Winter Nutrition Watch

        You’ve mended all the fences and you’ve laid in an extra supply of hay. Now you’re ready to endure nature’s wrath until spring calving time, right?  Well, maybe.

        The extra hay is a good thing, but is it good hay?  When should you feed more of it?  And when might you need more than just hay to keep your cows going?

        North Dakota State University Extension Beef Specialist Chip Poland says body condition of cows should not slide backward through the winter.   “If you have a cow that’s in ideal body condition for spring calving (score of 5 to 6 on a 1-9 scale), you need to maintain her condition.  More importantly, if you have a thin cow, you need to improve her condition before calving,” Poland advises.

        He says grain supplementation may be required if you’re relying on lower-quality forage or straw to stretch your winter feed supplies.  Thin cows with little insulating fat have especially serious needs.  “They need that extra energy just to maintain their body temperatures,” he says.  

        If you are using lower-quality forages and grain to get through the winter, those feeds are likely to be deficient in vitamin A.  Supplementing this essential nutrient will be important to maintaining body condition and fetal growth, and promoting good fertility at rebreeding, says Poland.

        Knowing exactly when and how much to supplement for harsh winter conditions can be assisted by using lower critical temperature indexes.

        Cold stress increases energy requirements for all cattle. Table 1 shows the lower critical temperatures (LCT) for cattle under different conditions and the percentage increase needed in TDN intake to offset the cold stress.

        For 1100 lb cows with dry winter coats, TDN requirements will increase 1% for every degree drop (ºF) in wind chill below 32ºF. If cattle are wet, TDN increases 2% for every degree below the LCT, which would be 59ºF. Therefore, a 1100 lb mature cow with a dry coat that is exposed to a -10ºF wind chill will increase her maintenance requirement from 8.8 lb TDN to 12.5 lb TDN (or 42% increase). That cow requires 20.9 lb TDN ({59-[-10}] = 69; 69 * 2 = 138; 8.8 lb TDN * 2.38 = 20.9) if she is wet under the same circumstances to maintain her weight.

        As you evaluate the supplements needed, consider RangeLand^TM  Feed Protein Tubs, which allow predictable consumption of high quality supplement by providing protein, energy, vitamins and minerals necessary for optimal performance on any forage diet.

        Attention to cows’ nutritional needs now will pay off with healthier calves at birth, heavier weaning weights down the road and improved fertility for dams at rebreeding – which hopefully means a bigger calf crop next year.  As proof, Table 2 shows the results of a Kansas State University experiment that studied the value of adjusting energy levels for cold weather.

        The researchers used 60 commercial cows fed in dry lot.  Half received a steady diet based on thermal neutral requirements for body weight maintenance.  The other 30 cows were fed a ration adjusted for 1% more feed for each degree of coldness. 

        The amount of additional feed to account for the cold weather events that winter was approximately 125 pounds of corn per cow.  Given the long-term impact that the additional energy had on the supplemented cows, the investment was well worth it.