“Crop residue or swath grazing are two great feed sources that can reduce the overall cost of feeding the herd. To fully use feed while keeping nutrition at a consistent level, limit grazing is recommended. If the herd is provided the entire area at once, the cows eat all the heads and finer matter first, leaving the stems and course material for later. This is counter-productive at a time when their plain of nutrition needs to be increasing, not decreasing.”
Hanson says that throughout the time the cattle are on a cereal based diet - high in phosphorus - to monitor their calcium/phosphorus ratio to ensure this remains optimum. “Magnesium is typically deficient in cereal crops, increasing the risk of downer cows, or winter tetany. Feeding a 3:1 mineral during this time may be necessary. The addition of limestone to a 1:1 or 2:1 mineral is recommended.”
Third trimester - As a cow gets closer to calving, her dietary requirements for calcium and magnesium increase due to the growing calf and the cow’s production of colostrum. Four to eight weeks before calving, the cow’s body begins to mobilize calcium and magnesium from her bones to develop the colostrum. As a cow ages, her ability to mobilize those minerals decreases and along with high milking cows that just require more calcium and magnesium in general.
"During the third trimester, producers should start to supplement the cow’s diet with an alfalfa grass hay to bump the calcium content in the ration and provide more protein,” says Hanson. “Legumes are high in calcium so saving that alfalfa or alfalfa-grass hay for the last months of the third trimester and into lactation is a good idea.”
Monitoring the weather throughout the winter feeding season is also extremely important. “Cows can withstand cold temperatures as long as they have the body condition, or fat, to insulate them. Days of cold weather with no extra energy provided can decrease a cow’s body condition. A 1350 lb. cow at the end of her second trimester, with a BCS of 3.5 on swath grazing can eat free choice barley or oat greenfeed without any nutritional concerns in a daytime temperature of -10 C and a 10 km per hour wind. When the weather changes to -40 C for a daytime high and the same wind speed, in order for her to maintain her body weight, she needs to consume an additional five lb. of barley grain.”
“Feed is the biggest expense in a cattle operation,” she adds. “Producers need a strategy for their feed supply at the start of the year when they have more choices and can ensure that the right feeds are provided during the best time of the feeding season. If feed resources need to be purchased, finding the proper forage or grain can ensure that the cows’ nutrition is optimized.”
Source : Alberta agriculture and forestry