Formula for Calculating Winter Hay Needs for Beef Cattle
Before you can calculate your winter hay needs, you need to gather some information first. Make sure you have the below information first:
- # of cattle you are feeding
- average weight of those cattle
- weight of one hay bale
- # of days you will feed hay
Take your best estimate if you are unsure of any of the above values. Better to estimate for more days than less and/or to overshoot cow weight, just to be safe. Probably want to do the opposite when estimating bale weight, though, if you are unsure of their weight.
Step 1: Average weight of cow x 3% (% of body weight eaten in hay daily) = lbs per day of hay per head
Step 2: lbs/day of hay per head x total # of cows = total cowherd lbs of hay /day
Step 3: total cowherd lbs of hay /day x # of days feeding hay = total lbs of hay needed for winter
Step 4: total lbs of hay for winter / weight of bale = # of bales need for winter
Step 5: Add anywhere from 20%-30% extra bales to this number, depending on your hay availability during the winter.
Read below for more information and advice.
Above is the formula we use when calculating our winter hay needs for our beef cattle. Below, I provide an example of using the formula to calculate hay bale needs for a cow herd of 10.
For this example, we will use a herd size of 10 cows, averaging 1300 lbs/cow. Beef cows consume an average of 2.5% of their body weight in feed a day. Due to the inevitable waste associated with each hay bale, (outer edges and bottom of the bales absorbing water from rain and groundwater, and the simple fact that some cows will consume more than others) we bump that up to 3% when calculating our winter hay bale needs.
Take 1300 lbs x 3% = lbs per day hay per head consumed. In this example, that would be 39 lbs/head/day of hay consumed.
Multiple 39 x 10 cows = 390 lbs of hay consumed /day for your entire herd.
Next, you want to figure out how many days you plan to feed-out hay. This number will vary, depending on your region and the winter conditions. Most regions will probably feed hay for 5 months or so during the winter. Let’s take that 390 lbs of hay consumed/day for the entire herd x 150 days = 58,500 total lbs of hay consumed for the herd for 150 days.
Divide 58,500 lbs by the average weight of one bale. Our round bales average 700 lbs and are 4 ft x 5 ft. So, take 58,500 lbs / 700 lbs = 83.57 -round up to 84 round bales.
Essentially, based on this formula, you can assume that you will need at least 84 round bales to feed a cow herd of 10, averaging 1300 lbs, for 150 days. We then recommend you add 20%-30% to that number to be safe. If you live in a region where hay is plentiful and you feel confident that you will be able to buy hay in the middle of the winter if need be, then maybe add only 20%. This would be an extra 17 bales or so. If you live in an area like us, where you would be hard-pressed to find hay to purchase in the winter, bump that up to 25-30%, adding 21-25 bales extra.
For more general information and tips on preparing for winter hay needs, please check out my next post!