The effect of Mycoplasma hyopneumoniae infection on growth in pigs with or without environmental constraints

L. Kirk Clark, DVM, PhD; Charles H. Armstrong, DVM, PhD; Alan B. Scheidt, DVM, MS; William G. Van Alstine, DVM, PhD

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To determine the effects of Mycoplasma hyopneumoniae on growth performance, 32 commercial barrows that were free of M. hyopneumoniae infection were assigned by litter and weight to four treatment groups. Group 1 pigs were left as unchallenged controls. Groups 2-4 were mixed with M. hyopneumoniae-infected seeder pigs at 8 weeks of age. Group 2 pigs, environment was otherwise the same as that of the control group (no diurnal temperature fluctuation and normal ammonia concentration). Group 3 was exposed to diurnal temperature fluctuation but no elevated ammonia concentration. Group 4 pigs were exposed to diurnal temperature fluctuation and elevated ammonia concentration similar to those of an enzootic pneumonia-infected commercial herd. Some intratracheally inoculated seeder pigs began coughing 2 weeks after inoculation and most continued coughing until they were necropsied 8 weeks later. Contact-exposed pigs began coughing 4 weeks after exposure.We observed no differences in any measures of M. hyopneumoniae infection among the three exposed groups of pigs ( P >.10). Data for the groups of exposed pigs were merged and compared to that of the control pigs. Control pigs did not develop clinical signs or lesions of M. hyopneumoniae, whereas all pigs except one in the exposed groups coughed or had other evidence of M. hyopneumoniae infection.Accumulated weight gain tended to be less (P <.10) in exposed pigs than in control pigs from 4 weeks to 10 weeks after exposure to seeder pigs except at 6 weeks after exposure.After 10 weeks, exposed pigs gained faster than control pigs such that subsequent accumulated weight gain was not different (P >.10). These results indicated that the ambient environment imposed in this study did not influence development of pneumonia due to M. hyopneumoniae. M. hyopneumoniae induced pneumonia and reduced weight gain during the early coughing period, but had little influence on overall gain when measured at slaughter.

Keywords: Mycoplasma hyopneumoniae, growth

RIS citationCite as: Clark LK, Armstrong CH, Scheidt AB, et al. The effect of Mycoplasma hyopneumoniae infection on growth in pigs with or without environmental constraints. J Swine Health Prod 1993;1(6):10-14.

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