INFGP = Infection status group; SEROPOS = seropositive pigs, SERONEG = seronegative pigs, VIR1 = PCR-positive pigs at bodyweight between 33 kg and 60 kg (GF1); VIR2 = PCR-positive pigs at bodyweight between 61 kg and 80 kg (GF2); VIR3 = PCR-positive pigs at bodyweight between 81 kg and 100 kg (GF3).
Mentions: Tables 2, 3 and 4 show that with SERONEG pigs as the reference, there were statistically significant marginal adverse effects on ADG and FCE in all infected groups (SEROPOS and VIRs 1–3). The marginal plots in Figures 2 and 3 show the predicted means of ADG and FCE while the covariates of BD, ADFI and Br were kept at the sample means. Only GF and INFGP were allowed to vary so that the effect of the virus infection on ADG and INFGP could be studied in the three strata of growth phases. The differences in the predicted FCE and ADG between the five groups of pigs in each of the three growth phases can then be attributed to infection status of the pig.Table 2

Bottom Line: 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).Reduced feed conversion efficiency led to lower average daily growth, additional feed requirement and longer time needed to reach the 100 kg bodyweight.

View Article: PubMed Central - PubMed

Affiliation: Norwegian Veterinary Institute, P.O. Box 750, 0106, Oslo, Norway. chiek.er@vetinst.no.

ABSTRACT

Background: Influenza 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).

Results: The 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.

Conclusion: Our study rejected the hypothesis that the virus infection had negligible adverse effects on growth performance of Norwegian pigs.

Show MeSH
Related in: MedlinePlus