Feed tests needed for top nutrition

Getting a feed test done and knowing what they have on the farm will allow producers to balance their rations

ROCKY MOUNTAIN HOUSE, Alta.— Feed testing is the best way to ensure cows are getting a balanced diet.

“Just visually looking at it isn’t going to give you those values of energy and protein. Your eye is not able to determine that,” said animal nutritionist Cornelia O’Keefe of Blue Rock Animal Nutrition in Innisfail, Alta.

The company works with producers in Western Canada on mineral packages, feed testing and nutrition recommendations.

A cow needs proper nutrition to conceive every year and wean a calf. The critical period is the post-partum interval after calving so the cow can start cycling again to get pregnant, O’Keefe said at an animal feed workshop held near Rocky Mountain House, Alta., last fall.

During mid-gestation at three to six months, cows need 55 percent energy in their diet. Requirements go up to 60 percent in late pregnancy.

The mature cow’s crude protein needs increase from seven, nine to 11 percent as pregnancy advances.

Bred heifers need a higher plane of nutrition because they are still growing.

“As they move through these different gestation phases, there are increased nutritional requirements. Having a feed test and knowing what you have on farm is going to allow you to balance those rations and make sure you are meeting her requirements,” she said.

Energy and protein requirements are highest at lactation.

Water consumption is correlated to feed intake so it should also be tested for pH levels, salinity, sulfates, high iron and nitrates or microbiological contaminants like E. coli bacteria.

The first step is having a feed test done, but the more important part is understanding the results so rations can be balanced.

Core samples are recommended when testing bales. At least 20 samples collected at random with a probe is recommended. Probes are often available through government agriculture offices or through forage associations.

Swaths can be sampled by collecting handfuls, starting at the end of the field and moving diagonally across.

When taking silage samples, follow an X pattern from the pit.

Standing corn can be randomly collected by grabbing entire plants across the field.

Chaff piles are harder to collect so try and take from the bottom of the pile.

Results may be from a near infrared reflectance spectroscopy (NIR) or wet chemistry test. NIR tests measures wavelengths to determine protein and energy while wet chemistry isolates nutrients using chemicals and heat.

The two tests may show differences in energy, fibre and mineral content like calcium and phosphorus.

The results show total digestible nutrients (TDN) like digestible fibre, protein, carbohydrates and minerals.

Neutral detergent fibre is the fibre or bulkiness of the feed, which is reported in percentage levels. NDF should be less than 60 percent of the diet. If feeds are too bulky, animals cannot consume enough to meet all their requirements even though their bellies are full.

Dry matter is the moisture-free content of a forage.

The water content of the forage will dilute nutrients but it does not usually have a great impact on animal intake. Therefore, it is important to balance all rations on a dry matter basis.

Acid detergent fibre represents the least digestible parts of the plants like cellulose and lignan.

Neutral detergent fibre indicates the amount of structural fibre and that is correlated with intake.

Test results include percentages of crude protein as well as minerals like calcium, phosphorus, magnesium, potassium, sulfur, copper, manganese zinc, molybdenum and iron. The results may also show the presence of mycotoxins like ergot.

Tetany ratio takes into account the levels of potassium, calcium and magnesium.

Older cows are more susceptible to tetany because of their decreased ability to mobilize skeletal magnesium. They may also have low levels of calcium.

High straw rations will be common this year because hay is in short supply. Straw is fibrous and impaction may occur because cows are not getting enough energy or protein to offset the amount of fibre they are eating. They also need adequate water.

Mineral and protein imbalances are possible as well so supplementation is needed.

Mineral nutrition is complicated and if there is a problem it may be difficult to fix quickly.

Minerals work together or can be antagonistic, such as how high sulfur works against copper. The mineral may be present in adequate amount but another inhibits its uptake.

Macro minerals are required in large amounts. Requirements change by age of animal, pregnancy and lactation cycle.

The macro nutrients are calcium, phosphorus, potassium, sulfur, sodium and magnesium. Micronutrients include copper, zinc, manganese, iodine, cobalt, selenium and iron.

Mineral levels vary in forages.

Pea straw is about four to five percent protein and higher in calcium than cereal straw.

Barley straw has less calcium and protein so supplementation is needed.

Corn is low in calcium but high in phosphorus.

Legume and grass-legume forage is higher in calcium but low in phosphorus.

Grass-type forage is intermediate for calcium and low in phosphorus.

Greenfeed and silage are low in calcium and moderate in phosphorus.

Cereal grains are lowest in calcium and highest in phosphorus.

Calcium is needed for healthy bones and teeth, muscle contraction, nerve impulse transmission, enzyme activation and blood clotting.

Phosphorus contributes to good bones and teeth and is important in energy metabolism.

Potassium is needed for membrane function, muscle contraction, osmotic pressure, nerve impulse transmission and water balance.

Magnesium is used for energy production, nerve impulse transmission and an enzyme co-factor.

During the summer months when the grass is green, vitamins are available from feed but supplementation is needed in the fall when grasses start to die.

Vitamins A, D and E are crucial six week before calving.

“Don’t wait for that wreck to evaluate your mineral program,” she said.

Vitamin A is critical for immune function, proper bone growth, vision, skin and hoofs and is especially important in fall and winter. Cows need 60 international units of vitamin A per kilogram of body weight. Levels should increase during lactation.

Deficiency signs include:

  • night blindness
  • reproductive failure
  • skin lesions
  • skeletal deformities
  • contracted tendons

Vitamin D is critical for calcium and phosphorus absorption. Sunlight provides it in summer but animals need 5.7 international units per kilogram of body weight later in the year.

Deficiency signs include:

  • rickets
  • leg weakness
  • swollen or stiff joints
  • tetany
  • anorexia

Vitamin E is needed for calf immunity. It does not transfer across placental walls, so cows need to receive it six weeks before calving so it is added to colostrum. A dry pregnant cow needs 400 international units per day and a lactating cow needs 500 IUs per day.

Deficiency signs include:

  • white muscle disease
  • weak calves with potential for heart failure
  • leg weakness
  • impaired suckle reflex
  • paralysis

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