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 cropâˆ’livestock systems encourages the use of dual-purpose cowpea varieties that produce high yields of both grain and fodder.
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 cropâˆ’livestock farmers.
Cowpea is an important component in mixed cropâˆ’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 residuesâ€”the stalks, stems, and leaves remaining after seed harvestâ€”make up a major component of livestock diets in mixed cropâˆ’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.
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.