Oat forage is often sown in mixture with a legume such as vetch (Vicia spp.), pea or berseem (Trifolium alexandrinum) (Ross et al., 2004; Undersander, 2003; Hechmi, 1999; Johnston et al., 1999). Intercropping oats with legumes is effective for reducing diseases, suppressing weeds, capturing a greater share of available resources and improving the nutritive (protein) value of the crop compared to oats alone, though DM yields are not necessarily improved (Bagg et al., 2013; Erol, 2009; Undersander, 2003; Johnston et al., 1999). Oat-vetch associations are important in the Mediterranean Basin, though they have declined during the 2000s in the Maghreb due to the high cost and non-availability of vetch seeds, making a more complex crop management system necessary (Anil et al., 1998; Suttie et al., 2004).
Oat forage as sole crop
Oat forage sown as sole crop may be managed in different ways:
In grain production systems, early-planted and well-managed spring oat forage is a good rotation crop that provides feed to livestock and limits weed populations. Worldwide, most oat forage production comes from spring cultivars (Suttie et al., 2004).
In cold areas, winter oats should be sown in summer or late summer to become well established before winter and to provide good quality forage (Bagg et al., 2013). However, winter oats are not as winter hardy as wheat and their forage yield may be lower than that of other small grains (Ditsch et al., 2005). Oats are prone to rust when seeded in autumn. They may be a reservoir of rust for subsequent spring cereals (Malik et al., 2011).
In warmer areas, spring oats should be sown in autumn to avoid summer heat and drought (Suttie et al., 2004). In these regions, oats provide forage when the DM of warm season perennial forages is reduced (Stevens et al., 2004).
Oat forage yields are very variable, depending on year and location. Average DM yields range from 4 to 15 t/ha, but much higher yields have been obtained (Assefa, 2006). In Pakistan, yields up to 18 t DM/ha have been reported (Bakhsh et al., 2007; Hechmi, 1999). Stage of growth at cutting and environmental conditions play an important role in determining yield (Malik et al., 2011). Spring oats are the first forage that can benefit from high moisture and cool temperature during early spring, and they provide fodder as early as one month after sowing even in cool conditions (Mues, 2011). For best quality and good regrowth, oat crops should be cut or grazed lower than 12-15 cm in height (DAFF, 2012). Cutting or grazing can be repeated after a one-month rest (Reed, 2009).
Using oat forage prior to grain production is a valuable way of managing oats. This method may avoid crop lodging and decrease foliage fungal diseases (DAFF, 2012; Hennessy et al., 2009). If grazing or mowing stops before first node elongation in the growing period, oat grain production and quality are not hampered. Grain yield decreases beyond this point, or when the crop undergoes heavy grazing (DAFF, 2012). Winter oats sown during early spring provide higher DM yields than spring oats but will be ready for grazing later than spring oats (MAFRI, 2013). Oat forage sown during spring outyields barley DM production but has a lower nutritive value (Suttie et al., 2004). However, grazing oats in autumn provides a system whereby cows can substantially improve their body condition when perennial forages are of poorer quality and limited supply (McCartney et al., 2004).
Oats should not be grazed when the soil is very wet as the crown and root will be damaged and regrowth will be slow and reduced (DAFF, 2012). Light continuous grazing (2 cattle heads or 15 weaned lambs per ha) is recommended for optimal animal performance and good stand regrowth (DAFF, 2012; Hennessy et al., 2009). Oat pasture can be striped-grazed along a wide front. Use of a back fence can maximise regrowth (Reed, 2009).
Swath grazing of oat forage or oat/legume mixes is a way to increase the grazing season in northern areas and has been developed during the last decade. Oats intended for swath grazing must be sown in early summer and cut in early autumn, or sown in summer and best cut at the boot stage (when the head start to swell) for optimum nutritive value, or, for maximum yield, when the grain contains 35% moisture (MAFRI, 2013). When oat forage is sown late, care should be taken to prevent diseases, such as rust, by using resistant cultivars or by appropriate fungicidal treatment (Scott, 2006). Oat forage can then be grazed through the autumn and winter, even under 0.5 m snow. Oat forage quality within the swath is preserved until the end of April. A mixture of oats and peas had a similar nutritive value to oats alone (Aasen et al., 2004). Swath grazing of oats in winter is one of the management systems that can lower the cost of wintering cows by up to 50% because it requires less work and less equipment than making silage or hay (Hutton et al., 2004).
Cut-and-carry systems are much used by smallholder farmers in developing countries. Cut-and-carry oat forage has several advantages: there is less waste than in grazed pastures, cutting height is properly managed and subsequent regrowth is favoured (Suttie et al., 2004).
When oat forage is intended for hay, the level of N fertilizer should not be too high as excess N increases stem fibre levels (ADF and NDF) and decreases water soluble carbohydrates. Cutting at the milky dough stage is the best compromise between high yield and high quality (Malik et al., 2011). After multiple cuts, the leaf:stem ratio decreases and the stems increase in thickness. A high sowing rate (up to 80 kg/ha) will improve the quality of hay by helping to reduce the thickness of stems (DAFF, 2012).
Oats are one of the main cereal forages used for silage in Northern America. In European countries, oat forage is mostly used for silage and haylage (Suttie et al., 2004). Oat yields more silage or green forage per ha than any other cereal crop, especially when fertilized with nitrogen (Hartman, 2000; Mahli et al., 1987 cited by Fraser et al., 2004). Oats can provide one of the best low-cost emergency forages (balage) after drought if timely rainfall is received for germination and growth (Bagg, 2012).
Oat forage intended for silage can be harvested at boot, milky dough or soft dough stage. When cut at boot stage, oat silage has a low DM, high palatability, high energy and high protein content. Wilting is necessary to reduce moisture and to prevent sewage during ensiling. When cut at the dough stage, oat silage has more DM and a higher energy value, but a lower protein content and palatability (Mickan, 2006). The choice of harvesting stage should be guided by animal requirements: boot stage when high nutritive value is required, such as for lactating dairy cows, and soft dough stage when forage quantity is required, for example in late pregnancy (Barnhart, 2011). Whether to cut oats at the milky dough stage or soft dough stage is much debated and depends on local conditions and requirements.
When silage is made at the dough stage, water soluble carbohydrates are lower and fermentation does not start easily. Because the thickness and hollowness of oat stems impedes the compressing necessary for anaerobic conditions, it is recommended to chop oat forage to a length of 10-20 mm (Suttie et al., 2004). Urea, enzymes and inoculants have been shown to improve aerobic stability, the fall in pH and lactic acid production in oat silage, which improve feed intake and milk production (Meeske et al., 2002).
Oat straw can be offered as sole roughage during winter provided it is adequately supplemented (Hamilton, 2010) (see also the Straws datasheet).