Joanna Fraser and Duane McCartney
SUMMARY
Oats (Avena sativa L.) are grown on over 1.8 million hectares in Canada and 800 000 ha in the United States of America, for human consumption as well as fodder. Oats are sometimes grazed, but the main use is for hay and silage, fulfilling an important role as feed for livestock operations in the Northern Great Plains of North America. Oats can be intercropped for silage and autumn grazing, and used as fodder for swath grazing. In winter oat growing areas, oats are integrated into pasture-silage systems. Cultivar selection is important: oat breeders, agronomists and livestock nutritionists need to work together closely to evaluate selection criteria for forage oats. With proper cultivar selection and management, there should be increased interest in oats for fodder where the economics warrant it.
In Canada, oat (Avena sativa L.) is grown as livestock feed in the form of grain, silage, hay and pasture; the food industry in North America uses approximately 110 million bushels of oats, about 90 percent being grown in Canada. (Quaker Oats Company, pers. comm., 2004). The racehorse industry uses about 80-85 million bushels of oat for feed and 90 percent originates from Canada. Oats for grain and forage or fodder are grown on over 1.8 million hectares in Canada (Statistics Canada, 2001) and 800 000 ha in the United States of America (USA) (USDA, 2003). In Canada, oats are among the top five crops in terms of area grown in British Columbia, Manitoba and New Brunswick (Statistics Canada, 2001). Manitoba and Saskatchewan in central Canada have the largest area sown to oats, with 40 percent being grown for human consumption (Dr B. Rossnagel, University of Saskatchewan, pers. comm., 2004). Over 40 percent of farm cash receipts came from oats in Manitoba, followed by Saskatchewan at 33.9 percent (Manitoba Agriculture, Food and Rural Initiatives, 2003). In Manitoba, the area sown to oats increased by about 10 percent between 1999 (810 000 ha) and 2002 (1.1 million hectares). Alberta has the most oats grown for feeding livestock (Hartman, 2001). In the USA, North and South Dakota, Minnesota, Iowa and Wisconsin have the greatest areas harvested for oats. North Dakota markets most of its oats outside the state, while in Wisconsin, growers retain most for on-farm feed. Oat areas are declining in the USA, with a corresponding increase in Canada. This trend was expected to continue (Lawrie, 1999) because of the reduced use of the grain for feed, and failure of yields to keep pace with increases in maize (Zea mays L.) and soybean (Glycine max (L.) Merr.) yields (Marshall, McDaniel and Cregger, 1992). USA imports over 70 percent of its oats from Canada (Lawrie, 1999), as feed for racehorses and for milling, cereal and pet food (Manitoba Agriculture, Food and Rural Initiatives, 2003).
In the USA, oat is the most popular cool season forage in the Northern Great Plains, i.e. North Dakota, South Dakota, Minnesota and Montana (Poland, Carr and Tisor, 2002). Oats, especially for feed, are normally used close to where produced, due to their bulk density, caused by the large hull, which is approximately 250 to 330 g kg-1 of kernel weight. Oat grain has an average protein content of 11.5 percent compared with 12.5-13 percent for barley (Hordeum vulgare L.) (Cowbytes, 2004). Oat hulls, a by-product of milling, is a feed commodity that contains hulls and fragments of the endosperm and constitutes up to 25 percent of the total weight of the grain (Thompson et al., 2000). In Canada, the oat hull has a high fibre content, with neutral detergent fibre (NDF) averaging 853 g kg-1 and acid detergent fibre (ADF) averaging 464 g kg-1 dry matter (DM) (Thompson et al., 2000). There is a large market for oat hulls as a source of fibre for feeding cattle, sheep and horses (Beauchemin, Farr and Rode, 1991; Schrickel, Burrows and Ingemansen, 1992). However, their nutritive value is similar to that of a low quality forage. Treating this by-products with anhydrous ammonia at 3 percent dry weight basis increased voluntary intake by growing steers and improved potential degradable NDF and ADF by 41 and 35 percent, respectively (Thompson et al., 2002).
Oat straw is grazed or fed (Figure 3.1), but feed quality is lower than at earlier stages of maturity (Youngs and Forsberg, 1987); it is often used as winter bedding and feed for beef cattle (Schrickel, Burrows and Ingemansen, 1992).
Figure 3.1
Feeding oat straw to cattle in
winter
In western Canada, oat and barley straw have average protein contents of 480 and 540 g kg-1, respectively, and have a higher feeding value than triticale (×Triticosecale Wittmack) or wheat (Triticum aestivum L.) straw (Coxworth et al., 1981; Wedin and Klopfenstein, 1985; Cowbytes, 2004). White, Hartman and Bergman (1981) in Montana compared the in vitro digestibility of wheat, barley and oat straw. Oat straw had the best digestibility, averaging 45 percent. It had slightly less crude protein (CP) than barley, but more than wheat. The addition of ammonia has a positive effect on the digestibility of oat straw used for feed. Horton (1978) and Horton and Steacy (1979) treated barley, oat and wheat straw with anhydrous ammonia, giving increased straw intake, CP and digestibility when fed to cattle. Other uses for oats, such as conservation (i.e. cover crops in no-till systems), or sowing as a companion crop, have been gaining relative to use for grain (Schrickel, Burrows and Ingemansen, 1992), but in livestock operations the greatest use of oats is for fodder or grain. The following sections review the role of oats for fodder (i.e. pasture, hay or silage) in North America.
Cereals such as oats are the first choice for annual pasture or silage in many regions of western Canada because seed is readily available and the crop is easy to establish (Aasen and Baron, 1993). Compared with other cereals, oats are more tolerant of acid soils and excessive soil moisture, but less tolerant of salinity than barley or wheat (Kirkland, 2004).
In a review of early pasture research in Ontario, central Canada, Clark and Poincelot (1996) reported that one approach to dealing with the seasonality of pasture yield involved the use of mixtures of annual and biennial forages, such as oats, sorghum (Sorghum bicolor L.), sweet-clover (Melilotus alba L.) and red clover (Trifolium pratense L.) for annual pastures, with annual yields averaging 3 000 kg DM ha-1 (Zavitz and Squirrell, 1919). At the Agriculture and Agri-Food Canada Research Centre, Brandon, Manitoba, in central Canada (Department of Agriculture, 1924), annual forage crops trials included oats, which yielded the highest, at 9 245 kg ha-1. At the Agriculture and Agri-Food Canada Research Centre in Lacombe, Alberta, western Canada, in the 1930s, oats were superior to barley and wheat as annual pasture (Experimental Station, Lacombe, 1936). By the 1940s, annual pastures were of considerable importance to the livestock industry in Alberta as they could be used as supplementary pastures for cattle, horses or sheep, and constituted the principal cultivated pasture for swine and poultry. Oat was the most satisfactory forage for annual pastures, especially late-maturing cultivars. However, oats alone did not yield as much forage as with autumn rye or rape (Dominion Department of Agriculture, 1940). Burgess, Grant and Nickolson (1972) in New Brunswick, eastern Canada, showed that forage oats should be harvested at the milk stage of growth to obtain the maximum yield of digestible DM while maintaining acceptable voluntary intake levels in sheep. Later studies in northern Saskatchewan (Robertson, 1980) used sheep to compare oats and barley pastures with brome-lucerne (Bromus inermis L. + Medicago sativa L.) pastures. The grazing season for the brome+lucerne began during the first week in June, and the annual cereals pastures were first grazed after mid-June. On average, oats provided 88 grazing days; barley, 82 grazing days; and brome+lucerne, 114 grazing days. Average liveweight gains per hectare during the experiment were similar for oats and for brome+lucerne (328 and 330 kg), followed by barley (305 kg ha-1). Annual DM yields averaged 5.9 t ha-1 for the annuals and 5.4 t ha-1 for brome+lucerne. Perennials were utilized more efficiently than annuals due to the greater degree of trampling and wastage on annual pastures. Robertson (1980) concluded that oats could produce gains equal to those obtained on perennial grass+legume mixtures and would be available for grazing within 6-7 weeks of sowing. The quality of the oat pasture could in part be controlled by subdividing the area to be grazed with cross-fences and spacing the dates of sowing by 2-3 week intervals. Oats could also provide pasture during the establishment year of perennial forages. Oat pastures could be used as a source of pasture and "emergency" feed by cattle farmers, but the input costs of growing annuals for pasture were considerably higher than perennials, although their potential is greatest when utilized to overcome shortages of perennial pasture in years of below-average precipitation.
In Alberta, research in 1979 indicated that the old recommendation for growing oats for summer grazing was being questioned. While oats were was found to have a place on Grey Wooded soils, DM yields on Black and on irrigated Brown soils were much lower than spring-sown winter cereals such as winter wheat, autumn rye or winter triticale (Riemer, 1988). In contrast, evaluations of oat under simulated grazing (two to five cuts) in central Alberta from 1979 to 1983 (Berkenkamp and Meeres, 1988) showed oats to be consistently the best pasture, with cv. Foothill averaging 3 347 and 2 106 kg ha-1 on two different soil types. Spring cereals, including oats, showed more rapid growth in the spring and were ready for grazing earlier, whereas Italian ryegrass (Lolium multiflorum L.) and spring-sown winter-type cereals such as rye grew more in midsummer, and into the autumn if moisture was adequate (Berkenkamp and Meeres, 1988).
Beacom (1991), in northeastern Saskatchewan, summarized several studies and reported that supplementary oat pastures yielded 3 800 to 6 000 kg ha-1, provided 100 to 150 steer days of grazing per hectare, and extended the grazing season by as much as 40 days. Kibite et al. (2002) evaluated oat and barley cultivars sown in mid-May and in late June on two soil types in central Alberta. Cultivars were harvested at their respective heading dates, and then two and three weeks later. Average DM yield of early sown cereals were about 5 000 kg ha-1, or 35 percent more than late-sown ones. For both early and late-sown groups, yields maximized at either two or three weeks after heading, but not consistently at either harvest date. Oat cultivars generally out-yielded the standard barley cultivar for forage by 2.6 and 3.2 t ha-1 for early and late sown crops, respectively. Early sown oats yielded 14.7 t ha-1, but the late sown oats yielded only 9.9 t ha-1. Barley generally had higher digestibility and protein than oats, but, unexpectedly, NDF was not always lower for barley than for oats. Sowing date had no consistent effect on nutritive value at time of harvest, so late sowing was not advantageous in this regard. Late sowing reduced yield and did not improve nutritive value.
Several studies in western Canada (Aasen and Baron, 1993; Baron et al., 1993a; Johnson, Kowalenko and Tremblay, 1998; McCartney et al., 2004a) have also shown that spring- or autumnsown cereals such as oat, barley, wheat, rye or triticale provide excellent summer or autumn pasture or silage. Oats are one of the three major cereals used for silage in western Canada. In central and northern Alberta, oat yields more silage or green feed per unit area than any other cereal crop (Hartman, 2000), especially when fertilized with nitrogen (Mahli et al., 1987). In northern Alberta, oats have the highest total DM and total energy of all cereals in the Grey Wooded soil areas. They yield more total DM, but not necessarily more digestible material per unit area than other cereals on Black soils in northern and central parts of the province. In southern Alberta, oat are recommended for silage production, but yield 5 to 30 percent less DM than other cereals, such as barley (Kirkland, 2004).
Christensen (1993) summarized 18 years of data on nutritive values of different forages in Saskatchewan and concluded that oat forage, for maximum nutritive value, should be harvested at the early dough stage, as it could lose feeding value with advancing maturity. In northeastern Saskatchewan, oat silage yielded 7 346 kg ha-1 DM, which was similar to barley and triticale. Barley and oat silage did not differ in chemical composition, and feed intake by heifers was similar. Average daily gain was greatest with barley (0.65 kg day-1) followed by oat (0.57 kg day-1). These results appeared to be primarily related to a lower digestibility of the oat silage. Where oats outyield barley, oats may be a more economical crop if supplemented with grain (McCartney and Vaage, 1994). In a plot trial to evaluate barley and oats for silage in northeastern Saskatchewan, oat silage yielded 8 330 kg ha-1 while the barley silage yielded 7 410 kg ha-1. However, the CP of the barley was 118 g kg -1 compared with only 103 g kg-1 for oats.
Abeysekara (2003) in Saskatoon evaluated three oat cultivars for feeding dairy cows: AC Assiniboia for silage; CDC Bell for hay; and CDC Baler for hay. The AC Assiniboia silage was comparable to AC Rosser, a six-row feed barley, in chemical and digestive characteristics and in production aspects. CDC Bell and CDC Baler hay were not comparable to the silages in chemical or digestive characteristics, but were comparable to each other in degradability characteristics. The author concluded that AC Assiniboia silage could be substituted for AC Rosser barley silage in dairy cow rations.
To date, there has been little research on oat varieties for hay in Canada. There is a definite demand for Manitoba oat hay for export, especially to Japan. Preliminary trials are in progress to evaluate cultivars that might be suitable for hay export (Kostiuk, unpublished). In years of drought, growing oats for hay could be a real advantage as an alternative to timothy (Phleum pratense L.) hay, as timothy requires more moisture for establishment.
In Wisconsin, trials on yields and forage quality of three oat cultivars over a range of sowing dates showed that the earlier oat is sown, the higher the milk stage yield per unit area and per tonne of forage (Oplinger and Maloney, 1997). Summer grazing trials in North Dakota in the Northern Great Plains region have shown that, in some years, oats have higher forage DM yields and more animal grazing days than barley, but in other years, cattle performance on barley or oats does not differ (Poland, Carr and Tisor, 2002). Trials in North Dakota showed that oat cultivars developed for forage, such as Celsia, Mammoth and Triple Crown, tended to produce more DM yield than cultivars developed for grain, such as Paul and Whitestone (Carr, Poland and Trisor, 2000). In earlier trials, oats cv. Dumont and cv. Magnum were superior to barley for yield when sown pure and when mixed with pea (Pisum sativum) (Carr et al., 1998), but in another study, DM yield of oats cv. Dumont did not differ from barley. This suggests that oat cultivar selection affects forage yield (Poland and Carr, 2002).
In North America, the use of oats in crop mixtures is common in marginal cropping areas. This is done to ensure some yield in case a pure stand fails. In Alaska, oats and pea are considered complementary, with pea compensating for the decline in oat quality when harvested at the early boot to milk stage (Brundage and Klebesadel, 1970; Brundage, Taylor and Burton, 1979). Pea+oat+vetch (Vicia spp.) mixtures are grown in Newfoundland. This mixture has traditionally been grown to provide a high quality ruminant feed in late summer and early autumn (McKenzie and Spaner, 1999). This mixture is normally cut as needed, and fed fresh daily. In Alberta, Berkenkamp and Meeres (1987) reported that on low fertility soils oat+sunflower (Helianthus annuus L.) mixtures yielded more DM than pure sunflower, but did not differ on fertile soils. In northeastern Saskatchewan, oat and spring-sown winter wheat were sown together. The regrowth of the winter wheat following removal of an oat crop for silage supported cows over a 60-day period from 5 August to 5 October, with a daily rate of gain of 0.5 kg (Beacom, 1991). In another study, at Melfort, winter wheat or autumn rye was sown with oats for silage and autumn grazing. The oat crop was removed as silage in June at 4.0 and 3.4 t ha-1 on the autumn rye and winter wheat fields, respectively. The under sown annuals plus oat regrowth provided 112 cow day ha-1 of grazing and supported a daily gain of 1.07 kg (Beacom, 1991).
Intercropping spring and winter cereals provides earlier grazing than winter cereals alone, due to the early growth of the spring cereal. Intercrops continue to accumulate DM later in the season compared with spring cereals alone (Baron et al., 1993a, b). The advantage of this system is that the forage distribution can be increased during the traditional grazing period and extended into the autumn (Baron et al., 1999; Poland et al., 2003; McCartney et al., 2004a). A silage-pasture intercrop system, utilizing a spring cereal (barley, oats or triticale) for silage and winter cereals (autumn rye, winter triticale or winter wheat) as regrowth pasture after the silage has been removed, is a system that provides a high quality silage crop along with autumn pasture (Aasen, 1992; Baron, Dick and de St Remy, 1994; McCartney, 2004a). However, adequate autumn regrowth depends on the time of the first harvest of the spring cereal component when mixed with winter cereals (Baron et al., 1995). In another study in Alberta, Baron, Dick and de St Remy (1994) showed that late sowing of oats either pure or in mixtures reduced total annual DM yield (2 cuts) by 42 percent, but that late sowing did not limit regrowth of winter cereals in mixtures given equal regrowth periods. With adequate moisture, the cereal intercrop system is a feasible alternative where annual forage is required for full season summer pasture. In a study of cropping systems for silage and pasture in northeastern Saskatchewan, McCartney et al. (2004a) evaluated herbage yield of spring and autumn cereal intercrops clipped for silage when barley (early cut) and oats (late cut) reached soft dough stage, and again late in the autumn. Silage yield of oat monocrop was 8 830 kg ha-1, exceeding oat intercropped (8 040 kg ha-1), barley pure crop (7 410 kg ha-1), barley intercrop (6 870 kg ha-1), late cut autumn cereal pure crop (4 700 g ha-1) and early cut autumn pure crop (3 670 kg ha-1). CP content was 14 percent to 35 percent higher in the intercrop system than in the corresponding spring cereal crop system. CP contents of oat intercrop and barley intercrop were similar. NDF of treatments containing barley were 15 percent lower than those containing oats. The ADF content of the barley treatment was 22 percent lower than the corresponding cropping system with oats. The ranking and relative productivity of the regrowth for autumn pastures was: deferred grazing treatment harvested only in the autumn (5 560 kg ha-1) > early cut autumn cereal (3 700 kg ha-1) > late-cut autumn cereal (2 730 kg ha-1) > barley intercrop (1 690 kg ha-1) > oat intercrop (1 330 kg ha-1) > barley (800 kg ha-1). The autumn pasture yield in cropping systems without spring cereals was 2.4 times that with spring cereals.
Seed rate and ratios of spring and autumn crop components can have an effect on annual forage production. McCartney et al. (2004c) found that the proportion of spring-sown oat sown with spring-sown autumn rye or Italian ryegrass rather than total stand seed rate, was the major factor affecting the silage and autumn regrowth yields. High seed rates may improve crop competitive ability and reduce the chance of problematic future weed infestations. The more rapid growth of the spring crop, such as oat, relative to the autumn crop helped to suppress weeds. The authors concluded that a forage sward with greater than 60 percent oats along with a higher than normal total spring and autumn crop component at a seed rate of 400 seeds m-2 represented a possible integrated weed management strategy, but the later silage cut time for oat compared with barley sometimes allowed for the development of weed infestation capable of reducing yields in the oat mixture.
In northern Ontario, growing oats with barley is a strategy whereby producers can optimize the output from fields that are variable from year to year. Growing mixtures can also serve as "insurance" against diseases that affect components separately (Rowsell et al., 1999). Oats mixed with pea for forage tend to yield equally to pure oats in the south of the province, but may be lower in the northern part (Johnston, Wheeler and McKinlay, 1999). Johnston and Garner (2000a) showed that, in northern Ontario, oats+winter triticale silage mixtures had significantly higher ADF (39.0 g kg-1 DM) than oats+autumn rye mixtures (35.1 g kg-1 DM). In the same study, where pasture yields and quality were measured, yield was highest in oats+annual ryegrass; overall yields ranged from 2.9 to 4.0 t ha-1 across sites (Johnston and Garner, 2000b).
In southwestern North Dakota, sowing either spring barley, oat or triticale with winter rye, triticale or wheat produced about 3 360 kg ha-1 DM by mid-July, with regrowth of the winter cereal contributing an additional 504 kg ha-1 in the autumn (Poland et al., 2003). Winter rye regrowth was sufficient to provide limited amounts of forage for grazing the following spring. In western North Dakota, Manske and Nelson (1995) reported that oat+pea intercrops, millet (Panicum spp.) and autumn rye worked well in annual grazing systems. In a study on water use and relative feed value in Montana, Pikul, Aase and Cochran (2004) showed that oat+pea hay was a suitable crop for the semi-arid growing conditions of the Northern Great Plains and met the needs of producers for high quality hay. When oat is used as forage in these regions, it is sown at 25-50 percent higher seed rates than normal for grain purposes, with similar fertility inputs (Cash and Wichman, 1997). Elsewhere, Oplinger and Maloney (1997) in Wisconsin reported that autumn forage DM yields of spring cereals were three to five times those of autumn cereals. They also indicated that oat, barley and triticale sown with a winter cereal in the autumn averaged 143 g kg-1 CP, compared with 190 g kg-1 in winter cereals sown alone. However, ADF (223 g kg-1) and NDF (407 g kg-1) were higher in winter than in spring cereals (wheat, rye, triticale or oats) sown alone in the autumn. ADF and NDF values were also much higher in the spring forage compared with autumn forage (Oplinger and Maloney, 1997). In Iowa, oat intercropped with berseem (Trifolium alexandrinum L.) had economic and biological advantages for use as a rotation crop. Holland and Brummer (1999) found that adding oat to berseem reduced DM of forage and weeds, clover stands and relative maturity of clover, but increased total crop DM. Oat and maize were included in pasture mixture studies for early weaned lambs in Minnesota (Wedin and Jordan, 1961). The authors reported that total liveweight gain per unit area was greatest for an oat+rape (Brassica napus var. biennis) mixture than for either oat+pea followed by Sudan grass (Sorghum bicolor (L.) Moench) or pea followed by sod-sown maize (350, 320 and 326 kg ha-1, respectively). In North Dakota, DM yields of winter and spring cereals, including oat, were lower in mixtures compared with the spring cereals when sown alone, with yield reductions of up to 20 percent in July (Poland et al., 2003).
The term "winter oats" is frequently used in a generic sense to indicate oats sown in the autumn and winter, and is not to be confused with "winter hardiness" in oats (Stevens et al., 2002). Winter oat is commonly used for pasture and forage in southern parts of the USA. Oat is valuable as a winter pasture as it provides excellent forage at a time when other high-protein feeds are scarce (Schrickel et al., 1992). Hoffman and Livezey (1987) reported that Texas ranked fourth in the USA in total area sown to oats, but produced only 4 percent of oats grown for grain. These oat pastures have complemented the expansion of the cattle industry in Texas. California produces more smallgrain hay than any other state and most of this hay is cultivated or wild oat (Schrickel et al., 1992). In California, where urban areas are often close to agricultural areas, lucerne+oat hay is often sold to horse owners, who prefer this forage mixture (Lanini et al., 1999). In this area, cv. Montezuma is preferred due to seed availability and favourable forage characteristics, and has provided equal or greater yields than other cultivars (Lanini and Bendixen, 1990). However, in Arkansas, oats generally produce less winter forage for grazing than do wheat, rye or annual ryegrass (Sandage, 2002).
When used for pasture or other forage, winter oats are sown at a seed rate 50 to 100 percent higher than when the crop is grown for grain (Shands and Chapman, 1961). Recommended seed rates have ranged from 100 to 150 kg ha-1 (Denman and Arnold, 1970). In Tennessee, the upper end of this range has yielded the most autumn forage under heavy grazing (Parks and Chapman, 1960). Early autumn sowing of winter oats increases the amount of forage that can be used before the weather becomes too cool for significant growth. Sowing dates depend on the location of the winter oats area, and whether the crop is intended for grain or forage (Marshall, McDaniel and Cregger, 1992).
In the coastal areas of southeastern USA, winter oats are commonly grazed in the autumn and early spring for part of the growing period, before allowing the crop to produce grain (Delorit, Greub and Algren, 1984; Schrickel, Burrows and Ingemansen, 1992). In the Coastal Plains, oats are clipped or grazed in early February, and further north, in the Piedmont areas of the southeastern USA, they are cut or grazed two weeks later (Schrickel, Burrows and Ingemansen, 1992). Burton et al. (1952) recommended that oat be rotationally grazed to a minimum of 75 to 102 mm. In a grazing study with steers in Texas over a 7-year period, Norris and Kruse (1967) found that a "medium" animal stocking rate of 1 ha-1 during the winter and 0.7 ha-1 during spring resulted in the highest gains per unit area. The same authors reported that steers grazing oats for an average of 97 days per season had average liveweight gains of 900 g d-1 head-1 for that period and 214 kg ha-1 for the season. The average daily gain of steers grazing oats oversown on coastal Bermuda grass (Cynodon dactylon (L.)) sod in Georgia was 1 kg head-1 (Utley, Marchant and McCormick, 1976). In Texas, under average conditions, Atkins, McDaniel and Gardenhire (1969) indicated that winter oat pastures may produce between 3.4 and 6.7 t ha-1 DM forage, and that with adequate fertilization and irrigation, yields might be as high as 11.2 t ha-1. In addition to grazing, the crop may be subsequently used for haylage, hay or silage (Marshall, McDaniel and Cregger, 1992). From one-quarter to three-quarters of the land area for winter oat in the Gulf Coast and Coastal Plain areas may not be used for grain, depending on the year. However, careful grazing management is needed if the crop is to produce a good crop of stored feed or grain. In Baton Rouge, Louisiana, winter oats were clipped in small plots from early December to either 15 February, 1 or 15 March during a 5-year period. Clipping until 1 or 15 March increased forage yields by an average of 672 and 1 400 kg DM ha-1 (Viator et al., 1982). Grain yields were not reduced when cutting was stopped on 15 February, but extending cutting to 15 March reduced grain yields by 44 percent.
Winter oat can produce good yields of silage or hay in northern areas, but is normally not grazed. In Maryland, forage DM yields at the soft dough stage ranged from 5.5 to 6.9 t ha-1. In mild winters, where the crop did not winterkill, yields ranged up to 10 t ha-1 (Coffman 1962). Oat cv. Norline was popular in northern areas of the winter oat region for a number of years for grain or forage (Marshall, McDaniel and Cregger, 1992). In southeastern Pennsylvania, Norline was sown in late September and cut at boot, milk and dough growth stages for assessing DM yield and quality. The highest CP yield - 745 kg ha-1 - was at the boot stage, and the highest total digestible nutrients (TDN) yield - 5.5 t ha-1 - was at the milk stage (Marshall and Yocum, 1971). The authors concluded that the value of the forage appeared to be substantially greater than the expected return from grain. In view of the value of winter oat for forage in the northern parts of the winter oat region of New York and Maryland, a winter-hardy cultivar, Walken, was developed for either forage or grain (Finkner et al., 1971).
Figure 3.2
Oats baled green to be used as green
feed
Oat has been used as a companion crop for sowing forages since the early 1900s in western Canada. In central Saskatchewan, oat was used at rates from 18 kg ha-1 to 72 kg ha-1 with 17 kg ha-1 of sweet clover (Melilotus officinalis, M. alba) (Tinline, 1924). In the 1920s, weed control options were very limited and the oat companion crop at 27 to 54 kg ha-1 helped suppress weeds and allowed the highest sweet clover hay yields. At the Agriculture and Agri-Food Research Centre, in southern Saskatchewan, Jefferson and Zentner (1994) sowed oats as a companion crop with lucerne on irrigated land. Lucerne sown alone produced much less than oat sown with lucerne or oats sown alone in the establishment year. Over the 3-year period, undersowing and harvesting the oats for hay (Figure 3.2) produced slightly more forage than lucerne sown alone. Oats as a companion crop provides some protection against soil erosion and helps in weed control, but the main problems with this system is that the oats compete with the perennial forage and weeds and may reduce production year yields and persistence (Tesar and Marble, 1988).
In Minnesota, Hartman and Stuthman (1983) recommended a seed for oats rate of 54-72 kg ha-1 when used as a companion crop, compared with 72-90 kg ha-1 when sown alone for grain. Peters (1961) reported that oats cut for forage at the late dough stage plus a cut of intersown lucerne yielded more than lucerne estab- lished with or without herbicides and harvested twice in the establishment year. In contrast, Brink and Marten (1986) showed that oat as a companion crop to lucerne had inferior forage quality compared with barley when the mixture was harvested in the sowing year. In California, Lanini et al. (1999) reported that oat intersown into an established (but declining) lucerne stand was comparable to using paraquat herbicide for weed control, with the advantage of increasing first harvest forage yield. Marshall, McDaniel and Cregger (1992) suggest that growers planning to use oats as a companion crop should use early maturing, lodging-resistant cultivars, and remove the oat forage early to favour the establishing perennial forage crop.
Figure 3.3
Swathing oats
Figure 3.4
Cattle grazing oats through the snow
in Canada. Oats were seeded in late May and swathed at the soft dough stage in
September before any killing frost, and grazed through the snow in
winter
Swath grazing of cereals is a relatively novel system for late autumn and winter grazing for beef cows, and is gaining popularity in western Canada (Alberta Agriculture, Food and Rural Development, 1998; Entz et al., 2002; McCartney et al., 2004b; Baron et al., 2004). Late-sown cereals are swathed (Figure 3.3) in the early autumn, from heading until dough stage. The livestock then graze the swaths through the snow (Figure 3.4). This is a form of stockpiling of forage for autumn and winter grazing when conventional pastures cannot meet the nutritional requirements of ruminants. The advantage is that the swathing consolidates the forage so that the cows can graze through the snow (Aasen et al., 2002). In northeastern Saskatchewan, oats were sown in mid- June and cows grazed the swaths beginning in November, for a 48-day period. Results showed that cows on swath grazing were in similar condition to those on stored feed at the end of the grazing trial (Alberta Agriculture, Food and Rural Development, 1998). Oat CP ranged from 106 to 116 g kg-1 from September to January (Alberta Agriculture, Food and Rural Development, 1998). In a later plot study on swath-grazed annual crops in central Alberta, oats, barley, autumn rye and annual ryegrass were mixed with peas or barley. September DM yields (3-year mean) ranged from 7 270 kg ha-1 (oats+peas) to 8 795 kg ha-1 (oats+barley) (Aasen et al., 2002), and autumn CP across sampling dates and years ranged from 109 g kg-1 to 192 g kg-1 DM. The protein concentrations of all crops at all sampling dates were more than adequate for wintering pregnant beef cows (Aasen et al., 2002). In southern Saskatchewan, oats were compared with other cool season and warm season annual crops for DM yields and quality for swath grazing (Klein, 2003). In this study, it was concluded that oats were less suitable for swath grazing compared with the later maturing foxtail (Setaria italica L.) and proso millets (Panicum miliaceum L.); part of this was due to the decline in DM yields with late sowing.
Winter or grass tetany, and, in some cases, milk fever, can occur in cattle fed cereal straw or green feed such as oats as the main forage in their winter feeding programme. Winter tetany is a metabolic disease caused by lower than average blood magnesium levels. It can occur when cattle graze on cereal grains such as oats (Bohman et al., 1983; Doig, Marx and Lastiwka, 2002). It is often seen in cows in late pregnancy or in the early stages of lactation. High producing cows are particularly susceptible, but dry cows and bulls are rarely affected. In western Canada, dry growing conditions and acidic soils can contribute to the accumulation of potassium in feeds, which in turn reduces the amount of magnesium absorbed from the ration (Doig, Marx and Lastiwka, 2002). Symptoms may start as nervousness, attentive ears and irritability, and, after several days, may lead to extreme excitement and violent convulsions. Prevention of this disease is through supplementation of the ration with magnesium oxide and limestone, the former mixed with grain, screeningsbased supplements or silage to increase intake (Doig, Marx and Lastiwka, 2002).
Oat appears to accumulate more nitrates than other small-grain crops (Garcia, 2002). Nitrate poisoning may occur if oat has been drought stressed, or damaged by hail or frost (Aasen and Baron, 1993). The risk is increased if the soil is high in plant-available nitrogen (Hartman, 2000). However, there are very few reported cases of nitrate poisoning in western Canada (Blakley, pers. comm., 2004). Rain after a drought can increase plant nitrogen uptake and the risk of nitrate poisoning during the next four to five days. During fermentation in the silo, 40 to 60 percent of the original nitrate can disappear, making ensiling the preservation method of choice when high nitrate levels are suspected. Supplementing the oat silage with grain at feed out will also decrease the chances of nitrate poisoning (Garcia, 2002).
A comprehensive review of oat diseases was prepared by Harder and Haber (1992), while breeding aspects have been covered by Burrows (1986). The main fungal diseases in North America are the rusts (Puccinia spp.) and the smuts (Ustilago spp.). Septoria leaf blight has been found to be prevalent in eastern Canada, with losses of 20 percent common in Ontario and up to 50 percent in Atlantic Canada (Clark et al., 1975). Barley yellow dwarf virus (BYDV) is a serious disease of oats (Burrows, 1986). In some areas, the sowing date may be delayed because of prolonged wet weather, which makes late-sown oat more susceptible to fungal and viral diseases (Burrows, 1986).
Disease and insect pests can reduce yields when growing winter oat for forage, especially where early sowing is used. In Texas, armyworm (Pseudaletia unipuncta Haw.), greenbug (Schizaphis gramimum Rondani) and aphids such as Rhopalosiphum padi (L.) are common, and important primarily because of their role as vectors for BYDV (Marshall, McDaniel and Cregger, 1992). Leaf rust (Puccinia coronata f.sp. avenae) not only lowers the quality of feed, but also hastens maturity, and therefore contributes to production loss (Song, 2004). The only practical solutions are to use resistant cultivars and to sow at the recommended time for the area.
Cultivar development in North America has been reviewed by McMullen and Patterson (1992), and breeding strategies for spring sown oats by Burrows (1986). Breeding has largely been in the domain of public agencies, such as Agriculture and Agri-Food Canada in Ontario and Manitoba, and a large number of state agricultural stations in cooperation with the United States Department of Agriculture (USDA). Most of the emphasis is on breeding oats for grain for human consumption (Stevens et al., 2002). The most critical issue relative to oat improvement is the marked decline in oat area over time, especially in the USA, and the gradual decline of oat research effort in the public and private sectors in North America (Wesenberg, 2000).
Improvement in winter hardiness is an important objective of winter oat breeding programmes in the northern and central winter oat areas of the USA. Recent additions include cv. Horizon 314, a new, full-season winter oat released by the Florida and Georgia Agricultural Experiment Stations in 1999 (Barnett et al., 2002). Breeding programmes have also included improvements in yield stability, seed quality, early or late maturity, lodging resistance and disease resistance. Grain quality factors such as test weight, groat percentage and protein concentration are also important considerations in oat cultivar development (McMullen and Patterson, 1992). Breeding programmes for dual-purpose (grain and forage) oats has been ongoing in Georgia, Texas, California and Alaska. Cv. Ensiler, a tall, forage-type cultivar, was released by the University of Wisconsin in 1990 (McMullen and Patterson, 1992). Cv. ForagePlus, a tall, late maturing oat with high forage yields and which can be harvested over a longer than normal period, was released by the University of Wisconsin-Madison in 2001.
Cv. Foothill, licensed and released by Agriculture and Agri-Food Canada in 1977, is a dual-purpose forage and grain oat (Schrickel, Burrows and Ingemansen, 1992). This cultivar has reasonably good quality but very poor lodging resistance (Kirkland, 2004). Cv. Foothill is being replaced by a newer cultivar, AC Mustang, in Alberta (Hartman, 2000). This cultivar, together with a hull-less (cv. AC Belmont) oat with improved yield and disease resistance, has recently been developed in Canada (Saskatchewan Agriculture and Food, 1995). Cv. Boudrias oat is a high yielding hull-less oat cultivar developed by Agriculture and Agri-Food Canada, Lacombe, Alberta, (Figures 3.5, 3.6 and 3.7) and released in 2001 (Kibite et al., 2004). Cv. AC Murphy has recently been released in western Canada as a highyielding, late maturing forage oat (Kibite et al., 2002). Cv. AC Assiniboia, with low lignin levels in the hull, is well suited for the oat-growing areas of western Canada and in particular the black soil zone of Manitoba and Saskatchewan (Abeysekara, 2003). Cv. CDC Bell was developed primarily for use by cattle producers in western Canada for annual green feed or oat hay. Cv. CDC Baler is a new forage oat that has wide leaves and produces higher energy and protein levels than other commonly grown varieties. However, it is susceptible to stem and crown rust (Quality Assured Seeds, 2004).
Figure 3.5
Oat plots at Agriculture and
Agri-Food,Canada, Lacombe, Alberta, Canada
Figure 3.6
Oat plots at Agriculture and
Agri-Food
As shown, the emphasis in plant breeding programmes has been towards developing new cultivars for grain for human consumption, with good agronomic and disease resistance characteristics. However, there has been relatively little emphasis on the impact of these selection criteria on the nutritional value for the animal. Animal nutritionists and the livestock industry have not always provided clear direction to plant breeders with respect to the desirable qualities of a feed oat for livestock. It may well be that it is unrealistic to expect nutritionists to speak with a unified voice as the characteristics of the ideal feed oat will differ depending on whether it is fed to horses, sheep or cattle, and whether it is fed as grain or fodder. Improved cultivars for fodder must have an ability for rapid growth, profuse tillering and remain vegetative over a longer period than grain types. They must also have leaf rust resistance since the appearance and spread of the disease coincides with the period when the crop is needed for grazing (Song, 2004). Research in North Dakota and elsewhere has shown that cultivar selection affects forage yield. Additional research, particularly at the producer level, is needed to determine the forage potential of oats in areas where it is used in livestock operations.
Pasture rejuvenation offers another possibility for the use of grazing oats. Sowing oats and other annual cereals into stands of perennial forage is a common practice in the south and southwest USA (Wedin and Klopfenstein, 1985). In Arkansas, sod-sowing annual ryegrass and rye into warm-season perennial pastures offers potential to provide high quality forage for growing weaned beef calves retained until spring (Coffey et al., 2002). Grazing of these sod-sown pastures offers the potential to improve land use efficiency (Moyer et al., 1995) and to improve animal gains over and above gains from cattle grazing dormant species over the winter (Wilkinson and Stuedemann, 1983). In a long-term pasture rejuvenation study in northeast Saskatchewan, McCartney, Waddington and Leftovitch (1999) found that growing annual cereals such as oat prior to reseeding old perennial forage pastures could be used to reduce the seed germination from the dormant grass seeds remaining in the seed bank in the old pastures. The authors suggested that after the pasture had been cultivated, oat could be grown and rotationally grazed for one or two seasons with the other perennial paddocks. This would reduce the need to lower the overall stocking rates on the entire pasture.
Figure 3.7
The late Dr Solomon Kibite, oat
breeder, inspecting a field of oats at Agriculture and Agri-Food Canada,
Lacombe, Alberta, Canada
There is limited research on forage oats in North America and most oat research is directed towards the human market. Entz et al. (2002) reviewed the potential of forages in the Northern Great Plains and suggest that annual forage systems including oat can fill a void at specific points in livestock operations, resulting in significant savings for the entire enterprise. Specific instances where annual crops such as oats could be valuable might be when DM production and quality in conventional pasture systems is insufficient to meet the grazing demands of the various classes of cattle. In cooler regions of North America, it is less expensive to overwinter beef cows on stored feed if they enter the winter grazing period in good body condition (Willms, Rode and Freeze, 1993; McCartney, 2003). The grazing of oats in the autumn provides a system whereby cows can substantially improve their body condition when perennial forages are of poorer quality and limited supply. Swath grazing of oats in winter is one of the current management systems that can lower the cost of wintering cows by up to 50 percent (McCartney et al., 2004b). In warmer regions, oats can be used as temporary cool season forage over the winter period when the DM of warmseason perennial forages is reduced.
New ways to divert land out of grain production are being evaluated, and grazing oat could become part of the process. With the changing farming population, an inexperienced livestock producer can initially start a grazing management system by incorporating oat pastures. Carrying beef cattle in the late summer and autumn on predominately annual pasture such as oats prior to entry into a feedlot is a means of supplying a low-cost animal to the feedlot system. As indicated earlier, grazing management systems have been developed whereby the regrowth from an oat silage intercrop system using autumn cereals can provide high quality forage for this purpose. In addition, respiratory health problems can be substantially reduced by providing this type of autumn grazing system for receiver calves from auction markets or assembly yards, rather than moving these animals directly into a confined feedlot (McCartney, 2000). An annual crop such as oats that is harvested as a grazed forage with livestock will be seen as giving added value to the grazing system. With the recurrence of drought in western Canada and the USA, producers are starting to re-evaluate the role of grazing annual crops such as oats. Hay and pasture rental costs have escalated in some regions to a point where they are no longer considered an economic option. Thus cropping systems that integrate hay, silage and autumn grazing become a viable option. Oats can be part of such a management system.
Significant improvement in forage oat yields in North America is possible with existing cultivars and management techniques, provided growers are made aware of what constitutes "good" management and the potential economic benefits. Growers need to be taught through education and demonstration that many good management practices require little if any extra monetary inputs, e.g. correct sowing time and depth. Several programmes, such as the "Oats Improvement Programme" sponsored by the Quaker Oats Company of Chicago, are designed to assist producers in the management of oats (Marshall, McDaniel and Cregger, 1992).
In general, there should be increased interest in the future for oats for grazing if the economics warrant the practice. In western Canada, one has seen general adoption of the concept of swath grazing, and new fencing and grazing management technology, with an increased interest in the potential of annual crops. There is now more information available on research and practical experience of "how to do it", which was not available years ago. This will definitely assist in the adoption and uptake of oats in grazing systems by North American cattle producers in the future.
