This study investigated the effect of dietary
Mn supplementation on eggshell quality, ultrastructure,
glycosaminoglycan (GAG), and uronic acid
content, and mRNA and protein expression of Galβ1,3-
glucuronosyltransferase (GlcAT-I). A total of 216 layers
(Hy-Line Grey) at age of 50 wk were divided into 3
groups. In the first 8 wk of the 12-wk feeding trial, all
groups were fed a basal diet that met all layer nutrient
requirements except for Mn. In the last 4 wk, each
group was fed 1 of 3 diets supplemented with Mn levels
at 0, 25, or 100 mg Mn/kg. Dietary Mn deficiency did
not affect the egg performance of layers. Dietary Mn
supplementation significantly improved the breaking
strength, thickness, and fracture toughness of eggshells
(P < 0.05). In photographs of eggshell ultrastructure,
the size of mammillary cones and cracks in the outer
surface were decreased by dietary Mn supplementation.
The contents of GAG and uronic acids in eggshell membrane
were significantly increased by dietary Mn addition
(P < 0.05). This result was further confirmed by
increased mRNA expression and protein expression of
GlcAT-I when Mn was added to the diet. This study
suggests that dietary Mn supplementation can improve
eggshell quality by enhancing the GAG and uronic acid
synthesis in the eggshell glands, which can affect the
ultrastructure of eggshells.
Key words: eggshellglycosaminoglycan
This study investigated the effect of dietaryMn supplementation on eggshell quality, ultrastructure,glycosaminoglycan (GAG), and uronic acidcontent, and mRNA and protein expression of Galβ1,3-glucuronosyltransferase (GlcAT-I). A total of 216 layers(Hy-Line Grey) at age of 50 wk were divided into 3groups. In the first 8 wk of the 12-wk feeding trial, allgroups were fed a basal diet that met all layer nutrientrequirements except for Mn. In the last 4 wk, eachgroup was fed 1 of 3 diets supplemented with Mn levelsat 0, 25, or 100 mg Mn/kg. Dietary Mn deficiency didnot affect the egg performance of layers. Dietary Mnsupplementation significantly improved the breakingstrength, thickness, and fracture toughness of eggshells(P < 0.05). In photographs of eggshell ultrastructure,the size of mammillary cones and cracks in the outersurface were decreased by dietary Mn supplementation.The contents of GAG and uronic acids in eggshell membranewere significantly increased by dietary Mn addition(P < 0.05). This result was further confirmed byincreased mRNA expression and protein expression ofGlcAT-I when Mn was added to the diet. This studysuggests that dietary Mn supplementation can improveeggshell quality by enhancing the GAG and uronic acidsynthesis in the eggshell glands, which can affect theultrastructure of eggshells.Key words: eggshellglycosaminoglycan
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