Optimal Dietary Level of 1α,25-Dihydroxycholecalciferol for Eggshell Quality in Laying Hens

Abstract

The optimal dietary level of 1α,25-dihydroxycholecalciferol [1,25-(OH)2 D3] for eggshell quality was established. White Leghorn hens, 59 wk of age, were fed one of eight diets that contained the same basal ingredients, including 3.1% calcium, but different levels (μg/kg) or forms of calciferol supplements: no calciferol supplement of any form (56 hens); 27.5 (control) or 55.0 μg of cholecalciferol (56 hens each); 3,5, or 7 μg of l,25-(OH)2 D3 (28 hens each); 5 μg of 24,25-dihydroxycholecalciferol [24,25-(OH)2 D3] with 28 hens; 5 μg each of l,25-(OH)2 D3 and 24,25-(OH)2 D3 (28 hens). All groups were fed the control diet prior to the 21-wk treatment. The group fed 5 μg 1,25-(OH)2 D3/kg diet ranked first in specific gravity (SG), e.g., 1.081 versus 1.077 for the control group at Week 21 (P<.05). The group fed 7 μg l,25-(OH)2 D3/kg consumed 30% less feed and laid 20% fewer eggs than the control, but shell quality was not affected. The groups receiving no calciferol supplement or receiving only 24,25-(OH)2 D3 laid eggs with significantly lower SG than the control after 2 wk of treatment (1.072 or less versus 1.082 at Week 2). The rest of the treatment groups mentioned were comparable to the control in eggshell quality and egg production. Groups fed the combination of l,25-(OH)2 D3 and 24,25-(OH)2 D3 per kilogram of feed, or 1,25-(OH)2 D3 alone at 5 μg/kg, had significantly higher tibial weights relative to the control group. All groups receiving the diets without cholecalciferol supplementation had markedly reduced hatchability. It was concluded that the optimal dietary level of 1,25-(OH)2 D3 for improving eggshell quality without affecting egg production was approximately 5 μg/kg and the toxic level was 7 μg/kg.