Submitted to: Poultry Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/26/2006
Publication Date: 5/20/2006
Citation: Peebles, E.D., Basenko, E.Y., Branton, S.L., Whitmarsh, S.K., Gerard, P.D. 2006. Effects of s6-strain mycoplasma gallisepticum inoculation at ten, twenty-two, or forty-five weeks of age on the blood characteristics of commercial egg laying hens. Poultry Science. 85:2012-2018, 2006. Interpretive Summary: The poultry pathogen Mycoplasma gallisepticum (MG) infects about 90% of the nations' laying chickens. MG is known to reduce egg production by as much as 15.9 eggs per hen over a typical 45 week laying cycle which corresponds to an economic loss of about $140 million annually within the table egg sector alone. This study was conducted to determine the impact of the age of exposure (10, 22 or 45 weeks of age) on various blood parameters of the chicken including hematocrit, plasma protein, serum cholesterol, triglycerides and calcium. Basically, all parameters tended to be higher over the course of the study implying that presence of the organism impairs egg production and reflects this in the blood concentration of the various components normally used in egg and eggshell formation.
Technical Abstract: In two consecutive trials of the current study, the effect of the age of application of S6-strain Mycoplasma gallisepticum (S6MG) inoculation on the blood characteristics of commercial layers housed and maintained under controlled conditions was determined. The ages of inoculation compared were those prior to lay at 10 wk of age, during onset of lay at 22 wk of age, and during post-peak lay at 45 wk of age. In each trial, hematocrit, plasma protein, and serum cholesterol, triglycerides, and calcium were determined at 20, 24, 32, 43, 47, and 58 wk of age. The data from both trials were analyzed together; whereas, data from wk 20 (effect of 10 wk S6MG inoculation), data from wk 24, 32, and 43 (effects of 10 and 22 wk S6MG inoculations), and data from wk 47 and 58 (effects of 10, 22, and 45 wk S6MG inoculations), were analyzed separately. At wk 20, hematocrit was higher in birds inoculated with S6MG at 10 wk compared to sham-inoculated birds, and across wk 24, 32, and 43, serum calcium was higher in birds inoculated with S6MG at 10 or 22 wk compared to those that were sham-inoculated. Serum calcium level across wk 47 and 58 was higher in birds inoculated with S6MG at 10 wk compared to sham-inoculated controls and birds inoculated with S6MG at 22 wk, with 45 wk S6MG-inoculated birds being intermediate. The response of serum cholesterol level at 47 wk to S6MG inoculation at either 10, 22, or 45 wk in comparison to controls was nearly opposite to that of the response observed at 58 wk. However, serum triglycerides were depressed only at wk 47 due to the 45 wk S6MG inoculation in comparison to all other treatments. Variable post-peak alterations in serum calcium and lipids occur in response to the timing of S6MG inoculation in layers housed under controlled conditions.