Collaborators: Pat & Jay Eaton’s Ranch (Valleyview), Denis Bouvier (Guy) & DuPont Pioneer
Research Coordinator: Dr. Akim Omokanye
From: Peace Country Beef & Forage Association 2015 Annual Report
In parts of the Peace, the practice of extended winter grazing with standing forage corn is continuing to gain more popularity among producers as new low corn heat unit varieties become available. The selection of corn hybrids for grazing should be narrowed to hybrids bred for silage or grazing. These have been bred for high forage yields, high digestibility, low fiber levels, and high fiber digestibility. Hybrid selection should start with identifying a group of hybrids that are adapted to the area in terms of days to maturity and the required heat units, disease and insect resistance, drought tolerance, and tonnage. Standing corn has the nutritive composition to meet the requirements for many categories of livestock. Research studies have shown that stocker cattle, beef heifers, and cows have excellent weight gains grazing corn. The objective was to evaluate growth, forage yield and quality of new versus old corn hybrids.
Site 1 - Corn Variety Evaluation (Pat & Jay Eaton’s Ranch, Valleyview, MD of Greenview)
Trial site: The study was carried out on Alder Ridge Road by RGE road 204 between Guy and Valleyview.
The following 5 DuPont Pioneer Roundup ready corn hybrids were seeded:
1. 39F44 (2000 heat units)
2. 7202 (2050 heat units)
3. P7211HR (2050 heat units)
4. 7332 (2050 heat units)
5. P7213 (2150 heat units)
Seeding was done on May 18 at 30,000 corn kernels per acre with a corn planter. Fertility was according to soil test recommendation and the field was sprayed with Roundup to control weeds. The 5 varieties were replicated two times. Harvesting for determination of forage yield and quality was done on October 7.
Plant height (Table 1) - P7211HR corn hybrid grew tallest (6.46 ft), followed by corn hybrid 7202 (6.23 ft) and then 39F44 (6.20 ft). Corn hybrid 7332 was very short (5.51 ft) compared to other corn hybrids.
Moisture content (Table 1) - Forage moisture content at harvest was also highest for P7211HR (66%), fol-lowed by 7202 (62%) and then 39F44 (57%).
Forage dry matter (DM) (Table 1) - The DM yield was highest for 39F44 (5.57 ton/acre), followed by 7332 (4.81 ton/acre) and then by 7202 (4.62 ton/acre). P7211HR had the lowest forage DM yield.
Protein (Table 1) - The crude protein (CP) varied from about 9% for P7211HR to 10% for other corn hybrids (7202, 39F44, 7332 and P7213R). The protein for the 5 corn hybrids appeared to be generally adequate for a dry gestating cow that requires 7% in the mid-pregnancy stage and 9% in the late pregnancy stage.
Minerals (Table 2) - Only P7211HR seemed to have sufficient Ca for a dry gestating cow (0.18% Ca). All 5 corn hybrids were able to meet the P, K and Mg requirements of a dry gestating cow, which requires 0.16% P, 0.60% K and 0.12% Mg. For the trace minerals (Table 2), only the iron (Fe) requirement of a dry gestating cow is met (50 ppm). Other trace minerals measured here (Cu, Zn and Mn) fell short of meeting the needs of a dry gestating cow.
Detergent Fiber and Energy - Acid Detergent Fiber (ADF) value refers to the cell wall portions of the forage that are made up of cellulose and lignin. These values are important because they relate to the ability of an animal to digest the forage. As ADF increases the ability to digest or the digestibility of the forage decreases. Neutral Detergent Fiber (NDF) value is the total cell wall which is comprised of the ADF fraction plus hemicellulose. NDF values are important because they reflect the amount of forage the animal can consume. As NDF percent increases, the DM intake generally decreases. The lower the values of ADF and NDF, the better the forage/feed. For both ADF and NDF, 39F44 had much lower values than other corn hybrids tested here.
Energy (%TDN) was generally above 65% for all corn hybrids. This shows that the different corn hybrids tested met and even exceeded the TDN requirements of mature beef cattle.
Conclusion - Though all corn hybrids tested have similar heat units (2000-2150), 39F44, a hybrid that requires the least heat units seemed to have performed better than the other hybrids. When compared to other corn hybrids, 39F44 had slightly higher forage yields, comparable protein, good ADF and NDF values and higher RFV. Because of the general inconsistencies of any particular hybrids meeting all the minerals requirements (macro and trace), it is essential that free choice minerals be provided to cows during grazing.
Site 2 - Corn Variety Evaluation (Denis Bouvier, Guy)
Two DuPont Pioneer Roundup ready corn hybrids were seeded (P7211HR - 2050 heat units and 39D95 - 2175 heat units). Seeding was done on May 14 on 3.5 acres. Fertility was 170 lbs of NPK+S fertilizer blend. The field was sprayed twice with Roundup to control weeds, first on May 26 with 0.45 L/acre and then another one on June 25 (0.66 L/acre).
Harvesting for determination of forage yield and quality was done on October 7. About 250 cow days was obtained for the trial field.
Plant height - P7211HR was taller than 39D95 (Table 1).
Moisture content at harvest was 56.4% for P7211HR and 59.6% for 39D95 (Table 1).
Forage yield (Table 1). - The forage DM yield was slightly higher for 39D95 (6.95 ton DM/acre) than P7211HR (6.22 ton DM/acre).
Forage Quality (Table 1).
The forage protein content (%CP) was slightly higher for 39D95 (8.89%) than P7211HR (7.99%). A dry gestating cow requires 7% CP in the mid-pregnancy stage and 9% in the late-pregnancy stage. This means that both corn hybrids were well within the 7-9% CP needed by a dry cow.
For the macro-minerals measured here (Table 2), both P7211HR and 39D95 met the K and Mg requirements of a dry gestating cow. Only P7211HR had sufficient Ca for a dry gestating cow. None of the 2 corn hybrids had adequate P, S and Na for a dry gestating cow.
Of the 4 trace minerals measured here (Cu, Zn, Fe and Mn) (Table 2), only Fe requirement for a dry gestating cow was met by both corn hybrids.
39D95 appeared to have better forage quality than P7211HR because of its lower ADF and NDF content as well as its higher TDN and RFV value (Table 2). 39D95 had 71% TDN, while P7211HR had 67% TDN, indicating that both corn hybrids exceeded the energy (TDN) requirements of mature beef cattle.
Conclusion - 39D95 corn hybrid appeared to have performed slightly better than P7211HR, particularly taking into consideration forage DM, protein, ADF and NDF as well as TDN and RFV contents. Both corn hybrids had comparable forage P, S and Na contents. Because of the general inconsistencies of any particular hybrids meeting all the minerals requirements (macro and trace), it is essential that free choice minerals be provided to cows during grazing.