Calculating Livestock Winter Hay Needs

Dr. Susan Kerr, WSU Northwest Regional Livestock and Dairy Extension Specialist
Publish Date: 
Fall 2013
Vol. VIII No. 4

Livestock producers can often realize feed cost savings by purchasingHay. Photo by David Shankbone, http://upload.wikipedia/commons/thumb/8/8e/Grass_hay_by_David_Shankbone.jpg their entire winter hay supply at one time. Obtaining an entire feeding season supply from a new hay crop certainly beats underestimating needs and having to cobble together purchases of more hay in late winter, when demand may outstrip supply and quality may be variable. There are four critical aspects of large hay purchases: knowledge of how much to purchase, adequate storage capacity, ability to work with the hay producer’s schedule and capital to make the purchase.

A few simple calculations can help livestock producers estimate how much hay they will need to get them through the winter. Estimates are based on livestock body weights, number of head to feed and days to be fed. Feeding records from each farm should help producers know how many days they may need to feed hay. Hay may have to be fed from October through March, perhaps even April. “But there is still plenty of green grass in October and again in March!” you may say. True. However, it is to your pasture’s long-term health and productivity for grazing to cease in the fall and not start too early in the spring; more details about this will be included in a future article.

Table 1 below includes estimates of daily dry matter intake (DMI) as a percent of body weight of various livestock species. Animals do not have DMI requirements. They do have requirements for the amount of water, protein, energy, vitamins and minerals needed for maintenance, various rates of gain and other forms of production. These nutrients must “fit” into the amount of food an animal can physically consume. DMI rates are estimates of how much dry matter (water component subtracted) an animal can consume in one day.

TABLE 1: Dry matter intake as percent of body weight of livestock species
Provided by: Dr. Susan Kerr


DMI as % of Body Weight


2 to 6

Beef Cattle

1 to 3

Dairy Cattle

3 to 4.5


1.5 to 3


2 to 5


4 to 6

* For hogs, up to 10% of the total ration dry matter can be forage

As a rule of thumb, as an animal matures and its weight increases, its DMI as a percent of body weight decreases. Other factors affect DMI as well. For example, less digestible high fiber diets fill the capacity of the digestive tract more quickly, limiting additional intake; more digestible and higher energy feeds are processed more quickly, leaving room for additional feed intake and resulting in higher production, as well.

Let’s say we want to calculate how much hay to purchase as the foundation for a ration for an 1,100# beef cow for a 6 month (182 day) feeding period. We’ll assume average quality grass hay, average weather conditions and no lactation during the feeding period. Using a moderate DMI of 2% of body weight, we can estimate her daily DMI as 22# of hay (24.2# as fed, adding back in 10% water weight for hay). Multiplying this daily intake times the number of days in the feeding period, we get 4404# (2.2 tons) of hay needed for this one animal. Multiply this number times the number of animals needing to be fed and you have the total amount of hay required for the winter feeding period. Depending on your feeding system, you will also need to figure in an additional 10 to 50Evidence of a balanced livestock diet% as hay waste. Chemical analysis of the hay being fed would be a valuable source of information and help guide feeding decisions.

If you are able to stockpile forage on pasture or hayfields and the ground is frozen, you may be able to do some winter grazing and reduce your hay feeding days. Only do so if you will be grazing dormant plants and animal impact will not be deleterious to pasture plants, soil and water. Bear in mind that this stockpiled forage will be very low quality and provide mostly fiber; energy, protein, vitamin and mineral supplementation will be required.

Back to our 1,100# beef cow: after we gave her the calculated 24.2# of average quality grass hay, free choice water and free choice trace mineral salt each day, we would monitor her for evidence that her nutritional requirements were being met (see inset box). Some animals may need additional nutrients to maintain the desired degree of body condition. Sometimes these added nutrients can be provided simply by offering more hay, but other times these animals may need more concentrated forms of nutrients, especially if they are already at their maximum DMI capacity. Assuming this animal was bred, we would also have to gradually increase her nutrients in the last three months of pregnancy to meet her increased nutritional requirements. Cold weather will require an increase in nutrients to meet increased maintenance requirements, as well. Diets based on low protein forages (crude protein below 8%) benefit from protein supplementation because rumen microbial populations are able to flourish and digest dietary fiber more effectively. Intake of less palatable high-fiber diets such as mature hay, straw and corn stalks can be increased by providing commercial supplements formulated with a highly-palatable molasses base.

Judicious livestock feeding is an art. It requires regular assessment of animal health, body condition, performance and feed costs, with adjustments and gradual changes made as necessary. Keeping feed costs manageable is a huge challenge for livestock producers, but securing winter hay supplies well in advance of the feeding period is one opportunity to realize some feed cost savings.