Food-fodder performance of food and malt barley cultivars in Ethiopian highlands

1 Department of Animal science, College of Agriculture and Veterinary Medicine, Jimma University, P. O. Box 378, Jimma, Ethiopia. 2 Department of Nutrition, Genetics, and Ethology, Faculty of Veterinary Medicine, Ghent University, Belgium. 3 International Centre for Agricultural Research in Dry Areas, P. O. Box 5689, Addis Ababa, Ethiopia. 4 School of Animal, Rural and Environmental Sciences, Nottingham Trent University, Brackenhurst Campus, Southwell, NG25 0QF Nottinghamshire, UK.


INTRODUCTION
Barley (Hordeum vulgare L.) is the fourth most important cereal crop in terms of worldwide grain production (FAOSTAT, 2017). The developing countries contribute to more than half of land area planted with barley crops. Moreover, barley is a multiple-purpose crop with high economic and social importance. It is grown to produce grain for human and straw for livestock consumption and malt for brewing (Kaso and Guben, 2015). However, growing barley is associated with a production of large quantities of straw which is used extensively as ruminant feed specially in developing countries during dry seasons.
According to the report of Jaleta et al. (2015) cereal straws (barley teff and wheat) appears to be preferred as  livestock feed by the farmers and share about 77-88% of animal feed in mixed crop livestock system, from cereals barley is higher than teff and wheat for livestock feed (Seyoum et al., 2020). It has been reported that crop residue biomass and nutritive value are key determinants in varietal selection by farmers in mixed crop-livestock systems (Jaleta et al., 2015;Schiere et al., 2004). Consequently, livestock researchers and crop breeders have launched research themes to upgrade straw yield and nutrient composition alongside grain yield using plant breeding approaches in pulses Blümmel et al., 2010;Jane Wamatu et al., 2017) and cereals (Addisu, 2018;Ertiro et al., 2013;Jensen et al., 2011). Exploiting differences in feed traits of barley types could provide novel breeding targets for new barley varieties with potentially higher food and livestock feed value that would be particularly useful in a range of diverse environments in mixed crop-livestock systems. Thus, the current study aimed to identify superior cultivars in terms of grain yield, straw yield and food-feed potential (dual-purpose use) for mixed farming systems in Ethiopian highlands.

Experimental sites and design
The study was conducted at Kulumsa Agricultural Research Center, Bekoji and Kofele experimental sites. The agro-ecological description of the experimental sites is presented in Table 1. The experiment comprised of twenty food and twenty malt improved cultivars drawn from National Variety traits (NVT) of the Ethiopian Barley improvement program. The cultivars were planted using randomized complete block design with three replications during the main cropping season (June to November) under rain-fed condition, with a plot size of 2.5 m × 1.2 m. Spacing between plots and blocks was 0.5 m and 1 m, respectively. All plots were equally managed as per recommended agronomic practices for barley growing in Ethiopia, Fertilizer was applied at a rate of 50/100 kg/ha urea /DAP respectively.

Data collection and sampling
At physiological maturity (maturity date varied from 121 days early matured to 154 days late matured) all above ground biomass of each plot was harvested and air-dried for two weeks to constant moisture. Plots were manually harvested over 4 middle rows of each plot and the total biomass yield was taken, then threshed. Straw yield of each plot was calculated by subtracting grain yield from total biomass yield. Representative samples from each plot were taken and ground to pass through a 1 mm sieve, then stored for feed nutritional analysis.

Laboratory evaluation
All grain and straw samples were analysed for crude protein (CP), neutral detergent fibre (NDF), metabolizable energy (ME) and in vitro organic matter digestibility (IVOMD) using a combination of wet chemistry analyses and Near Infrared Reflectance Spectroscopy (NIRS); Instrument FOSS 5000 Forage Analyzer with WINISI II software package in the 1108-2492 nm spectra range). A good-offitness barley NIRS equation (Wamatu et al., 2019) was used for the prediction of dry matter (DM), nitrogen, neutral detergent fiber (NDF) and in vitro digestibility (IVOMD). Validation of the NIRS equation was undertaken by analyzing 20% of representative samples using conventional wet chemistry. Crude protein was determined according to AOAC (1990). The neutral detergent fiber (NDF) was determined according to Van Soest and Robertson (1985), IVOMD was determined according to Tilley and Terry (1963) and the metabolizable energy (ME) was estimated from digestible energy and IVOMD using regression and summation equations developed by NRS (2001).

Calculations and statistical analysis
A general linear model was used to test the effect of cultivar on grain yield, straw yield and potential utility index (PUI). PUI, which estimates the proportion of utilizable portion of total barley biomass for food and feed was calculated according to the following equations.
HI, Harvest Index (W/W), Grain yield (GY) (t/ha), Straw yield (SY) (t/ha). Data of the study was subjected to the analysis of variance according to the following model: Where Y ijk is the response variable, M is the mean, G i is the effect of barley cultivar i, L j is the effect of the location j, B k (L i ) is the effect of the block k within k location i, (G×L) ij is the interaction between the cultivar and the location and E ijk is the random error.

Grain and straw nutritive quality
A wide range in grain nutrient and energy concentration was observed across the cultivars for food and malt  (Table 4 for malt  type barley and Table 5 for food type barley). Also for straw, large variation in nutritive value was found across cultivars for food and malt barley cultivar: straw CP: 4.1-5.7% and 4.9-6.2%, straw NDF: 73.5-76.7% and 72.9-76.1%, straw ME: 5-5.6 MJ/kg and 5.3-5.8 MJ/kg (Table 4 for malt type barley and Table 5 for food type barley). Multiple differences were found between cultivars, but with a significant cultivar-location interaction, meaning that the growing location had an impact on the performance of the cultivars and their concomitant PUI ranking. The overall grain quality in Kofele was superior to that in Bekoji. The difference between low and high yielding cultivars was presented in Table 6 (Food barley) and Table 7 (Malt barley ). Table 8 presents the relationship between straw yield and nutritive value as well as grain yield and nutritive value across food and malt barley cultivars. The correlation between grain yield and straw yield was positive for both food and malt barley cultivars regardless of the location (r > 0.7). Grain yield was correlated weakly to moderately (r < 0.39) with straw nutritive value parameters for both food and malt barley in both locations.

Food-fodder correlation
Generally, the linear correlations between nutrient composition of grain (grain CP, grain NDF and grain ME) and nutrient composition of straw (straw CP, straw NDF and straw ME) were weak to moderate (r < 0.44) for food and malt barley in Bekoji and Kofele.

DISCUSSION
Exploiting differences in feed traits of barley types could provide novel breeding targets for new barley varieties with potentially higher food and livestock feed value that would be particularly useful in a range of diverse environments in mixed crop-livestock systems. These genotypes would promote sustainable use of resources in the farming systems by increasing biomass production for human and livestock production. Cultivar improvement of straw traits along with grain traits requires information on the cultivar-environment interactions between grain and straw traits and the relationship between these traits across different environments. The current study showed that cultivar variation in yield and quality traits depends on location. That means that the selection of an optimal barley cultivar should be based on location. Further research is therefore warranted to identify the parameters (e.g., soil type, precipitation and slope) that could predict the location effect on barley performance.
Cultivar performance depended on growing location as shown previously in for instance chickpea (Alkhtib et al., 2018;Wosene et al., 2015) and maize (Ertiro et al., 2013). It implies that other cultivars may be selected when tested at another location.
Genotype-environment interaction is known to account for the variation in nutritive value of cereal straw (Seyoum et al., 2020) (Birhanu et al., 2020) also identified IBON 174/03 as a high grain yielder although only grain quality and not straw quality was evaluated in that study. Our study evaluated both grain and straw quality and added HB1963 and Traveller in addition to IBON 174/03. Large variation in food and malt barley cultivars has been demonstrated in several studies (Pearce et al., 1988;Reed and Yilma, 1986;Wamatu et al., 2019). Our study walks the same trail but also adds the insight that not only grain quality but also straw quality showed an interesting range for selection. A factor that complicates easy selection of superior cultivars is the impact of growing location observed in both barley types. Tsige et al. (2020) already identified this effect but our study clarifies that some traits are more sensitive to changes in growing conditions than others. For instance, there was a huge difference between locations in ME compared to other traits. The ME at the Kofole site was higher than the ME in Bekoji which may originate from the high rainfall in Kofele compared to Bekoji. High rainfall was correlated to  Crude protein (CP) and neutral detergent fibre (NDF) are in % of dry matter while metabolizable energy (ME) is in MJ/kg dry matter.
high ME in straw (Acone and Wootton, 1999). It was not the purpose to compare malt barley with food barley, but malt barley outperformed food barley in both yield and nutritive value. This difference was expected because of feed use of barley, since features of grains and straw were clearly affected by location with different effect sizes, meaning that the overall value of food-feed barley may vary more widely than just grain yield.

Conclusions
The wide cultivar variation in straw yield and nutritive value combined with the poor association between yield and nutritive value for grain as well as straw allows for upgrading of straw yield and its nutritive value without decreasing grain yield and its nutritive value. This improvement could be achieved by employing appropriate breeding approaches.
Considering the environmental impact on the cultivar performance, three superior varieties were identified, that is, IBON174/03 (as grain yielder), HB1963 (as grain and straw yielder) and Traveller (as straw yielder). To evaluate how well the straw of these cultivars suits animal nutrition, a trial with regional livestock is required to evaluate the digestive and metabolic responses to the identified promising barley cultivars.