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Testing of Four Corn Hybrids for Extending the Grazing Season

Updated: May 25, 2023

Collaborating Producer: Bruce and Lorraine Jack, Happy Valley

Research Coordinator: Dr. Akim Omokanye

PCBFA is constantly responding to new and emerging innovative ideas to address cow-calf producers needs in a researcher designed and producer managed type of on-farm field trials. Also, creating awareness through on-farm trials and demonstrations geared towards increased technology transfer across the Peace is one of the several services provided by PCBFA. There has been growing interest on the use of corn for grazing in the Peace for extending the grazing season and reducing winter feed costs. In 2011, in a corn for grazing trial with Odell & Lillian Raymond, north of Peace River, 108 cows with an average weight of 1400 lbs grazed a 30 acre corn field for 72 days (259 cow days/acre), with the producer not having to start the tractor for that period. The study indicated lower winter feed costs, reduced operating expenses and saved time, as no harvesting is required, confirming years of observations by Sam king in Manning. PCBFA continues to collaborate with cow-calf producers across the Peace with the main goal of testing available corn hybrids with lower corn heat units (CHUs) for suitability for a particular area based on agronomic adaptation, feed value and animal performance. We also examine the direct input cost of corn versus oats or barley.

Methods The trial took place in Happy Valley (land location: NW 11-78-08-W6), near Spirit River, Saddle Hills County. The site was worked last fall. The site was again harrowed in the spring. Following a soil fertility test, the site was broadcast with 46 lb actual N/ac + 45 lb actual P/ac + 20 lb actual K/ac + 7 lb actual S/ac on May 12, 2012. We seeded 4 Roundup Ready corn hybrids (Pickseed 2219 RR, Pickseed 2501 RR, Pickseed Silex BT and Pioneer P7213R) with CHUs varying from 2050 to 2300. The corn hybrids were arranged in a randomized block design on 25 acres of land. Seeding was done on May 13, 2012 at the rate of 30,000 kernels/acre with a 6-row corn planter at 30-inch row spacing and at a seeding depth of 1.5-2 inches. Weeds were controlled once with Roundup at 0.67 L/ac.

On October 5, 2012, each corn hybrid forage yield was determined from six 17.5ft long corn rows. The corn forage samples were weighed, then we chopped some corn plants with a corn chopper for determination of moisture content and feed value in a laboratory. On the sampling day, the numbers of cobs per plant, moisture content and cob maturity were determined.

The total direct input cost of corn was calculated and this was compared to the cost of seeding oats.

The corn hybrids will be strip-grazed with 110 cows in the fall/winter. The cows will be allowed only enough forage for two to three days by utilizing an electrified temporary fence. Grazing will be across the 4 corn hybrids.

Results and Discussion

Numbers of Cobs, Moisture and Cob Maturity

The mean numbers of cobs per plant varied from 1.05 cob/plant for P7213R to 1.45 cobs/plant for Silex BtRR (Table 1). At sampling, whole plant moisture content varied significantly from 69.68% for P7213R to 76.55% for 2219RR. Generally, all corn hybrids were in the two-third milk stage at sampling. A few stands of 2501RR was in the half milk line stage. Some of the P7213R were approaching early dough stage. Corn hybrid 2501RR had reduced cob size and number of kernels per cobs compared to the other corn hybrids.

Forage Dry Matter (DM)

Yield Corn DM yield varied from 6974 lb/acre for 2219RR to 8782 lb/acre for Silex BtRR (Table 1). When the forage yield was adjusted to 65% moisture content for the purpose of estimation of how much silage yield each hybrid would have produced, Silex BtRR gave the highest silage yield with a yield of 15 t/acre while 2219RR gave the lowest with 11 t/acre silage yield. The DM yield of individual corn plant parts was not determined in this trial, but several studies show that 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 2501RR in this trial could partly be due to its CHU requirement, reduced cob size and number of kernels per cobs.

Feed Value

Protein content was generally below 9% for all corn hybrids (8.11- 8.26% CP) (Table 1). The protein contents of all the corn hybrids were only adequate for cows in the mid pregnancy stage which require 7% CP. Cows in the late pregnancy stage which require 9% CP would therefore need to be supplemented with a protein source. For this purpose, placing a good legume hay or protein blocks should be sufficient. The feed test results in this trial therefore confirm the need for a whole corn plant feed tests (before grazing starts), which should be compared to the requirements of cows to be grazed and provide supplements if necessary for a balanced feed ration.

Ca content was between 0.20 and 0.24%. P7213R had the highest P (0.17% P) and K (1.31% K) contents (Table 1). The forage Ca content of all the corn hybrids tested in this trial were adequate to meet the requirements of 0.16% Ca of dry gestating cows. But however slightly fell short of meeting the amounts of Ca required by those cows in the lactating stage. Corn forage contents were generally low for all corn hybrids (except for P7213R) and slightly fell short of the 0.16% P required by dry gestating cows. Because of the low P contents of the corn hybrids, providing contents of the corn hybrids, providing free choice minerals to make up for low values in the corn plant would be necessary.

ADF values are inversely related to digestibility, so forages with low ADF concentrations are usually higher in energy. This is true with our feed test results for the 4 corn hybrids. P7213R had the lowest ADF value and appeared to have the higher TDN than the other 3 corn hybrids. All the corn hybrids have high energy contents varying from 60.94 % TDN for 2501RR to 63.62% TDN for P7213R. The hybrids had adequate amounts of energy needed for dry gestating cows.

Direct Input Cost of Corn Versus Oats

As expected, the total direct input cost of corn was higher than those of oats. Corn was seeded at a cost of $234.18/acre, while oats was seeded at $93.05, giving a difference of $141.13/acre. The higher cost from the corn is mainly due to the costs of seed and fertility, which both make up 85% of the total cost (Table 2). Spreading of manure and cows grazing corn for some time on a particular site will help reduce fertility over time. It is important to note that, no significant additional costs would probably be incurred from grazing standing corn during fall/winter. But for oat, additional costs will include cost of swathing and baling, hauling and feeding during winter.


Based on forage yields (both for grazing and silage), Silex BtRR, followed by P7213R appeared to perform better than the other corn hybrids. When the corn hybrids were cut for forage yield determination on Oct 5, 2012, only P7213R seemed to be with the range of moisture content needed for silage. Getting to an average of 65% moisture for silage at a later date for other corn hybrids would probably mean compromising on forage silage yield. Looking at the feed nutritive values for all the corn hybrids, it appeared that P7213R (though had slightly lower cobs/stand) did better, generally for both forage yield and quality at the trial site. Both P7213R and Silex BtRR would therefore be suggested for use in the Happy Valley and area. P7213R also has a lower CHU of 2050.

Future Plans

The corn field will be grazed in fall/winter with 110 cows. The grazing will be monitored for feed wastage, animal behaviour and actual cow days/acre and the cost/cow/day.


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