Severe deficiencies have led to resorption of fetuses, poor udder development, almost complete absence of milk secretion, and birth of small, weak, or dead calves. Researchers are not sure exactly how the heifer' s reproductive processes are affected by zinc deficiency, but this deficiency does cause lowered fertility in heifers and may increase susceptibility to infections. Vitamin A Deficiency. Dams deficient in vitamin A may abort in the last half of pregnancy. Evidence suggests that diets grossly deficient in vitamin A may cause irregular estrus and reduced fertility.
Gross deficiency suppresses ovulation or prevents implantation of the fertilized egg in the uterus.
Vitamin A deficiency also makes animals more susceptible to infection. This is also true for vitamin E deficiency. Young calves with cobalt deficiency show lack of appetite and poor growth. Cows with cobalt-deficient diets produce milk that is low in vitamin B12. Because soils in the Northeast are low in cobalt, feeds in this region of the country must be supplemented with this mineral.