Chapter XI - FODDER OATS IN EUROPE

Atanas Kirilov

SUMMARY

In Europe, the same varieties of oats as are used for grain are usually used for fodder. They are the preferred companion crop for peas and vetch because of their coarse stems. Oats are most important in cold, northern countries. Areas are decreasing since maize and barley provide more of the higher energy feed required for intensive livestock production, and fully mechanized silage has largely replaced hay. Oats retain their importance as winter fodder in Mediterranean climates, where they may first be grazed and then grown on for grain. Oats have adequate soluble carbohydrates to make good silage, but are difficult to consolidate to provide good anaerobic conditions for ensiling.

Introduction

This chapter presents a review of the current and prospective importance in Europe of oats used as whole-crop forage.

Oats (Figure 11.1), like rye, came into cultivation later than wheat and barley. The cultivated species are descended from the wild forms that were probably found as a weed in cultivated cereals in the Mediterranean region, Asia Minor, North Africa and Transcaucasia. Oats are an annual cereal, widely grown for grain (Figure 11.2), which is mainly used as food for livestock, and to a lesser extent for humans. Whole-crop oats are a good source of forage and many farmers use it as hay, silage or pasture for cattle and sheep. Oats grew to importance because of their suitability for feeding horses, and were the preferred grain feed for the horses that were the main means of work and transport in time of peace and war.

The fact that the nutritive value of a kilogram of medium-quality oats was chosen in 1922 in the former Soviet Union as a Feed Unit, called also Russian Feed Units, and the use of Oats Feed Unit (1 425 kcal) as reference value for Kellner’s system in Germany, also speaks for the popularity of oats as feed grain. Later, the Oats Feed Unit was introduced into Bulgaria, Yugoslavia and some other countries. In a similar way, barley was accepted as a Feed Unit (1 730 kcal) for reference to estimate the energy nutritive value of food for ruminants in countries such as France, Belgium and the Netherlands.

The oat grain is a good source of protein, starch, fats and vitamins (B1, B2). It is used as flakes, flour and meal for human consumption, and as a coffee substitute, but it is fairly low in gluten, so it is not suitable for making bread, but is made into oat-cakes. It is present at breakfast as cereal porridge and in special varieties of bread. There has been an increase in oats used for human food. Human consumption of oats is important in some countries, such as the United Kingdom (41 percent of total production in 1993-94 (Valentine, 1995) and 49 percent in 2000 (Valentine and Mattsson, 2000)) and Germany. The grain is also good for people with stomach problems and for reducing blood cholesterol.

Figure 11.1
Oats (Avena sativa L.)

Oat grain is very good dietetic food for young ruminants because of its high hull and fibre content. It is recommended that a small quantity be fed during the suckling period to habituate young ruminants to consumption of forages and to develop their rumen. The presence of a larger quantity of cellulose in the grain coat dilutes the nutritive energy value of oats compared with barley, for instance. Oat grain can be used in a quantity of 4 to 8 kg in the daily ration of horses, up to a third of ruminant rations, but should not exceed 15-20 percent in the feed of pigs and poultry.

Fodder oats are grown for whole-plant use for grazing, green forage, silage or hay, as well as for grain. They are often used in mixture with legumes for forage production. The straw is important bedding for livestock, as well as good roughage. The growing of whole-crop oats gives livestock farmers the opportunity to have additional forage resources in dry summer weather, when yield from conventional forage crops is restricted.

Characteristics

There are many species of Avena (about 70), but only a few are of economic and practical importance. All are annuals and belong to one of three groups according to their chromosome number (Maksimovich, 1998):

• Diploid 2n = 14 chromosomes (Avena strigosa; Avena strigosa brevis; Avena clauda; Avena longiglumis),

• Tetraploid 2n = 28 chromosomes (Avena strigosa weistii; Avena barbata) and

• Hexaploid 2n = 42 chromosomes (Avena sterilis; Avena byzantina; Avena fatua; Avena sativa).

Avena sativa L. has the widest distribution as a crop in Europe (about 90 percent of all oat production), with A. byzantina occupying most of the balance (ca 10 percent). Small oat (A. strigosa Schreb.) and naked oat (A. nuda Hojer) are also found.

Oat development as a crop is similar to that of wheat and barley. There are spring and winter forms growing in areas with mild winters, such as UK, Portugal and the Mediterranean region. In contrast to wheat and barley, oats are less frost resist ant and die at temperatures below minus 14°C. When assessing suitable cereal components for the winter pea variety Pleven 10, it was found that when the minimum winter temperatures reached -18- -20°C, only 64 percent of the overwintering oat plants (A. sativa) survived, compared with 100 percent for rye, 75 percent for triticale and 65 percent for barley (Sachanski and Kirilov, 1988). High temperatures also exert an unfavourable influence on oats, particularly during flowering: at 35-38°C, it is less hardy than wheat.

Figure 11.2
Oats being grown for grain

The water needs of A. sativa are greater than those of barley and wheat. For seedling emergence, oats require more moisture than barley. In order to germinate, the oat grain must take in 65 percent of its weight in moisture, while barley emergence occurs at 50 percent. The greater requirement of oats for moisture explains why the crop finds optimum conditions in the moderate and humid climate of Europe and in regions of higher rainfall. The moisture needs of A. byzantina are lower and it is better adapted to the drier, hot climate of the Mediterranean and North Africa.

In contrast to the other closely-sown cereals, oats has a better-developed root system that penetrates to greater depth and uses soil moisture and nutrients better, so while not a good pioneer crop on poorer soils, it is good in the crop rotation. In some cases, oats are used as a nurse crop for sward establishment. There is a positive relation between the degree of root system development and above-ground biomass. The roots show a great assimilative ability with regard to soil nutrients. Oats are adapted to a wide range of soils and can grow on light, medium and heavy soils, and can thrive in neutral as well as acid and basic soils.

The most popular oat type in Europe is A. sativa, bred and grown mainly for grain, and the same cultivars are used for grain as for forage. In Europe, few institutes and companies are engaged in oat breeding, and in particular of fodder oats. The reason is the limited demand and distribution of oats for forage, which also includes low return on the funds put in. In UK, oats are included in breeding programmes, and growing oats for human consumption is important. At the Institute of Grassland and Environmental Research (IGER), Aberystwyth, Wales, UK, oat cultivars are developed for human consumption and for feeding to ruminants as well as for monogastrics (Cowan and Valentine, 2001). For ruminant feeds, breeding projects are directed to the development of thin-husked oats, with high digestibility. The best criteria for selecting cereal cultivars for whole-crop silage are, therefore, to select those with a high yield, good diseases resistance and good resistance to lodging (Ingram, 1990).

Figure 11.3
Oats growing in mixture with peas

Oats are preferred companion crops in mixed stands with peas and vetch because of their strong stems. The sowing of oats in a mixture with peas (Figure 11.3) or vetch has a dual effect: the presence of oats minimizes the lodging of peas and vetch, so decreasing harvesting losses and increasing yield, and the overall nutritive value of the forage obtained is improved compared with pure stands of either constituent (Sachanski and Kirilov, 1988). As a companion crop, oats are suitable for peas and vetch since their maturity coincides. Oats can be established as both spring and winter mixtures with peas or vetch. A major disadvantage is the difficulty of choice of herbicides for weed control, but this disadvantage decreases with the earlier harvesting of the mixed stands for forage. Due to their lower winter hardiness, oats are not suitable for winter mixtures with leguminous crops in countries with cold winters.

TABLE 11.1
Oat production in Europe

Distribution

Oats ranks sixth or seventh by area and importance in the world after wheat, maize, rice, barley and sorghum. In some countries, such as Finland, it ranks second, and in Bulgaria it ranks fifth. Oats are mainly grown for grain, but can also be used as a whole crop for green forage or silage. Europe is the place where oats is grown on the greatest area; North America ranks second and Africa last. In Europe, most oats are grown in the Russian Federation, Poland, Ukraine, Finland and Spain (Table 11.1).

During the last decades the areas sown with oats has decreased steadily, in the world and in Europe. For example, during 1934-1938, the area sown with oats averaged 58 100 000 ha, in 1967, there were 31 679 000 ha and 25 583 000 ha in 1986 (Maksimovich, 1998). In this period, in some regions, such as Sardinia in Italy, the area increased during 1940-70 because of an increasing dairy sheep flock. Steep slopes were cleared of scrub or native pasture to sow annual forages, including oats, but this increased the problem of soil erosion (Porqueddu, Sassari, Italy, pers. comm.).

Currently there is still a tendency for the oat-sown area to decrease. From 1990 to 2000, in only ten years, the area in the world occupied by oats decreased from 20 600 000 ha to 12 700 000 ha, i.e. by about 40 percent. However, as a result of the increase in average yield during the same period, the decrease in grain production was only 27 percent (FAO, 2002). The worldwide tendency for oat areas to decrease at the expense of other forages, particularly maize for silage (Poole, 1990), is also apparent in Europe (Table 11.1) (FAO, 2002).

There are several reasons for the fall in oat area in the world and Europe:

• The number of work horses has dropped sharply, along with the need for oats for feed.

• In human nutrition, oats are of less interest than wheat or rice.

• Contemporary livestock rearing is characterized by highly productive, high-yielding animals that need forage with high concentrations of energy and protein.

• New cultivars of maize and barley have been developed that have a higher nutritive value and can be grown in the areas occupied traditionally by oats.

• In energy yield per unit area, oats are inferior to maize for silage, and a feed unit from whole-crop oats is often more expensive than that from maize silage.

• Ensiling - a completely mechanized, easy method for conserving green forages - has replaced in great part the haymaking formerly important for animal feed in winter. Maize became the most widespread silage crop due to its indisputable qualities: high yield, high-energy concentration in DM, high content of water-soluble carbohydrates and ease of ensilage.

• The area occupied by silage maize increased considerably during the last thirty years and, together with pastures based on ryegrass, they became the main forages for ruminants, particularly dairy cattle in contemporary intensive stock raising in Europe.

Against the background of the situation described above, there are no exact data on the areas sown to oats intended for use as whole-crop forage. Many farmers produce and use their own oat seed, in particular for mixtures with legumes. An additional difficulty for accurate statistics is that in official statistics oats are classified as a grain, alongside wheat, barley and other cereals.

In the Czech Republic, 10 percent of oats are grown for forage, mainly as a nurse crop for clover and legume+grass mixtures for silage (A. Kohoutek, Prague, pers. comm.). The same use of oats for whole-crop silage is found in Slovakia (M. Polak, Grassland and Mountain Agricultural Institute, Slovakia, pers. comm.). In Greece, the share of oats used for hay or grazing is considerable, and the production obtained represents a considerable proportion of forage (Table 11.2)

TABLE 11.2
Use of fodder oats in Greece (data for 1992).

Source: National Statistical Se rvice of Gre e ce, 1995.

Oats are grown in Greece, especially in western Greece, which receives higher annual precipitation than the rest of the country (Papanastasis, Aristotle University of Thessaloniki, pers. comm.). In Greece, two species of Avena are cultivated: A. sativa and A. byzantina. In recent years, there has been growing interest in using oats in extensive farming systems. In Portugal and Spain, some oats are grazed in winter and thereafter are harvested for grain or hay. This reflects the emergence of new cultivars that have a great capacity to produce biomass at the beginning of the cycle and an excellent re-growth capacity after grazing. In the most intensive systems, as in dairying regions, oats have become a ryegrass substitute and are used as a second crop to grain. Oats are sown in autumn, harvested for silage in May, then the land is used once again for maize grain or silage. An increase in the oat area is expected (M.T.P. Dentinho and O.C. Moreira, Estação Zootécnica Nacional, Fonte Boa, Portugal, pers. comm.).

In Mediterranean regions where forage systems are mainly based on natural and sown pastures, a small portion of the animal feed is sometimes provided by annual forages. These are usually mixtures of cereals (barley and oats) and annual legumes (vetch, and crimson and berseem clovers) (Porqueddu and Sulas, 1998).

In other countries, such as Germany (Spatz, pers. comm.) and Slovenia (B. Kramberger, University of Maribor, pers. comm.), the use of fodder oats is symbolic. Because of their low nutritive value, oats are not a crop of choice for silage in Denmark (Søegaard, pers. comm.), but are used in mixtures with peas in feeding dairy cows in Sweden (Rondahl and Martinsson, 2003). In Estonia, oats are not used for grazing, green forage (zero grazing) or haymaking, but are occasionally used for silage (Selge, pers. comm.). In Latvia, oats are used mainly as a nurse crop when establishing meadows and pastures, and for green mass when grown in mixtures with peas and vetch, and for grain production in pure stands (A. Adamovich, Latvia University of Agriculture, pers. comm.). In Latvia, oats are very rarely used as silage or hay.

In some regions of the Russian Federation, mixtures of oats and peas, vetch or rape are used in rotation with other forages, such as rye for zero grazing, maize for silage or barley as a catch crop, to obtain 2-3 additional forage harvests per year (Novoselov, Rudoman and Lobanov, 1988; Kuvshinova, Arharova and Rozanskaja, 1987). Forage systems like this make for better use of machinery, better use of soil moisture and nutrients, and protect arable land from water and wind erosion.

Potential of oats as forage

The dry mass yield and nutritive value of forages are a determining factor for the farmer when choosing forages. These characteristics depend on the species and composition of forages, climatic and soil conditions, the suitability for intensive growing, mode of use and many other factors. The lower nutritive value of oats compared with silage maize, wheat or barley has often been strongly emphasized as a cause for the decrease in the area and interest in oats as feed and forage. The nutritive value of oats almost equals that of triticale and rye, in terms of the net energy content per kilogram of dry matter at the same developmental stage (milk stage). However, it is about 70 percent of that of maize, 80-85 percent of that of barley and 90 percent of that of wheat.

Nutritive value

The nutritive value or feeding value of forages is a generalized concept that could be considered as a combination of chemical composition, digestibility and intake (the dry matter quantity from a given forage that can be ingested by the animals when fed ad libitum).

Feeding value = chemical composition
+ digestibility + intake

Many other forage characteristics are of direct or indirect importance to the nutritive value: the species, plant morphological composition, the physical form in which the forage is offered to animal, whether the forage is offered fresh or after preservation as silage or hay, the quality of silage affecting intake and digestibility, forage pollution with soil, the proportion of inedible plants and weeds, etc.

When studying the changes in the composition and nutritive value between flowering and grain ripening of wholeplant oats, wheat and barley, Demarquilly (1970) found that the dry matter content increased from 15-20 percent during flowering to 35-40 percent at the dough stage. During the growing season, the crude protein (CP = N × 6.25) and crude fibre (CF) content decreased, whereas the amount of starch increased. During this period, according to the same author, the crude protein content of oats decreased from 10 to 7 percent of dry matter (from 12 to 9 percent in wheat and barley) and crude fibre fell from 33 to 27-28 percent. Similar data for CP and CF content are also given in the French tables of forage composition and nutritive value of forages for ruminants (INRA, 1988) and in Bulgarian tables (Table 11.3). These values are lower than those determined by the author in Bulgaria, and shown in Table 11.4. CP content decreases during the whole growing season of oats and that of crude fibre increases until the beginning of grain formation, and then decreases slightly.

This outcome for cereals reflects a natural situation where the grain’s development and the increase of its proportion in the total plant mass compensates for the fibre increase in the stems, so the fibre content decreases in the whole plant. The crude protein content of the grain due to presence of the glumes is low and does not lead to significant changes in the CP content of the whole plant. Staples (1989) reported data similar to this author’s results for the CP content in oats, which were 20.5 percent CP at the boot stage, 14.6 percent at the milk and 11.9 percent at the dough stage. It is impressive that, in the more recent studies, the protein content in the whole plant is higher than that indicated in the studies of Demarquilly (1970) or in the tables for forage nutritive value by INRA (1988) or Todorov (1995), probably due to use of newer cultivars and better agricultural practices.

The content of water-soluble carbohydrate (WSC), which has a direct relation with successful ensiling of oats, increases until the milk stage and then falls, as for most cereal crops. That decrease is related to conversion of WSC into grain starch and b-glucanes, and the low WSC content in the whole plant militates against successful silage fermentation. According to Demarquilly (1970), the content of WSC is 9.7 percent until the beginning of grain formation and decrease to 3.3 percent by the beginning of the dough stage. During this time, the starch content increases from 0.6 percent to 16.3 percent.

TABLE 11.3
Composition of oats

Key: NDF = Neutral detergent fibre. ME = Metabolizable energy
Source: Todorov, 1995.

TABLE 11.4
Changes in chemical composition during the growing season of oats

Key: DM = dry matter. CP = Crude protein. CF = Crude fibre. NDF = Neutral detergent fibre. DMD = Digestibility of dry matter in pepsin-cellulase.

Digestibility

Many studies on oat nutritive value, as well as of other whole-crop cereals, were carried out in the 1960s (Nehring and Beyer, 1965, 1966; Demarquilly, 1970). It is difficult to find newer data on oats forage for ruminants, because interest has dwindled: the low nutritive value and low yield of oats renders it a less attractive forage crop than maize or ryegrass, so interest in it on the part of farmers and researchers decreases constantly. Due to the higher proportion of grain in the total mass, wheat and barley have a higher digestibility than oats. Their dry matter digestibility remains relatively constant, at about 60 percent, from mid-June until harvest. In contrast, oat digestibility decreases during the same period, from a level similar to that of barley, about 60 percent, down to 50-55 percent (Ingram, 1990).

According to Bulgarian studies, oat digestibility decreases continuously during the period from early vegetation to the milk stage, but increases slightly in early full ripeness (Table 11.4). This increase late in the growing season is probably due to the increased proportion of grain in the total mass. During that period, the stem: leaf: grain ratio was 39: 35: 26. The increasing proportion of the grain, the digestibility of which is high and constant, compensated for the decreased digestibility of the other parts of plant, in particular the stems (Demarquilly, 1970). According to the data of Bozinova and Hristozov (1979), dried oats had the highest digestibility at milk stage and lowest at dough stage. They also mentioned that the digestibility of spring oats is higher than that of winter oats at the same maturity stage.

Intake

Intake is a relatively new parameter, which has been included recently in the system of estimation of nutritive value of forages, so it is difficult to find much data on oats. According to Demarquilly (1970), dry matter intake measured as DM ingested per kilogram of metabolic weight for wethers, decreases rapidly down to 45 g kg^-1 W0.75 at the start of grain formation. Thereafter there is a slight increase until the dough stage. More complete data on the intake of oats as whole-crop may be found in the tables of INRA (1988), France. According to them, oat intake is highest at the start of booting (80 g DM kg^-1 W^0.75), decreases until flowering (47 g DM kg^-1 W0.75) and then slightly increases as the grain fills and is greater in proportion. Oat intake is similar to that of wheat and barley, but higher than that of rye and triticale.

Yield

The yield of oats increases and reaches a maximum under Bulgarian conditions in the second half of June and until the early dough stage. According to studies carried out in France (Demarquilly, 1970), dry matter yield per unit area quickly increases up to the milk stage and then more slowly from milk to dough stage, when it reaches a maximum value of 10.6 t ha^-1. Postiglione and Basso (1986), in a hilly area of southern Italy, obtained a higher yield from barley grown as a pure crop (7.7-8.9 t DM ha^-1) than from an oat+vetch mixture.

In Spain, it has been widely recommended to introduce mixtures of annual with cereals, with the aim of increasing animal production. Under the conditions of central Spain, the yield of a mixture of oat+Vicia sativa under rainfed conditions was 6.7-6.4 t DM ha^-1 and oat+Vicia villosa yielded 6.3-7.5 t DM ha^-1 (Caballero and Goicoechea, 1986). In Portugal, oats grown in pure stand or in mixture with vetch gave higher yields compared with triticale (Trindade and Moreira, 1987).

Kertikov (2000) reported that the highest yield of dry matter and protein was obtained from a mixture of vetch and oats at 3: 1 ratio and fertilizing with N: P:K at 90:50:40 kg ha^-1. The yield was 9 to 13 t DM ha^-1 depending on the fertilizer rates, of which oat contributed 6- 7 t DM ha^-1. The same author (Kertikov, 1999) announced a 15-21 percent higher grain yield from spring peas when using oats as a supporting crop to reduce both pea lodging and harvesting losses.

According to Tetlow (1992), dry matter yields of winter cultivars of oats between the end of May and the end of July reached a maximum of approximately 12 t DM ha^-1 at the end of July, at a mean DM content of 43 percent. Spring varieties, harvested from mid-June to mid-August, had maximum yield of 10-12 t DM ha^-1, at a mean DM of 44 percent. The same author drew attention to the newer cultivars of oats, which gave maximum yields of about 15 t DM ha^-1 in mid-June when grown on plots.

In some regions of the Russian Federation, such as the Non-chernozem zone or West Siberia, where soil and climatic conditions are not so suitable as elsewhere in Europe (sum of positive temperatures during the growing season is 2236°C days with average precipitation of 235 mm, while total annual precipitation is 414 mm), the yield of mixtures of oats with peas or vetch is higher than from pure stands, but far below the averages for Europe (Kuvshinova, Arharova and Rozanskaja, 1987; Novoselov, Rudoman and Lobanov, 1988; Dverina, 1989).

Regarding oat yield in Europe, there is a trend to increase from the south to north, which is related to the more favourable climate and rainfall during the oat growing season. On the basis of the changes in oat composition, digestibility, intake and yield during the growing season, earlier cutting and harvesting decrease the yield, but increase the quality of forage, both digestibility and intake, and improve the possibility for making a higher quality silage.

Use of whole-crop oats

Oats is a suitable forage crop for grazing, silage or making hay, and is often used as an additional forage to ensure the forage quantity for the farm, as well as other annual cereals (wheat, barley or rye).

Grazing

Oats can be grazed when the plants are young and reach a height of 20-25 cm. During this period it has a high crude protein content, low cell wall fibre level and high digestibility. The inconvenience is that oats do not stand trampling, and grazing should be light, controlled and rationed using electric fencing. If lightly grazed, oats recover and a second grazing or harvest of hay, silage or grain can be produced. Oats are grazed in some Mediterranean countries with unfavourable conditions, dry climate and insufficient rainfall for development of grasslands, but a mild winter. Greece is a country with typical Mediterranean climate and insufficient rainfall in summer, and oat grazing is a good alternative. Oats are an additional source for grazing, as well as for hay (Table 11.2). Light grazing is done in other countries with a mild winter, such as Portugal and Spain. On areas sown in October-November, the grazing is in January-February and then they are harvested for grain, hay or silage.

Silage

Whole-crop oats is most often used as silage or haylage for feeding ruminants in central and north European countries. In UK, the annual quantity of silage from wheat, barley and oats is estimated to be about 200 000 t of dry matter (Wilkins and Kirilov, 2003). Successful ensiling depends on the quantity of fermentable water-soluble carbohydrates (WSC) and the DM content. Good WSC content, in particular before grain formation, allows the making of good silage from oats, especially in combination with preliminary wilting. In the literature, there are often descriptions of mediocre oat silages, made at the dough stage, when the aerobic stability is lower. At the dough stage, when the yield is close to maximum, the WSC content is lower, but in combination with higher DM content it ensures good silage fermentation. Oat stems are hard and hollow, which impedes compressing of the mass and the creation of anaerobic conditions for successful ensiling. The hollow stems and high residual WSC create additional problems after opening silos, because air enters more deeply, provoking secondary fermentation and causing degradation of residual WSC and lactic acid.

In a comprehensive study on the use of whole-crop cereals, including oats, in the UK, Weller (1992) found that harvesting for silage was between the cheesy dough and hard dough stages, and the crops were mown at between 7.5 and 15 cm above soil level.

Le Gall and Pflimlin (1997) noted that, taking account of ensiling losses, harvesting costs and the low energy value of silage from whole-crop cereals in France, the price of a kilogram of silage dry matter was equivalent to the price of a kilogram of cereal grain, which had 40 percent higher energy value. So ensiling wholecrop cereals is not so attractive, even in years of forage deficiency.

Through mowing higher, the energy value of oat silage can be increased at the expense of yield. Increasing mowing height from 10 cm above the ground to 15 cm below the ears, Demarquilly, Paquiet and Andrieu (1969) achieved an increase in digestibility of 10 percentage points. The negative effect on yield can be decreased if grazing follows harvesting for silage. Increase in nutritive value may be achieved by earlier harvesting for silage. Earlier mowing decreases dry matter yield, but increases quality and intake of forage and clears the land for the next crop.

When determining the optimum time of harvest and ensiling of oats or other whole-crop cereals, there is a compromise between high yield, which increases until hard dough stage, and obtaining silage of higher nutritive value, which decreases continuously during the growing season. In cereal silage made at the hard dough stage, the grain is hard and part passes almost intact through the cattle’s gut. Part of the energy is lost and silage making from cereals at the late stage is not recommended, in particular if destined for cattle.

Harvesting oats and other cereals at the milk to soft dough stage is recommended (Staples, 1989; Bozinova and Hristozov, 1979); the yield is lower, but nutrient concentration in dry matter is higher. At a low dry matter content level, as occurs frequently in some regions of the Russian Federation, wilting the mass before chopping is recommended. The aim is to increase the dry matter content up to 35 percent to improve fermentation, to avoid juice out-flow and nutrient loss. Undesirable butyric acid bacteria develop poorly at moisture contents below 70 percent and their development ceases below 65 percent.

The length of chopping is an important factor for the success of ensiling. A theoretical chop length of 10-20 mm is considered optimal (Bozinova and Hristozov, 1979). Finely chopped silage is ingested in greater quantity than long. Fine chopping can be done after opening the silo, just before feeding the silage to the animals. In trials, supplementary chopping of silage from a pea-cereal mixture increased the proportion of particles below 20 mm from 22 percent to 67-68 percent, and the dry matter intake for wethers increased by 75 percent compared with the same silage, but long chopped (Kirilov and Sachanski, 1989). The positive effect of the fine chopping of silage on the intake is greater for sheep than for cattle.

Fine chopping facilitates silage packing and mechanized distribution, improves fermentation processes and intake by the animal. The finely chopped mass is easier to pack in the silo and that is important since the hollow stems of oats retain residual air in the silage, which leads to additional WSC loss. When silage is not well packed, on opening the silo air penetrates deeper into the silage and it is necessary to take a greater quantity of silage every day to refresh the open surface. Poorly packed silage has low stability when exposed to air.

Urea, enzymes and inoculants are used to improve silage from good quality whole-crop cereals. Urea increases the nitrogen content and exerts no substantial influence on fermentation. Silage with urea has good aerobic stability. Enzymes added to the silage degrade hemicellulose, cellulose and starch into WSC, which becomes accessible to micro-organisms and facilitate the fermentation processes. Inoculant adds strains of lactic acid bacteria to direct fermentation and use WSC in priority production of lactic acid and quick decrease in silage pH. Sometimes this is related to addition of molasses and other carbohydrate additives. The inoculant treatment of oat silage increases dry matter intake and milk production of dairy cows (Meeske et al., 2000).

Hay

Oats are occasionally used for haymaking in countries with suitable conditions of enough sun and warmth during the haymaking period. Oats are cut for hay before full grain formation in order to avoid grain loss during manipulation, tedding and baling. Up to that stage, oats have better digestibility and nutritive value than later. Mowing machines with crimping rollers to permit faster moisture release are used for faster drying and to decrease the time the mown crop is in the field, thus reducing the risk of rain and wetting and consequent quality loss. Swath tedding contributes to even drying and decreases the time necessary for drying. Oats are also suitable for hand cutting with a scythe and for manual haymaking.

In Bulgaria, some cooperatives and private farmers grow oats as a pure stand or in mixture with vetch and peas and make hay for household livestock. Households pay for this service to cooperatives and keep the hay for the winter (Figures 11.4a and b). This practice is convenient for the small-scale stockholder "farmers" having one or two cows and 5-6 sheep or goats.

Straw

Oat straw and chaff are softer and finer than the straw of the other white-straw cereals and have a higher nutritive value (Table 11.5). It is a favourite by-product for feeding ruminants or for bedding. In Bulgaria, oat straw and other cereal byproducts are very often used as forage in winter domestically (Figure 11.6).

Conclusion and prospects

Oats as grain and whole-crop have a lower nutritive value than maize and some cereals, and cannot meet the energy requirements of high-yielding animals. This is one of the main causes for the decrease in oat areas on a global scale.

Figure 11.4a
Bales of oat hay

Figure 11.4b
Close-up view of baled oat hay

Figure 11.5
Oat hay stacked for winter feed

TABLE 11.5
Composition and nutritive value of straw

Key: CP = crude protein. CF = crude fibre. NDF = Neutral detergent fibre. ME = Metabolizable energy.
Source: Todorov, 1995.

However, the high content of watersoluble carbohydrate in the whole plant means oats make good silage and can thus supplement the forage needs of the farm. Grazing or harvesting at an earlier stage can compensate for the low energy concentration and low nutritive value of oats. At that stage, the protein content is high and fibre is low, so the nutritive value is high. The use of oats for forage is a sign of extensive farming and forage production, but is a good alternative for many farmers in Europe.

Although the oat area is decreasing, it seems that the interest in it as an alternative forage will remain. In unfavourable years, forage oats, with their longer growing season, provide farmers with the possibility of obtaining forage by harvesting areas destined for grain.

Figure 11.6
Forages stored for the winter in Bulgaria (lucerne hay, oat straw, maize stover and pumpkins)

In the dry Mediterranean zone, where extensive pastoral systems with sheep, goats and cattle predominate, oats will continue to have a role as a substitute for ryegrass for grazing and for hay. In this region, there is a trend for the area sown to forage oats to remain stable, or even to expand.

Against the background of global warming and potential drought in southeastern Europe, many farmers and small stockholders will rely on oats in pure stand or in a mixture with peas or vetch for silage and hay, using the winter-spring soil moisture. In other regions of Europe, the use of oats as a nurse crop at sward establishment will persist.

In parts of the Russian Federation, oats will remain the preferred cereal companion crop in mixtures with legumes for production of protein for ruminants. Earlier harvesting of cereals for silage or hay makes possible double cropping of the land, which gives additional forage and has also a positive ecological effect, as the land remains covered with vegetation for longer during the year.

The prognoses for use of whole-crop oats as forage in countries with intensive livestock farming and forage cropping zones are not optimistic. Intensive forage production in the countries of northwestern Europe is based on silage maize and grassland, dominated by ryegrass, for which the soil and climatic conditions are favourable. In these countries, there is no trend to increased forage oat area, except on organic farms in crop rotations giving a "health crop rotation" for both diseases and weeds. Sometimes in circumstances when a low yield is expected, oats grown for grain might be profitably harvested as silage or hay. In all other cases, wholecrop oats remain a good alternative to additional forage production.