Evaluating pellet and meal feeding regimens on finishing pig performance, stomach morphology, and carcass characteristics.

A total of 2,100 pigs (PIC 327 × 1050; initially 31.2 kg BW) were used in a 118-d trial to determine the effects of pellet or meal feeding regimens on finishing pig growth performance, stomach morphology, and carcass characteristics. Pens of pigs were balanced by initial BW and randomly allotted to 1 of 6 dietary treatments (14 pens/treatment with 25 pigs/pen). Pens were sorted by gender allowing for 7 barrow pens and 7 gilt pens per treatment. The same corn-soybean meal-based diets containing 15% dried distillers' grains with solubles were used for all treatments and fed in 5 phases. Phases were fed from d 0 to 28, 28 to 56, 56 to 84, 84 to 98, and 98 to 118. The 6 treatments included a meal or pelleted diet fed from d 0 to 118, a meal diet fed from d 0 to 70 followed by pellets from d 70 to 118, a pelleted diet fed from d 0 to 70 followed by a meal diet from d 70 to 118, or pellets and meal rotated every 2 wk starting with meal or pellets. On d 110, 4 pigs from each pen were harvested and stomachs collected, from which a combined ulcer and keratinization score was determined for each pig. Overall, there were no differences in ADG across feeding regimens. Pigs fed meal throughout had the greatest ( < 0.05) ADFI, whereas pigs fed pellets throughout had the lowest ( < 0.05), with all other treatments intermediate ( < 0.05). Pigs fed pelleted diets throughout had the greatest ( < 0.05) G:F, whereas pigs fed meal throughout had the worst G:F ( < 0.05), with all other treatments intermediate ( < 0.05). When pelleted diets were fed for the last 58 d or for the entire trial, the incidence of ulceration and keratinization increased ( < 0.05), whereas pigs fed meal for the last 58 d had a lower incidence ( < 0.05), with all other treatments intermediate ( < 0.05). Feeding pellets throughout increased ( < 0.05) the number of pigs removed per pen compared with all other treatments. Pig removals were determined by an on-site farm manager when pigs were at risk due to weight loss, health, or animal welfare concerns and needed to be separated from the general population. There were no differences for any carcass characteristics measured including HCW, carcass yield, backfat depth, loin depth, and percentage lean. In conclusion, feeding pelleted diets improved G:F but increased stomach ulceration and pig removals; however, rotating pellets and meal diets provided an intermediate G:F response and moderated stomach ulcerations compared with feeding only pellets.

Infection dynamics of pandemic 2009 H1N1 influenza virus in a two-site swine herd.

Influenza A viruses are common causes of respiratory disease in pigs and can be transmitted among multiple host species, including humans. The current lack of published information on infection dynamics of influenza viruses within swine herds hinders the ability to make informed animal health, biosecurity and surveillance programme decisions. The objectives of this serial cross-sectional study were to describe the infection dynamics of influenza virus in a two-site swine system by estimating the prevalence of influenza virus in animal subpopulations at the swine breeding herd and describing the temporal pattern of infection in a selected cohort of growing pigs weaned from the breeding herd. Nasal swab and blood samples were collected at approximately 30-day intervals from the swine breeding herd (Site 1) known to be infected with pandemic 2009 H1N1 influenza virus. Sows, gilts and neonatal pigs were sampled at each sampling event, and samples were tested for influenza virus genome using matrix gene RRT-PCR. Influenza virus was detected in neonatal pigs, but was not detected in sow or gilt populations via RRT-PCR. A virus genetically similar to that detected in the neonatal pig population at Site 1 was also detected at the wean-to-finish site (Site 2), presumably following transportation of infected weaned pigs. Longitudinal sampling of nasal swabs and oral fluids revealed that influenza virus persisted in the growing pigs at Site 2 for at least 69 days. The occurrence of influenza virus in neonatal pigs, but not breeding females, at Site 1 emphasizes the potential for virus maintenance in this dynamic subpopulation, the importance of including this subpopulation in surveillance programmes and the potential transport of influenza virus between sites via the movement of weaned pigs.

Detection of airborne influenza a virus in experimentally infected pigs with maternally derived antibodies.

This study assessed whether recently weaned piglets with maternally derived antibodies were able to generate infectious influenza aerosols. Three groups of piglets were assembled based on the vaccination status of the dam. Sows were either non-vaccinated (CTRL) or vaccinated with the same (VAC-HOM) strain or a different (VAC-HET) strain to the one used for challenge. Piglets acquired the maternally derived antibodies by directly suckling colostrum from their respective dams. At weaning, pigs were challenged with influenza virus by direct contact with an infected pig (seeder pig) and clinical signs evaluated. Air samples, collected using a liquid cyclonic air collector, and individual nasal swabs were collected daily for 10 days from each group and tested by matrix real-time reverse transcriptase polymerase chain reaction (RRT-PCR) assay. Virus isolation and titration were attempted for air samples on Madin-Darby canine kidney cells. All individual pigs from both VAC-HET and CTRL groups tested positive during the study but only one pig in the VAC-HOM group was positive by nasal swab RRT-PCR. Influenza virus could not be detected or isolated from air samples from the VAC-HOM group. Influenza A virus was isolated from 3.2% and 6.4% air samples from both the VAC-HET and CTRL groups, respectively. Positive RRT-PCR air samples were only detected in VAC-HET and CTRL groups on day 7 post-exposure. Overall, this study provides evidence that recently weaned pigs with maternally derived immunity without obvious clinical signs of influenza infection can generate influenza infectious aerosols which is relevant to the transmission and the ecology of influenza virus in pigs.

Transmission of influenza A virus in pigs.

Influenza A virus infections cause respiratory disease in pigs and are a risk to public health. The pig plays an important role in influenza ecology because of its ability to support replication of influenza viruses from avian, swine and human species. Influenza A virus is widespread in pigs worldwide, and influenza A virus interspecies transmission has been documented in many events. Influenza A virus is mostly transmitted through direct pig-to-pig contact and aerosols although other indirect routes of transmission may also exist. Several factors contribute to differences in the transmission dynamics within populations including among others vaccination, pig flow, animal movement and animal introduction which highlights the complexity of influenza A transmission in pigs. In addition, pigs can serve as a reservoir of influenza A viruses for other pigs and other species and understanding mechanisms of transmission within pigs and from pigs to other species and vice versa is crucial. In this paper, we review the current understanding of influenza virus transmission in pigs. We highlight the ubiquity of influenza A virus in the pig population and the widespread distribution of pandemic H1N1 virus worldwide while emphasizing an understanding of the routes of transmission and factors that contribute to virus spread and dissemination within and between pig populations. In addition, we describe transmission events between pigs and other species including people. Understanding transmission is crucial for designing effective control strategies and for making well-informed recommendations for surveillance.