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Using Corn For Grazing

Updated: May 12, 2023

Collaborating Producer: Guy and Kathy L’Heureux, Joussard

Research Coordinator: Dr. Akim Omokanye

Feed costs have been identified as the largest single cost of livestock production, making up 50 to 70% of the total cost of production. To reduce feed cost particularly during winter, producers are exploring options to extend the grazing season. A recent viable option in parts of the Peace is the use of standing corn for fall/ winter grazing. Using livestock to graze corn reduces the need for investment in harvest and feeding equipment. With the potential to produce more than 10 tons of forage dry matter to the acre, few annual crops can compare to corn in terms of dry-matter (DM) yield per acre and cost per pound of gain. Standing corn has the nutritive composition to meet the requirements for many categories of livestock. The objective of this trial is to assess corn hybrids for agronomic adaptation and feed value in Joussard.


The trial is located at Guy & Kathy L’Heureux’s ranch in Joussard, AB. The site had been under pasture for years and recently used to feed cows. The site was worked prior to planting. Following a soil fertility test, the site received a broadcast of 85 lb actual N/ac + 15 lb actual P/ac. The soil test showed sufficient amount of K and S, so we did not include either K and S in the fertilizer blend. We planted 5 corn hybrids with corn heat units (CHUs) varying from 2200 to 2350. The CHUs rating is an indicator of how many heat units are required for the grain to reach maturity. On average, 200 fewer CHUs are required for grazing or silage corn to reach 65 per cent whole plant moisture (35 per cent dry matter) as compared to grain corn. This moisture level is normal when silage corn is ready to harvest. To increase the chances of a high yielding and high quality corn crop for grazing, it is advisable to select a variety that will match the CHUs rating for your area. Silage varieties of corn are more palatable and better suited to grazing than grain corn.

The corn hybrids planted were: BrettYoung Fusion RR, Pickseed 2219 RR, BrettYoung Edge R, Pickseed 2501RR and Pickseed Silex BtRR. These are all Roundup Ready corn hybrids. The corn hybrids were arranged in a randomized block design. Planting was done on May 17, 2012 with a John Deere hoe drill, which was adapted to planting corn kernels. The John Deere was modified to plant at 21 inches row spacing and at an average of 6.5 inches between stands. Seeding rate was 30,785 kernels per acre. A total of 18 acres was planted. Weeds were controlled once with Roundup at 0.67 L/acre.

On September 4, 2012, forage yield for each corn hybrid was determined from six random 22.5ft long corn rows. A few corn plants were selected and chopped with a corn chopper for determination of feed value in the laboratory. On the sampling day, plant height, number of cobs per plant, cob maturity, and moisture content from chopped samples were also determined. From planting to corn harvest for yield determination, notes were taken regularly on the performance of the different corn hybrids.

Results and Discussion

Plant Height, Number of Cobs, Cob Maturity and Moisture Content

Silex BtRR was the tallest (11.78 ft), followed closely by Fusion RR (11.49ft). The shortest was 2501RR hybrid with 7.57 ft tall. The number of cobs per plant was similar for all corn hybrids. All corn had close to 2 cobs per plant. The cobs of both Silex BtR and Fusion RR were mostly at the late milk stage on sampling day (September 4), while the cobs of other hybrids were in the half milk line stage. With the exception of Edge R, all corn hybrids developed a full cob of corn kernels. Moisture content of the corn hybrids at sampling on September 4 varied from 73.10 to 77.32%.

Corn Forage Yield

Corn dry matter (DM) yield was significantly the highest for Fusion RR with 8.38 t/ac, followed by Silex BtRR with 7.59 t/ac, 2501RR (5.35 t/ac), 2219RR (4.64 t/ac) and Edge R (4.00 t/ac) in that order. Overall, in terms of DM yield, both Fusion RR and Silex BtRR respectively, out yielded other corn hybrids by 57-110% and 42- 90%. Generally, the amount of DM yields obtained for all the corn hybrids (4.00 to 8.38 t/ac) is really good for an extensive grazing system. The DM yield of individual corn plant parts was not determined here, but several studies show that 50 - 60 per cent of the dry matter yield of corn comes from the cob, grain and husk while the leaf, stalk and tassel provide less than 40 per cent of the dry matter yield. The lowest DM yield recorded for Edge R could partly be due to its CHU requirement, reduced kernels number per cob and insufficiently filled kernels. Edge R grew slowly compared to other corn hybrids.

Feed Value

Protein content was highest for Silex BtRR with 10.33% CP and lowest for Edge R with 7.37% CP. All corn hybrids tested were well above the 7% CP requirements for beef cows in the mid pregnancy stage. Only 2219RR and Silex BtRR had sufficient amount of 9% CP needed for cows in the late pregnancy stage. None of the corn hybrids had up to 11% CP that is needed for cows after calving.

The corn forage Ca content was generally below 21% for all corn hybrids. 2501RR had the lowest Ca content (0.12% Ca). Fusion RR, 2219RR and Silex BtRR respectively had higher P, Mg and K contents than other corn hybrids. Fusion RR had the least ADF content (34.40%).

Energy (TDN) content was just slightly below 60% TDN, but these values would still be sufficient for cows that are in the mid to late pregnancy stages.

Corn Input Costs

The total input costs for planting corn in this trial was $227.82, with the cost of seeds making up about 50% and fertility (without labour cost) taking 36% of the total costs. This is expected because of the higher cost associated with corn seeds and fertility. Corn has a high fertility requirement, but fertilizer costs may be lower if manure is used. It is important to note that these costs will vary and calculations must be based upon values for each individual cow/calf operation. In summary, this trial shows that corn has sufficient amount of energy and protein levels that will normally match the nutritional needs of a dry cow in mid and late pregnancy. It also has the potential to produce more dry matter than tame hay or forage cereals. By replacing other forms of feed with standing corn, labor time, machinery use and associated costs are reduced as no summer feed harvesting is required and winter supplemental feeding is limited.

Corn Grazing

The site is being grazing by 165 cows + 6 bulls. Guy and Kathy L’Heureux were impressed with the performance of the calves. They noted that the calves during grazing gained 40-50 lbs above sales weight and the calves were even 2 weeks younger at sale than the previous ones sold years back.

Tips for Growing and Grazing Corn

  • Test a few corn hybrids from different sources to see what hybrids suit your area. Use corn with lower CHU requirements.

  • Use hybrids bred for silage or grazing - they have high forage yields, high digestibility, low fiber levels, & high fiber digestibility.

  • Do whole corn plant feed test analysis and compare the feed analysis to the requirements of cows grazing and provide supplements if necessary for a balanced feed ration. Protein blocks can be used as a protein supplement.

  • Provide free choice minerals to make up for lower mineral content (Ca in particular) in the corn plant. Alfalfa grass hay can also be used as supplement to meet the calcium requirements.

  • Wait until the ground is frozen before turning the herd into the field. This will reduce the losses from trampling feed into the mud.

  • Limit access for the cows to maximum of 2-3 days of grazing per area.

  • Watch the cows for symptoms of grain overload in years where cobs are fully developed and abundant. Cows eat the cobs first, and only once all the cobs are eaten will they then eat the stalks.

  • Have a backup feeding plan in case of bad weather or excess snow.

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