Influence of supplemental dietary poultry fat, phytase, and 25-hydroxycholecalciferol on the egg characteristics of commercial layers inoculated before or at the onset of lay with F-strain Mycoplasma gallisepticum

Abstract

The effects of supplemental dietary poultry fat (PF), phytase (PHY), and 25-hydroxycholecalciferol (D3) on the egg characteristics of commercial layers inoculated with F-strain Mycoplasma gallisepticum (FMG) were investigated in 2 trials. Sham and FMG inoculations were administered at 12 (before lay) and 22 (onset of lay) wk and 4 dietary treatments [basal control diet (BCD); BCD with 0.75% supplemental PF; BCD with 1.50% supplemental PF; BCD with 1.50% supplemental PF, 0.013% PHY, and 0.025% D3] were initiated at 20 wk of age. Percentages of albumen, yolk, and eggshell weights; yolk:albumen ratio; yolk moisture and lipid concentrations; and eggshell weight per unit of surface area were determined at 24, 34, 44, 50, and 58 wk of age. Inoculation with FMG reduced yolk lipid concentration at wk 24 and increased yolk moisture concentration at wk 58. In birds inoculated on wk 22, percentage of yolk weight was lower in those inoculated with FMG compared with those that were sham-inoculated. Yolk:albumen ratio was lower in birds that were FMG-inoculated at 22 wk of age compared with those that were sham-inoculated at the same age or that were FMG-inoculated at 12 wk of age. Percentage of yolk weight was greater in birds inoculated at wk 22 and fed the BCD with 1.50% supplemental PF treatment compared with those inoculated at wk 22 and fed the BCD or BCD with 1.50% supplemental PF, 0.013% PHY, and 0.025% D3 treatments and compared with birds inoculated at wk 12 and fed the BCD with 0.75% supplemental PF treatment. In conclusion, inoculation with FMG before or at the onset of lay caused a decrease in yolk lipid content early in lay but an increase in yolk moisture late in lay, and FMG reduced percentage of yolk weight in birds inoculated on wk 22. Furthermore, when used in combination with added 1.50% PF in birds inoculated on wk 22, supplementary PHY and D3 prevented an increase in percentage of yolk weight that occurred in response to diets supplemented only with 1.50% PF.