Enriching livestock diets with cowpea

Loaded on camel-back, covering roofs, stored in tree tops, and traded in the market, cowpea haulms can be seen throughout the semiarid tropical regions being stored, marketed, and used as livestock feed. Expanding the intensification of crop−livestock systems encourages the use of dual-purpose cowpea varieties that produce high yields of both grain and fodder.

Farmer feeding sheep with cowpea haulms. Photo by ILRI.
Farmer feeding sheep with cowpea haulms. Photo by ILRI.

Research on yield and quality of cowpea haulms by centers belonging to the Consultative Group on International Agricultural Research is leading to improvements in livestock production and the associated incomes of crop−livestock farmers.

Cowpea is an important component in mixed crop−livestock systems in the semi-arid regions of the tropics. It is being grown more and more to provide high levels of fodder for livestock in addition to producing grain for people. Since the late 1980s, cowpea breeding programs have worked toward producing dual-purpose varieties that emphasize the production of grain and fodder resulting in varieties that can yield over 1 t/ha of grain and 2 t/ha of fodder.

Crop residues—the stalks, stems, and leaves remaining after seed harvest—make up a major component of livestock diets in mixed crop−livestock systems. Improving the nutritional quality of crop residues is thus important to enhance the productivity and profitability of these farming systems. Demand for livestock products through much of the semi-arid tropics will be likely to continue to increase along with the use of purchased feedstuffs. For this reason, sales of cowpea fodder have been expanding, providing cowpea farmers with additional opportunities for marketing their surplus crop.

Late-maturing varieties of cowpea are often used for fodder because they can take advantage of a longer growing season to amass more biomass. Where the longer growing period can make the crop susceptible to late drought, varieties may be preferred with a high fodder yield produced within a more moderate growing period. A collaborative program between IITA and the International Livestock Research Institute (ILRI), which was started in the 1980s to evaluate and develop dual-purpose varieties, has produced several that have become well accepted when tested on-farm.

Woman farmer tending to her goat. Photo by ILRI.
Woman farmer tending to her goat. Photo by ILRI.

It is useful to know the differences in performance of livestock fed on different varieties of cowpea. Some varieties have been tested for their ability to increase the weight of small ruminants or improve the milk yield of cows. However, only a few varieties can be compared at one time in live animal trials. This makes the systematic screening of cowpea genetic resources important for advancing the development of dual-purpose varieties.

Screening tools that can rapidly assess the nutritional quality of different varieties greatly aid the evaluation process. Near-infrared reflectance spectroscopy (NIRS) is one such tool, allowing the fast and inexpensive analysis of small quantities of plant biomass. This technique uses near-infrared light to measure nutritive quality, such as the amounts of nitrogen and fiber, or the digestibility of the fodder, all of which are related directly to animal performance. The technique takes only a few minutes, replacing the hours of chemical analysis that were once needed to evaluate ground samples of fodder. Once screened, selected varieties could be tested further to verify their performance potential.

The greater nutritional quality of legume residues allows them to be used as a supplement to livestock diets based on cereal stovers and other low-quality forages. Optimizing the amount of cowpea haulms in livestock diets was one focus of a research project sponsored by the CGIAR Systemwide Livestock Program on the use of cowpea fodder. As smallholder livestock systems evolve and become more market-oriented, the type of diets fed to livestock often changes. Legume fodders remain an important part of these changing diets. The development of cowpea varieties that feed both people and their farm animals better will give farmers new and wider choices.

There is still much to be done. With significant variation existing within cowpea germplasm collections, we can continue to improve dual-purpose varieties. Modern technologies are available to allow the rapid screening of important quality traits. Techniques such as NIRS for quality analysis and marker-assisted selection for desirable traits promise to speed the future development of new varieties of dual-purpose cowpea.

To conserve or not to conserve?

IITA maintains more than 15,000 accessions of cowpea in its genebank. Photo by IITA.
IITA maintains more than 15,000 accessions of cowpea in its genebank. Photo by IITA.

Crop improvement through breeding and biotechnology is one way of tackling the challenges of feeding the world. Conservation of genetic resources is an important component of crop improvement, providing a pool of materials for the researchers to draw from.

IITA’s Genetic Resources Center (GRC) created in 1975, maintains over 28,000 accessions of six main staple crop collections that are available to food and agriculture researchers worldwide working on crop improvement. They are cowpea or “black-eyed pea” (Vigna unguiculata L.), maize (Zea mays L.), soybean (Glycine max (L.) Merr.), cassava (Manihot esculenta Crantz), yam (Dioscorea spp.), and banana (Musa spp.).

Over 50% of the collection is made of cowpea collected from 89 countries, mainly in Africa, and other Vigna spp. It is also the most shared, with 54 of all the germplasm materials being distributed.

Ex situ conservation in IITA genebank: medium-term storage, 5 °C. Photo by IITA.
Ex situ conservation in IITA genebank: medium-term storage, 5 °C. Photo by IITA.

Since 1985, IITA has distributed germplasm of cowpea and its wild Vigna relatives for genetic improvement research to institutions in sub-Saharan Africa, Asia, USA, and South America. This has contributed to the development of new cultivars or varieties currently adopted by rural farmers in the regions.

The effectiveness of the distribution system from the genebank, the use of the distributed germplasm, and conservation costs were assessed in a study conducted by Victor Manyong, Dominique Dumet, and A.T. Ogundapo from IITA and D. Horna from the International Food Policy Research Institute. Likewise, the impact of the conservation of germplasm of cowpea and wild relatives was examined to justify the conservation efforts.

Methodology
Questionnaires were e-mailed to partners who had collected germplasm from GRC between 1975 and 2009 to determine the ease of accessing material and their use. To estimate the cost of conserving a unit of the two crops, the Decision Support Tool (DST) developed by IFPRI was used.

Ex situ conservation in IITA genebank: medium-term storage, in vitro. Photo by IITA.
Ex situ conservation in IITA genebank: medium-term storage, in vitro. Photo by IITA.

Only about 13% of the beneficiaries responded but they accounted for about 84% of the accessions distributed to beneficiaries in West Africa, Asia, East Africa, Europe, and North America.

No responses were received from beneficiaries in Australia, the Caribbean, Central Africa, the Middle East, North Africa, South Africa, and South America. This may partly have been due to lack of updated contact details in the genebank’s electronic database. This needs to be improved for future feedback surveys.

Use of cowpea and wild Vigna germplasm
The study findings show that most of the distributed cowpea and wild Vigna accessions were used for breeding followed by activities in agronomy and biotechnology research. However, in many cases, they had multiple uses, such as breeding, biotechnology, and agronomy.

Between 2001 and 2005, about 76% of the accessions were used for various agricultural research activities and were found adaptable to different agroecological zones, from forest to the savanna in the tropics and subtropics. Derived, Sudan, and Sahel savannas were recognized as the adaptable agroecological zones for the cultivation of cowpea and wild Vigna.

Ex situ conservation in IITA genebank: long-term storage, −196 °C. Photo by IITA.
Ex situ conservation in IITA genebank: long-term storage, −196 °C. Photo by IITA.

The majority of the users of the germplasm found it easy (32%) to very easy (68%) to get the material from the genebank. Only a few experienced difficulties. These included the inability of the genebank to supply the required quantities (3% of accessions), poor collaboration with NARS and universities (3%), long bureaucratic procedures to acquire germplasm (2%), and improper documentation of the passport database of accessions (1%).

Desired traits
High yield and pest resistance were the two traits desired by the majority of agricultural researchers who made requests, irrespective of their specialization. Other desired traits included compatibility to cross with other accessions, seed color and size, nutritive value, palatability and attractiveness, drought tolerance, nematode resistance, early flowering, and storability.

Moreover, many were satisfied with the accessions they received. Findings show that 68% of the accessions received by agronomists met their desired traits, 76% for food technologists, but only 3% for breeders where the main issue was the low level of resistance to pests and diseases. However, the breeders recorded 100% satisfaction in the exploitation of accessions for seed color, seed size (good), and compatibility with crossing. Likewise, 95% satisfaction was achieved on high seed yield and 74% on the combination of high yield and pest resistance by some of the breeders.

Cost of conservation
The structure cost of the genebank in the DST has four categories: capital, quasi-fixed, variable labor input, and variable nonlabor input. Capital inputs include infrastructure, such as germplasm storage and genebank facilities, and equipment for field operations and offices.

Ex situ conservation: field genebank, IITA. Photo by IITA.
Ex situ conservation: field genebank, IITA. Photo by IITA.

Using 2008 as a reference year, US$358,143 and $28,217 was spent annually on the conservation and management of cowpea and wild Vigna. The capital cost took the major share of the costs, followed by quasi-fixed costs for scientific staff, nontechnical labor, and nonlabor supplies and consumables. Each accession cost about $72 for cowpea and only about half of that for wild Vigna. A large share of the expenditure, $28,537, went into the regeneration of 2,228 accessions of cowpea, at an average cost of approximately $12.81 per accession.

Cowpea germplasm is regenerated in the screenhouse to produce high quality germplasm, with considerations of purity and sanitation, hence the relatively high cost per accession. Seed health testing ($13.94/accession) and distribution ($22.63/accession) were the other high costs.

One way to reduce these costs is by increasing the number of accessions, thus lowering the unit cost. Also, upgrading and expanding the current infrastructure to improve the efficiency of the genebank were recommended.

Using molecular tools to develop Striga-resistant cowpea

Striga-infested field. Photo by IITA.
Striga-infested field. Photo by IITA.

Witchweed, Striga gesnerioides (Willd.), continues to be a major menace to production in West and Central Africa, where cowpea is an important crop.

This parasitic weed feeds on cowpea plants, leading to severe chlorosis or yellowing, wilting, stunting, and even the death of susceptible hosts. Annual yield losses are estimated in millions of tons.

Collaborative project
A collaborative project funded by the Generation Challenge Program has taken a close look at the Striga problem and is using molecular tools to identify new sources of resistance. Marker-assisted selection or breeding (MAS or MAB) is being used to facilitate the selection of lines with resistance to Striga. In 2008 and 2009, the Institut National de l’Environnement et des Recherches Agricoles (INERA) of Burkina Faso and IITA undertook a study to identify potential sources of Striga resistance, worked with farmers to articulate their problems and preferences, and tested new Striga-resistant improved lines developed using MAS.

Prior to the breeding activity, participatory rural appraisal (PRA) and farmers’ participatory variety selection (FPVS) sessions were organized in seven Striga hot-spots in Niger and Burkina Faso, which are major cowpea-producing areas. During the 2 years, in Niger, 403 farmers contributed to the FPVS and several of their preferred cowpea lines were selected.

To determine farmers’ preferences in Niger, germplasm of 24 cowpea varieties with various characteristics (seed color, seed size, plant type, maturity, and Striga resistance) were planted in farmers’ fields and used for the PRA and FPVS. The same 24 accessions were also planted in two fields at IITA’s Minjibir Experimental Farm as checks.

Trial sites for 2009 FPVS activities in NIger and Nigeria
Trial sites for 2009 FPVS activities in NIger and Nigeria

In Niger, researchers and local agricultural agencies worked with farmers in their fields. Based on interviews and responses to questionnaires, farmers acknowledged that Striga is a serious problem that seems to be increasing, said IITA scientists Satoru Muranaka and Ousmane Boukar, and Jean Baptiste Tignegre of INERA, who collaborated on the project. Farmers, they added, also suggested that the use of resistant varieties could be a solution. This reconfirmed the importance of Striga resistance as a breeding goal.

The project has also confirmed farmers’ preference for IT00K-1148 and IT90K-372-2-1 because of their agronomic traits. These lines are susceptible to the dominant race of Striga in Niger. In the FPVS, farmers preferred new lines, such as KVX30-309-6G and TN256-87, which also lacked resistance to Striga.

Of the top five genotypes selected by the farmers in the seven locations, only two—IT99K-573-2-1 and IT98K-205-8—were picked by farmers because these met their preferences for Striga resistance, early maturity, and high yield potential.

Farmers preferred the white-seeded variety for consumption but genotypes with brown seed color that are early maturing and high yielding were also acceptable. The surveys and FPVS activities showed that farmers use consistent selection criteria based on various traits.

Because of unstable rainfall and other problems in 2009, farmers did not get good grain yields, although in a few cases, Striga-resistant IT99K-573-2-1 showed 4−6 times more grain yield (average 214 kg/ha compared with 37−51 kg/ha for local varieties).

Both IT99K-573-2-1 and IT98K-205-8 showed resistance to Striga in all the locations used for the trial. These varieties could be recommended for cowpea production in Southeastern Niger where Striga and drought are major constraints, and for use as sources of resistance genes in breeding other varieties.

Marker-assisted breeding
Using MAB, pot and field experiments in 2008 and 2009 evaluated backcrossed varieties (crossed to their parents) for various traits, such as resistance to Striga, flowering and maturing dates, disease resistance (to bacterial blight, virus, and leaf rust), and seed characteristics.

Farmers selecting cowpea varieties in Niger. Photo by IITA.
Farmers selecting cowpea varieties in Niger. Photo by IITA.

Of the 60 genotypes tested in a pot screening trial in the Maradi station of the Institut National de Recherche Agronomique du Niger (INRAN) from October 2008 to November 2009, 18 showed Striga resistance. Results confirmed that the Striga race (SG3) dominant in two locations in northern Nigeria is also dominant in the four trial locations in southeastern Niger. Field trials had been conducted earlier in Kano and Borno States in Nigeria. Hence, the same Striga-resistant genetic resources could be used for breeding varieties for these areas.

Two existing sequence characterized amplified region (SCAR) markers, 61R and MahSE2, were earlier identified to have the potential for use in MAB for SG3 Striga resistance. To confirm this, pot experiments were conducted using Striga-resistant lines that had been developed using MAS. Results showed a higher percentage of resistant plants in the MAB-developed populations than in the control (those that did not use MAB). SCAR marker MahSE2 showed 88% and 96% marker efficiency for evaluating Striga resistance in backcrossed populations.

Pyramiding or building up Striga resistance in these breeding lines via MAB is important. However, further exploration of appropriate markers is needed to develop efficiently the varieties preferred by farmers. Likewise, more markers linked to various traits that meet farmers’ preferences identified in the PRA and FPVS also need to be converted to SCARs for use in MAB.

This project was able to identify germplasm lines with resistance to Striga races predominant in the Niger Republic; identify farmers’ constraints and preferences to aid in selecting for important traits to combine with Striga resistance; and conduct with farmers the participatory field testing of the new Striga-resistant improved lines developed via the MAB method. It also confirmed the efficiency and effectiveness of MAB for Striga resistance

Cowpea scientists meet in Senegal

Scientists are meeting in Saly, Senegal, this month for the Fifth World Cowpea Research Conference. The meeting will discuss threats to the survival and production of black-eyed peas—one of Africa’s oldest and most resilient and nutritious crops.

They will also discuss key constraints to cowpea production, share progress being made in advanced cowpea genomics, and consider the best ways to unlock cowpea’s potential as a hedge against climate change, hunger, and poverty.

IITA is hosting the World Cowpea Research Conference with the Government of Senegal, the Dry Grain Pulses Collaborative Research Support Program, and Purdue University.

Among the issues to be discussed:
• Rescuing cowpea from extinction: Progress on global efforts to rescue the cowpea gene pool.
• “Designer” peas: State-of-the-art genetic research to develop “designer,” insect-resistant black-eyed peas.
• Cashing in on cowpea: Improved varieties offer a pathway out of poverty.
• Cowpea genemap: Update work to produce a new genetic map for cowpea to accelerate efforts to breed improved varieties.
• Biological controls for cowpea pests: Using genomics tools to develop and deploy biocontrol agents to manage insect pest populations.
• Green-er farming: How farmers are using cowpea as “green” fertilizers to revitalize degraded soils, and use crop waste as energy-rich feed for cows, sheep, and goats.
• Postharvest: Millions of African farmers are using hermetic storage without insecticides to safely store cowpea.
• Cowpea-based food entrepreneurship: Cowpea-based street foods provide income for thousands of women in West and Central Africa.

5th World Cowpea Conference

worldcowpeaconferencelogo

IITA and partners will host the 5th World Cowpea Research Conference in Dakar, Senegal from 27 September to 1 October 2010. The meeting will tackle research issues to enhance the profile of cowpea as a viable income-generating and food security crop.

The conference will cover a wide range of topics—from cowpea genetic improvement and use of molecular tools, to human nutrition and processing and enterprise development.

Known as “black-eyed peas”, cowpea (Vigna unguiculata L. Walp.) is an annual legume and is one of the most ancient crops known to man.

Cowpea seller in market. Photo by IITA.
Cowpea seller in market. Photo by IITA.

Worldwide, it is grown on about 10.1 million ha, with an annual grain production of approximately 4.99 million tons (FAO 2008). The largest production is in Africa; Nigeria and Niger are the biggest producers. The largest areas under cultivation are in Central and West Africa. Brazil, Haiti, India, Myanmar, Sri Lanka, Australia, the US, Bosnia, and Herzegovina also have significant production.

Conference partners include the Dry Grain Pulses Collaborative Research Support Programme (Pulse-CRSP), Purdue University, and the Institut Senegalais de Recherches Agricoles.