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

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

Research Coordinator: Dr. Akim Omokanye

From: Peace Country Beef & Forage Association 2012 Annual Report


Corn is an option for producers looking to extend the grazing season and reduce feed costs per cow per day. Continued interest in corn varieties for late fall and winter grazing has led the Western Beef Development Centre (WBDC) to develop a protocol to evaluate different varieties of corn hybrids with low heat units in comparison with AC Ranger barley. The main objective is to evaluate 3 different corn varieties (1 Monsanto; 1 Pioneer; 1 Hyland) and 1 forage barley (Ranger) for quality and yield grown at 4 different sites in the Parkland area of Western Canada. The project started in the spring of 2012 and is taking place at 4 locations: 2 in Saskatchewan at Melfort and Glaslyn; 2 locations in Alberta at Evansburg and Fairview. Here, the results of forage yield and nutritive value of 3 corn hybrids and AC Ranger barley planted in Fairview this year are being presented.


Methods

The trial took place at the Fairview Research Farm (RR #35, MD of Fairview). The site was left to fallow in the summer of 2011, but had a canola variety trial in 2010. Prior to seeding, a soil test was done for N, P, K and S and then the site was harrowed a few times. The site had a pH of 5.2 and 8.1% organic matter.


There were 4 treatments: (i) Monsanto corn hybrid DKC 26-25; (ii) Pioneer corn hybrid P7443R; (iii) Hyland corn hybrid 2D093; (iv) "AC Ranger" barley. AC Ranger is a feed barley and has smooth awns. The treatments were arranged in a randomized complete block design with four replications. Plot size was 3.81m x 14m. There was a 0.5m gap between treatment plots and a-3m gap between replications.


Corn and barley were both seeded on May 28, 2012. Con hybrids were seeded with a 6-row Pioneer corn planter (at a row spacing of 30 inches) at 30,000 seeds/acre at 1.5-2.0 inch depth. There was only 1 planter pass per corn hybrid plot. For the AC Ranger barley plots, a 7-row plot drill (spaced at 7 inches between rows) was used. Barley was seeded at 100 lb/acre to a seeding depth of about 1.5 inches. Just before seeding, corn plots were fertilized with 100 lb actual N/acre + 40 lb actual P/acre, while the barley plots received 40 lb actual N/acre + 23 lb actual P/acre. The fertilizer was drilled into the plots using a small plot drill.


On June 16, 2012, the barley was sprayed with 2-4 D amine at 0.67L/acre at the 4-leaf stage. On June 21, 2012, corn was sprayed with roundup at 0.67 L/ac application rate at the 5-leaf stage.


On August 4, 2012, barley plots were sampled for estimation of forage dry matter (DM) yield at the soft dough stage from randomly placed three 1m x 1m quadrats per plot. On October 4, 2012, each corn hybrid forage yield was determined from three 17.5ft long corn rows/plot. The corn forage samples were weighed fresh and then sub-sampled, weighed and dried for DM yield estimation. Randomly corn plants were selected from each replicate for each corn hybrid and then chopped with a corn chopper for determination of feed value in a laboratory. On the sampling day, the numbers of cobs per plant and cob maturity were assessed.


Results

Numbers of Cobs and Cob Maturity

2D093 had the most cobs per plant followed by DKC 26-25 and then P744R. On the sampling date, both P744R and DKC 26-25 were mostly in the 2/3 milk line stage. A few cobs particularly from P744R were observed to be in the early dough stage. But for 2D093, the cobs were mostly in the half milk line stage. Generally, all varieties had good cob development by the end of the growing season.


Forage Yield

Percent dry matter (DM) varied from 32.1% for AC Ranger barley to 41.1% for DKC 26-25. The wet yield was lowest for AC Ranger barley (9.40 t/acre) and highest for P744R (15.75 t/acre). All corn hybrids generally had >14 t/acre wet yield. The DM yield did not vary much between the 3 corn hybrids, but all the corn hybrids significantly had higher DM yield (5.34 - 6.01 t DM/acre) than AC Ranger barley, which had 3.01 t DM/acre.



Forage Quality

Protein content was higher for AC Ranger barley (11.05% CP) than the 3 corn hybrids which had 7.27 to 7.47% CP. Taking into consideration the protein requirements of beef cattle, only AC Ranger barley had sufficient amounts of 7 to 11% CP required by gestating and lactating cows. The 3 corn hybrids were only adequate for cows in the mid pregnancy stage. Cows in the late pregnancy stage grazing these corn hybrids would therefore need some form of protein supplementation using protein blocks or good legume hay with high CP content.


Forage Ca content was highest for AC Ranger barley with 0.50% Ca and lowest for DKC 26-25 with 0.23% Ca. Of the 3 corn hybrids, forage Ca content of DKC 26-25 was much lower than for other corn hybrids. All crops tested here had sufficient amounts of Ca needed for dry gestating cows. None was however adequate to meet the 0.58% Ca required by lactating cows. Only DKC 26-25 was short of meeting the 0.31% Ca requirements of growing and finishing beef cattle.


Forage P content was between 0.21 and 0.25% for corn hybrids and AC Ranger barley tested. These values were within the ranges suggested for growing and finishing beef cattle (0.21% P) and dry gestating cows (0.16% P). But for lactating cows, which require 0.26% P, the crops fell short in meeting their P requirements. This therefore indicates that for cows in the late pregnancy stage, some form of mineral supplementation to address the short fall of both forage Ca and P contents is needed.


Forage P content was between 0.21 and 0.25% for corn hybrids and AC Ranger barley tested. The resulting Ca:P was highest for AC Ranger barley (2.38:1) and lowest for corn hybrid DKC 26-25 (1.10:1). Generally, all corn hybrids had <2.0:1 Ca-P ratios.


Both P744R and 2D093 had a higher forage Mg content than DKC 26-25 and AC Ranger barley. For forage K content, 2D093 had the highest K content, followed by DKC 26-25 and then by both P744R and AC Ranger barley. Both Mg and K met and even far exceeded the amounts of Mg and K contents required by dry gestating cows. For lactating cows, the Mg contents from both DKC 26-25 and AC Ranger barley were lower than the 0.26% Mg required during the early stages of nursing. The K contents obtained in this study were more than adequate for growing and finishing beef cattle, dry gestating and lactating cows.


Energy is probably the most important nutritional consideration in beef cattle production. A range of 55-65% TDN and 0.90-1.32 Mcal kg.-1 NEM have been recommended for beef cows by the National Research Council (NRC). The NEM is an estimate of the energy value of a feed used to keep an animal in energy equilibrium, i.e., neither gaining nor losing weight. Generally, all corn hybrids and AC Ranger barley tested had sufficient amounts of TDN (69.19 -71.59%) and NEM (1.61 –1.68%) needed for mature beef cattle during pregnancy and nursing of calves. The ability of these to be able to meet beef cows energy requirements is important to cow-calf producers in the Peace Region, particular during winter, as this will mean a substantial savings in feed energy costs.

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