Forage production, economic performance indicators and beef cattle nutritional suitability of multispecies annual crop mixtures in northwestern Alberta, Canada

ABSTRACT A 2-year field study compared annual crop mixtures and monoculture cereal crops (controls) for forage yield and quality value for beef cattle production. Each of the mixtures consisted of 2 to 9 crop species. The cropping treatments investigated significantly influenced (P < 0.05) forage dry matter (DM) yield, quality and economic performance parameters. Forage DM yield was up to 9.25 t/ha for the mixtures compared to 7.72 t/ha for the control crops. Forage yield advantage from mixtures was up to 50% over controls. Forage crude protein (CP) was >13.0% for most mixtures, while CP for controls was ≤12.0%. All mixtures and controls mostly exceeded the suggested required levels of K, Mg, Na, S, Fe and Zn for beef cattle. The four top ranked mixtures in terms of marginal returns and benefit/cost ratio were mixtures #4, 8, 10 and 12 in that order. Study results demonstrated that growing a minimum of 3 annual crops, rather than 1 or 2 crops, increased forage production and offered a forage-based diet that, which in most cases, was able to adequately meet the nutritional requirements of beef cattle. The mixture with the highest forage yield consisted of crops from 3 different species categories: Poaceae, Leguminosae and Brassicaceae.


Introduction
In western Canada, feed accounts for a large portion of the total cost of beef cattle production. Winter feeding costs alone account for more than two-thirds of the total annual feeding and management expenses in beef cow-calf production (Damiran et al. 2016;Krause et al. 2013;Kaliel 2004). Traditionally, the winter feeding period for a cow/calf enterprise lasts approximately 200 days (McCartney et al. 2000). Beef cows are commonly fed hay from perennial forages, greenfeed from annual crops or cereal grain silage, and limited amounts of feed grains such as barley (Hordeum vulgare L.), during this period. Beef cows are also managed extensively through swath grazing with cereal crops such as oats (Avena sativa L.) or triticale (X Triticosecale Wittmack).
Typically, annual cover crops are sown as monocultures within annual crop rotations to protect soil from erosion or give other agroecosystem services such as building soil fertility and organic matter, retaining nutrients, or suppressing weeds during periods when cash crops are not actively growing (Smith et al. 2011;Snapp et al. 2005;Teasdale 1996). Forage production from cereal-legume intercrops have been widely reported in western Canada and elsewhere (Gill and Omokanye 2018;Ojeda et al. 2018a;Strydhorst et al. 2008;Aasen et al. 2004;Carr et al. 2004). In northern Alberta, the latest trend among beef cattle producers is growing a multispecies annual crop mixture for forage production. Growing multi-species annual crop mixtures (4 to 6 or greater number of species) (Malézieux et al. 2009) or annual crops sequences/intercrops (Ojeda et al. 2018b) may often be considered as a practical application of ecological principles based on biodiversity, plant interactions and other natural regulation mechanisms as well as improved soil C stocks. Such mixtures could increase forage production (BCRC 2016;Davis et al. 2015;Smith et al. 2014;Wortman et al. 2012), improve water and soil quality, increase nutrient cycling, moisture conservation, and crop productivity (Chu et al. 2017;Hobbs et al. 2008). A multispecies annual crop mixture can be selected from a diversity of plant families (Polygonaceae, Brassicaceae, Poaceae, and Fabaceae), corresponding to different plant functional groups (Lavorel et al. 1997). Each crop species in a mixture may reach maturity at slightly different times, therefore providing available immature forage continuously through the growing season (BCRC 2016).
Several new annual crop mixtures are currently available on the market in western Canada. When making decisions about which annual crop species to include in a mixture, producers need to be aware of the adaptation, potential forage productivity and ecological stability of any newly introduced crop species (warm season crop such as sorghum (Sorghum bicolor L. Moench), cowpea (Vigna unguiculata L. Walp.), mungbean (Vigna radiate (L.) R. Wilczek) in their area (Omokanye 2018). Cool season annual forage-type cereal crop varieties such as barley, oat, triticale and field peas (Pisum sativum L.) are well suited to western Canadian growing conditions and provide acceptable forage yield and quality for winter grazing Kelln et al. 2011;Gill et al. 2013;Gill and Omokanye 2018).
The present study had two objectives: (1) evaluate annual crop mixtures for forage yield and quality; and (2) estimate production costs and associated economic performance of mixtures in comparison to commonly grown cool season forage-type cereal crops. Our first hypothesis was that a multispecies annual crop mixture could provide greater forage production and quality, and offer a diet that is better able to meet the nutritional requirements of beef cattle, compared with a single crop. Secondly, using forage biomass as benefit, we hypothesized that a single crop and a multispecies annual crop mixture would differ in economic outcomes (returns and benefit/cost ratios), which would greatly be in favour of a multispecies annual crop mixture.

Site information and pre-sowing soil tests
Field experiments were carried out over two growing seasons from May 18 to August 2, 2016 and from May 31 to August 14, 2017 at the Fairview Research Farm, located in Fairview Alberta (56°04' 53" N, 118°26' 05" W; 670 m above sea level), which is found in northern Alberta, Canada. The site has a subarctic climate (boreal climate), which is characterized by long, usually very cold winters, and short, cool to mild summers. The soil type at the experimental site is a Gray Luvisolic soil with eluvial and Bt horizons (Soil Classification Working Group 1998). The surface soil characteristics (0-15 cm soil depth) during the field experiments are shown in Table 1. Long-term averages (over 30 years) and monthly-recorded precipitation during the 2016 and 2017 growing seasons (Table 2) were collected from the nearest Alberta of Agriculture and Forestry metrological station, which was within the premises (100-200 m) of the fields used for the present study.

Planting procedure and crop management
Pure cereal crops were sown at recommended sowing rates (Table 3). For the mixture sowing rates (Table 3), a substitutive approach (proportional replacement design) was used as described by Jolliffe (2000). The substitutive method ensures that sowing rates for each species in the mixture are proportional to their monoculture rate. With this approach, the sowing rates for individual species in the mixture were determined by dividing each recommended sowing rate by the total number of species in the mixture (e.g. 6 for mixture #1 and 3 for mixture #8). It is important to note that this approach can only adjust for the number of annual crop species in a mixture but not the number of seeds per kilogram for the different species. Therefore, the total number of seeds per ha varied between mixtures. However, the substitutive approach minimizes potentially confounding effects of a higher overall sowing rate in the mixture and preserves the ability to use well established intercropping indices such as the land equivalent ratio (Jolliffe 2000;Smith et al. 2014).  (Jong and Shields 1988) 250 Each year, land preparation prior to sowing included disking and harrowing. The seeds were pre-weighed and mixed before sowing. The seeds were sown using a plot drill equipped with disc-type openers on 23 cm row spacing. Six rows that were 8 m long were sown per plot. Sowing was done on May 18, 2016 and May 31, 2017. An extended period of precipitation and high soil moisture caused a delay in sowing in 2017. Sowing depth was 1.90 to2.50 cm. In both years, no fertilizer was applied to any of the treatments including monoculture cereal crops. This was done to mimic most of the production practices in growing annual crop mixtures by beef cattle producers in the study area. It is important emphasize that beef cattle producers would normally apply dry fertilizers to monoculture cereals for forage production in northwestern Alberta.
All legumes in the mixtures (except for mixture #7) were inoculated with Cell-Tech® granular nitrogen-fixing inoculant at sowing. Both mixtures #6 and #7 contained only 2 species (barley and hairy vetch). The hairy vetch in mixture #6 was inoculated at sowing, but the hairy vetch in mixture #7 was not. This was done to allow us to examine how the nature of soil Rhizobial populations can affect hairy vetch in a new environment.
Three days after sowing and before any crop emergence, Roundup WeatherMax® herbicide was sprayed as pre-emergent herbicide at 0.8 L/ha. No in-crop spraying of herbicide was carried out to control weeds after crop emergence. Instead, hand weeding was conducted ∼5 weeks after sowing on all treatment plots. *Winfred forage brassicaa cross between a turnip and a kale. **Goliath forage brassicaa rape and kale interspecies cross. ***Hunter forage brassicaan intra-specific hybrid developed by crossing turnips with related Asiatic leaf vegetables of the same species. ****Sorghum Sudan grass (Sorghum × drummondii (Nees ex Steud.) Millsp). *****T-raptor forage hybrid brassicaa cross between a forage turnip and a forage rape.

Forage yield determination and nutritive value analysis
For each treatment plot, the above ground biomass was harvested from the 4 inner rows, in a strip 2 m long, and weighed fresh on August 2 2016 and August 14 2017. Approximately 0.7 kg of freshly harvested material (sub-sample) was oven-dried at 50°C to a constant weight for dry matter content (% DM). The DM was weighed, and the data were extrapolated to t ha −1 forage dry matter yield (FDMY). For both mixtures and monoculture cereals, harvesting was done at soft-dough stage for barley and late milk stage for oat, triticale and soft white wheat. Mixture #9 which did not have any cereals, was harvested when the forage peas were in the midpod stage.
The oven-dried samples were used for nutritive value analysis. The forage nutritive value (% DM basis) was determined by A&L Canada Laboratories Inc., London, Ontario using 2 dry composite forage samples per treatmentone for replications 1 & 3, and the other for replications 2 & 4. Mineral content (macro minerals-P, K, Ca, Mg, S, Na; micro minerals -Zn, Fe, Mn, Cu) were determined by wet chemistry, using modified AOAC 968.08 and 935.13A procedures (AOAC 1995). The laboratory used near infrared reflectance spectroscopy (NIR) to measure crude protein (CP), acid detergent fibre (ADF), neutral detergent fibre (NDF), soluble crude protein (Sol-CP), undegraded intake protein (or bypass protein, UIP), acid detergent fibre crude protein (ADF-CP) and neutral detergent fibre crude protein (NDF-CP). A&L laboratory determined the following parameters from prediction equations provided by Adams (1980): net energy for gain (NE G ), net energy for lactation (NE L ), net energy for maintenance (NE M ), total digestible nutrients (TDN), digestible energy (DE), metabolizable energy (ME) and relative feed value (RFV). The non-fibre carbohydrate (NFC) content (DM basis) was a calculated value based upon nutrient percentages subtracted from 100% of forage DM. Both DM intake (DMI, % of body weight) and DM digestibility (DDM, % DM) were calculated from equations provided by Undersander and Moore (2002), while digestible CP (DCP, % DM) was calculated as DCP = 0.929CP -3.52 (Demarquilly and Weiss 1970).
Both nutrient yield per hectare for CP yield (CPY) and TDN yield (TDNY) were calculated by multiplying crop forage yield (tonne/ha) by the respective nutrient content of CP and TDN to allow a comparison of nutrient yield potential for animal feed production among the cropping treatments.

Partial budget analysis
A partial budget analysis of the input costs and output revenue (forage DM yield & hay price) to determine returns and benefit: cost ratios (BCR) on a per hectare basis was done for all cropping treatments including the four monoculture cereal controls. Custom field work rates from AgriProfits Cropping Alternatives were used (AAF 2018).
Other direct input costs that were applied to all treatments came from tillage and sowing costs, and greenfeed cutting, baling and hauling. In the present study, no fixed costs, crop insurance premiums or paid capital interest were used.
Revenue was estimated as forage DM yield (kg ha −1 ) multiplied by the average unit price of hay/greenfeed (CAD $0.18 kg −1 ) in Alberta from August to October 2018. Returns were derived by subtracting total variable costs from revenues. For each cropping treatment, BCRs were calculated by dividing returns by total variable costs. The results of the BCR analyses were compared to a standard index of 1:1 to assess the performance of the cropping treatments. The higher the BCR, the better the economic and management efficiency of the treatment. In the present study, the only revenue used was forage DM yield. No economic adjustments were made for different nutrient values (e.g. CP and TDN).
Forage DM yield per CAD $ spent on seed was calculated by dividing forage DM yield (t/ha)/seed cost. The cost per ton of protein was derived from: seed cost/CP yield.

Data analysis
Data were analyzed using a pre-defined model procedure from the CoStat -Statistics Software (version 6.2; CoStat 2005) to determine cropping treatment effects on all measured parameters. For the partial budget analysis data, only seed costs were not subjected to any statistical analysis because of the uniformity in seed costs for both years and replications for any particular cropping treatments. Where ANOVA indicated significant effects, the means were separated by the least significant difference (LSD) at the 0.05 probability level. Significant differences in the text refer to P < 0.05. Of the 33 monitored forage yield and quality parameters, the ANOVA for only 11 (FDMY, Sol-CP, ADF-CP, UIP, P, Mg, S, Fe, DMI, TDNY, RFV) indicated significant annual crop mixture x year interactions. Here, only the means of the measurements for the annual crop mixtures (across both years) are presented in tables and discussed in text.

Forage dry matter yield and notes on crop growth
The forage dry matter (DM) differed significantly (P < 0.05) between cropping treatments. Except for mixture #8, which had similar (P > 0.05) forage DM yield to mixture #4, forage DM yield was generally significantly higher for mixture #4 (9.25 t ha −1 ) than other mixtures and controls (monoculture cereal crops, Table 4). Three of the mixtures (#4, #8 and #12) had >8 t ha −1 forage DM yield, while other mixtures and monoculture cereals had values <8 t ha −1 forage DM. Among the monoculture cereal crops, triticale had significantly greater forage DM yield than oat and barley, but not soft white wheat. Also, triticale gave higher (P < 0.05) forage DM yield values than five of the fourteen mixtures (#3, #7, #9, #13 and #14). The forage yield advantage from mixtures was as high as 37, 48, 29 and 20% respectively over barley, oat, soft white wheat and triticale. Only 3 of the mixtures (#4, #8 and #12) appeared to have consistently higher forage yield advantage (>5%) over all of the monoculture cereal crops. Other mixtures did not seem to have consistent forage yield advantages over the annual cereal crops. However, on several occasions other mixtures did have some yield advantage over barley and oat crops. Also, 2-3 way mixtures with only cereals and legumes showed yield advantages of 0.17-2.27 t ha −1 forage DM yield over control cereals.
It was observed that BMR sorghum and forage sorghum, hunter forage rape and teff performed poorly in the mixtures. These species had poor seed germination and limited establishment in stands. It was also noted that the barley in mixture #6 grew slightly taller than the barley in mixture #7. Generally, the monoculture cereal crops seemed to grow slightly taller than their counterparts in mixtures. Though control cereal crops grew taller, no lodging was observed during any of the 2 growing seasons.
The forage ADF, NFC and RFV were all significantly affected (P < 0.05) by cropping treatments (Table 5). Monoculture oat crop had significantly higher ADF and NDF level compared to most mixtures, as well as other cereal crops. Overall, mixtures #11, #12 and #13 seemed to fare better than other mixtures with lower forage ADF and NDF, and higher forage NFC. Three (mixtures #11, #12 and #13) of the 14 mixtures showed significantly higher RFV than other mixtures and monoculture cereal crops.
The forage TDN and other determinations of energy (NE L , NE G and NE M ) value, and TDNY were all significantly affected (P < 0.05) by cropping treatments (Table 5). In most cases, 3 of the mixtures (#11, #12 and #13) produced significantly higher (P < 0.05) forage energy (TDN) than other mixtures and monoculture cereals. The forage TDN varied from 62 to 69% for all cropping treatments. The forage TDNY was highest for mixture #4 (6.01 t TDNY ha −1 ), followed by mixture #11 (5.64 6.01 t TDNY ha −1 ). The other forms of forage energy measured (NE L , NE G and NE M ) were all significantly higher for mixtures #11, #12 and #13 than monoculture cereal crops. Monoculture oat crop consistently gave the least NE L , NE G and NE M values.
All forage macro minerals (Ca, P, K, Mg, Na and S) and trace minerals (Cu, Fe, Zn and Mn), as well as Ca:P and tetany ratios measured here were affected (P < 0.05) by cropping treatments (Table 6). Except for mixture #9 (forage K and S), the forage Ca, P, Ca:P, K, Mg, S and Fe differed significantly from most mixtures as well as all monoculture cereal crops. Forage Na was by far higher for mixture #12 than other mixtures and monoculture cereals. As shown in Table 6, mixtures #3 and #8 had higher forage Mn values than other mixtures, while pure oat and triticale showed higher forage Mn values than other cereals and most mixtures. Mixture #9 had higher forage Cu and Zn than other mixtures and pure cereals. The forage tetany ratio was significantly higher (P < 0.05) for pure cereals than mixtures, ranging from 3.24:1.0 to 3.87:1.0 for monoculture cereals and 0.95:1.0 to 2.88:1.0 for mixtures.
The forage digestible feed energy (DFE), digestible crude protein (DCP), dry matter intake (DMI) and digestible dry matter (DDM) were all significantly affected (P < 0.05) by cropping treatments (Table 7). Three mixtures (#11, #12 and #13) appeared to be consistently higher (P < 0.05) in forage DFE, DCP, DMI and DDM than other mixtures as well as monoculture cereal crops.   Table 8 shows the economic performance of pure cereal crops (controls) and 14 mixtures investigated. The estimated revenue, returns and BCR were influenced significantly (P < 0.05) by cropping treatments. The estimated revenue was highest for mixture #4 (CAD $1664/ha), followed closely by mixture #8 (CAD $1528/ha) and then mixture #12 (CAD $1486/ha). Except for mixture #8, the revenue generated from mixture #4 was significantly higher than other mixtures and monoculture cereal crops. Other than mixtures #4, #12 & #14 and pure triticale crop, estimated total input costs were significantly (P < 0.05) higher for mixture #6 (CAD $563/ha) than other mixtures and pure cereal crops. Except for mixtures #8 (with a marginal returns of CAD $993/ ha), the estimated marginal return was significantly higher for mixture #4 (∼CAD $1112/ha) than other cropping treatments, including cereal controls. Triticale had higher marginal returns than the other cereal crops (Table 8). Only 7 of the mixtures (#4, #5, #6, #8, #10, #11 and #12) consistently had more profits (CAD $20-466/ha) over all cereal crops compared to the mixtures. Overall, there were more profits from mixtures compared to barley and oat than soft white wheat and triticale. Mixtures #7 and #13 did not result in any profits over any of the pure cereal crops.

Partial budget analysis comparison
The estimated BCR for all cropping treatments was generally >1.00. With the exception of mixture #8, the BCR was significantly higher for mixtures #4 and #10 than other mixtures and all pure cereal crops. Only both mixtures #4 and #10 had >2.00:1:00 BCR. Other mixtures, as well as pure cereal crops, had between 1.18:1.00 and 1.85:1.00 BCR.
Overall, oat was the least expensive in seed cost (CAD $40/ ha), while dual crop species mixtures #6 and #7 were the most expensive in seed cost. The higher seed cost from mixtures #6 and #7 resulted from the seed cost of hairy vetch, which was about 66% of the total seed cost. Forage DM yield per dollar spent was highest for pure oat crop (0.16 t/CAD $), followed by both mixtures #3 and #4, with about 0.13 t/CAD $. The least forage DM yield per dollar spent came from mixture #7, which consisted of barley + non-inoculated hairy vetch. The cost per ton of protein was highly variable, with the most expensive in the mixture #7 (CAD $157), followed by mixture #6 (CAD $121) and pure barley and triticale crops (CAD $102). The least cost to produce a ton of protein came from mixture #11 (∼CAD $38). Overall, mixtures #3, #4, #11 and #10 could be considered the least expensive mixes to produce for both dry matter and protein yield. The most expensive mixtures were #6, #7, #9 and #14.

Discussion
Multispecies annual crop mixtures have recently become more popular in northern Alberta. Producers need information on the performance of mixtures to implement successful production/ farming operations.
This study evaluated the forage yield and quality obtained from growing several multispecies annual crop mixtures compared with the traditional monocrop cereals grown for forage in the study area. Profit potential for beef cattle producers depends on producing enough forage per hectare, with adequate feeding value including crude protein and mineral level, low fibre and high energy and digestibility, in order to keep production costs below selling price. The findings from the present study are discussed as relating to assessing diverse mixtures of annual crop species in comparison with the traditional (monoculture) cereal crops (oat, barley and triticale) for use in beef cattle production systems, with a focus on nutritional quality in relation to the National Research Council (NASEM 2016) nutrient requirements of beef cattle (Table 9) and economic performance.

Forage dry matter (DM) yield
In the present study, the top 3 forage treatments for DM yield were mixtures #4, #8 and #12, with 8.26 to 9.25 t/ha forage DM yield. Mixtures #4, #8 and #12 had 3 to 9 crop species in the mixtures. This shows that increasing plant community diversity with different complementary functional groups above monoculture and binary mixtures can significantly result in higher forage production. In the United States, Wortman et al. (2012) reported that a 6-species mixture seemed to be the most promising out of the 2-, 4-, 6-and 8-species mixtures evaluated. Diversity-productivity theory suggests that increased productivity associated with species diversity is due to more efficient resource use (Ojeda et al. 2018a;Tilman 1999;Trenbath 1974).
Overall, the mixtures investigated established successfully in both years in the present study. However, certain crop species which are new to the study area did not grow well in mixtures #10, 12, 12 and 13. Three warm season crops (forage sorghum, BMR sorghum and teff) and a cool season crop (hunter forage turnips) performed poorly during the study. This therefore shows that care would need to be taken by producers in including crops that are not adapted to an area and in particular those that may not have had evidence of good production potential in a new environment. It is important to note that mixture #4, which had the highest forage DM yield consisted of the top performing forage-type crops (when grown as monocrops) in the study area.
The differences in forage DM yield (0.64 t ha −1 ) between mixtures #6 (inoculated hairy vetch) and #7 (with non-inoculated hairy vetch), which was in favour of mixture #6 further confirms the need to inoculate legumes with appropriate rhizobia species and strains before sowing, especially if a legume species is new to an area or if effective rhizobia are not present in the soil in sufficient quantities. Hairy vetch would be considered new to the study area.

Forage nutritive value
Matching the nutrient requirements of beef cattle and the nutrients supplied by forage type feeds will help identify nutritional sufficiency and inadequacies. In the present study, in almost in all cases, the mixture had better forage nutritive value than the pure cereal crops (controls). The better forage nutritive value from most mixtures than pure cereals could be attributed to complementary N functions in mixtures that included legume (s). Complementary N function can lead to facilitation, an increased N availability to non-legume species due to the presence of N 2 fixing legumes. Including other non-legume crop species like Italian ryegrass and forage brassicas like Winfred, Goliath and T-Raptor were thought to have improved forage quality of mixtures that consisted of any of these crops.
The forage CP, TDN, Ca, K, Mg, Na, S, Fe, Zn, Mn and RFV were greater for mixtures #9, #10, #11, #12 & #13, compared to other mixtures and the control cereals. This shows that a mixture with the right type of multispecies crops can be fed reliably to beef cattle as another forage feed source in the study area.
The NASEM (2016) model for diet of mature beef cows suggests 7% CP for maintenance in mid pregnancy, 9% CP for a beef cow in late pregnancy, and 11% CP for lactating cows (See Table 9). The TDN is a useful measure for energy content of beef cow rations that are primarily forage. For a mature beef cow, using percent TDN, NASEM (2016) suggests 55% in mid pregnancy, 60% in late pregnancy and 65% after calving (Table 9). Going by these recommendations, it is evident that all mixtures as well as control cereals tested in the present study, exceeded the CP and TDN requirements of dry, pregnant BCR stands for Benefit/cost ratio *Significance at P < 0.05. Means within a column with the same superscript (s)/letter(s) were not significantly different according to LSD (P < 0.05). + NA = not available. Note: This is only a simple cost analysis and is not intended as an in depth study of the cost of production. The costs are in Canadian Dollar (CAD $). CAD $1 = US $0.78. Total variable consisted of seed costs, tillage, sowing, forage conservation processes (e.g. cutting, hauling). (gestating) beef cows. For a lactating beef cow, which requires 11% CP and 65% TDN, only the control oat and triticale treatments appeared to not meet CP requirements, while none of the monoculture cereal crops and mixtures #1 and #3, had the 65% TDN required for beef cattle. For young beef cattle, 12-14% CP and 65-70% TDN is suggested for their total diet content (NASEM 2016). In the present study, in most cases, the mixtures (except for # 7 and #8) exceeded the CP requirement for young beef cattle. In the control group, only barley was able to meet the 12-14% CP required. Most mixtures appeared to be within the 65-70% TDN suggested for young beef cattle, while none of the control cereal crops had sufficient TDN. In the present study, because of the failure of most mixtures to be in the upper limit of the required TDN for young beef cattle, producers will need to test their mixtures for feed quality and use energy supplementation where needed to ensure that the TDN requirements are met. Further research is therefore needed to determine the right mixture of cover crop species, their sowing rates, and the appropriate stage to cut for silage or geenfeed for back grounding beef calves in the environment of northern Alberta. The net energy system separates the energy requirements into fractional components used for tissue maintenance, tissue gain, and lactation (NASEM 2016). All tested mixtures and monoculture cereals exceeded the NE M levels suggested for a mature beef cow (1.19 to1.28 Mcal kg −1 NE M ) and were well with the 0.53 to 1.37 Mcal kg −1 NE G suggested for growing and finishing beef calves (NASEM 2016).
Mineral imbalances and/or deficiencies can result in decreased performance, decreased disease resistance, and reproductive failure, which results in significant economic losses (GOS 2015). The NASEM (2016) suggested requirements for minerals for beef cattle are shown in Table 9. In the present study, all mixtures as well as pure cereal crops far exceeded the suggested minimum target levels of K, Mg, Na (except for pure soft white wheat), S (except for mixture #14), Fe and Zn for young and mature beef cattle. All mixtures and pure cereal crops had enough Ca and P for a mature gestating beef cow. However, for a lactating beef cow, all pure cereal crops and mixtures #6, #7, #8 and #14 fell short of meeting the Ca requirements of this category of beef cows. Only mixtures #12 had sufficiently met the P requirements of a lactating beef cow. No cropping treatments (mixtures and pure cereal crops) met the requirements for Cu, and some mixtures (mixtures #2, #5, #6, #7 and #10) did not meet the required amount of Mn needed by mature beef cattle. In the present study, forage Cu, Fe, Zn and Mn contents were far lower than the maximum tolerable levels for beef cattle as provided by NASEM (2016).
For growing and finishing calves, all of the mixtures had adequate Ca, while only one of the pure cereal crops (barley) was able to meet the 0.31% Ca needed by these calves. Also for young beef cattle, all mixtures and pure cereals met the suggested minimum levels of K, Mg, Na (except for pure soft white wheat), S (except for mixture #14), Fe and Zn. Only 8 of the 14 mixtures and pure triticale conveniently met the 0.21% P requirement for calves.
Six NDF and ADF based forage quality standards (prime, 1, 2, 3, 4 & 5) have been described for beef cattle (Ball et al. 2007). In the present study, only 5 of the mixtures (mixtures #9, #10, #11, #12 and #13) qualified for the prime standard (<31% ADF and <40% NDF). No pure cereals could be considered for the prime standard. The ADF values are important because they inversely relate to the ability of an animal to digest the forage. The NDF values reflect the amount of forage the animal can consume. In the present study, pure cereals generally had higher forage ADF and NDF values than mixtures. Mixtures #11, #12 and #13 had lower ADF and NDF values than other mixtures and pure cereals. With the lower ADF and NDF values obtained for mixtures #11, #12 and #13, when all the treatments tested here are presented side by side to cows in a preference study, mixtures #11, #12 and #13 would likely be preferred and consumed more than other treatments. Future study is needed to determine how beef cattle will utilize and respond in terms of growth performance to mixtures versus traditional cereal crops used for livestock production in western Canada.
Mixtures with brassicas species seemed to improve forage CP, TDN, detergent fibres (ADF and NDF) and forage Ca more than mixtures without brassica species. Brassicas have a readily digestible carbohydrate content but are relatively low in fibre so cattle should be provided a fibre source to prevent rumen acidosis or bloat (Arnold and Lehmkuhler 2014;Lemus and White 2014).

Economic performance indicators
The economics of a mixture depends primarily upon the costs and returns associated with forage DM production and nutritive value.
As expected, mixtures #4, which had the highest forage DM yield, also had the highest revenue from forage production as well as significantly higher returns than the other mixtures and pure cereals. The significantly higher revenue obtained for mixture #4 compared to other mixtures (except for #8, which had similar revenue), and pure cereal crops in particular, was a reflection of the benefits of growing a mixture containing a functionally diverse and adaptable group of cover crops representing different plant families (Brassicaceae, Fabaceae and Poaceae; C4 and C3 grasses; nitrogen-fixers, nutrient scavengers).
Seed costs for 8 of the mixtures were within the CAD $40-80/ha seed costs for the more traditional pure oat and barley crops for forage production in the study area. Higher seed costs for some mixtures could be attributed to higher seed costs of some imported annual crop species such as hairy vetch, brassicas and annual clovers (Crimson and Frosty berseem). Local seed production of such crops that have great forage production potential in northwestern Alberta would help reduce seed and total input costs/ha when such a crop is included in a mixture.
In the present study, the BCR was generally >1, an indication that the cropping treatments' benefits outweigh the costs. On a BCR basis, mixtures #4 and #10 were more profitable, followed by mixture #8. Overall, mixtures #1, #7, #9, #13 and #14 did not seem to have any improvement in BCRs over the more traditional oat and barley crops grown in northwestern Alberta for livestock feed. It is important to note that grazing animals (e.g. annual pasture or swath grazing) would be the key to making mixtures work better on a cow-calf operation. This will eliminate forage processing costs (e.g. cutting, baling, silage and hauling) and make the mixtures more profitable. But where mixtures are to be harvested and stored for later use, silage would work better due to the higher moisture content of most mixtures at harvest compared to the traditional oat or barley monocrop.
Forage DM yield per CAD $ spent was highest for the pure oat crop (0.16 t/CAD $), followed by both mixtures #3 and #4, with about 0.13 t/CAD $. The difference in the forage DM yield per CAD $ spent between both mixture #6 (inoculated hairy vetch) and #7 (un-inoculated hairy vetch), which was in favour of mixture #6, further confirms the need for a legume inoculation, particularly when the legume is new to an environment. The cost per ton of protein was highly variable. Overall, in the present study, mixtures #3, #4, #11 and #10 could be considered the least expensive mixes to produce both forage dry matter and protein.

Conclusion
The study demonstrated that growing the right annual crop mixture can increase forage production and provide beef cattle with a diet that in most cases is able to adequately meet the nutritional requirements for gestating beef cattle. Overall, in terms of forage yield advantage, marginal returns and benefit/cost ratio, 3 of the mixtures (#4, #8 and #12) were consistently satisfactory compared to all the monoculture cereal crops. Most of the mixtures had >12.0% forage CP compared to <12.0% forage CP for controls. Because most mixtures did not meet the required TDN level for young beef cattle, some form of energy supplementation would still be needed to ensure that TDN requirements are met. The present study results therefore suggest that growing an annual crop mixture with diverse plant functional groups compared to a monoculture cereal, can be used to improve forage production in northwest Alberta.