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Minerals in Beef Cattle, Part 2

10 November 2009

Following on from last weeks article Minerals in Beef Cattle, Part 1, Part 2 looks at mineral supplementation and vitamins.

Mineral supplementation

Supplementation of minerals may occur through a variety of means, including free-choice loose mineral mixes, trace mineral blocks, and fortified energy and/or protein supplements. Mineral fertilisation of forage is not as efficient as direct supplementation of the animal. Forages should be fertilised to meet the growth characteristics of the plant.

Free choice loose mineral supplements
Loose mineral supplements are an effective, cost-efficient means of delivering adequate mineral supplementation in most cases. Although formulations vary greatly, the common base mix should contain approximately 20 to 25 per cent salt. “Average” intake is often targeted at two to four ounces per head per day.

Seasonal variation in consumption
Body mineral reserves can be mobilised in time of need and deficiencies can take long periods of time to develop. During the summer months, cattle may readily consume saltbased mineral supplements. In winter months free-choice intake may be reduced by 15 per cent or more. To avoid over consumption in the summer, offer mineral every 10 to 14 days at a level slightly exceeding the target intake. It is acceptable for the feeder to remain empty for a few days prior to the next scheduled day of mineral offered. In the winter you could blend your mineral with your winter supplement.

Trace mineral blocks
When cattle producers are physically unable to provide loose mineral or fortified supplements on a regular basis, trace mineral fortified salt blocks provide an opportunity to offer long-term mineral supplementation, therefore lessening the potential for trace mineral deficiency.

Energy-protein supplements
If consumption of adequate levels of minerals are a problem, a solution may be incorporating your free-choice trace mineral supplement with a protein-energy supplement.

Palatability
Monitoring and recording the average daily intake of free-choice supplements will allow the supplement formula to be adjusted if necessary, to increase or reduce intake. Cattle only possess the desire to consume salt at the level of their requirement. Consequently, by altering the salt inclusion in mineral mixes, mineral intake can be both encouraged and discouraged.

If cattle are over-consuming a mineral, consider adding plain white salt directly into the trace mineral mixture. Once mineral intake has normalised, remove the additional salt. Phosphorus and magnesium sources are unpalatable and may reduce mineral supplement consumption. Do not provide plain white salt and trace mineral supplement separately. A rule of thumb is the more acidic types (sour tasting) are more palatable than the alkaline (bitter tasting).

Analysis of herd trace mineral status

If a trace mineral deficiency is suspected, a producer may wish to conduct an evaluation of herd trace mineral status. The first step in identifying trace mineral deficiencies is to attempt to rule out other contributing factors. Make sure the mineral supplement is in an accessible location, and that the product provides a balanced mineral profile which is consumed at an appropriate level.

Forage mineral concentrations
Grazing cattle selectively consume higher quality forage than hand-clippings of the same pasture. Availability of forage mineral varies with the specific mineral, soil mineral concentrations and forage maturity and weathering, most data indicate that minerals of forage origin are between 50 and 90 per cent available to the ruminant animal.

Animal mineral status
Directly measuring animal mineral status through blood and liver tests can be costly and time consuming. However, if animal performance is below what is expected and there are no other explanations, it may be necessary. Liver concentrations of copper, manganese, selenium, and zinc provide the best indication of trace mineral status. Liver iodine and iron concentration are not indicative of nutritional status. Any biopsies should be carried out by a veterinarian. Blood samples can be an unreliable approach for measurement of mineral levels unless the cattle are severely deficient. Blood analysis can be occassionally used for copper, iodine, iron, selenium and zinc.

Blood enzymes and metabolites are also used as indicators of mineral status in cattle. Glutathione peroxidase is an indicator of selenium status, alkaline phosphatase, superoxide dismutase, and metallothionein are indicators of zinc status. Ceruloplasmin, superoxide dismutase, and metallothionein are indicators of copper status. Vitamin B12 and methylmalonic acid are indicators of cobalt status.

Analyses of minerals in milk and urine are seldom useful in mineral assessment. However, molybdenum and iodine in milk are exceptions and reflect dietary intake. Selenium and iodine levels in milk and urine could have a role in indicating excess intakes if reference values were ever established. Mineral content of hair, wool, and hoofs lack reference standards, are too slowly responsive to intakes, and can be easily contaminated.

Vitamins

Vitamins are classified as either faT-soluble (A, D, E, and K) or water soluble (B, thiamin, niacin and choline) based upon their structure and function. Fat-soluble vitamins contain only carbon, hydrogen, and oxygen, whereas the water-soluble B vitamins contain these elements and either nitrogen, sulphur, or cobalt.

Vitamin A
This is considered by many to be the most important vitamin. It is necessary for proper bone formation, growth, vision, skin and hoof tissue maintenance as well as energy metabolism.

Green leafy forage, green hay, silages, dehydrated alfalfa meal, yellow corn, and whole milk are good sources of carotene. In cattle, 1 mg of beta-carotene is converted to the equivalent of about 400 international units (IU) of vitamin A. Carotene can be destroyed as the plant matures and with exposure to sunlight, air, and high temperatures.

Thiamin
A thiamin deficiency results in central nervous system disorders, as thiamin is an important component of the biochemical reactions that break down the glucose supplying energy to the brain. Other signs of thiamin deficiency include weakness, retracted head, and cardiac arrhythmia. As with other water-soluble vitamins, deficiencies can result in slowed growth, anorexia, and diarrhea.

Vitamin B-12
These vitamins are abundant in milk and other feeds. A vitamin B-12 deficiency is difficult to distinguish from a cobalt deficiency, but affects the rumen.

Vitamin D
D vitamins are essential for bone growth and maintenance because it is directly involved in calcium absorption as well as phosphorus absorption. Sun-cured hay contains high concentrations of vitamin D. However, cattle synthesise vitamin D when exposed to sunlight and so rarely require supplementation. Cattle housed indoors for long periods of time and consuming low quality forage may be victims of vitamin D deficiency such as rickets and other bone abnormalities.

Vitamin E
This occurs naturally in feedstuffs as alpha tocopherol. It serves as an antioxidant and is important in muscle growth and structure. The vitamin E requirement for cattle has not been firmly established. For young growing cattle, the requirement is estimated to be between 7 and 27 IU/lb of feed dry matter. However 50 to 100 IU per head per day has been suggested for older, growing and finishing cattle.

Signs of deficiencies in young calves are characteristic of white-muscle disease including general muscular dystrophy, weak leg muscles, crossover walking, impaired suckling ability caused by dystrophy of tongue muscles, heart failure, paralysis, and hepatic necrosis.

Co-product feed focus

Co-product feeds can be economically competitive sources of protein and energy compared with traditional sources such as corn and soybean meal. However, co-product feeds may not have mineral profiles similar to corn and soybean meal. Production of co-product feeds can remove some nutrients while concentrating others.

Corn gluten feeds and distiller’s grains products can have high concentrations of sulphur. See TheCattleSite article Sulphur Content in Cattle Feeds for information concerning distillers grain and sulphur toxicity.

Bioavailability

Total content of a mineral element has little significant unless it is qualified by bioavailability. Before a nutrient is utilised, it must be consumed, digested, absorbed and transported where needed in the body. Cost is an important factor but the cheapest product per ton is not always the cheapest product per desired nutrient(s). Producers (and researchers) are often interested in differences of performance in response to various sources of minerals (organic vs inorganic). Organic mineral sources have improved growth and reproductive performance in some studies where high levels of performance (embryo transfer or response to estrous synchronisation and artificial insemination) were expected.

To work out the most cost effective product, divide the $/lb of ingredient by the nutrient content. This will give the cost per lb of nutrient. Divide this figure by the bioavailability to get the cost per lb of available nutrient.

Further Reading

- You can find more details on bioavailability in different sources by clicking here.
November 2009

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