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Effects of biological type of beef steers on vitamin D, calcium, and phosphorus status¹

J. L. Montgomery^*,2, J. R. Blanton, Jr.^*, R. L. Horst, M. L. Galyean^*, K. J. Morrow, Jr.^,3, D. B. Wester and M. F. Miller^*,4

^* Department of Animal and Food Science and and Department of Range, Wildlife, and Fisheries Management, Texas Tech University, Lubbock 79409; and National Animal Disease Center, USDA-ARS, Ames, IA 50010; and and Department of Cell Biology and Biochemistry, Texas Tech University Health Science Center, Lubbock 79409

⁴ Correspondence: Box 42162 (phone: 806-742-2804; fax: 806-742-0169; e-mail: mfmrraider{at}aol.com).

Feedlot steers (n = 36) from three biological types (Bos indicus, Bos taurus-Continental, and Bos taurus-English) were used to determine the Ca, P, and vitamin D₃ status of feedlot cattle. The USDA yield and quality grade traits were measured at slaughter, and the concentrations of vitamin D₃ (VITD) and the metabolites 25-hydroxyvitamin D₃ (25-OH D) and 1,25-dihydroxyvitamin D₃ (1,25-(OH)₂ D) were determined in LM, liver, kidney, and plasma. Plasma and muscle Ca and P concentrations also were determined. Biological type of cattle affected a number of carcass traits. Carcasses from Bos taurus-English cattle had more marbling, resulting in higher quality grades (P < 0.05). Carcasses from Bos taurus-Continental cattle had lower calculated yield grades (P < 0.05) than did carcasses from cattle in the other biological types. In general, differences in carcass traits resulting from biological type were consistent with other reports. Plasma and LM Ca and P concentrations were not affected (P = 0.06) by biological type of cattle, indicating that Ca and P homeostasis is a conserved trait across the different types of cattle. Plasma VITD and 25-OH D concentrations were not affected (P = 0.41) by biological type, whereas plasma 1,25-(OH)₂ D concentration was lower (P < 0.05) in Bos taurus-English cattle than in Bos taurus-Continental and Bos indicus cattle. Liver VITD and 25-OH D were not affected by biological type (P = 0.76), but liver 1,25-(OH)₂ D concentration was greater (P < 0.05) in Bos indicus cattle than in Bos taurus-Continental cattle. Kidney vitamin D metabolite concentrations were not affected by biological type of cattle (P = 0.21). Muscle VITD concentration was greater (P < 0.05) in Bos taurus-English cattle than in the other two biological types, and muscle 25-OH D concentrations were greater (P < 0.05) in Bos taurus-English cattle than in Bos indicus cattle. Muscle 1,25-(OH)₂ D concentration was less (P < 0.05) in the Bos taurus-Continental cattle than in the other two biological types. Cooking eliminated vitamin D metabolite differences among the biological types. Our results suggest that Bos indicus cattle had greater 1,25-(OH)₂ D (the biologically active form) in tissues, and greater 1,25-(OH)₂ D plasma concentrations than Bos taurus cattle. Thus, the need for VITD supplementation and optimal levels of Ca and P in feedlot diets might differ between Bos indicus and Bos taurus cattle.

Key Words: Beef • Breeds • Calcium • Phosphorus • Vitamin D