Newborn calves that are slow to get up and do not respond right away could be affected by a trace mineral or vitamin deficiency.
If pregnant cows are low in selenium in the fall, the calves may be wobbly when they are born the following spring. They could suffer from a variety of maladies, including lesions on the tongue and heart that are seen only under the microscope.
“A calf with muscle lesions in its tongue will not suck well and does not get enough colostrum,” said researcher Cheryl Waldner of the University of Saskatchewan’s Western College of Veterinary Medicine.
“It may die from other infections.”
Surveillance studies among western producers have shown that selenium deficiencies have declined because more attention is paid to supplementation, but some problems still appear.
Producers need to talk with their veterinarians to see if weak calves are the result of a deficiency or other factors such as a hard delivery in which dams and babies are hurt.
“You just see the calves that aren’t doing right,” Waldner said.
“Those calves may have scours or end up with pneumonia. They may be the calves that get hurt. They are not quick to get out of the way and get stepped on.”
Large scale studies of herds across Western Canada found varying levels of reproductive success when beef cows had low levels of selenium in their blood.
Based on a study from 2001, they found that low serum selenium was most common in thin cows where feed selenium was low and from areas with more precipitation or with black or gray soils.
Low serum selenium at pregnancy testing was not associated with an increased risk of reproductive failure, but it was connected to an increased risk of weakness in the subsequent calf crop.
Producers need to talk with local veterinarians about the best supplements because selenium deficiencies vary by region.
The highest frequency of selenium-deficient grains and roughages has been reported in black, dark-gray, and dark-brown soil zones in Western Canada. For example, selenium deficiencies are well known in the region west of Highway 2 in Alberta.
Vitamin A and E deficiencies may also place calves at risk. They can get what they need from green grass, but stored forage loses vitamins. As well, drought can increase the challenges associated with ensuring optimal nutrition in cow–calf herds.
Waldner’s research team looked at drought impacts on productivity after the dryness of 2002.
For example, cows from regions with less than 200 millimetres of precipitation during the 2001 growing season were more likely to have stillborn calves the following spring after accounting for differences in individual cow body condition score.
Diseases such as scours and pneumonia are commonly reported reasons for treatment and death loss in Western Canada, but infectious disease does not explain all calf deaths. Postmortem examinations of calves that died in 200 herds from across Western Canada in the spring of 2002 suggested that noninfectious factors, including nutrition, were important causes of loss.
Vitamins A and E were identified as the two most common micronutrient deficiencies potentially associated with death in calves born alive.
Vitamin E and selenium work together.
One of Waldner’s studies showed calves with low serum vitamin E concentrations had an increased risk of enteritis.
Vitamin E concentrations were also lower in calves from herds that did not administer selenium with vitamin E at birth and in calves from herds on pastures that received less than 200 mm precipitation in the previous growing season. Concentrations of vitamin E also varied among regions.
Cattle receive vitamin A primarily through bioconversion of beta-carotene found in forages.
The intensity of green colour in a plant is a good indication of its carotene content, and in a growing plant, all green parts are rich in carotene.
The amount of vitamin A in cows’ colostrum and milk depends on their intake during late gestation. Concentrates are a poor source of vitamin A and beta-carotene.
Reduced quality and quantity of forage during drought conditions during the growing period decrease the availability of carotene for vitamin A production in the cow and, therefore, its transfer in the colostrum.
Newborn calves must get most of their vitamin A from colostrum because they are born with limited vitamin reserves.
A lack of vitamin A can result in decreased disease resistance and increased mortality, particularly in growing animals.
Increased susceptibility to bacterial infections, particularly mastitis and pneumonia, reproductive failure, and postpartum diseases such as retained placenta and metritis, have been associated with a deficiency.
Vitamin A is stored in the liver and can serve as a source to the animal for a long period of time. Vitamin E can be stored in body fat and muscle, but stores are more limited.
Producers should consider supplementing their cows and particularly heifers in spring calving herds. This is particularly important following drought years because vitamins have been depleted in stored forage, and liver vitamin A stores may be lower in cows and heifers that grazed in drought conditions during the previous growing season.
Injection of calves with selenium and vitamin E at birth is recommended, especially where selenium in feed is known to be deficient.
The skinny on selenium
- Selenium is a chemical element discovered in 1817. Its benefits for mammalian health were discovered in 1957.
- Selenium is naturally present in the soil. It can be found in several different forms, but the level of selenium in soil varies widely between regions, depending on geology.
- Plants absorb selenium from the soil, and their ability to do so depends on its mineral composition, pH, rainfall and rate of fertilization as well as the particular plant species and its growth stage.
- Certain plants are selenium accumulators, storing high levels in leaves and stems when they are grown in selenium rich soils. Such species have caused toxicity in animals grazing them. However, typical cereal, oilseed and forage species are non-accumulators. They incorporate selenium into proteins within the plant, which ensures that they don’t accumulate toxic amounts.
- Animals and humans can consume selenium naturally, but the amount found in plants is also low if levels are low in the soil.
- Therefore, in most areas of the world it is necessary to add selenium to animal feed. Poor performance, health and fertility issues will result if animals’ requirements aren’t met.
Source: 200 Years of Selenium