Table 1

Active variables used in multiple correspondence analysis for the introduction of replacement animals, on 161 southern Ontario sow farms
Variable Categories Value label Percentage
a. Time (days) between last natural exposure of replacements to live animals or feedback and entry into breeding herd 0 days 5 20.5%
1 to 60 days 4 6.8%
61 to 90 days 3 1.9%
91 days or more 2 0.6%
Not applicable 9 70.2%
b. Replacements are exposed to serum from viremic pigs or sows via injection prior to entry Yes 5 14.3%
No 1 85.7%
c. Time (days) between last exposure to injected serum and entry of replacements into breeding herd 0 days 5 1.9%
1 to 60 days 4 5%
61 to 90 days 3 4.3%
91 days or more 2 0.6%
Not applicable 9 88.2%
d. Number of breeding herd sources from which replacements have been obtained in last two years 4 or more 5 1.9%
3 4 0.6%
2 3 13%
1 2 64%
0 1 20.5%
e. Source of replacement animals Some or all purchased from other production systems/genetic suppliers 5 52.2%
Some or all from other sites outside the pig flow but within the same production system, none from outside the production system 4 4.3%
Some or all from other sites within the same pig flow as this site (e.g., downstream nursery or grow/finish/developer), none from outside the same pig flow 3 3.7%
Closed herd at this site (replacements are born at site, moved to another site and later returned as replacements) 2 9.3%
Closed site (replacements are born and raised at site and never moved from site) 1 30.4%
f. PRRS virus status of breeding herd(s) from which replacements are sourced One or more sources positive active – this is positive by ELISA and producing PRRSV infected weaned pigs 5 8.7%
One or more sources with unknown status, none positive active 4 1.9%
One or more sources positive stable – that is positive by ELISA but producing non-infected weaned pigs, none positive active or unknown status 3 34.2%
All sources currently negative by ELISA but one or more have been positive in the past 2 40.4%
All sources have always been negative (naive) 1 14.9%
g. PRRS virus status of breeding female replacements in isolation/acclimation Negative at entry but field virus positive from natural exposure at exit 5 18.6%
Field virus positive from natural exposure at entry 4 15.5%
Negative at entry & negative at exit 3 29.2%
Not applicable 9 36.6%
h. Response when group of replacement animals in isolation/acclimation becomes positive by PCR or ELISA to PRRS virus from natural field virus exposure Introduced into breeding herd on regular schedule 5 14.9%
Introduced into breeding herd after holding period of less than 30 days 4 4.3%
Introduced into breeding herd after 30 to 90 day holding period 3 11.2%
Introduced into breeding herd after holding period of more than 90 days 2 2.5%
Replacements are marketed and not used for breeding purposes 1 26.1%
Not applicable 9 41%
i. Isolation/acclimation period (days) 0 or less 5 41.3%
1 to 60 days 4 41.3%
61 to 90 days 3 8.8%
91 to 120 days 2 5.6%
121 days or more 1 3.1%
j. Replacement animal acclimation flow Continuous flow 5 28%
All in/all out by room 4 3.7%
All in/all out by barn 3 3.1%
All in/all out by site 2 0.6%
Not applicable 9 64.6%
k. Replacement animal isolation flow Continuous flow 5 20.5%
All in/all out by room 4 12.4%
All in/all out by barn 3 13.7%
All in/all out by site 2 0.6%
Not applicable 9 52.8%
l. Location of replacement animal acclimation housing relative to this site On-site in same air space as sow herd 5 19.3%
On-site in different air space as sow herd 4 10.6%
Off-site (different site from sow herd) 3 5.6%
Not applicable 9 64.6%
m. Location of replacement animal isolation housing relative to this site On-site in same air space as sow herd 5 4.3%
On-site in different air space as sow herd 4 28.6%
Off-site (different site from sow herd) 3 14.9%
Not applicable 9 52.2%
n. Serum testing of replacement animals for PRRS virus or antibodies by PCR or ELISA upon entry into acclimation/isolation site(s) No routine testing done 5 66.5%
A sample subset of incoming animals are tested upon entry 4 4.3%
All incoming animals are bled and tested upon entry 3 0.6%
Not applicable 9 28.6%
o. Serum testing of replacement animals for PRRS virus or antibodies by PCR or ELISA upon exit from acclimation/isolation site(s) No routine testing done 5 59%
A sample subset of incoming animals are tested upon entry 4 11.8%
All incoming animals are bled and tested upon entry 3 1.9%
Not applicable 9 27.3%

Note: for some variables, there may have been additional response options that were not selected by any of the herds in our sample. These categories are not presented in the table.

Bottoms et al.

Bottoms et al. BMC Veterinary Research 2012 8:217   doi:10.1186/1746-6148-8-217

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