Nutritional needs rise as mercury dips

Deficiencies have long-term effects | Cows lacking nutritional requirements may produce smaller, poor performing heifers

Talk turned to the coldest, darkest days of winter during a sunny field day in June.

Kim Ominski of the University of Manitoba’s animal science department reminded producers at a recent Western Beef Development Centre event that the nutrient demands of cattle increase when temperatures dip and the wind picks up.

“Mother Nature can be very harsh,” Ominski said.

“I think in the last two winters in Western Canada, we’ve certainly seen that.”

She said there are more days of extreme cold than many producers may remember. Temperatures in the Saskatoon area fell below -20 C approximately 70 times last winter.

The same area recorded 94 days below -15 during the previous year.

January also saw 14 days where winds topped 30 km-h.

“We all lived through that and I think that we forget as time passed because obviously those conditions are pretty extreme,” she said.

Ominski said producers who use an extended winter grazing system are particularly vulnerable.

Delivery of processed and stockpiled forages and bale and swath grazing have been widely adopted in Western Canada and may offer cost advantages, but producers must keep a close eye on cattle.

Nutrient deficiencies affect birth weight and colostrum quality and quantity in the short term, but researchers are also finding more long-term affects in animal performance.

“We’re learning more about the impact of heifers in terms of age of puberty and pregnancy rate and also in terms of carcass weight and marbling score,” she said.

Ominski said studies have found that restricting nutrients during mid-gestation produces calves with fewer muscle fibres and ultimately de-creased muscle mass.

“There is generally an increasing body of knowledge that shows the impact of nutrient restriction specifically prior to calving can impact carcass quality,” she said.

The most significant fetal growth occurs in the final trimester, which is also when the animal’s nutrient requirements rise.

She said producers should keep this in mind and use body condition scoring to identify deficiencies. It’s also important to test feed in storage and on pasture and keep an inventory.

“Knowing the value of those feeds and then looking at how you can strategically place the use of each individual feed to meet the nutrient requirements of the cow as it changes throughout the course of the winter,” said Ominski.

“Strategically identifying what do I have, what’s my inventory of feeds, what’s the quality of them and then strategically using those to meet the nutrient requirements of the cow.”

She said having an alternative water source is paramount in winter grazing systems. Snow can be a sufficient water source for animals, but the quality, amount and water content of snow can vary.

Cold temperatures lead to drier snow and less water content.

Ominski said dry cows, bred heifers and bulls can consume 43 to 67 litres of water per day, while lactating cows with calves consume more.

A 2012 survey of Canadian producers found that the lack of a winter watering system and too much snow were the major reasons for not winter grazing.

“Mother Nature forces us to have a Plan B and sometimes, even, a Plan C,” she said.

“Flexibility in those systems is the key in order to be able to adapt to whatever she throws our way.”