As my wife and I prepare to move to a different house, I find myself carrying a lot of boxes. Many of the boxes are the uniform type that reams of paper are shipped in. Although all the boxes are filled, some feel like they are stuffed with bubble wrap while others are anvil-like in weight. In other words, these same-sized boxes offer drastically different hernia potentials.
Along similar lines, the size of a box isn’t always correlated with the weight of the box; there are some heavy, small boxes and relatively light, large boxes. These same filled-box characteristics occur with bales, and it can cost hay buyers, sellers, and feeders a lot of money.
There is still a lot of hay in the U.S. that gets sold by the bale. Livestock often get fed according to the number of bales per feeding or unit of time. None of this is necessarily bad if the weight of the bale is also known so that price per ton or animal intake can be determined.
Through the years, I have seen many types of demonstrations to prove our inadequacies in guessing bale weights. Similar to forage quality, there are weight factors that can’t be easily discerned with the naked eye.
Some of the factors that impact bale weight are bale density, bale moisture, time of sale, forage species (grass or legume), forage maturity (percent leaves and stems), and the model and age of the baler.
It’s intuitive to think that the size of a bale will impact bale weight, but what may be overlooked is the degree of change that occurs when a bale is only 1 foot wider or 1 foot greater in diameter. The latter accounts for the largest change.
A bale that is 4 feet wide by 5 feet in diameter (4x5) has 80% of the volume of a 5x5 bale. However, a 5x4 bale has only 64% of the volume of a 5x5 bale. Those percentages also translate to differences in weight, but only if all other factors such as moisture and density are equal.
One factor affects another
Bale density, which typically ranges from 9 to 12 pounds per cubic foot, also plays a large role in final bale weight. In a 5x5 bale, the difference between 10 and 11 pounds of dry matter per square foot accounts for over 100 pounds per bale when moisture is in the 10% to 15% moisture range. Miscalculating the weight of a bale by 10% adds to significant dollars when multiple tons are being purchased or fed.
Forage moisture also plays a role in bale weight but to a lesser degree than bale density — unless bales are extremely dry or wet. Wrapped bales, for example, can vary in moisture from 25% to over 60%. When purchasing baleage, it is always recommended to either weigh the bales or have a rock-solid moisture test.
Time of purchase impacts bale weight in two ways. First, if you’re purchasing bales out of field, they are likely going to be at a higher moisture level and weight than they will be after being cured in storage. There is also a natural tendency for dry matter loss during storage that the buyer will incur if bales are purchased immediately after baling. As has been documented by research, storage losses can range from below 5% to over 50%, depending on storage method.
Forage species also plays a role in bale weight. Grass bales generally weigh less than legume-based bales of similar size. This is because legumes tend to result in a denser bale. In one Wisconsin study, the average weight of a 4x5 legume bale was 986 pounds. This compared to 846 pounds for grass bales of the same size.
Plant maturity also impacts bale density and weight. Leaves pack better than stems, so as plants mature and develop a higher percentage of stems to leaves, bales generally become less dense and weigh less.
Finally, there are many models of balers of differing ages. This variation, coupled with operator experience, lends further variability into the bale density and weight discussion. New baler technologies enable farmers to make a much denser bale than those achieved with most older balers.
Given the number of variables that determine actual bale weight, buying and selling large round bales — or bales of any type — based on a weight guess is likely going to result in a transaction that is either above or below market value. Moreover, feeding bales without knowledge of their weight and quality makes it difficult to achieve optimal livestock performance.
