Now is a good time to double-check hay inventories and test hay quality. When evaluating potential hay needs and inventories, it is critical to estimate pounds and not just bales. The weight of hay bales can easily vary by 500 pounds or more. The example below taken from the publication Bale weight: How important is it? demonstrates the differences in bale weight due to size (density was held constant in this example).
- 4X5, 880 pounds
- 5X5, 1,100 pounds
- 4X6 foot, 1,267 pounds
- 5X6 foot, 1,584 pounds
As a general guideline, a lactating cow will consume about 2.3% to 2.5% of her bodyweight per day of moderate-quality hay on a dry matter basis. A non-lactating cow will consume about 1.8% to 2% of her bodyweight per day of the same hay. Hay contains some moisture (water), so consumption must be adjusted for the moisture content. If the moisture content of the hay is 10%, then it is only 90% dry matter. The example below illustrates how much hay would be needed per day if the moisture content (10%), storage losses (8%) and feeding losses (5%) are accounted for.
- 1,350-pound lactating cow x 2.5% of her bodyweight = 33.75 pounds of hay per day on a dry matter basis
- 33.75 pounds ÷ 0.9 dry matter = 37.5 pounds per day on an as-fed basis
- 37.5 pounds ÷ 0.92 for storage loss = 40.76 pounds
- 40.76 pounds ÷ 0.95 for feeding loss = 42.9 pounds
If hay feeding lasted for 120 days, then estimates from this example would indicate that each lactating cow would need about 5,148 pounds of hay going into the winter. Using the bale weights in this first example, this would result in 5.85 bales that weighed 880 pounds or 4.06 bales that weighed 1,267 pounds.
These calculations can be done by hand. However, many university extension services have spreadsheets to help with these and other calculations. One example is the annual cow cost spreadsheet from Texas A&M. To access this spreadsheet, go to the Texas A&M Department of Animal Science website, click on publications, and then scroll down to spreadsheets. The estimating costs tab of the annual cow cost spreadsheet has a section for estimating annual hay needs and cost.
