Hemp, Tropical Corn and Other Alternative Annual Forages: Opportunities for Feeding Beef Cattle in Five Easy Lessons!

Improving Forage Options

Following the forage shortage and high prices seen in 2012, OMAF and MRA staff and University of Guelph researchers are investigating more forage opportunities for Ontario livestock producers. One direction within this area was the repurposing and characterization of a number of existing and novel crops for the purpose of stored forage. Of those investigated in 2013, each shows some potential for this purpose. Lesson #1: If it can be cultivated (if it grows on a farm) there is a good chance cattle can make use of it!

The annual crops investigated included hemp, which is currently grown for biomass and fibre, specialty biofuel and sweetener crops (high-sugar Millet and high-sugar Sorghum) and two specialty long-season tropical corn varieties developed by Dr. Fred Below at the University of Illinois. The tropical corn varieties tested included both a biofuel variety and a forage variety. Since corn originally evolved in the tropics, the name "Tropical Corn" needs explanation. The key here is that Tropical Corn has not been bred for photoperiod adaptation and is exceptionally long-seasoned. The millet, sorghum and corn varieties were grown at Canada's Outdoor Farm Show location (Woodstock) and the hemp on private plots near Kemptville. It should be noted that plots of the corn, sorghum and millet were also seeded near Elora but due to late seeding and lack of timely weed control these were abandoned. Lesson #2: planting dates and weed control are key to success with annual forages. Agronomics matter!

Figure 1 shows the trends in TDN content of the 4 forage types over the 2013 growing season year. These species are Hemp, Sweet Millet, Sweet Sorghum, and Tropical Corn. As a reference, the baseline for the graph is 52%

Figure 1. Total digestible Nutrient (TDN) Content by Date

Figure 1 shows the trends in TDN content of the 4 forage types over the 2013 growing season year. These species are Hemp, Sweet Millet, Sweet Sorghum, and Tropical Corn. As a reference, the baseline for the graph is 52%, well above the 45% TDN which is typical of Ontario wheat straw when used in a ration. The lowest TDN observed which was Sweet Millet (57%), which is equal to many first cut hays in Ontario.

Figure 1 shows the trend in percent total digestible nutrient (TDN) in these various crops by date. As evident, the crops that will develop grain (e.g. sorghum, millet) have different TDN curves than those that would not, such as perennial grasses, which show a classic and degrading feed quality response to maturity. Neutral detergent fiber (NDF) data was not included in the graph but was as follows:

  • Hemp: NDF ranged from 40 to 59% in three repeated samplings, but not in progression.
  • Sweet Millet: NDF ranged from 55 to 65% in repeated samplings with a general upward trend as it matured
  • Sweet Sorghum: NDF ranged from 46 to 60% in repeated samplings, but no real trend associated with maturity
  • Tropical Corn: NDF ranged from 56 to 62% in three repeated samplings, and also not in any progression.

As a reference, the TDN and NDF of Ontario wheat straw is often seen at about 45 and 75% respectively Wheat straw was included in many beef rations in 2012 and 2013. Lesson #3: Many existing and emerging crops have greater feed value than we give them credit for!

Potential Species for Ontario

The remainder of this article contains information on the species represented by this sampling and discussed thus far. In the future, palatability and intake checks may need to be performed to match up with the chemical analysis as seen in the 2013 plots. Lesson #4: Other jurisdictions already have information on the forage potential of crops which we don't yet realize can be forages!


High quality hemp is cultivated throughout Canada. It is possible to cut hemp for silage to mix with corn silagei, and by mixing hemp in with corn silage, cows had improved weight gains. Hemp is a common crop in the Netherlands as it is an alternative to straw and is low in dust and is very absorbent. One report in the popular press there suggested that dairy cows fed hemp give a little more milk and seem to be really healthy. When considering hemp, it is important to realize that all hemp growers need to obtain a licence from the government of Canada.

Sweet Pearl Millet

Sweet pearl millet is commonly used as a biofuel crop, and the residues produced are often used in livestock feedii. In addition to sweet pearl millet, regular (RMR) and brown midrib (BMR) pearl millet varieties are also available. Although BMR shows improved quality through increased digestibility, BMR yield is lower which offsets value so that both BMR and RMR are approximately equal in overall feed value per unit area growniii. Sweet millet differs from regular pearl millet in that the plant has longer and narrower leaves, profuse nodal tillering with asynchronous maturity, short thin spikes, and very small grains. Sweet millet has been found to have twice the amount of soluble sugar in comparison to regular pearl millet varietiesiv, and hence its name.

Millet has long been grown for forage and grain in areas of Africa, Asia, and the Southern US. However, in the 1990's the hybrid Pearl millet was developed for use in the sandy soils of Eastern Canadav.

Sweet Sorghum

Sweet sorghum is a very efficient crop to grow in areas prone to droughts due to its water use efficiency and enlarged root system. Under drought stress, sorghum is able to maintain similar physiological activity to well watered sorghum, unlike drought stressed corn. Total biomass production in sorghum under drought stress is reduced by about 40% compared to an almost 50% reduction in drought stressed cornvi. A 2009 studyvii compared sweet sorghum with both brown midrib (BMR) and grain type sorghum varieties. The study found that lignin content was lower in the sweet sorghum than both of the other varieties; consequently, sweet sorghum was found to have higher digestibility than either BMR or grain varieties.

photo of sweet sorghum stalks in the back of pickup truck

Figure 2. Sweet sorghum stalks

Figure 2 shows Ron Lackey (OMAF and MRA) with sweet sorghum grown at the Canada's Outdoor Farm Show site (October 2013). These stalks were being processed into mini-silos to determine potential on a pilot level.

Sweet sorghum silage has been shown to be a suitable substitute for corn silage when feeding growing calves. In another studyviii , Hereford and Angus calves were fed either sorghum silage, corn silage, or fescue hay. The feeds were determined to be comparable in terms of dry matter intake, crude protein, and gross energy. Sweet sorghum silage may also be a suitable substitute for alfalfa silage when feeding lactating cows. Research has demonstrated that although milk yield was lower for sweet sorghum fed dairy cows, dry matter intake, energy corrected milk yield, and feed efficiency were similar between the two feeds.

Tropical Corn

There is currently very little knowledge about growing tropical corn in the mid to northern USA and Southern Ontario. However, a trial in Wisconsinx at 45°N latitude and found that tropical corn grown for silage at this location was earless and did not produce any grain. The earless corn silage was included at 50% of DM in the diet fed to Holsteins heifers and did not appear to have any significant effect. Having less grain content than conventional or temperate corn hybrids, Tropical Corn may have applications in things like beef cow rations as it has the large yield of corn silage, but at much lower or zero grain content.

photo of a man holding a stalk of tropical corn

Figure 3. Tropical Corn

Figure 3 shows forage variety Tropical Corn grown in the Canada's Outdoor Farm Show plots. Note the immature ear in this photo taken October 4th, 2013. This variety was developed and provided courtesy of Dr. Fred Below of the University of Illinois.

When planted in mid-summer in the southern USA, tropical corn produces higher DM and grain yields than temperate hybrids planted at the same time. This is because temperate hybrids have been developed for spring plantings and are not as productive when planted later in the summerxi,xii. This indicates potential for Tropical Corn as a second crop grown later in the season.

photo of corn in the back of a pickup truck and a man holding a stalk of tropical corn

Figure 4. Tropical Corn, biofuel variety

Figure 4 shows a biofuel variety of Tropical Corn developed by Dr. Below. This photo, also taken October 4th; note the immense size of the plant and lack of a cob.

photo of a man packing chopped alternative crops into plastic pails

Figure 5. Making mini-silos of alternative annual crops.

Figure 5 illustrates the making of mini-silos for testing the ensilability of annual Tropical Corn (2 varieties), Sweet Millet and Sweet Sorghum in 20 litre pails. This is done using a hydraulic ram as packing matters in all silos, especially little ones!

Increased Forage Options for Cattle Producers

While the focus of this article has been on selected annuals, there may be a number of feeds available that have been planted for industrial or forage purposes, which can serve as feed in an Ontario beef system. Some of these have been piloted in Ontario as shown in Figures 2, 3, 4, and 5. They may be purposeful, opportunity, salvage, or emergency feeds but remain options outside of the regular crops should the need arise. Lesson #5: the forage options are many and this article only scrapes the surface when it comes to options for feeding the versatile beef animal!


i Mosjidis, J., Burke, J., & Hess, J. (2012). The Facts about Sun Hemp Toxicity. Crop Science. 52: 1469-1474.

ii LeBlanc, Vincent; Vanasse, Anne; Belanger, Gilles; & Seguin, Philippe (2012) Sweet pearl millet yields and nutritive values as influenced by fertilization and harvest dates. Agronomy Journal. 104.2:542-549

iii Hassanatt, F.; Mustafa, A.F.; & Seguin, P. (2006) Chemical composition and ensiling characteristics of normal and brown midrib pearl millet harvested at two stages of development in south-western Quebec. Canadian Journal of Animal Science. 86.1:71-80

iv Appa Rao, S.; Mengesha, M.H.; & Subramanian, V. (1982) Collection and preliminary evaluation of sweet-stalk pearl millet (Pennisetum) Pennisetum Amaricanum, sugar content. Economic Botany. 36.3: 286-290

v Banks, Scott & Stewart, T. (1998) Forage Pearl Millet. OMAF Factsheet. agdex # 126 and order number 98-045.

vi Zegada-Lizarazu, Walter; Zata, Alessandro; & Monti, Andrea (2012) Water uptake efficiency and above and below ground biomass development of sweet sorghum and maize under different water regimes. Plant and Soil. 351.1-2:47-60

vii Di Marco, O.N.; Ressia, M.A.; Arias, S.; Aello, M.S.; & Arzadun, M. (2009) Digestibility of forage silages from grain, sweet, and bmr sorghum types: Comparison of in vivo, in situ, and in vitro data. Animal Feed Science and Technology. 153.3-4:161-168

viii Aclewakun, L.O.; Famuyiwa, A.O.; Felix, A.; & Omole, T.A. (1989) Growth performance, feed intake, and nutrient digestibility by beef calves fed sweet sorghum silage, corn silage, and fescue hay. Journal of Animal Science. 67.5:1341Amer, S; & Mustafa, A.F. (2010) Effects of feeding pearl millet silage on milk production of lactating dairy cows. Journal of Dairy Science. 93.12: 5921-5925

ix Hoffman, P.C.; Esser, N.M; Bauman, L.M.; Denzine, S.L.; & Engstrom, M. (2001) Effect of dietary protein on growth and nitrogen balance of Holstein heifers. Journal of Dairy Science. 84.4:843-847

x Overman, D.L. & Gallaher, R.N. (1989) Growth and partitioning of dry matter between temperate and tropical corn. Southern Conservation Tillage Conference. Special Bulletin 89-1

xi Johnson, J.C. Jr.; Gates, R.N.; Newton, G.L.; Wilson, J.P.; & Chandler, L.D. (1997) Yield, composition, and in vitro digestibility of temperate and tropical corn hybrids grown as silage crops planted in summer. Journal of Dairy Science. 80.3:550-557

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