Cow nutrition requires special care in drought

RED DEER — In dry years like this, cows may not get the nutrition they need when the grass starts to turn brown.

“If we stay dry, vitamin supplements may be needed in the summer,” said Kristen Rison-Bennett, a nutritionist with Blue Rock Animal Nutrition at Innisfail, Alta.

Carotene in fresh grass plummets when it dries out and could cause a vitamin A deficiency, meaning more open cows. Vitamin levels also drop off after alfalfa plants bloom and they are not present at appreciable levels in preserved feeds, she said at the recent Grey Wooded Forage Association annual meeting held in Red Deer.

Discovering potential mineral and vitamin deficiencies is a good reason to have feed tested.

“Smell and visual inspection is not the best way to test,” she said.

Near infrared technology or wet chemistry are used to test feedstuffs. Wet chemistry is more expensive but it can be used effectively on mixed feeds and total mixed rations. The big difference between the two tests is variable results on important minerals like calcium.

More people are also using alternative feeds to reduce costs so it is important to know if that feed is nutritious and balanced.

Proper sampling techniques are important. Remember quality, protein and energy will change throughout the growing season.

When collecting baled hay samples take 20 samples with a probe from the string side of bales. When collecting swaths go diagonally across the field and take 15 samples, Rison-Bennett suggested.

For corn grazing, take whole plants and submit five or six stems. Corn grazing may result in a calcium deficiency so extra minerals are needed. During the third trimester of pregnancy, the cow may not receive enough protein or energy so supplements may be needed.

Silage samples can be collected off the face of the pit. Or, probe into bags and cover the holes with duct tape.

When silage is being dumped it is also useful to grab handfuls then freeze them for sampling later. The nutritional quality will not change.

Cover crops are very nutritious but they may pass through the rumen at a quick rate so added fibre is needed. They are a good soil amendment but can have excess nitrates around a frost. A large proportion of brassicas may have sulfur accumulation and cause polio.

They also tend to be high in protein at around 20 percent when the cows only need 11 percent during lactation. Excess protein passes through the rumen too fast and manure is loose. Birth weights may be heavier than normal and the quality of colostrum is lowered.

Excess energy increases the risk of obesity, extra fat in the mammary glands and birth canal. There is decreased milk production and harder births.

Testing should be done before there is a problem.

Most tests cost $55 to $75 but ultimately it is cheaper to have feed analyzed rather than having sick or dead cows.

“These cows are what they eat so you may as well be meeting requirements,” she said.

Mineral relationships are receiving more attention because animals could be harmed if there is an adverse interaction between minerals.

“Test and make sure you have the right mineral in front of them,” she said.

For example, excess levels of phosphorous impair cows’ ability to use calcium effectively. Excess potassium ties up magnesium and sulfur in water can tie up copper.

Trace minerals include zinc, manganese, copper, cobalt, iron, selenium and iodine. Most of these are associated with immunity. Zinc for example is good for healthy skin and hoofs. Copper is needed for reproduction. If the animals’ coat is faded there could be a deficiency. Not enough selenium could result in weak or dead calves.

“When we see these signs we are probably too late,” she said.

A graphic on mineral interactions is available here.

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