As fall begins, winter is not too far behind. Cattle producers are starting to decide how much hay will be needed to make it through the winter. Some basic calculations can be used to help determine an appropriate amount to have on hand.
First calculate the basic needs. According to research at the Iowa Beef Center, a basic calculation of daily dry matter intake is 2.25% to 2.5% of body weight per animal. In a herd with an average cow size of 1,200 pounds, the daily need calculates to approximately 30 pounds DM per day per cow (1,200 lbs. x 2.5% = 30 lbs. DM/day).
Using this base calculation, the next questions to answer are how many head will be fed and for how long? Continuing the example with 150 head of cows in the herd and planning on 180 days feeding hay, the calculation of hay needs comes to 810,000 lbs. (405 tons) of total DM. (30 lbs. DM/day x 150 hd. x 180 days = 810,000 lbs. DM).
Knowing the dry matter value of the hay being used can then help calculate a more accurate amount of hay to be consumed. Hays normally range from 80% to 90% DM. Using 85% DM for this example, divide the base total hay needs (405 tons) by the percentage of DM to find the need increases to 476 tons (405 tons ÷ 85% DM = 476 tons DM).
There will also be some feed wasted. Cattle tend to pull out, step on or leave in a feeder, a portion of the hay they are fed. Large round bales tend to be the most prominent used in winter hay feeding.
According to studies by the University of Missouri, waste can be limited to less than 6% on a 7-day supply of hay when using a hay ring for feeding. Calculating in a 5% hay loss, the total hay needed increases again to 501 tons (476 tons DM ÷ 95% = 501 tons DM).
This example calculates for a cow herd. Calculations also need to be done for any bulls, replacement heifers and calves as well. Having extra hay on hand for inclement weather should be considered as well. How much to calculate for the weather is more dependent on your location and typical winter needs than a formula that can be developed.
Another consideration is the nutritional value of the hay being fed. There is quite a considerable difference in feeding an alfalfa grass mix hay versus a native grass hay. Supplemental feed may be needed to increase the nutritional value of the daily ration and help cows to maintain body condition during the winter months. Supplementation can be done by using higher TDN hay, feeding concentrates or using supplement tubs to increase energy and protein levels during winter feeding.
