Growth and humoral immune effects of dietary Original XPC in layer pullets challenged with Mycoplasma gallisepticum

Abstract

Effects of dietary Original XPC (XPC) in commercial layer pullets challenged with the virulent, low passage R strain of Mycoplasma gallisepticum (R low MG) were investigated. Hy-Line W-36 pullets sourced from MG-clean breeders were fed a basal diet with or without (CON) XPC (1.25 kg/metric ton) from hatch until 12 wk of age (woa). At 8 and 10 woa, half of the birds in each dietary treatment were challenged with R low MG. Body weight was recorded at 3, 8, and 12 woa, and ovary, ceca, and bursa weights were recorded at 3 and 12 woa. Blood samples were taken immediately before the initial R low MG challenge at 8 woa and again at 12 woa to test for IgM and IgG antibody production against MG. All birds were evaluated for MG lesion scores at 12 woa. Regardless of challenge, inclusion of XPC in the diet did not significantly alter BW at 3 or 8 woa or relative organ weights at 3 or 12 woa. However, at 12 woa, BW of XPC-fed birds, regardless of challenge was significantly ( P = 0.0038) heavier than CON by 25.7 g. All birds tested negative for MG antibodies before the 8 woa challenge. Respective percentage serum plate agglutination and ELISA positive birds at 12 woa were 0 and 0% (CON, nonchallenged), 1.4 and 0% (XPC, nonchallenged), 100 and 47.2% (CON, challenged), and 100 and 50.0% (XPC, challenged). Diet did not significantly affect ELISA titers, but they were significantly ( P < 0.0001) increased due to challenge. Furthermore, lesion scores were significantly higher for R low MG-challenged birds ( P = 0.0012), and dietary treatment with XPC in challenged birds numerically reduced MG lesion scores from 0.278 to 0.194. In conclusion, although dietary XPC did not significantly alter the humoral immune response, antibody titer levels, or severity of MG lesions in layer pullets that were or were not challenged with R low MG, it led to an increase in their rate of growth through 12 woa.

Effects of dietary Original XPC on selected blood variables in layer pullets challenged with Mycoplasma gallisepticum,,

“…In the previous companion trial by Elliott et al. (2020) in which the same birds were tested, it was shown that all birds in the control and XPC dietary treatment groups tested negative for MG-specific serum IgM and IgG antibody titers before the first 8 woa challenge.…”

“…Beginning on the day of hatch, Hy-Line W-36 pullets were continuously fed 1 of 2 dietary treatments for the duration of the study (12 woa). The dietary treatments were a basal control diet ( CON ) or a basal control diet containing XPC at 1.25 kg/metric ton ( Elliott et al., 2020 ). In each of 4 rooms in an environmentally controlled facility, there were 2 replicate floor pens belonging to each of the 2 dietary treatments (4 pens per room; 16 total pens).…”

“…Frey's broth base ( Frey et al., 1968 ) was used as the medium for the sham challenge, and the R low MG was diluted in Frey's broth base for the actual challenge. The challenge dosages and their application methods were those used in the companion article by Elliott et al. (2020) .…”

“…In the article by Elliott et al. (2020) in which these same treatments were used, it was reported that the combined incidences of lung conjunctivitis and airsacculitis at 12 woa were significantly increased by the RMG challenge treatment.…”

“…Furthermore, XPC was more recently shown to increase the yolk weight and percentages of yolk yield and yolk solids of eggs laid by Hy-Line W-36 layers ( Suarez Martinez et al., 2018 ). In a companion article by Elliott et al. (2020) , it was also reported that dietary XPC increased the growth rate of Hy-Line W-36 layer pullets through 12 wk of age ( woa ) and numerically reduced the air sac MG lesion scores at 12 woa of pullets that had been previously challenged with the virulent, low-passage (13 in vitro passages) R strain of MG ( R low MG ) at 8 and 10 woa.…”