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Title: EFFECTS OF BROILER REARING ENVIRONMENT ON TRANSMISSION OF F-STRAIN MYCOPLASMA GALLISEPTICUM FROM COMMERCIAL LAYER HENS TO BROILER CHICKENS: ROLE OF ACID-BASE BALANCE

Author
item Olanrewaju, Hammed
item Purswell, Joseph - Jody
item Collier, Stephanie
item Branton, Scott

Submitted to: International Journal of Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/3/2009
Publication Date: 3/3/2009
Citation: Olanrewaju, H.A., Purswell, J.L., Collier, S.D., Branton, S.L. 2009. Effects of Broiler Rearing Environment on Transmission of F-Strain Mycoplasma gallisepticum From Commercial Layer Hens to Broiler Chickens: Role of Acid-Base Balance. Avian Diseases 8(2):145-150.

Interpretive Summary: Mycoplasma gallisepticum (MG) is a major respiratory bacteria that infects approximately 85% of the commercial table egg layer chickens in the U.S. In the United States alone, economic losses associated with MG infections are significant and have exceeded $150 million annually with the loss primarily attributable to decreased egg production of approximately 16 eggs/hen although internal egg characteristics are also impacted. Three commercial vaccines are available to the poultry industry’s layer sector to combat these losses; none are ideal and each has specific strengths and weaknesses. The present study was conducted to determine the effects of broiler rearing environment and the transmissibility of F-strain Mycoplasma gallisepticum (FMG) inoculation on blood pH, blood gases, hematocrit, and hemoglobin in mycoplasma free and FMG contact-infected broilers and FMG inoculated layers. Results of this study show that the FMG inoculated layers had the highest partial pressure of O2 and the lowest partial pressure of CO2 as compared with the other treatment groups. Red blood cell level and pO2 concentrations were slightly higher in FMG contact-infected broilers than the other treatments groups. Mycoplasma gallisepticum inoculation also resulted in a significant increase in blood concentrations of K+, a decrease in Na+, but no significant effects on blood concentrations of Ca2+ and Cl-. Results indicate that inoculation of layers with FMG vaccine results in changes in plasma acid-base status along with changes in other blood metabolic variables. However, the FMG inoculation did not prevent homeostatic regulation of acid-base balance, as indicated by constant blood pH. There was a significant increase in pO2, which is generally associated with an oxygen-dependent improvement in tissue oxygenation. Elevated arterial partial pressure of oxygen is beneficial to maximize oxygen transport capacity along with high concentrations of hemoglobin and hematocrit to carry oxygen throughout the body. It could be concluded that in addition to protecting birds from MG infection, FMG vaccine may improve the layer chicken’s ability to withstand the harmful effects of stressors on their performance and well-being.

Technical Abstract: Two trials were conducted concurrently to determine and compare, blood pH, blood gases, hematocrit, and hemoglobin in mycoplasma-free, F-strain Mycoplasma gallisepticum (FMG) inoculation layers, and FMG contact-infected broilers. FMG-inoculated layers had the highest partial pressure of O2 and the lowest partial pressure of CO2 as compared with the other treatment groups. Blood pH values were unaffected by FMG inoculation. Hematocrit and blood concentrations of hemoglobin were slightly higher and HCO3- levels were lowest in FMG contact-infected broilers in comparison to the other treatments groups. Mycoplasma gallisepticum inoculation layers also resulted in a significant increase in blood concentrations of K+, a decrease in Na+, but no significant effects on blood concentrations of Ca2+ and Cl-. There were no differences in plasma glucose, cholesterone, triglyceride, and anion gap, but osmolality was significantly reduced in FMG contact-infected broilers. Results indicate that inoculation of layers with FMG vaccine results in changes in plasma acid-base status along with changes in other blood metabolic variables. However, the FMG inoculation did not prevent homeostatic regulation of acid-base balance, as indicated by constant blood pH. There was a significant increase in pO2, which is generally associated with an oxygen-dependent improvement in tissue oxygenation. Elevated arterial partial pressure of oxygen is beneficial to maximize oxygen transport capacity along with high concentrations of hemoglobin and hematocrit to carry oxygen throughout the body. It was concluded that in addition to protecting birds from MG infection, an FMG vaccine may improve the layer chicken’s ability to withstand the harmful effects of stressors on their performance and well-being.