Mycoplasma gallisepticum in the commercial egg-laying hen: A historical perspective considering the effects of pathogen strain, age of the bird at inoculation, and diet on performance and physiology

Abstract

SUMMARY The effects of Mycoplasma gallisepticum (MG) on the performance and physiology of the commercial laying hen have been shown to vary in relation to the strain of MG and the age of the bird when challenged. In an effort to protect birds against more virulent field strains of MG on multiple-age commercial farms where eradication is not feasible, milder strains of MG have been introduced as live vaccines to help displace the natural field strains. The benefits and drawbacks of the individual and combined use of these various vaccine strains are discussed in this article, along with a comparative analysis of their subsequent effects on various performance and physiological variables and their interrelationships. Prelay inoculations of either the 6/85- or ts11-strains of MG used in conjunction with an overlay of the F-strain of MG during lay have the potential of being an effective vaccination regimen for the continual protection of commercial flocks against field strain MG infections while preventing the adverse effects on performance associated with an individual inoculation of the F-strain of MG. In an additional effort to positively modify the effects of MG vaccination regimens on layer production, outcomes of the use of various dietary supplements have been explored. A 1.50% level of poultry fat alone or the combination of phytase and 25-hydroxycholecalciferol alone have shown potential in alleviating depressions in the egg production of layers by as much as 6.3 and 2.7%, respectively, as a result of being vaccinated with the F-strain of MG. Consideration of the information provided in this article concerning differences in the effects of the MG strain, the age at which MG vaccines are given, and the use of dietary supplementation on laying hen performance and physiology may be useful in improving the productivity and profitability of the commercial egg industry.