Effects of vitamin D3 metabolites on physiological traits of White Leghorn hens

This study was conducted to determine the effect of feeding vitamin D3(D3) metabolites on BW of hen, weight of uterus, plasma Ca, jejunal and uterine adenosine triphosphatase (ATPase), and carbonic anhydrase. At 416 days of age each of 7 groups of laying hens was fed the basal ration supplemented with one of 7 concentrations (micrograms per kg) of D3 or its metabolites as treatments: 0 micrograms of D3; 27.5 micrograms of D3; 3, 5, or 7 micrograms of 1,25(OH)2D3; 5 micrograms of 24,25(OH)2D3; and 5 micrograms of 24,25(OH)2D3 plus 5 micrograms of 1,25(OH)2D3. Treatment effects were compared at various periods after the start of the study. Hens fed the unsupplemented ration had lower (P less than .05) values for all traits than hens fed the D3-supplemented ration by 162 days after the start of treatment. In a comparison of all dietary treatments except the one involving 0 micrograms D3, from 154 to 161 days after the start of the experiment, treatment effects were significant (P less than or equal to .05) for BW, uterine ATPase, and carbonic anhydrase; hens fed 5 micrograms of 24,25(OH)2D3 per kg of ration ranked the lowest of all treatment groups for these traits. Hens fed 27.5 micrograms of D3 and those fed 5 micrograms of 1,25(OH)2D3 per kg of ration did not differ (P greater than .05) for any traits studied. The results suggest that 5 micrograms of 1,25(OH)2D3 per kg of ration can replace 27.5 micrograms of D3 per kg of ration but that 5 micrograms of 24,25(OH)2D3 per kg of ration tends to have a negative effect on physiological systems of the hen.