UNL research identifies the importance of vitamin A for newborn calves

In recent research, the University of Nebraska-Lincoln (UNL) has discovered vitamin A is important to a healthy immune system in newborn calves.

Two studies were conducted to evaluate the correlation between cow and calf vitamin A status and how vitamin A status in cow/calf pairs were influenced by maternal vitamin A supplementation. 

In the March 13 edition of the UNL BeefWatch Newsletter, UNL Beef System Specialist and Associate Professor Mary Drewnoski states, “Colostrum is the only way calves can get the vitamin A they need to fight off bacteria that will make them sick.”

However, it has been revealed not all colostrum contains enough vitamin A, and UNL research concluded what once was “enough” is truly not adequate.  

Importance of vitamin A

Vitamin A is needed for calves to have healthy skin and eyes, digestive tracts and respiratory systems.

“Calves are born deficient in vitamin A and depend on colostrum from the mom to provide what they need,” Drewnoski says. “Calves which don’t get enough vitamin A from colostrum are prone to scours and respiratory disease.”

The research notes vitamin A concentrations in colostrum have been reported to be six to 14 times greater than that of milk, so colostrum is critical for establishing vitamin A stores in a young calf. 

Drewnoski further notes the amount of vitamin A in colostrum depends on the cow’s diet in late pregnancy and how much she has stored in her liver. 

Fresh green forage contains high amounts of beta carotene, a vitamin A precursor, and is used by the cow to synthesize vitamin A, UNL research notes.

However, what is stored in the cow’s liver is not enough to fortify colostrum, meaning vitamin A must come from her diet as well.

Cows fed diets primarily consisting of stored forage and concentrates are at risk for vitamin A deficiency because these feeds contain low amounts of beta carotene.

The only option to ensure pregnant cows are receiving a sufficient amount of vitamin A is through supplementation, according to the research at UNL.

“A cow needs more vitamin A in her diet than previously recommended to provide enough to her newborn calf,” she adds.

Supplementation

UNL research concludes a cow with adequate vitamin A liver stores at the time of calving does not ensure the calf will have adequate vitamin A liver stores. 

“Therefore, a sound mineral and vitamin program is vital for the success of any cow/calf operation. We now suggest 75,000 International Units (IU/d) per day, which could come from a mineral mix assuming four ounces per head per day. Producers need to look for a supplement with about 300,000 IU/d per pound,” Drewnoski explains. 

She adds, “The previous recommendation was 30,000 to 50,000 IU/d.”

UNL research identified a cow’s milk is customarily low in vitamin A, and supplementing during lactation will not meet the calf’s needs so it is of utmost importance for a calf to get adequate colostrum.

“Colostrum replacers and milk replacers do contain vitamin A and can help when colostrum isn’t available. There are also injectable vitamin A options,” Drewnoski says. “These can be used to ‘top-up’ a cow or calf that likely has low vitamin A levels, but they aren’t an effective primary source and aren’t necessary with a good nutrition program.”

In addition to choosing the right mineral supplement, UNL reports it’s important to make sure all cows have access to vitamin A and that it’s always available. 

Drewnoski recommends providing one mineral source per 30 head of cattle, noting it is important the mineral doesn’t run out because the most aggressive cows will hog it when it’s available again. 

If mineral does run out, she suggests providing loose salt for a day to satisfy cravings before putting out the mineral mix again.

“Developing a free-choice mineral supplement can be tricky with so many options available, but it does not have to be expensive nor is cost correlated with effectiveness,” she says. “Mineral supplementation is not magic, and feeding more of a mineral will not necessarily improve performance. Responses will only be observed when correcting a deficiency.”

Thus, the goal, she remarks, is to provide enough mineral to meet cows’ needs without feeding more than needed, thereby adding to cost without providing a benefit.

Melissa Anderson is the editor of the Wyoming Livestock Roundup. Send comments on this article to roundup@wylr.net.