Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/15/2007
Publication Date: 12/15/2007
Citation: Peebles, E.D., Branton, S.L., Burnham, M.R., Whitmarsh, S.K., Gerard, P.D. 2007. Effects of Supplemental Dietary Phytase and 25-Hydroxycholecalciferol on the Digestive and Reproductive Organ Characteristics of Commercial Layers Inoculated Before or at the Onset of Lay with the F-Strain of Mycoplasma galli. Poultry Science. 86:1805-1809. Interpretive Summary: Supplementation of layer diets with dietary phytase or 1, 25 dihydroxycholecalciferol (25-D3) depresses body weight of commercial laying hens; however, vaccination with the F strain of Mycoplasma gallisepticum (FMG) ameliorates the depressive effects of phytase or 25-D3 on body weight. The present study was designed to characterize possible changes in the digestive and reproductive organ characteristics of layer chickens in response to FMG vaccination at either 12 or 22 weeks of age in addition to dietary supplementation with phytase and 25-D3. Results of this study showed that duodenal intestinal length relative to the length of the entire small intestine was greater in hens inoculated with FMG at 12 weeks of age as compared to 22 weeks of age. Also, independent of FMG inoculation and timing, the reproductive organ and digestive systems of laying hens may be influenced by dietary supplementation with phytase and 25-D3.
Technical Abstract: In 3 trials, the effects of dietary supple mentation with phytase (PHY) and 25-hydroxycholecalciferol (25-D3) on the digestive and reproductive organ characteristics of commercial layers that were inoculated pre-lay (12 wk of age) or at the onset of lay (22 wk of age) with F-strain Mycoplasma gallisepticum (FMG), were assessed at 58 wk of age. Experimental layer diets which included either a basal control diet or a control diet supplemented with 0.025 % PHY and 25-D3 were fed from 20 through 58 wk of age. As a percentage of total oviduct weight, magnum weight was lower in birds that were inoculated (sham or FMG) at lay onset compared to those that were inoculated pre-lay, and in FMG-inoculated birds, relative duodenum length was greater in those inoculated at 12 compared to 22 wk. Also, as percentages of organ weight or length, infundibulum length and isthmus weight were increased, whereas duodenum length was decreased by dietary supplementation with PHY and 25-D3. The overall timing (12 versus 22 wk) of inoculation can affect the reproductive organ characteristics of layers; whereas, more specifically, the timing of an FMG inoculation may affect their digestive organ structure. Furthermore, independent of inoculation timing and type, both the reproductive organ and digestive systems of laying hens may be influenced by dietary supplementation with PHY and 25-D3.