High haulm biomass and palatability for livestock feed add value to grain legumes
Stalks and stems of legumes can make excellent animal fodder
Of the many virtues of grain legumes, one is little recognized. Visitors to the livestock fodder markets of West Africa are always surprised to see groundnut and cowpea haulms (stalks and stems of legume plants) sold at prices that exceed that of cereal grains and not infrequently even that of groundnut and cowpea seeds, particularly during periods when sheep keepers are fattening their animal for slaughter at festivities such as Tabaski.
In fact, the haulms of these legumes have proved excellent animal fodder of such high palatability that sheep can gain liveweight quicker than when fed many forage grasses planted for that purpose. In these times of increasing fodder demand fueled by the on-going ‘livestock revolution’, as well as decreasing land and water resources, producing good-quality fodder for animal stock from the same land and water as that used to grow food crops becomes increasingly important.
Sceptical breeders of legume plants for human consumption might worry about the trade-offs in breeding for both human and livestock consumption, as well as the feasibility of such breeding and the overall challenges of trait extensions and proliferations in already complex breeding environments. Fortunately, several collaborative studies conducted by ICRISAT, IITA and ILRI shed light on these concerns.
Importantly, substantial genotypic variation exists in haulm quantity and fodder quality traits that can be exploited by simple phenotyping without detriment to primary traits. And no sophisticated equipment is needed to record haulm yields, which is an initial important step in looking at how best to optimize use of the whole plant for better cost-benefit ratios.
However, phenotyping for haulm fodder quality traits such as protein, cell-wall fractions and available nutrients does require special equipment. The good news is that such equipment in the form of Near Infrared Spectroscopy (NIRS) already exists. Recent work by ICRISAT, IITA and ILRI has produced a road map for improved sharing, networking and NIRS hub generation that will increase the phenotyping capability of grain legume work substantially. Collaboration through two CGIAR research programs, one on grain legumes and the other on livestock and fish, can provide the logistical framework needed to make the road map a reality.
While haulms from grain legumes are far superior to cereal straws and stover in fodder quality, cultivar-dependent variations within haulms of a grain legume deserve attention. In India, for example, the average daily liveweight gains of sheep fed exclusively on groundnut haulms varied from about 65 to 132 grams per day, depending on the cultivar provided. In West Africa, the liveweight gain of dwarf goats fed exclusively on groundnut haulm ranged from about 0 to 40 grams per day.
Anecdotal evidence of adoption of a dual (food and feed) purpose groundnut variety in mixed crop-and-livestock systems where groundnut is the dominant crop suggest that high haulm quantity and quality in a cultivar would likely boost its adoption rates. The advantage of this groundnut cultivar for one farmer, for example, was 10% higher pod yield, haulm yield and haulm fodder quality (the latter was estimated by observing increases in milk production) than this farmer’s competitor. The farmer praised these three accumulating benefits, which made this dual-purpose cultivar more appealing than cultivars improved solely for pod yield.
This collaborative research indicates that breeding legumes for several traits – high haulm as well as seed yield, high haulm palatability, and high protein content and nutrient availability – would be a boon to livestock keepers, fodder traders, fodder processers and crop growers alike.