By Dr. Louisa E. Koch, Ph.D., P.A.S.
You have likely heard a thing or two about the fat-soluble vitamins A, D, and E. Did you know, however, that the water-soluble B-vitamins play essential roles in the cow, as well? The B-vitamins are a group of water-soluble vitamins that have key roles as enzymatic cofactors or intermediate components in major metabolic functions. (Table 1; i.e. propionate conversion to glucose in the liver.)
In the past, B-vitamins were not commonly supplemented to dairy cows because it was believed that rumen bacterial synthesis of these vitamins was sufficient to meet her needs. Today’s high-producing dairy cows, however, have greater nutrient requirements. The necessity of additional B-vitamins at the feed bunk is therefore being reevaluated.
Even the most logical ration changes can result in marked fluctuations in the rumen environment. The microbial population can degrade dietary components differently depending on the nature of the ration. Given this, many ask if nutritionists should provide additional B-vitamins in the diets of dairy cows to overcome the fluctuation in rumen supply?
You will notice from Table 1 that many of these B-vitamins play a role in energy metabolism. More specifically, pantothenic acid, biotin, vitamin-B12, riboflavin, and niacin are all necessary to convert propionate to glucose in the liver. (Figure 1.) Research in lactating and transition cows has found that a number of B-vitamins are insufficient in supply. Riboflavin and choline in particular have a 99% ruminal disappearance rate (Santschi et al., 2005). Biotin is only about 60%. Because B-vitamins are degraded easily in the rumen, suggested ways to deliver them to the animal are injection or in the diet via a rumen-protected form (most common).
One B-vitamin that is often supplemented in the diet is biotin. Biotin is commonly used to improve hoof health and integrity. Biotin can improve hoof health by reducing heel warts, white line separations, and sole ulcers, for example. Studies have reported an increase in milk production when biotin was supplemented 15 to 20 mg per day. (Midla et al., 1998; Fitzgerald et al., 2000; Hedges et al., 2001.)
More recently, a 2019 meta-analysis involving nine trials with 1,923 dairy cows evaluated unprotected biotin vs. a protected B-vitamin blend (containing folic acid, B12, pyridoxine, pantothenic acid, and biotin). It showed that the protected blend significantly increased milk, milk fat (% and yield), and protein (% and yield). Agri-King’s Hoof King® will supply 20 mg of biotin when fed at 0.05 pounds per cow per day. You should consider it for your nutrition program if you struggle with hoof health.
Another B-vitamin receiving a lot of attention lately is niacin. Although a requirement for niacin has not been established, its integral role in energy metabolism suggests that it is important for milk production. Schwab and Shaver (2005) did a meta-analysis of 27 studies that fed unprotected niacin at the 12-gram level and noted that milk increased 1.1 pounds, fat increased 26 grams, and feed efficiency rose 0.03 units.
However, more recent work has focused on rumen-protected niacin. Several investigations found that just 3.5 grams of rumen-protected niacin resulted in increased DMI and reduced ketosis. It did not, however, impact milk components or milk yield. The current recommendation for transition cows is 3 grams of rumen-protected niacin. Numerous studies have examined niacin’s impact on heat stress, as it is a vasodilator that has the potential to lower body temperature and increase sweating rate during times of elevated temperatures.
Choline is one of the more important B-vitamins in practical dairy nutrition today. Many regard it as a quasi-B vitamin because it does not fit the typical description of a vitamin. Choline can also be made from methionine. So if your diet is below the recommended methionine levels, you may not require additional choline. Because the rumen degrades choline, it must be provided in a protected form in order to reap these benefits.
Rumen-protected choline has helped prevent the development of conditions such as fatty liver. It does this by helping transport fatty acids out of the liver. This has great implications for prepartum cows struggling with conditioning. Typically, choline is fed to transition cows, although some research has shown a carryover effect through lactation of higher milk overall. Grummer (2012) evaluated 13 research studies in a meta-analysis on rumen-protected choline and found an increase of 4.9 lbs of milk.
The interest in B-vitamin supplementation to dairy cows is increasing and there will likely be a new breadth of data on B-vitamins in the coming years. Contact your local Agri-King area manager or a member of our nutrition department for guidance on utilizing these B-vitamins to maximize the performance of your dairy herd. AK
Complete references available upon request.
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