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This article describes the in vitro and in vivo effects of a 25-hydroxycholecalciferol (25[OH]D) treatment in layer hens during a mixed coccidia challenge. HD11 cells (chicken macrophage cell line) were treated in vitro with a coccidia antigen or in a medium supplemented with either 1,25-dihydroxycholecalciferol (1,25[OH]2D) or 25(OH)D. HD11 cells treated in vitro with 200 nM of 1,25(OH)2D had increased nitrite production (P < 0.01) compared with HD11 cells treated with 0 or 200 nM of 25(OH)D. Treating HD11 cells with 25(OH)D decreased IL-10 mRNA by 1.7-fold, but 1,25(OH)2D treatment increased the amount of IL-10 mRNA by 2.7-fold (P < 0.01) compared with the group treated with 0 nM of 25(OH)D. Post-coccidial antigen stimulation, 25(OH)D or 1,25(OH)2D treatment decreased (P < 0.01) 1α-hydroxylase mRNA amounts in HD11 cells. Stimulating primary T cells in vitro with Concanavalin A (Con-A) decreased (P = 0.020) the 1α-hydroxylase mRNA amounts by 3-fold. ConA-B1-VICK cells (chicken T cell line) stimulated with 100 nM 1,25(OH)2D or with supernatants from HD11 cells treated with 25(OH)D plus lipopolysaccharide (LPS) had 1.3-fold less (P < 0.01) interferon (IFN)-γ mRNA compared with the group treated with 25(OH)D. Layer birds were fed a basal diet supplemented with 25(OH)D at 6.25, 25, 50, or 100 μg/kg, and at 21 d of age orally challenged with 1 × 10(5) live coccidia oocysts. Compared with birds fed similar levels of 25(OH)D and unchallenged with the coccidia oocyst, birds challenged with the coccidia oocyst had 15% reduced BW gain in the groups supplemented with either 6.25, 25, or 50 μg/kg of 25(OH)D, but only a 4% reduced BW gain in birds fed 100 μg/kg of 25(OH)D (P < 0.01). Birds fed 100 μg/kg 25(OH)D had decreased (P = 0.012) CD8+ cell percentages in cecal tonsils in both coccidial oocyst challenged and unchallenged birds, compared with birds fed 6.25 μg/kg 25(OH) and unchallenged with coccidial oocysts. At 15 d post-coccidia challenge, birds fed 100 μg/kg 25(OH)D and challenged with coccidial oocysts had 17% more CD4+CD25+ cells (P = 0.018) in the cecal tonsil compared with the birds fed 100 μg/kg 25(OH)D and unchallenged with coccidial oocysts. At d 6 post-coccidia challenge, birds fed 100 μg/kg 25(OH)D had a 3.5-fold increase (P < 0.01) in IL-10 mRNA amounts in the cecal tonsils compared with birds fed 6.25 μg/kg 25(OH)D. In conclusion, supplementing birds with 100 μg/kg 25(OH)D could be a nutritional strategy to reduce the production losses post-coccidia challenge.

Three experiments were conducted to study the effects of 25-hydroxycholecalciferol supplementation on BW gain, IL-1β, and 1α-hydroxylase mRNA expression in different organs of broiler chickens following a lipopolysaccharide (LPS) injection. In experiment I, birds were fed a basal diet supplemented with either cholecalciferol (3,000 IU/kg) or 25-hydroxycholecalciferol (69 µg/kg). At 21 and 35 d of age, birds were injected with LPS. Post-LPS injection, birds supplemented with 25-hydroxycholecalciferol gained approximately 2.5% (P = 0.03) and 3.8% (P < 0.01), respectively, more BW than the birds supplemented with cholecalciferol over the 24-h period. In experiment II, birds were fed basal diets supplemented with 25-hydroxycholecalciferol at 6.25, 25, and 50 µg/kg of feed or cholecalciferol at 250 IU/kg of feed. At 35 d of age, birds were injected with LPS. Birds fed 25-hydroxycholecalciferol at 25 and 50 µg/kg and injected with LPS had approximately 7-fold and 3-fold less (P = 0.010) IL-1β mRNA in the liver compared with those birds fed 6.25 µg/kg of 25-hydroxycholecalciferol and the cholecalciferol (250 IU/kg) group. In experiment III, birds were fed a basal diet supplemented with either cholecalciferol (3,000 IU/kg) or 25-hydroxycholecalciferol (69 µg/kg). At 28 d of age, birds were fed 25-hydroxycholecalciferol and injected with LPS had 1.1-fold less (P < 0.01) IL-1β mRNA in the liver than the cholecalciferol-fed group. After an LPS injection, birds supplemented with 25-hydroxycholecalciferol had increased 1α-hydroxylase mRNA amounts in the liver (P = 0.07). In conclusion, 25-hydroxycholecalciferol supplementation at higher doses improved growth performance and decreased inflammatory gene IL-1β mRNA amounts in the liver post-LPS injection.

Pure cultures of three species of bifidobacteria (Bifidobacterium longum, Bif. adolescentis and Bif. bifidum), Lactobacillus acidophilus and a mixed culture of Lact. delbrueckii subsp. bulgaricus and Streptococcus salivarius subsp. thermophilus were each enumerated on two differential media and six selective media for the enumeration of bifidobacteria. The appearance of the colonies on the differential media was as expected but when mixed cultures were present, it proved extremely difficult to distinguish one species from another. Of the selective media, AMC, RMS, NPNL and BL‐OG performed well in that they gave good recoveries of bifidobacteria and were inhibitory to the growth of Lact. delbrueckii subsp. bulgaricus, Strep. salivarius subsp. thermophilus and Lact. acidophilus. However, of these four media, AMC was most convenient as it is based on a commercially available medium, whereas the others must be made up from individual constituents. The AMC agar is thus a good choice for the routine enumeration of bifidobacteria from mixed cultures.