Dietary poultry fat, phytase, and 25-hydroxycholecalciferol influence the digestive and reproductive organ characteristics of commercial layers inoculated before or at the onset of lay with F-strain Mycoplasma gallisepticum.

Effects of 2 supplemental concentrations of dietary poultry fat (PF) and the combination of PF, phytase (PHY), and 25-hydroxycholecalciferol [25(OH)D] on the gross digestive and reproductive organ characteristics of commercial layers inoculated with F-strain Mycoplasma gallisepticum (FMG) were investigated in 2 trials. Sham and FMG inoculations were administered at 12 wk (before lay) or 22 wk (onset of lay), dietary treatments [basal control diet (BCD); BCD with 0.75% supplemental PF (LPFD); BCD with 1.50% supplemental PF (HPFD); HPFD additionally supplemented with 0.013% PHY and 0.025% 25(OH)D] were initiated at 20 wk of age, and organ characteristics were determined at 58 wk of age. In proportion to small intestine weight, jejuna were heavier in birds inoculated at 22 wk rather than at 12 wk of age. In hens inoculated at 22 wk of age, percentage of infundibulum weight was increased by FMG. The proportional length of infundibula in birds fed HPFD with PHY and 25(OH)D was longer than in those fed LPFD. In birds inoculated with FMG at 22 wk of age, BW was greater in those fed HPFD with or without added PHY and 25(OH)D in comparison with those fed LPFD, whereas LPFD increased percentage of oviduct and magnum weights when compared with the HPFD and BCD groups, respectively. Percentage of duodenum weight in birds that were fed HPFD with PHY and 25(OH)D was greater compared with those fed LPFD in the wk 22 sham and wk 12 FMG inoculation groups, but was also greater than in those fed BCD in the wk 12 FMG inoculation group. Conversely, percentage of duodenum weight was greater in birds fed LPFD compared with those fed HPFD after a wk 22 FMG inoculation. However, despite the effects of the supplemental combination of 1.50% PF, PHY, and 25(OH)D on the oviduct and small intestine structures, it did not result in a subsequent influence on layer performance, as indicated in a previous companion report.