Haying Legumes

The goal when harvesting legumes, including crops such as alfalfa, red clover, and birdsfoot trefoil, is to maximize the economic yield of nutrients (forage quality) while ensuring stand persistency. The stage of maturity at which legumes are cut influences feed quality as nutritive value declines with maturity. Leaf loss during harvesting reduces protein content, while rain prior to baling reduces the levels of soluble carbohydrates due to leaching. Regardless of the harvesting and storage methods some dry matter and nutrient losses occur and will vary with management practices.

Desired forage quality and the length of the cropping rotation dictates cutting frequency. Frequent cuttings produce high quality forage while less frequent cuttings generally result in increased stand longevity. Carbohydrates stored in the taproots and crowns are the energy reserves essential for winter hardiness, initial spring growth, and subsequent regrowth after cutting. Energy reserves are the highest when plants are in full bloom and lowest shortly after cutting when the plant is actively growing. Winter hardiness is a key factor influencing stand longevity. Legume varieties with early fall dormancy tend to be more winter hardy. Less dormant varieties tend to have faster regrowth with higher yield potential but are more susceptible to winter injury. Research is being conducted to identify genes that support late fall growth and winter survival of alfalfa (See BCRC Factsheet: Increasing fall productivity in winter-hardy alfalfa).

Alfalfa is the most productive and widely adapted legume. Under good management it has good persistency and longevity. High quality alfalfa can be harvested when cut at the bud-to-early bloom stage. Risks to alfalfa stand persistence can be minimized by allowing at least one harvest during the growing season to reach 10% or greater bloom, along with high levels of fertility and proper timing of fall harvest, which allows higher energy reserves to accumulate in the roots.

Hay Desiccants and Preservatives

Compounds to reduce field curing time of forages include two types of products, both of which are applied through a spray system, however they each employ a different mode of action and are used at different stages of hay production¹⁰.

Desiccants can be applied to legume crops (they are ineffective on grasses) at cutting time to reduce the time needed for curing and drying. Desiccant compounds (containing potassium or sodium carbonate) disturb the waxy cuticle of legume stems to allow the plant to dry faster. Effectiveness varies with climatic conditions with improved efficacy under good drying conditions as compared to poor drying conditions.

Preservatives are applied at baling to prevent heating and spoilage when hay is baled at higher moisture levels. Moisture and temperature are the fundamental control variables for storage, and the role of a preservative is to prevent microbial growth and activity. Mold growth that occurs in baled forages increases dustiness, reduces palatability and can impact animal health. The use of preservatives for hay above 35% moisture is not recommended.

The most effective preservatives for alfalfa are organic acids, primarily propionate (propionic acid) and acetate (acetic acid). Propionic acid is the most effective organic acid preservative for baling moist hay that is commercially available. Rates of propionic acid application vary depending on the moisture content of the forage.  Acetic acid is about half as effective as a preservative and therefore requires twice as much product for equal preservation. As organic acids function as fungicides they must be applied to contact as much of the plant surface as possible, which is usually at the pick-up on the baler. It is important to note that organic acids can be corrosive to equipment and a neutralized solution is recommended.

Anhydrous ammonia is an effective preservative for grasses. It can also be used as a source of non-protein nitrogen to improve the feeding value of low-quality forages, including straw, by increasing protein content and assisting in the breakdown of the fibre fraction of mature forages. The response to anhydrous ammonia is controlled by moisture content of the forage (minimum 10-12% moisture required, with ideal at 15-20%), the time of ammoniation, air temperature, and the amount of ammonia provided. Anhydrous ammonia must be applied at 2% of forage dry weight when used as a preservative for high moisture forages or applied at 3-5% of forage dry weight to improve the feeding value of low-quality forages.  The ammoniation process can be accomplished by injecting into bales or released into a stack of bales covered and tightly sealed with plastic to make an airtight environment. For ammoniation to be effective the stack must be completely sealed for up to four weeks. Three to five days before feeding ammoniated forages, one end of the stack should be opened to allow any excess ammonia to escape. Note that anhydrous ammonia should not be used as a preservative on alfalfa because alfalfa is generally high in protein already, and the interaction between alfalfa and ammonia can cause toxic chemicals to form.

Hay Storage

Losses in quality and quantity result when baled forages are exposed to the weather. The amount of loss will vary depending on precipitation, storage site location and preparation, and the original condition of the bale. Understandably, losses are more significant in higher rainfall conditions than under drier environments.

The external layer of a bale represents a substantial loss of yield and quality due to weathering. The size of the bale has an impact on the proportion of hay that is in the surface layer with larger bales having less exposed surface as a percentage of total feed in the bale. A 4” layer of weathered material on a six-foot diameter round bale represents 20% of the bale volume while the same 4” layer on a five-foot bale represents 25% of the volume¹¹. In high moisture conditions it is possible to have up to eight inches of spoiled hay on the outside of a round bale.

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Increased bale density enhances the ability of round bales to shed water. Even, uniform windrows make formation of consistently shaped and dense bales easier. Smaller windrows generally result in denser bales, as there are more layers per roll. Large hard-core bales lose less value than smaller soft-core bales.

Selecting the most appropriate type of storage is driven by economics and depends on the end-use for the forage, the specific livestock feeding situation and the needs of the producer. Storage losses can be reduced by two-thirds with indoor storage and by one-half with good covering outside. Main areas of concern are weathering on the tops and sides of the bales but also where the bales contact the ground. Moisture will move from the ground up into the bale through a "wicking" action. All storage sites regardless of the type of storage, should be well drained. A firm base of coarse rock, preferably not gravel or concrete, will help to minimize moisture movement from the ground up into the bales. If possible, avoid areas where moisture and/or snow can accumulate or where drainage is restricted.

Storing bales outside on the ground without cover is the cheapest method of storage but has the greatest potential for weathering loses, especially under extended storage periods. Large round bales without cover should be stored end-to-end in single rows in a north-south orientation with space between the bales to facilitate good air circulation and drying. Uncovered pyramid stacking exposes lower levels of bales to increased weathering as rain shed off the top bale row filters into the lower levels. Two-bale "mushroom" stacking where the bottom bale is placed on end and the top bale on its side minimizes the amount of ground contact, but moisture shed off the top bale can accumulate in the lower bale significantly increasing spoilage.

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Greenfeed

There are a wide variety of annual crops that can be cut and baled for use as a feed source. Barley and oats have traditionally been the most widely used cereals grown for harvest as a forage source. Triticale, wheat, corn stover, or peas can also be grown as a monoculture crop or in combination with other cereals for greenfeed production.

The traditional recommendation has been to cut cereals for greenfeed at the late-milk to early dough stage. However, more recent research suggests that harvesting oat and barley at the hard-dough stage has the potential to improve forage yield without compromising dry matter intake, feed sorting, ruminal fermentation characteristics or digestibility¹². Cautions when cutting at a later stage of maturity include the potential for grain loss in the field due to shelling and the risk that feeding more mature cereal forages may cause acidosis.

Generally, annual crops provide a safe and nutritious feed source, but producers should be aware of several possible animal health concerns. Environmental factors such as frost or drought, as well as plant diseases can adversely affect feed quality. Feed testing is essential. Feeding annuals during the winter requires a mineral package formulated to ensure animal needs are being met. Winter tetany or milk fever symptoms are often associated with feeding grain, straw or greenfeed rations. Cereal forages are low in magnesium and calcium and may accumulate excessive levels of potassium that impairs magnesium absorption and causes tetany. Canola can be high in sulfur, which increases the risk of copper deficiency in cattle. Many annual greenfeed crops are prone to high levels of nitrate which can cause death or abortions in cattle. Factors which can increase feed nitrate levels include high levels of soil nitrogen, type of crop, and frost, hail, or drought which reduces or stops growth of the plant causing plant nitrates to accumulate to an unsafe level. Nitrate levels in forages greater than approximately 0.5% Nitrate (NO₃) should be fed with caution and carefully managed as part of a balanced ration.

When growing barley for greenfeed, smooth-awned varieties are recommended as rough-awned barley greenfeed has been known to cause physical injuries in the mouth which may lead to infections. It is important to watch for lumps on the jaw and consult a veterinarian for treatment.

The inclusion of greenfeed within an annual management plan can provide winter feed as well as additional grazing resources as regrowth of stubble from crops grown for greenfeed can provide good quality grazing late in the season. Crops and varieties that have good regrowth characteristics will provide this advantage.

Straw and Chaff

Many cow/calf producers have recognized the potential for straw and chaff residues to help reduce winter feeding costs. Compared to hay, straw and chaff is inexpensive and is often available as a by-product of annual grain crop harvest, whether from the operation’s own land base or neighboring grain producers.

In most cases, straw has a lower energy content than grass hay and is low in digestible protein. Protein must be supplemented in a straw or chaff diet to maintain rumen microbial activity needed for fibre digestion. Diets low in protein lead to lower dry matter intakes, lower fibre digestion and possible impaction.

In general, oat straw is better quality than barley straw, which is superior to wheat straw. Year old straw tends to be more palatable than freshly baled straw. Pea and lentil straw have higher levels of protein and energy than cereal straws. Feeding limited amounts of hay will improve a straw-based ration. In all cases, a balanced ration will require the use of added feedstuffs (hay, grain, mineral, etc.) to supplement the straw and ensure that nutritional needs are being met.

Chaff is made up of glumes, hulls, unthreshed heads and pods, short straw, leaf material, and whole or cracked seeds from cereal, oilseed and pulse crops. Weed seeds are also a major component of chaff. Chaff can be dropped on top of the straw swath and baled, or it can be collected and blown into a chaff wagon using a chaff collector. Newer technology allows for a complete separation of grain and chaff using one machine. Chaff piles left in the field may be grazed or moved to a central feed pile and fed. Field feeding of chaff is inexpensive, efficient and effective. Chaff pile grazing is preferable to confined feeding due to reduced yardage costs. Farmers should be aware that mats of chaff will remain at the field feeding sites and these areas may suffer from both poor germination and weed infestation the following year if not managed properly.

Straw and chaff quality vary with type of crop, stage of maturity, weed content, method of harvest, combine settings, and crop and field variability. The feed value of chaff and straw can be improved through ammoniation or supplementation with protein to improve digestibility. Chaff and chaff/straw type roughages are only suitable for mature animals in good body condition and are best fed as part of a balanced ration to cows in early gestation (first or early second trimester).

Yellowfeed

Yellowfeed is produced when an annual cereal crop is sprayed with glyphosate and allowed to stand until dry. Once dry, it can be cut, baled and used as feed. Significantly lower losses from weathering is the main benefit of yellowfeed because it is left standing to dry, instead of laying the crop on the ground in windrows. Once the crop is dry, cutting and baling can occur in a single day. A haybine should not be used to cut yellowfeed as it may cause shattering of heads and leaves resulting in lower overall forage quality.

Recommendations include spraying the crop five days earlier than when it would normally be cut for greenfeed, as the plants will keep growing for a few days after spraying until the herbicide takes effect. In ideal conditions, a rate of 1.0 L/ac of glyphosate can be sprayed. In wetter weather, increased rates of 1.25-1.5 L/ac are recommended. Drying times range from 12 days under good drying conditions to up to 30 or more days in wet weather.

On average, a small increase in yield (10-15%) will occur after the glyphosate has been applied due to short term continued plant growth. In trials, the protein content of oat and barley yellowfeed crops declined slightly (0.9-3.3%) after spraying while the response of total digestible nutrients (TDN or energy content) was variable¹³. Producers using yellowfeed as a feed source report palatability equal to or greater than greenfeed.

A listing of glyphosate products registered for pre-harvest use on livestock forage can be accessed through each province’s Guide to Crop Protection publication.

Yellowfeed can also be a management system used in early seeded crops harvested for swathgrazing. Glyphosate will stop plant growth of the crop when desired following which the crop can stand for three weeks or more before swathing. This extended time period prior to swathing, allowing the crop to stand rather than lying in windrows, reduces its vulnerability to summer and fall rains and maintains its quality. This also takes advantage of the higher yield potential of an earlier seeded swathgrazing crop.

An additional benefit of spraying a crop with glyphosate for yellowfeed production includes control of perennial weeds. A disadvantage is the elimination of any potential fall regrowth for grazing use. 

Silage

Ensiling is an effective method of preserving feed with a minimum of nutrient loss. If ensiled properly the feed nutritive value is only slightly less than the standing forage crop. Typically, lower field losses occur through ensiling than when haying.

Silage Production

Preserving forage as silage depends on exclusion of oxygen from the forage mass and reduction of pH through bacterial fermentation¹⁴. Fermentation is controlled by the type of microorganisms that facilitate the fermentation process, the available substrate (water-soluble carbohydrates) for microbial growth, buffering capacity, and moisture content of the forage crop¹⁵. Lactic acid-producing bacteria utilize water-soluble carbohydrates in the chopped forage to produce lactic acid, the primary acid responsible for decreasing pH in silage. Plant proteins increase the buffering capacity of silage. The higher the buffering capacity of forage, the longer it takes to ensile, and more water-soluble carbohydrates are required. Lack of air (anaerobic conditions) prevents the growth of yeast and molds and a low pH prevents the growth of most bacteria after fermentation is complete. Silage can be kept for prolonged periods of time if these conditions are maintained. 

The ensiling process can be divided into four phases^{14, 16, 17}: 1) aerobic phase, 2) lag phase, 3) fermentation phase, and 4) stable phase (Figure 3). In the aerobic or pre-seal phase, plant cells and microbes metabolize sugars and starch in the presence of oxygen. Naturally occurring aerobic bacteria present on the forage surface quickly begin to degrade the ensiled forage and silage temperature is elevated. During the lag phase, plant cells are broken down providing a food source for bacteria to grow. As oxygen levels decline the active fermentation phase begins and lactic acid-producing bacteria proliferate. These bacteria make use of available plant carbohydrates to produce ethanol, acetic acid, lactic acid and CO₂. Acid production reduces pH, creating conditions whereby those bacteria that produce only lactic acid begin to dominate the fermentation process, lowering the pH of the silage to between 4.5 and 3.8. At these low pH values, providing exclusion of oxygen is maintained, growth of all microorganisms is inhibited. The pit or pile must be sealed at least 14 days to complete the ensiling process. Once the stable phase is reached, nutrient quality of the silage can be maintained almost indefinitely. However, upon feed-out, silage is once again exposed to oxygen allowing spoilage microorganisms to become active once again. For this reason, the largest losses in silage dry matter often occur during the feed-out phase¹⁸.