Trace elements in dairy diets
Vitamin E and selenium perform important functions in the cow. Deficiencies of one or both of these nutrients have been implicated in white muscle disease, retained placentas, oxidized milk, lower immune function and mastitis.
The roles of these two nutrients are closely related. Both selenium and vitamin E protect cells from the detrimental effects of oxidation but they do so in different ways. Vitamin E, an antioxidant present in the cell membrane, prevents the formation of harmful free radicals. Selenium functions throughout the cell to destroy peroxides, another harmful compound.
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This explains why selenium will correct some deficiency symptoms of vitamin E and not others. Although feeding elevated amounts of selenium does reduce the need for vitamin E and vice versa, high levels of one nutrient do not eliminate the need for the other.
Agriculture Canada regulations allow diets to be supplemented with up to 0.3 mg/kg supplemental selenium. This equates to seven mg/day for lactating cows. Dry cow diets are also limited to 0.3 mg/kg which corresponds to about three mg per day. This may be insufficient for dry cows given feed grown in selenium deficient areas. Selenium levels in commercial feeds can be increased with a veterinary prescription.
Although selenium is a necessary nutrient it can also be toxic at fairly low levels. It is important that only one source of supplemental selenium is provided and that care be taken to avoid toxicity.
Information from clinical and field studies indicates that vitamin E recommendations from the National Research Council do not promote optimum udder health. Green forages are good sources of vitamin E. However, the vitamin E content of feedstuffs decreases during drying and storage. Industry recommendations for cows receiving stored forage are 500-600 IU of supplemental vitamin E/day for milking cows and 800-1,000 IU/day for dry cows.
Although mineral mixes do contain some vitamin E, the levels are usually very low (40-500 IU/kg). Some mineral mixes do contain elevated levels of vitamin E (1500 IU/kg) but at normal levels of intake still do not provide sufficient vitamin E. Feeding 13 g of a vitamin E premix with 40,000 IU/kg will provide milking cows with 520 IU of supplemental vitamin E per day.
Selenium and vitamin E can also be injected. A vitamin E-selenium injection can be given about two weeks prior to calving to boost circulating blood levels when problems persist.
– Animal Nutrition Update
Measuring muscle contractions
SASKATOON (Staff) – There’s a red hot, yet cool new way to make meat tender.
Cooling meat too quickly after slaughter causes muscle tissues to contract, making meat tough. Conversely the shelf life of the product is extended by cooling the tissues as soon after killing as possible.
That has created a dilemma for the meat industry of having to choose between shelf life and tenderness.
But now, new technology, developed by researchers at Ontario’s Guelph University, will allow packing plants to cool off the meat faster than before without risking muscle contraction.
The new device allows a near infra-red beam to pass through the meat. When muscles contract, the sarcomeres are tightly packed and orderly, causing the light passing through the meat to split into two beams. This creates a double image on the other side. The greater the contraction in the sarcomeres, the more distinct the double image becomes.
The process enables packers to measure muscle contraction and stop cooling when the meat reaches optimum conditions to yield tender product with a long shelf life.
Infra-red light will not heat the meat or leave any trace that it has passed through the product.
Development is continuing on the equipment to convert the technology into a probe that could be easily inserted into cooling meat in a packing plant.
