Ingram, S., Agriculture and Natural Resources Agent, University of Georgia Extension, Jackson County
Dillard, L., Post-doctoral Research Scientist, Crop and Soils Department, The University of Georgia
Hancock, D., Extension Forage Specialist, University of Georgia Extension
Stewart, R.L., Jr., Extension Animal Scientist, University of Georgia Extension

ABSTRACT

A reseach trial was conducted to illustrate appropriate grazing management strategies that optimize stocker calf production and the seed yield of canola (Brassica napus L.). Four treatments were utilized and included an ungrazed canola control (canola-no graze; CNG); canola lightly grazed (canola-early graze; CEG); canola heavily grazed (canola-late graze; CLG); and winter wheat grazed to jointing. Eighteen Angus steers were randomly assigned to one of twelve grazing paddocks. Herbage mass was assessed at two-week intervals. Calves were weighed on d 0 and 50. All canola and wheat treatments were harvested to determine total biomass and seed yield. The average herbage mass during the grazing period did not differ among treatments. ADG was similar across all treatments Seed yield did not differ among treatments. The CNG trended lower for net return over establishment in comparison to CEG, CLG and WW. These data show that implementation of appropriate grazing management strategies can optimize stocker calf production and not compromise seed yield in canola.

INTRODUCTION

Beef cow-calf operations represent the largest agricultural land use in major land resources areas for Southern Appalachian ridges and valleys and the Southern Piedmont. The majority of pastures and hayfields in this region contain tall fescue and bermudagrass (Ball et al., 2007). If canola production in the Southeast (SE) expands, it will likely be in converted pastures and hayfields.

Forage production to fill the winter feed gap is a key objective of a dual-purpose crop (Kirkegaard, 2012). Brassicas, such as canola (Brassica napus L.), can produce substantial amounts of herbage during the late fall and early winter. This is a time when established perennial forages begin to decline in nutritional value and yield, which is a critical period in the nutritional management of SE cow herds (Reid et al., 1994). Brassica crops are also palatable, have a low dry matter content, and low concentrations of cellulose and detergent fibers (Pelletier et al., 1976; Faix et al., 1979), which result in a forage that is highly digestible and can greatly increase animal performance. Recent research has shown that there may be the potential to utilize canola as a dual-purpose crop in integrated crop-livestock production systems (Heer, 2006; Kirkegaard et al., 2008; Kirkegaard et al., 2012; Begna et al., 2017). Winter canola cultivars are grazed by cattle in the Great Plains region of the U.S., but the harsh winters can cause significant yield losses as a result of delayed maturity caused by grazing (Heer, 2006). In the SE region of the U.S., less severe winter conditions and a longer spring growing season provide a significant opportunity to produce more biomass for a longer winter grazing period and a longer period of plant recovery to increase seed yield in the spring.

In order to balance the value of the forage and oilseed yield, dual-purpose canola will rely on successful and timely establishment, an appropriate match of canola variety to environment, and careful grazing management (Kirkegaard et al., 2008). Previous literature has reported that lambs grazing dual-purpose canola in Australia increased body weight 0.46 lb/d in the winter (Kirkegaard et al., 2008). Kirkegaard et al. (2012) reported insignificant yield losses when terminating grazing prior to the predicted growth stage 3.1 (Harper and Berkenhamp, 1975) and favorable spring growing conditions followed. With favorable weather conditions and timely grazing management, there was little to no effect of winter grazing on canola seed yield (Kirkegaard et al., 2008; Kirkegaard et al., 2012). However, no literature is available evaluating canola as a dual-purpose crop for beef cattle production.

The goal of this research was to evaluate the potential of canola as a dual-purpose (forage and oilseed) crop in the SE. The objectives were to compare stocker cattle performance and oilseed yield of canola when grazing occurred and was terminated by the safe stage or the sensitive stage (as defined by Kirkegaard et al., 2012) relative to the oilseed yield of ungrazed canola and the cattle performance and grain yield of dual-purpose winter wheat. This current research was conducted as part of a larger experiment to evaluate crop establishment, production, and animal production of dual-purpose canola in the SE United states (Ingram, 2011).

 

METHODS AND MATERIALS

All practices and procedure used in this study were examined and approved by the University of Georgia Animal Care and Use Committee. The experiment was conducted at the J. Phil Campbell, Sr. Research and Education Center in Watkinsville, GA.

Treatment and Design

Twelve 1.6-ac paddocks were blocked by previous tillage history and randomly assigned to one of the four treatments: 1. canola not grazed by steers (CNG); 2. canola lightly grazed by steers with the grazing period being terminated prior to growth stage 3.0 and a targeted post-grazing residual equal to, or greater than 1340 lb of dry biomass/ac throughout the grazing period (CEG); 3. canola heavily grazed by steers with the grazing period being terminated prior to growth stage 3.1 and maintaining a targeted post-grazing residual equal to, or less than, 900 lb. of dry biomass/ac throughout the grazing period (CLG); and 4. winter wheat grazed by steers with the grazing period being terminated prior to jointing  (Feekes growth stage 6; Wise et al., 2011) and maintain a post-grazing residual at a height greater than the height of the first node throughout the grazing period (WW). The canola management strategies were compared against dual-purpose wheat to serve as a benchmark for animal production and agronomic performance.

Forage Management

On 4 October 2013, a Great Plains no-till drill (1006NT, Great Plains Mfg., Inc., Salina, KS) with row spacings of 7.5 in was used to plant canola seed (cv. ‘Inspiration’, a winter hybrid) at a seeding rate of 4 lb/ac. On that same day, a different Great Plains no-till drill (3P605NT) but essentially of the same design was used to plant winter wheat seed (cv. ‘AGS2038’, a dual-purpose winter variety) at a seeding rate of 110 lb/ac. Approximately 1 wk after emergence, all treatments received 50 lb N/ac applied via liquid N (32% urea ammonium nitrate). The paddocks of grazing treatments were divided into two sub-paddocks and rotationally grazed throughout the experiment.

Sample Collection

Paddocks were sampled immediately prior to the initiation of grazing on each sub-paddock throughout the grazing period to measure growth stage, herbage mass, and nutritive value. Since CNG was not grazed, samples were collected coinciding with the beginning, approximate middle, and termination of the grazing period. In each paddock, three locations were identified by throwing a 1-ft² quadrat randomly throughout the paddock.

Growth stage of the crop was visually assessed within each quadrant and was conducted by a single observer throughout the experimental period. Canola growth stage was assessed based on Harper and Berkenkamp (1975). Winter wheat growth stage was assessed based on Wise et al. (2011).

Herbage mass within each of the three 1-ft² quadrats was assessed using a Filip’s Manual Folding Plate Meter (Jenquip Agri-Business, New Zealand), otherwise known as a rising plate meter (RPM). After all non-destructive samples were obtained; a destructive sample was hand-clipped to a stubble height of 1.2-in in each quadrat for the purpose of quantifying herbage mass. These measurements were subsequently used to create a calibration equation ( R²=0.67):

  

This equation could be used to quantify available forage mass using subsequent RPM measurements throughout the paddock (approximately 40 observations per paddock

Herbage mass from each destructive sample was collected for determination of dry matter (DM) content and nutritive value. The forage samples were weighed initially on a scale, then dried in a forced-air oven at 60º C for 72-hr to calculate DM ((dry weight/wet weight) x 100)). Forage samples were then ground to pass a 1 mm sieve in a Model 4 Wiley Mill (Thomas Scientific, Sweensboro, NJ). Nutritive value of treatment samples was determined by near 37 infrared reflectance spectroscopy using a model 6500 (FOSS NIRSystem Inc. Laurel, Maryland) NIR analyzer at the University of Georgia’s Agricultural & Environmental Services Laboratory.

Animal Management

On 23 January 2014, 18 steers (542 ± 24 lb.) were weighed after fasting in a dry lot for a period of 12 hours, blocked by weight, and randomly assigned to one of the three grazing treatments (CEG, CLG, and WW). During the grazing experiment, steers had ad libitium access to water and shade and were provided a free-choice mineral supplement at 4 oz per head per week (16% Ca, 4% P, 15% NaCl, 15% Mg, 50 ppm Co, 1,250 ppm Cu, 250 ppm I, 2,000 ppm Mn, 26.4 ppm Se, 3,750 ppm Zn, 300,000 IU/lb Vit A, 25,000 IU/lb Vit D, and 100 IU/lb Vit E). At the termination of grazing, weights of steers were collected after fasting in a dry lot for a 12-hour period.

Crop Management

Total biomass and seed production were assessed at the end of the experiment in three randomly located 5-ft² areas in each paddock. The entire crop within each area was clipped to a 1.2-in stubble height. All clipped biomass was placed on a tarp and weighed on a hanging scale immediately before the collected biomass was thrashed using Hege plot combine (Wintersteiger, Inc., Salt Lake City, UT). The seed collected was used to calculate seed yield for each paddock. Separated seed samples were submitted to Resaca Sun Feeds, LLC (Resaca, GA) for analysis of oil content via nuclear magnetic resonance (NMR) as described in Hocking, Kirkegaard, et al. (1997).

Economic Return

The economic returns were calculated using production cost and estimated crop value. The production cost included seed, fertilizer, pesticide, planting and harvest costs. The crop values were based on local cash values, and calve values were estimated based on the average price received for similar preconditioned calves being sold from the same herd.  Net return was calculated for the year the trial was conducted (2014) and the current year (2018) to illustrate potential variability in all markets.

Statistical Analysis

Data were analyzed using the GLM procedure of SAS (SAS Institute, 2010) in a randomized complete block design with the four treatments of CEG, CLG, CNG and WW, three replications, and two observations per paddock. Individual paddocks were considered the experimental unit and individual steers were considered an observational unit within each paddock.

 

RESULTS AND DISCUSSION

Forage Response

Despite different grazing management treatments, the average herbage mass determined by clipping was not different (P > 0.9512) between all treatments for the growing season (Table 1). Weekly RPM estimation was not different (P > 0.6642) among the treatments and was similar to clipped samples for the canola treatments but not the WW. The similarity between our bi-weekly clipped mass samples and weekly RPM estimation suggests RPM estimations can provide accurate information for estimating forage availability in canola pastures. Bi-weekly clipped mass samples and RPM estimations indicate target residual DM forage for grazed treatments CEG (1340 lb. DM/ac) and CLG (900 lb.DM/ac) were achieved.

 

Table 1. The mean herbage mass during the grazing period for the canola-no graze (CNG), canola-early graze (CEG), canola-late graze (CLG), and winter wheat (WW) paddocks immediately prior to grazing. The herbage mass was assessed by bi-weekly hand clipping from three 1-ft² areas/paddock and weekly measures of compressed sward height with a rising plate meter (RPM) in ca. 40 observation sites along a randomly located transect within each paddock and calculating the herbage mass using the calibration equation above. SEM=standard error of the mean.

	Treatment
Herbage Mass Assessment Method	CNG	CEG	CLG	WW	SEM	P-value
Bi-Weekly Clipped Mass, lb DM/ac	1335	1247	984	1163	181	0.9512
Weekly RPM Estimation, lb DM/ac	1251	1494	932	1639	178	0.6642

 

 

Forage quality variables are presented in Table 2. Forage DM (P > 0.02) and NDF (P > 0.0001) were lower on all canola treatments compared to the WW. Lower DM could potentially limit DM intake, however in the current study, that did not appear to affect animal performance. Crude protein was greater for all canola treatments (P > 0.0001) compared to WW, however all treatments exceed the protein requirement for growing cattle. Relative forage quality, ADF, and TDN were similar across treatments. All treatments provided high quality forage to support animal gains above 2.5 lb/d base on nutrient requirements (NRC, 2000).

 

 

Table 2. Forage quality characteristics of canola-no graze (CNG), canola-early graze (CEG), canola-late graze (CLG), and winter wheat (WW) collected throughout the 49 d grazing period. Items: DM = Dry Matter, RFQ = Relative Forage Quality, CP = Crude Protein, NDF = Neutral Detergent Fiber, ADF = Acid Detergent Fiber, and TDN = Total Digestible Nutrients. Means within a row with different superscripts differ (P < 0.05).

	Treatment
Item1	CNG	CEG	CLG	WW	SEM	P-value
DM, %	17.6a	15.6a	17.4a	21.8b	1.23	0.0101
RFQ	197	200	192	203	3.6	0.1359
CP, %	24.6a	23.9a	25.3a	19.5b	0.65	< 0.0001
NDF, %	30.1a	30.7a	30.2a	39.6b	0.64	< 0.0001
ADF, %	20.7	20.8	20.6	20.8	0.49	0.7841
TDN, %	70.6	71.1	69.9	71.6	0.56	0.1287

 

 

Animal Response

Initial BW, final BW, and ADG was similar (Table 3) across all treatments. Figure 1 shows cattle grazing the canola in early February. No other study has reported ADG for cattle grazing canola as a dual-purpose crop. The ADG reported for this study can only compare to forage brassicas and dual-purpose canola being grazed by sheep. Kirkegaard (2008) observed 0.46 lb/d for sheep grazing dual-purpose canola, while Reid (2008) reported similar gains. Expressed as a percentage of BW, these gains are consistent with this current study. These gains would support necessary growth for a stocker operation.

 

Figure 1. Cattle grazing canola in early February.

 

Table 3. Body weight gains of stocker cattle grazing the canola-early graze (CEG), canola-late graze (CLG), and winter wheat (WW) treatments. 

	Treatment
Item	CEG	CLG	WW	SEM	P-value
Initial BW, lb	544	544	539	6	0.9224
Final BW, lb	675	682	676	7	0.9297
Average Gain, lb/d	2.85	2.61	2.75	0.13	0.7868
Gain per acre, lb/ac	186	225	217	11	0.1728

 

 

Crop Production

Total biomass tended to be lower (P = 0.17) for the CLG treatment compared to CNG, CEG, and WW (Table 4).  Seed yield was not affected by treatment (P > 0.3896), however the CLG was numerically lower compared to other treatments. Figure 2 show canola from both grazing treatments approximately 28 d after cattle were removed. These findings suggest that utilizing a grazing method similar to the CEG treatment can maintain total biomass and not affect seed production. Additionally, there was no effect (P > 0.5624) of treatment on oil content in the canola seed. These findings are consistent with previous studies by Kirkegaard et al. (2008) which noted no difference in seed oil concentration due to grazing. Oil content is commonly influenced by temperature during pod fill, declining 2.7% for every 1 ºC increase in average temperature during seed filling (Hocking, Randall and DeMarco, 1997). If flowering delays occur from grazing, it is possible to push flowering into the warmer portion of spring. However, the management strategies for grazing canola are designed to avoid such delays, minimizing an impact on seed yield or oil content.

 

 

Table 4. The mean total aboveground biomass and seed yield produce by the canola-no graze (CNG), canola-early graze (CEG), canola-late graze (CLG), and winter wheat (WW) treatments, and oil content within the seed of the canola treatments.

	Treatment
Item	CNG	CEG	CLG	WW	SEM	P-value
Total Biomass, lb/ac	9705	9437	6622	8862	1079	0.1712
Seed Yield, lb/ac	2256	2547	1683	3297	288	0.3896
Oil Content, %	44.1	45.1	44.6	-	0.4	0.5624

 

 

Figure 2. Canola early graze (CEG; left) and canola late graze (CLG: right) approximately 28 d after grazing was terminated.

Economic Returns

The added value of gain from the calves and crop was similar across treatments based on the canola, wheat, and cattle prices from the year they were harvested (2014; Table 5), Additionally, the added values when applying the prices of canola, wheat, and cattle values for the current year, 2018, were similar across treatment (Table 6). No differences for crop values (P > 0.7087) were noted between treatments. Net returns after production costs for CNG trended (P > 0.1455) lower in comparison to all grazing treatments, suggesting proper grazing of canola can have a higher return than the ungrazed canola.

 

 

Table 5. Value of the calf and crop production and total net returns based on 2014 prices for the canola-no graze (CNG), canola-early graze (CEG), canola-late graze (CLG), and winter wheat (WW) treatments. Based on calf value of $200/cwt; $9.25/bu canola; and $5.25/bu wheat. Net return calculation: (lb of animal x calf value, $/lb) + (bu of seed x crop value, $/bu) – production cost of $200/ac = net return over production. Cost of production included seed, fertilizer, pesticide, planting and harvest costs.

	Treatment
Item	CNG	CEG	CLG	WW	SEM	P-value
Calf Value, $/ac	-	$ 371.33	$ 450.00	$ 431.33	22.58	0.1728
Crop Value, $/ac	$ 417.32	$ 471.32	$ 311.40	$ 288.50	47.27	0.6395
Net Return, $/ac	$ 217.40	$ 642.65	$ 561.40	$ 519.83	64.69	0.1374

 

 

Table 6. Value of the calf and crop production and total net returns based on 2018 prices for the canola-no graze (CNG), canola-early graze (CEG), canola-late graze (CLG), and winter wheat (WW) treatments. Based on calf value of $155/cwt; $7.40/bu canola; and $4.65/bu wheat. Net return calculation: (lb of animal x calf value, $/lb) + (bu of seed x crop value, $/bu) – production cost of $200/ac = net return over production. Cost of production included seed, fertilizer, pesticide, planting and harvest costs.

	Treatment
Item	CNG	CEG	CLG	WW	SEM	P-value
Calf Value1, $/ac	-	$ 287.78	$ 348.75	$ 334.28	17.50	0.1728
Crop Value2, $/ac	$ 333.92	$ 377.05	$ 249.12	$ 255.52	36.98	0.7087
Net Return3, $/ac	$ 133.92	$ 464.84	$ 397.87	$ 389.81	51.10	0.1455

 

 

CONCLUSIONS

This research has shown that utilizing canola as a dual-purpose crop can be profitable. Weight gains for steers were similar to those of steers grazed on winter wheat. The management strategies used in the current experiment conserved seed yield and oil content. This research demonstrates that utilizing canola as a dual-purpose crop using grazing management similar to the CEG treatment can be profitable.

 

REFERENCES

Ball, D., Hoveland, C., and Lacefield, G. (2007). Southern Forages. 4^th ed. International Plant Nutrition Institute. Norcross, GA.

Begna, S., Angadi, S., Stamm, M., and Mesbah, A. (2017). Winter canola: A potential dual-purpose crop for the United States southern Great Plains. Agron. J., 109:2508-2520.

Faix, J.J., Kaiser, C., Graffs, D., Lewis, J., Mansfield, M., and Jung, G. (1979). Evaluation of various root crops, kale, and rape in sod seedings. Illinois Agric. Exp. Sta. Dixon Springs Agric. Ctr., 7:103-110.

Heer, W.F. (2006). Grazing winter canola in the southern Great Plains. In ‘Abstracts of ASA-CSA-SSSA 2006 International Annual Meetings’. 12-16 November, Indianapolis, USA. Available at: http://a-c-s.confex.com/crops/2006am/techprogram/P23808.HTM  (accessed 20 August 2014). 

Harper, F.R., and Berkenkamp, B. (1975). Revised growth-stage key for Brassica campestres and B napus. Can. J. Plant Sci., 55:657-658.

Hocking, P.J., Kirkegaard, J.A., Angus, J.F., Gibson, A.H., and Koetz, E.A. (1997). Comparison of canola, Indian mustard and Linola in two contrasting environments. I. Effects of nitrogen fertilizer on DM production, seed yield and seed quality. Field Crops Res., 49:107–125.

Hocking, P. J., P. Randall, and D. DeMarco. (1997). The response of dryland canola to nitrogen fertliser: partitioning and mobilization of dry matter and nitrogen and nitrogen effects on yield components. Field Crops Res., 59:291-302.

Ingram, S.H. (2011). Canola and calves: An integrated crop-livestock farming system for producing canola and stocker cattle in the Southeast. M.S. thesis. Athens, GA: University of Georgia.

Kirkegaard, J.A., Sprague, S., Hamblin P., Graham, J., and Lilley, J. (2012). Refining crop and livestock management for dual-purpose spring canola (Brassica napus). Crop Pasture Sci., 63:429-443.

Kirkegaard, J.A., Sprague, S., Pymer, S., Salisbury, P., and Howlett, B. (2008). Dual-purpose canola- a new opportunity in mixed farming systems. Aust. J. Exp. Agric., 59:291-302.

NRC. (2000). Nutrient Requirements of Beef Cattle: Seventh Revised Edition: Update 2000. The National Academies Press, Washington, DC.

Pelletier, G., Donefer, E., and Darisse J. (1976). Effects of dates of seeding and levels of N fertilization on yields, chemical composition and in vitro digestibility of forage kale. Can. J. Plant Sci., 56:63-70.

Reid, R L., Puoli, J., Jung, G., Cox-Ganser, J., and McCoy, A. (1994). Evaluation of brassicas in grazing systems for sheep: I. Quality of forage and animal performance. J. of An. Sci., 72:1823-1831.

Wise, K., Johnson, B., Mansfield, C., and Krupke, C. (2011). Managing wheat by growth stage. Purdue Extension Bulletin ID-422. Purdue University, LaFayette, IN.

SAS Institute. (2010). SAS user’s guide: Statistics. Version 9.3 ed. SAS Inst., Cary, NC.

---