Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/4/2006
Publication Date: 3/15/2007
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 Blood Characteristics of Commercial Layers Innoculated Before or at the Onset of Lay with the F-Stain of Mycoplasma gallisepticum. Poultry Science. 86:768-774.
Interpretive Summary: The bacteria Mycoplasma gallisepticum (MG) causes annual losses of approximately $140 million due to reduced egg production in table egg chickens. No antibiotic is capable of removing MG from the chicken once the bird is infected. As a consequence, almost 90% of the 270 million layer chickens in the US are infected with MG. In an attempt to utilize dietary components to ameliorate losses associated with MG, the enzyme phytase and 25-hydroxycholecalciferal (D3) were added to the feed and chickens were inoculated with the F strain of MG. Results of the study showed that the additon of phytase to commercial layer diets resuted in lower hematocrits and that the D3 and phytase together resulted in lower hen body weights.
Technical Abstract: In 3 trials, the effects of dietary supplementation with phytase and 25-hydroxycholecalciferol on BW and the blood 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 34, 50, and 58 wk of age. Experimental layer diets which included either a basal control diet or the same diet supplemented with 0.025% phytase and 25-hydroxycholecalciferol were fed from 20 through 58 wk of age. The supplemented diet decreased blood hematocrit values across bird age, inoculation type (sham versus FMG), and age of inoculation (pre-lay versus onset of lay). Phytase and 25-hydroxycholecalciferol supplemented diets reduced bird BW in sham-inoculated control birds across bird age and age of inoculation. This effect was not observed in FMG-inoculated birds. Across inoculation type and age of inoculation, supplemented diets also reduced serum triglyceride levels in birds that were 34 wk of age. Furthermore, across diet (control versus supplemented) and inoculation type, total plasma protein concentration at 34 wk of age was higher in birds that were inoculated at the onset of lay compared to those inoculated pre-lay. Diet, inoculation type, and inoculation age had no effect on mortality, reproductive organ histopathological lesion scores, or serum cholesterol and calcium concentrations. In conclusion, throughout lay, the supplementation of commercial layer diets with phytase may lower hematocrit, and inoculation with FMG pre-lay or at the onset of lay may ameliorate the depressing effects of dietary phytase and 25-hydroxycholecalciferol supplementation on hen BW.