Vitamins for dairy cows

Vitamin

Function

Source

Adequate intake (NASEM 2021)

Achilles Heel

Deficiency symptoms include

Upper safe level

Comments

A

Natural antioxidant, helps prevent night blindness and is essential for growth, bone development, reproductions and immune response

β-carotene is a yellow pigment considered abundant in green plants which is converted to vitamin A in the intestinal wall and liver.

For cows giving up to 35L milk, adequate intake of supplemental vitamin A = 110iu/kg body weight = 55,000 IU per 500kg cow

Less stable than many other vitamins. Most grain and grain byproducts contain very little β-carotene, levels in forages decline after harvest.

Reduced appetite, rough coat, retained placenta, swelling of joints, low conception rate, abortions, stillbirths, reduced oestrous, blind calves, night blindness, low heat tolerance, increased mastitis and respiratory diseases.

66,000 IU/kg diet DM – cost will keep supplementation well in the safe zone

The primary benefit seen by supplementing vitamin A to cows that are not deficient are primarily health and reproductive rather than increased milk production. The transition period is associated with increased demand due to stress and transfer to the colostrum. Blood tests for when cows are stressed or in poor condition for retinol or β-carotene can help determine if supplementation might be beneficial.

D3

‘Sunshine’ vitamin or ‘antirickets’ vitamin essential in calcium and phosphorus metabolism related to bone formation and strength.

A range of pro-vitamins present in most feeds are converted to vitamin D3 after irradiation by sunlight.

Cattle that are grazing need less vitamin D3 because of sunlight exposure. Lactating cows in Norway producing 20kg/day required about 10IU vitamin D3 per kg body weight/day

No appreciable stores in land animals. Springers, winter milking cows on high silage diets and cows that are housed for extended periods are most likely to benefit from supplementary D3.

Decreased growth rate and appetite. Rickets or stiff gait. Decreased milk production, inhibited oestrous, milk fever

4000 IU/kg complete feed. Maximum tolerable level over 60 days is 2,200 IU/kg feed or about 40,000 IU for pasture-based cows eating 18kg DM/day.

A special form of D3 called 25-Hydroxyvitamin-D3 is considered more available and effective than standard vitamin D3 and is being used by some dairy farmers at high levels throughout lactation to support milk production and bone quality. Use during the transition period, for winter cows on high silage diets and during period of extended periods in housed systems may be easier to justify

E

Biological antioxidant that helps protect cells from damage, working closely with selenium. Stimulates antibody production and immune response.

Fresh grass and clover are rich sources, conserved green forages and cereals are poor sources.

Adequate intake for lactating cows and growing heifers = 0.8 per kg body weight – 400 IU/day for a 500kg cow. Fresh forage reduces the requirement for supplemental vitamin E by 50IU/kg DM fresh pasture consumed.

Low selenium status requires additional vitamin E. Stress, exercise, infection and tissue trauma increase requirements.

White muscle disease in calves is a classic sign of deficiency. Increased days to first oestrous, days to first mating and conception, returned services, increased mastitis.

Relatively nontoxic - safe upper dietary level suggested as 75 IU/kg body weight /day.

The vitamin E requirement of cows within 3 weeks of calving is considered higher, at 3 x bodyweight at a time when fresh pasture intake is often limited by the limited rumen capacity or to help reduce milk fever risk associated with the high potassium level in pasture.