Evaluation of Low Heat Unit Corn Hybrids Compared to Barley for Grazing

Research Coordinator: Dr. Akim Omokanye

Collaborator: Dr. Bart Lardner, Western Beef Development Centre (WBDC), Humboldt, Saskatchewan

From: Peace Country Beef & Forage Association 2013 Annual Report

Corn is an option for producers looking to extend the grazing season and reduce feed costs per cow per day. One of the initial concerns was getting corn hybrids with heat unit requirements that will match the heat units of the Peace Region and elsewhere in Alberta and parts of Saskatchewan. Advances in plant breeding have resulted in hybrid corn varieties that require less crop heat units and therefore can be grown more successfully in these areas. Western Beef Development Centre (WBDC) developed a protocol to evaluate corn hybrids with low heat units in comparison with AC Ranger barley for grazing in parts of Alberta and Saskatchewan. The project started in the spring of 2012 and will continue until the early fall of 2014. The main objective is to evaluate 3 different corn varieties (1 Monsanto; 1 Pioneer; 1 Hyland) and 1 forage barley (AC Ranger) for quality and yield grown at different sites in the Parkland area of Western Canada.


One of the locations for the trial is Fairview, MD of Fairview. In Fairview, the trial took place at the Fairview Research Farm (NW5-82-3W6) on RR #35. Prior to seeding, the site was harrowed and then Credit® was sprayed for pre-seed weed control. The site had a canola variety trial in 2011 but left to fallow in summer of 2012. The site had a pH of 5.4 and 8.8% organic matter.

3 corn hybrids (Monsanto corn DKC 26-25, Pioneer corn P7443R & Hyland corn 2D093) and AC Ranger barley variety. AC Ranger is a 6-row feed barley and has smooth awns. The crops were arranged in a randomized complete block design with four replications. Small plots measuring 1.4 m x 8.5 m were used. Corn and barley were both seeded and fertilized on May 23, 2013 with a Fabro plot drill equipped with double shoot Atom jet openers. Seeding rates were 30,000 seeds/acre for corn hybrids and 100 lb/acre for AC Ranger barley seed. All plots received equivalent amounts of fertilizer, based on the soil tests done (corn - 90 lb actual N/acre + 30 lb actual P/acre & barley - 40 lb actual N/acre + 23 lb actual P/acre). In crop spraying of Roundup at 0.67 L/ac application rate at the 5-leaf stage was carried for corn hybrids. For barley, 2-4 D amine at 0.67L/acre at the 4-leaf stage was used. Hand weeding of volunteer canola took place twice in the corn plots.

On August 1, 2013, barley plots were harvested at the soft dough stage, weighed to obtain wet yield, sub-sampled and subsequently dried for dry matter (DM) yield estimation. On September 26, 2013, each corn hybrid was harvested for estimation of wet and dry forage yields. Randomly, corn plants were selected from each replicate for each corn hybrid and then chopped with a small wood chipper for determination of feed quality in a commercial laboratory. On the sampling day, the numbers of cobs per plant and cob maturity were assessed.

Results and Discussion

Number of Cobs, % DM and DM Yield (Table 1)

The number of cobs per corn plant did not vary much among corn hybrids. Cobs/plant for Pioneer corn P7443R, Hyland corn 2D093 and Monsanto corn DKC 26-25 were respectively as 1.35, 1.10 and 1.15.

At harvest for determination of forage DM yield, the % DM was significantly higher for Pioneer corn P7443R (27.84%) than the other corn hybrids tested (25.02-25.88%). Generally, the cobs were at the 1/2 to 2/3 milk line stage.

In terms of DM yield, all corn hybrids tested had higher yield than AC Ranger barley by 0.58 -2.08 ton/acre. For the corn hybrids, Pioneer P7443R had the highest DM (5.64 ton/acre), followed by Monsanto DKC 26-25 (4.57 ton/acre) and then Hyland 2D093 (4.14 ton/acre). It is evident from the trial that corn DM yield is dependent on corn heat unit requirements. The lower the corn heat unit, the higher the DM yield.

Feed Quality (Table 1)

Generally, AC Ranger barley had higher protein (15.11%) than the three corn hybrids tested (9.71 - 11.00%). For the corn hybrids, the order of protein was: Hyland corn 2D093 (11.00%) > Monsanto corn DKC 26-25 (10.57%) > Pioneer corn P7443R (9.71%). The protein obtained in all the corn hybrids and barley exceeded the suggested protein requirements of dry gestating cows. This therefore shows that protein supplementation in form of a good legume hay or protein block is not required during grazing with dry gestating cows.

The suggested Ca and P contents in feeds for a dry gestating cow respectively are 0.18 and 0.16%. AC Ranger barley had 0.46% Ca, while Ca content for corn hybrids varied from 0.25-0.40%. Barley and corn hybrids had between 0.21 and 0.28% P. The values obtained for both Ca and P therefore show that both Ca and P requirements of dry gestating cows were met by all crops.

Energy gives the ability to use the building blocks for growth and other productive purposes. Using total digestible nutrients (TDN) per cent as a measure of energy, for a mature beef cow to maintain her body condition score (BCS) through the winter, the ration must have a TDN energy reading of 55 per cent in mid pregnancy, 60 per cent in late pregnancy and 65 per cent after calving. The three corn hybrids and AC Ranger barley tested in this trial met the energy requirements of these categories of cow and exceeded 65% TDN suggested for lactating cows.


All 3 corn hybrids produced good yields and were of suitable quality to meet nutrient requirements of grazing beef cows in the mid and late pregnancy stages.

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