When it comes to beef cattle nutrition, vitamin nutrition isn't usually a big concern for a mature cow. This time of year, however, is when deficiencies can become most noticeable, especially in cattle that have been consuming hay for a long time.
The main vitamin of concern is vitamin A. Vitamin A is usually not needed in the diets of cattle consuming green, growing forages because adequate levels of carotene are available that is converted to vitamin A in the animal. In a normal winter, vitamin A deficiency may not occur because it's stored in the liver. A two- to four-month supply is available under normal conditions.
Drought, such as last summer's drought, will result in early use of vitamin A stores. Coupled with a long, hay feeding season, cattle without access to green grass until April may experience vitamin A deficiency.
Sub-clinical vitamin A deficiency may result in a lower calf crop percentage or later calving season next year. Vitamin A deficiency can result in poor conception rates, abnormal embryonic development and fetal death. Reduced maintenance of the skin and tissue lining of the respiratory/digestive system can increase infections. Clinical deficiency symptoms include night blindness.
Vitamin A deficiencies can be overcome by providing supplemental sources of vitamin A. In general, most feedstuffs fed to beef cattle during winter are considered low in vitamin A, other than green forages and corn.
Many complete mineral supplements provide supplemental fat soluble vitamins (A, D, and E). The level of vitamin A in these feedstuffs will vary. A mineral designed for 4-ounce intake contains 150,000 IU of vitamin A, which will deliver about 75 percent of a mature, lactating beef cow's vitamin A requirement.
Cattle consuming a mineral with an adequate level of vitamin A shouldn't have a vitamin A deficiency unless the cattle are consuming the mineral at the expected rate and the mineral has been stored for a long period of time. This will result in the degradation of vitamin A.
A common option for providing supplemental vitamin A is with an injectable vitamin. If a complete mineral with a high level of vitamin A hasn't been offered to the herd, the injectable form is preferred since the spring breeding season will begin soon.
Shane Gadberry is an Extension livestock specialist with the University of Arkansas, Division of Agriculture.