Effects of F-strain Mycoplasma gallisepticum inoculation at twelve weeks of age on digestive and reproductive organ characteristics of commercial egg laying hens

Department of Poultry Science, Mississippi State University, Mississippi, USA.

Experimental inoculation with the F-strain of Mycoplasma gallisepticum (FMG) between 8 and 18 wk of age is known to affect reproductive performance in commercial layers. Therefore, two trials were conducted to determine if changes in digestive and reproductive organ characteristics also occur in commercial laying hens infected with FMG at 12 wk of age. In Trial 1, liver weight, liver lipid and moisture contents, ovary weight, ovarian follicular hierarchy, and the weights, lengths, and histologies of the infundibulum, magnum, isthmus, uterus, and vagina were determined. In Trial 2, fatty liver hemorrhagic syndrome (FLHS) incidence and the weights, lengths, and histologies of the duodenum, jejunum, and ileum were determined in addition to the parameters examined in Trial 1. In both trials, the average number of mature (diameter > or = 12 mm) ovarian follicles was lower in FMG-inoculated hens in comparison to controls. Also, magnum/oviduct (cm/cm) length was reduced in treated birds. In Trial 2, isthmus/BW and isthmus/oviduct (g/ g) weight were decreased at 46 wk of age, and vagina/ BW and vagina/oviduct (g/g) weight were decreased at both 20 and 36 wk of age due to FMG treatment. In Trial 2, FMG treatment resulted in a 50% increase in the number of FLHS birds. Furthermore, treatment caused a decrease at 20 wk of age and an increase at 44 wk of age in liver moisture content. However, the intestinal characteristics examined were not affected by FMG inoculation. Altered liver, ovarian, and reproductive organ characteristics were associated with FMG infection in commercial layers. More specifically, FMG inoculation at 12 wk resulted in a higher incidence of FLHS, ovarian follicular regression, and decreased isthmal and vaginal proportions of the reproductive tract. These data clearly demonstrate that alterations in performance and egg characteristics of layers inoculated with FMG at 12 wk of age are related to mutual functional disturbances in the liver, ovary, and oviduct without concomitant intestinal changes.

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