Effect of a mycoplasma vaccine on average daily gain in swine

A Mycoplasma hyopneumoniae vaccine (ResPiSure@,SmithKline Beecham Animal Health, Exton Pennsylvania) was tested for its effect on pig growth rate in a ISO-sow farrowto-ffnish unit in North Carolina using all-in-all-out flow in the farrowing and nursery. From October 1991 to December 1991, 625 nursery pigs from ffve weaned groups were sorted into pens by gender and similar weight, eartagged, and allocated to vaccinate or control groups by pen. Vaccinates received 2 mL of the mycoplasma vaccine on the day they were allocated to treatment and 14 days later. Pigs were weighed individually when moved between buildings at approximately 23 kg (51 Ib), and 33 kg (73 Ib), and prior to slaughter at 92 kg (202 Ib).Average daily gain was not different (P =.24) between vaccinated and control pigs when averaged over all ffve groups. Barrows grew faster (P =.003) than females when averaged over all three stages of growth. However, vaccine did not affect this difference (P =.37). The weight of pigs entering the nursery was a signiffcant determinant of average daily gain for nursery (P =.000 I), growing (P =.0053), and ffnishing (P =.0001) phases of growth. These data indicate that the mycoplasma vaccine did not improve average daily gain in the trial herd and may not improve average daily gain in similar herds with a low prevalence of infection.