Estimating Winter Forage Needs of the Cow-Calf Herd
As winter approaches and cool-season grass growth begins to diminish, cattle producers should start thinking, if they haven’t already, about how much forage they will need to maintain their animals through the winter.
The first step to estimating winter forage needs is to determine animal inventory. Producers should note the number and size of animals within each class that they plan to maintain throughout the winter: pregnant cows, lactating cows, weaned calves, yearlings, mature bulls.The animal class is important because growing, early- to mid-lactation, and late-gestation (third trimester) cows will require higher quality forages for optimal performance.It is equally important to know the average size of the animals within each class because that will dictate roughly how much forage will be consumed. Body condition should also be considered.Animals that are thin going into winter will require additional, higher quality forages, in order to achieve adequate condition.This is critically important for pregnant cows and heifers, which should be calving at a condition score of around 6 in the springtime.
Producers should also consider current forage inventory and availability.This requires not only looking at the quantity of forage available, but also the quality. Not only is forage quality important when feeding different classes of animals i.e., pregnant cows vs. growing yearlings vs. breeding bulls), but it also can affect how much forage animals will consume. High quality grass forages (>60% total digestible nutrients and >8% crude protein) digest quicker in the rumen than low quality forages (<55% total digestible nutrients and <8% crude protein) and allow the animals to physically eat more.
Daily forage consumption can be estimated based on animal size and forage quality.As a general rule of thumb, animals will consume around 1.5 to 2.5% of their body weight each day on a dry matter basis. If feeding high quality forage, intakes may approach 2.5% of body weight; if feeding low quality forage, intake can be expected to be closer to 1.5% of body weight.
When calculating the amount of forage that should be supplied daily, it is important to remember to make adjustments for the moisture content of the forage: dry hay is usually around 15 to 10% moisture, while baleage is typically around 40-60% moisture. It is also important to account for forage losses, which can be highly variable depending on storage and feeding methods.
The last important piece of information for calculating winter forage needs is the length of the winter feeding period. While no one can predict how soon spring pastures will be ready, this is still an important component of the equation. Typically, cool-season perennial pastures are ready to graze in March.
In the following example, the winter forage needs for a spring-calving cow-calf herd with 15 cows is estimated.It is assumed that the cows will be in their second and third trimesters of gestation during the feeding period (December-March), and will be fed moderate- to high-quality forage during this time, with an average nutrient content of 58% total digestible nutrients and 10% crude protein. With this forage, daily dry matter intake is assumed to be 2% of body weight.Assuming an average cow weight of 1300 pounds, daily forage consumption for each cow is around 26 pounds of dry matter, or 390 pounds of dry matter for the whole group. After adjusting for the moisture content of the hay (assume 10%), this translates into 433 pounds of hay that that will be consumed on an as-fed basis. If forage losses due to storage and feeding are assumed to be 15%, then the group of cows should be supplied with at least 498 pounds of hay per day. If the winter feeding period is assumed to be December 1 to March 1 (90 days), then approximately of 45,000 pounds (or 22.5 tons) of hay will be needed to overwinter the cows in this example.
As with any feeding program, it is important to routinely evaluate cattle performance throughout the winter to ensure nutrient requirements are being met. The easiest way to assess the nutrition program is to evaluate body condition regularly (at least monthly). This is especially important for pregnant cows and heifers getting ready to calve in the spring. In most cases, cattle should retain a condition score of 5-6 throughout the winter. Loss of condition is indicative of inadequate nutrient supply and warrants a reevaluation of the feeding program.