Winter Grazing Stockpiled Corn
D. THOMPSON1, D. VEIRA1 and E. MOORE2
1Agriculture and Agri-Food Canada, 2BC Ministry of Agriculture, Fisheries and Food, Kamloops, British Columbia
Winter feed is very costly for livestock operations, and beef producers with generally small profit margins are particularly interested in low-cost feed alternatives. Grazing stockpiled forage after the growing season reduces harvesting and feeding costs. Most perennial forages are harvested for multiple cuts; leaving a standing crop for a long period results in very poor feed quality. But with corn, the entire season’s growth can be left standing with less threat of deterioration, resulting in a potentially high carrying capacity. At Kamloops the 2 year average yield for stockpiled corn was 18 t/ha (8 T/ac) which provided feed for 1080 cow-days/ha (430 cow-days/ac). By comparison, only 5 t/ha (2.3 T/ac) of tall fescue could be stockpiled (270 cow-days/ha or 110 cow-days/ac). Significant quantities of standing corn were also reported in Brandon, MB (15 t/ha or 6.7 T/ac), Brookes, AB (13 t/ha or 5.8 T/ac) and Lacombe, AB (13 t/ha or 5.8 T/ac) (1, 2). Stockpiled corn has the potential to extend the grazing season as the plants stand above the snow. The nutritional value of standing corn should be adequate to support pregnant beef cows in the first and second trimester (3).
Corn varieties specially designed for grazing are generally lower yielding than conventional hybrids. ‘Amaizing graze’ corn yielded 5 to 7% less than conventional early hybrids at Lacombe and Brooks. At Kamloops ‘Amaizing Graze’ yielded 15% less than Pioneer 34G81. ‘Amaizing Graze’ has very high CHU requirements compared to the hybrid corn varieties grown in these regions, accounting for the lower yields. An unusual short stature variety ‘Canamaize’ yielded 20% less than the conventional hybrids at Lacombe and 25% less Brooks.
A key question to consider is how well stockpiled corn weathers. Averaged over three early-season hybrids, the proportion of the late Sept. corn still standing in late Jan. was 75% at Brooks and 80% at Lacombe. At Kamloops 80% of the material stockpiled by mid-Nov. was still standing on Jan. 15. The losses are due mostly to shedding of leaves which decompose quickly on the ground.
When the cattle are turned into a fresh strip of standing corn, they pick off the cobs and leaves (Fig. 1) and in the process trample down the stems (Fig. 2). It is necessary to restrict access with electric fences to minimize trampling (Fig. 3). On frozen ground, cattle will eat the downed stems, but when the ground is not frozen the stems may by trampled into the mud. At Kamloops we observed 80-90% utilization of standing corn from mid-Dec. to Jan. on frozen ground but only 70% utilization on unfrozen ground.
Figure 1. Cow preparing to swallow a whole corn cob; no choking was noticed.
Figure 2. Cows grazing corn on frozen ground at Gus Fischer’s farm near Cache Creek.
Figure 3. Cows strip grazing corn at Kamloops; notice preference for cobs and leaves.
What quality does stockpiled corn offer to cows and how does it vary over the winter? Average winter-time levels of ADF ranged from 25% in Brooks, 29% in Lacombe and 38% in Kamloops. The high values at Kamloops were likely due to the more advanced maturity of the crop. At all sites there was a slight increase in ADF through the winter. Whole-plant NDF values in late Sept. averaged 53% at Lacombe and 51% at Brooks. There was a slight increase in NDF throughout the winter. With increased NDF, there is generally a reduction in forage intake by cattle. Stockpiled corn averaged 7 to 9% crude protein (CP), which meets the minimum value of 7% for beef cows in early or mid pregnancy (NRC 1996). The crude protein content did not decline substantially throughout the winter at any of the sites.
‘Amaizing Graze’ corn tended to have slightly greater CP than the conventional hybrid at Lacombe (10 vs 9%) and at Kamloops (9 vs 8%) but not at Brooks. Higher CP can be tied to an earlier stage of maturity at harvest.
How do pregnant cows perform on grazing corn? It appears that grazing corn provides an adequate maintenance diet for pregnant cows in winter. At Kamloops cow gains averaged 0.1 kg/day (0.05 lb/day) confirming an earlier report from Lethbridge, Alberta (3). In fact, at mid-gestation beef cows can afford a minor loss in condition. So if the cows are in good condition before grazing corn, they are likely to maintain their condition.
Some economics for grazing corn:
The cost of grazing corn is estimated at $0.96/day compared to $1.65/day for hay and $1.68/day for corn silage (Keyes 2002, unpublished). Although it costs more to plant and grow corn than other forages, considerable savings are realized with no harvesting costs and low feeding costs.
Challenges of grazing corn
- Specialized seeder or modified grain drill needed for planting.
- Weed control
- Moulds (eg. Fusarium) on leaves and cobs under wet conditions which can be a health hazard for cattle (see Moulds and Mycotoxins in Corn Silage section).
- Soil compaction can be minimized by excluding cows after grazing. However, compaction may be a problem in lanes or around troughs. Moderate levels of compaction may be alleviated by frost heaves during the remainder of the winter and by spring tillage.
- Replanting may be difficult due to stalk residue.
- Only feasible in geographic areas where there is adequate moisture and heat for corn growth and but where the winters are cold and dry enough to minimize trampling and mould.
- Stockpiled corn may be very susceptible to wildlife depredation; blackbirds can feed on developing cobs while deer or elk may consume and knock over standing corn in winter.
Weed control for the non-corn grower
Corn grazers ma y be able to accept a greater amount of weeds in their crop so long as the corn is not smothered. Weed control may be the major challenge for most corn grazers. Planting corn directly into the residue from a winter cover crop such as cereal rye or annual ryegrass, sprayed with glyphosate (Roundup), helps to control weeds. Another strategy is to delaying seeding the corn until after the first flush of weeds is sprayed with glyphosate. In both these cases corn is direct-seeded into the dead plant cover. Another option is using ‘Roundup Ready’ corn hybrids but know that they are genetically modified. Non-herbicide options are limited. Start with ‘clean’ land and use inter-row cultivation. If a fall cover crop such as annual ryegrass winter kills, seed directly into it. Be aware that even if your previous alfalfa stand was free of annual weeds, you are still likely to get a flush of annual weeds; weed seeds can lie dormant in the soil for many years until conditions are right for their germination. Because corn is planted later than most forages, intensive competition from ‘warm season’ annual grasses such as barnyard grass and foxtail is likely unless they are controlled (see Weed Control section).
1. McCuaghey, P., J. Small, S. Scott and B. Irvine 2002. Foxtail Millet and Corn: New crops to extend grazing season and cut feeding costs. Brandon Res. Centre News Notes. Feb. 2002.
2. Baron, V.S., H.G. Najda, D.H. McCartney, M. Bjorge, and G.W. Lastiwka 2003. Winter weathering effects on corn grown for grazing in a short-season area. Can. J. Plant Sci. 83, 333- 341.
3. Willms, W.D., L.M. Rhode, and B.S. Freeze 1993. Winter performance of cows on fescue prairie and in drylot as influenced by fall grazing. Can. J. Anim. Sci. 3, 881-889.