this may be a little lengthy but it is a good way to estimate hay needs for the winter.
A quick easy way to estimate feed requirements is on the basis of animal units. This is done based on a mature cow or bull equal to one unit, yearlings equal to one-half unit, and calves equal to one-fourth unit. Utilizing this method, each animal unit will require approximately 25 pounds of average to good quality hay.
For a herd of 35 cows, one bull, and 8 replacement heifers with a winter feeding period of 120 days and (assuming 80% calving rate) 28 calves for 60 days, the following is an example calculation of stored feed requirements:
35 cows x 1 animal unit = 35 units
1 bull x 1 animal unit = 1 unit
8 replacement heifers x ½ unit = 4 units
Total for herd is 40 animal units.
40 animal units x 120 days x 25 pounds of hay per day = 144,000 pound of hay.
In addition if you have calves for say half of the feeding period.
28 x ¼ animal unit = 7
7 animal units x 60 days x 25 pound of hay per day = 10500 pounds of hay
For a total for the entire herd = 154,500 pounds or 77.25 tons.
When estimating hay supply for the winter don't guess at the weight of the bales. Take a few bales have them weighed to get an accurate estimate for bale weight. Keep in mind that this weight will vary from year to year or season to season, depending on the forage type and quality.
Also take into consideration that round bales of hay stored outside may sustain substantial losses during storage and feeding.
Utilizing animal units to estimate feed requirements is just that – a quick estimate. To be more accurate consideration must be given to exact nutritional requirements for the size of animal and stage of reproduction or growth. Feed supply can be more accurately estimated if you have a forage analysis done to determine the exact nutrient content of stored feeds as well.
