Research Coordinator: Dr. Akim Omokanye
Collaborating Producer: Koos & Barbara Bos, MD of Peace
From: Peace Country Beef & Forage Association 2014 Annual Report
Corn is not a traditional grazing crop in the Peace region, but results from several on-farm trials suggest that grazing corn could be part of an extended grazing program. Grazing your herd on corn can lower your winter feed costs, reduce your operating expenses and save you time. Corn also has the potential to produce more dry matter than tame hay or forage cereals. By replacing other forms of feed with standing corn, labour time, machinery use and associated costs are reduced as no summer feed harvesting is required and winter supplemental feeding is limited. Our collaborating producer, Koos Bos, has been grazing corn for some years now and every year he continues to test different corn hybrids with the aim of selecting a few corn hybrids that work well for his area.
The trial site was at Koos & Barbara Bos, Peace River. The site has had corn for 5 years and has not received any fertility in the last 3 years, so no fertilizer was applied to this year’s corn as well. We seeded 7 Roundup® corn hybrids: P7632HR (Pioneer)- 2200 corn heat units (CHUs), P7213R (Pioneer) - 2050 CHUs, 39F44 (Pioneer)- 2000 CHUs, 39D97 (Pioneer)- 2250 CHUs, EA7417R (BrettYoung) - 2200 CHUs, Fusion (BrettYoung)- 2200 CHUs, and DKC27-55RIB (Dekalb)- 2200 CHUs.
Seeding was done on May 27 with a 12-row corn planter. Spraying to control weeds was done with Round-up®. The calculated CHUs from seeding date to harvest for forage yield determination was 1775.05 for the Peace River area.
Forage Dry Matter (DM) Yield
The forage DM was highest for P7213R (3.6 tons DM/acre) (Figure 1). Only 4 of the 7 corn hybrids had 3.0 ton DM/acre or more. The 2 corn hybrids which require less CHUs to full grain maturity (P7213R and 39F44) were in the top 3 corn hybrids with higher forage DM. 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 normally 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. Select an early-maturing silage corn variety. Silage varieties of corn are more palatable and better suited to grazing than grain corn.
The forage protein (crude protein, CP) of corn hybrids varied from 8.69% CP for 39F44 to 10.6% CP for 39D97 (Figure 2). All corn hybrids were able to meet the 7 and 9% CP respectively required by a cow in mid and late pregnancy. But for a lactating cow, which requires 11% CP, only 39D37 just barely met this protein requirement, all other corn hybrids fell short of satisfying the protein needs of a nursing cow.
The forage energy (total digestible nutrients, TDN) was generally above 65% TDN for all corn hybrids (Figure 3). Going by the TDN required by a mature beef cow, which is 55-65% TDN, all corn hybrids therefore have been able to meet the energy requirements of a dry gestating and a lactating cow.
The forage Ca lowest (0.22% Ca) for EA7417R and highest (0.30% Ca) for both Fusion and DKC27-55RIB (Table 1). Generally, all corn hybrids had sufficient Ca for a dry gestating cow, which requires 0.18% Ca. But for a nursing cow, which requires 0.42% Ca, none of the corn hybrids had adequate Ca for this category of mature cow.
A dry gestating cow requires 0.16% P and after calving, it requires 0.26% P. Looking at Table 1 below, all corn hybrids have been able to sufficiently meet the 0.16% P needed by a cow in mid and late pregnancy. But all corn hybrids fell short of meeting the 0.26% P needed by a nursing cow.
The forage Mg and K content respectively varied from 0.23-0.27% Mg and 1.34-1.54% K (Table 1). The requirements of both Mg and K by growing and finishing calves as well as a mature beef cow have sufficiently been met and exceeded by all corn hybrids tested.
All corn hybrids however fell short of meeting the Na requirements of growing and finishing calves as well as that of a mature cow.
The lack of any fertilizer application in 2014 resulted in huge savings. This benefit came as a result of subsequent corn grazings for some years now at the site. In general, Pioneer corn P7213R with 2050 heat units appeared to have slightly higher DM yield than other corn hybrids. Because cows selectively graze cobs first, it is important to control access to the corn to ensure proper utilization, and to provide a good water source and mineral/salt package to address any short falls.