The challenge of meeting the growing nutritional demand is also related to a reduced dry matter intake (DMI) during the transition period. Dairy cows will adapt their metabolism and will utilize their body reserves to satisfy their needs.
From an energy standpoint, dairy cows adapt their lipid metabolism by mobilizing fat reserves as non-esterified fatty acids (NEFAs) to meet the energy demand and will get into a state known as negative energy balance (NEB).
Part of the NEFAs are directly utilized as a fuel source by some tissues like the mammary gland; however, the majority will pass by the liver to be metabolized.
Some will be oxidized completely or incompletely for energy production, and the excess will be incorporated into very low-density lipoproteins (VLDL) for exportation out of the liver.
Liver fat- processing ability is limited and, when large amounts of NEFA are entering the liver, it could result in fatty liver and ketosis problems, compromising the cow’s health and performance.
Due to the negative impact of health disorders on dairy farms’ profitability, various dietary and management strategies have been developed to prepare cows to defy transition. Among them, the supplementation of protected B vitamins has recently gained importance.
Although it is often assumed that requirements for these nutrients can be met by ruminal synthesis, researchers suggest that in the modern dairy cow, some of these vitamins are not produced in adequate amounts for maximizing health and performance.
Since these vitamins are extensively degraded in the rumen, rumen-protection technologies have permitted an efficient supplementation of these nutrients.
During the transition period, it has been observed that the supplementation of riboflavin, folic acid, B12 and choline is beneficial for dairy cows. The objective of this article is to point out specific functions of these vitamins on transition cows’ health and performance and to show the synergistic effect of supplementing them together.
Choline
Technically, choline is not a vitamin, but due to its chemical and physical characteristics, it has been classified among the B vitamins group. Choline has a variety of metabolic roles, all related to its function as a methyl group donor and component of phosphatidylcholine and acetylcholine.
In transition cow nutrition, choline potential application has been based on its role in fat metabolism, since phosphatidylcholine is required for VLDL synthesis and released from the liver. Choline also mediates indirectly hepatic lipid oxidation, preventing and correcting liver fat deposition and improving hepatic function.
These benefits have been confirmed when rumen-protected choline was fed to transition cows, finding less hepatic fat concentration and, in some studies, a reduction in fatty liver occurrence.
Likewise, a reduction in mastitis incidence has been observed but without any significant improvement in retained placenta, uterine diseases or displaced abomasum. Protected choline has reduced ketone bodies in one study but not in others.
The supplementation of rumen-protected choline has not shown any effect on DMI prepartum but tended to increase DMI postpartum.
Milk and energy-corrected milk are generally increased when feeding protected choline during the transition period, but this does not always occur. Despite improving health status postpartum, reproductive performance is not improved in general.
Part of the inconsistent results with the supplementation of choline could be explained by the interrelation between various methyl donors such as methionine and folic acid.
Folic acid (B9) and B12
In mammals, folic acid biochemical function is to donate and accept methyl groups, being essential for DNA synthesis and methionine synthesis modulation.
For dairy cows, folic acid sufficiency has been questioned due to its high demand to support fetal growth and because serum folates levels drop by 40 percent from late gestation to early lactation. Being a methyl donor, like choline, folic acid is also involved in the hepatic metabolism of fat.
B12 is involved in two essential metabolic reactions in ruminants: allowing the use of propionate for liver glucose synthesis, and the transport of methyl groups, needed for methionine and other methyl donors synthesis.
This last function shows how the role of B12 is interrelated with folic acid and that their benefits on cow metabolism cannot be separated.
Studies supplementing both folic acid and B12 during the transition period have reported an increase in metabolic efficiency, milk production and milk protein production during early lactation.
Recent research in transition cows have found that these vitamins reduce the NEB extent and promote follicular development and ovulation, improving their reproduction.
Riboflavin (B2)
Riboflavin is required as a cofactor for multiple enzymes in carbohydrate, fat and protein metabolism. This vitamin and its related compounds are perhaps involved in more reactions than any other vitamin.
Among its most relevant functions, riboflavin mediates indirectly many oxidation and reduction reactions, which are involved, among others, in energy production for the dairy cow.
Although less studied than the other vitamins above, riboflavin has been identified to reduce oxidative stress, which increases during the transition period and has a negative impact on the immune system and reproduction. Additionally, riboflavin plays an important role in the activation of immune cells, allowing dairy cows to fight against infections more effectively.
B vitamins blend
With this supportive information about the role of each vitamin and some research studies done with dairy cows, a rumen-protected vitamin supplement for transition dairy cows has been developed containing choline, folic acid and riboflavin.
This blend has demonstrated remarkable benefits during this critical period by promoting immune function, energy balance and metabolism of dairy cows.
In an experiment, the supplementation of this protected vitamin blend during the transition period increased significantly DMI prepartum.
Since the supplementation of protected choline alone does not improve the DMI prepartum, the increase observed with the blend of vitamins could be due to riboflavin, folic acid or an interrelation among the three vitamins. This effect allows cows to improve their energy balance, avoiding excessive reserves mobilization.
In the same study, cows fed the protected B vitamins blend had better health with a reduction of their postpartum blood ketone bodies and the occurrence of mastitis and metritis.
Reproduction was also improved in the B vitamins blend-fed group, doubling the percentage of cows bred at 100 days in milk compared with the non-supplemented group.
Considering the results obtained with the protected B vitamins blend and those obtained with protected choline alone, it was of interest to evaluate if the addition of riboflavin and folic acid to choline resulted in differences on the health status, milk production and reproduction in comparison to choline alone when fed to dairy cows during the transition period.
In this regard, an evaluation was performed in a commercial dairy herd in which it was found that, compared with the group fed with protected choline alone, cows supplemented with the protected B vitamins blend had lower subclinical ketosis prevalence and showed an improvement in their health status and productive and reproductive performance (Table 1).
Even though choline enhances fat metabolism and hepatic health, these results support the addition of other B vitamins, along with choline, to bring additional benefits to transition dairy cows.
Folic acid, B12, riboflavin and choline each have a specific function and, when added together, represent a substantial improvement for dairy cow health and performance (Table 2).
B vitamins are essential nutrients for transition cows and are involved in various metabolic processes to facilitate their adaptation during this critical period, allowing them to remain healthier and express their potential.
Though each B vitamin plays important metabolic roles, supplementing them together is more beneficial for transition cows than when supplemented alone, evidencing an effect of complementarity and synergy.
Producers and consultants could now consider supplementing a protected B vitamins blend as a practical and effective tool to help cows achieve a successful transition. PD
Rodrigo Molano provides ruminant technical support for Latin America with Jefo Nutrition Inc. Hélène Leclerc offers technical support and R&D for Jefo Nutrition Inc. She can be reached by email.
References omitted due to space but are available upon request. Click here to email an editor.
