Minerals and vitamins Table 4 presents the NRC recommendations for minerals and vitamins for high producing cows. Trace mineral recommendations are provided on a concentration basis as well as an amount assuming 52 pounds of dry matter intake. Vitamin levels are provided as daily amounts as recommended by NRC, and as amounts commonly recommended by nutritionists and veterinarians. P ratios of less than 1.5 or greater than 3.5. Feeding a phosphorus-deficient diet results in delayed onset of estrus, inactive ovaries, and repeat breeder problems.
High phosphorus intakes along with low calcium intakes also depress fertility.
As discussed earlier, concentrations of trace minerals in forages, grains and by-products can vary a great deal. Many producers meet at least half of the NRC requirement for trace minerals from supplemental sources, such as a good quality trace mineral salt, premix, or commercial mineral or feed. Nutritionists and veterinarians generally recommend supplemental vitamin A and D in amounts greater than NRC recommendations. Supplementing rations for high producing and early lactation cows with more than 150,000 units of vitamin A and 40,000 to 50,000 units of vitamin D per cow per day is unnecessary. Recommended macromineral, trace mineral and vitamin content of rations for early lactation and high producing dairy cows.