For further information contact: Michael Peters

The Forage Potential of Tanniniferous Legumes

Ruminants play an important role as assets and sources of high quality food and income for rural populations in the developing world. Ruminant productivity is usually low due to inadequate nutrition (i.e. protein deficiency). Promising forage species, mainly legumes, have been identified to overcome these limitations. Many of these legume species contain tannins that could be either advantageous or disadvantageous in terms of feed efficiency and metabolizable protein supply to the animal.

Thus the Forage Project aims to develop efficient feeding systems based on tanniniferous shrub and tree legumes in order to improve livestock productivity and to alleviate poverty of smallholders in the tropics. This will by achieved through (i) studying the effect of plant nutritional status on the accumulation of condensed tannins in legumes, and the influence of these tannins in ruminant nutrition and the nitrogen fertilizer value of animal excreta for plants, and (ii) designing optimal feeding strategies based on the use of mixtures of tropical forage legumes with contrasting tannin contents to overcome the limitations of ruminant diets in protein supply.

The outcomes of this work will provide the necessary background information for better feeding practices based on tanniniferous legumes. By dissemination and adaptation of the project outputs with farmers, we hope that the new management and feeding strategies will improve the nutrient supply for the ruminant animals, which will increase feed use efficiency and animal productivity in low-input livestock systems. This, in turn, will increase competitiveness and income of the farm households.

Selecting Brachiaria Hybrids with High Forage Quality

Selecting for improved forage quality is justifiable if genetic variation for digestibility or crude protein is greater than variation resulting from G × E interactions. Previous work at CIAT with accessions of B. brizantha and B. decumbens had shown that genotype caused four times more variation in in vitro dry matter digestibility (IVDMD) than did G × E interactions. Thus, one objective of the on-going Brachiaria improvement program is to produce hybrids with high forage digestibility. In addition, we are interested in screening Brachiaria hybrids for crude protein (CP) content.

By using near-infrared spectroscopy (NIRS), we can analyze large numbers of samples in the CIAT Forage Quality Laboratory for IVDMD and CP. We have also developed a procedure for sampling leaf tissue from hybrids planted in pots that gives repeatable results. As a result we currently screening for IVDMD and CP Brachiaria hybrids coming out of the breeding program.

Dry Season Feeding Alternatives

Milk production is an option for smallholders in the tropics with variable rainfall, but production is limited by low availability of good quality forage in the dry season. Conserving forages as hay or silage are well known options to maintain productivity during the dry season. Despite much research work on silage and hay production, adoption of forage conservation technologies by small-scale farmers has been low due to the high investment that is required to implement traditional forage conservation methods. It follows that for silage and haymaking technologies to be attractive to smallholders, it should be of low cost, low risk, and also profitable. One alternative for ensiling forages in smallholder farms is the use of plastic bags, coined as "little bag silage" (LBS).

Silage and hay from selected grasses and legumes will be evaluated for nutritional quality in a series of in vitro experiments and in vivo trials under both controlled and farmer conditions. The in vitro rumen simulation technique, RUSITEC, will be used for evaluating ensiled and sun-dried grasses and legumes alone and in different mixtures with respect to various parameters describing rumen fermentation pattern, such as ammonia-N, methane, and volatile fatty acids content. Milk yield of cows grazing low-quality grasses and supplemented with conserved forages will be measured to test the quality and utility of plastic bag silage and hay.

Through on-farm research, the feasibility of hay and silage production in smallholder systems will be evaluated. Detailed protocols for on-farm trials involving animals will be elaborated in consultation with farmers. The cost effectiveness will be assessed of the use of silage and hay as supplements to feed cows in the dry season and for sale to farmers who have a need for dry season supplements. A Decision Support Tool (DST) will be developed for farmer assessment of the quality of hay and silage.

Forages for Monogastric Animals

One new area of research is looking at the utility of forage legumes to feed monogastrics in smallholders systems. A promising option is to use forage legumes to improve village pig production systems. Recently, farmers in Lao PDR and Vietnam have reported significant benefits from supplementing their pigs with leaf of the forage legume Stylosanthes guianensis CIAT 184, including faster growth rates, greater survival of suckling piglets and reduced labour requirements to collect feed. Despite such reports, very little is known about the role and potential impacts of forage legume leaf in pig diets. To address this we propose to:

1. To select forage legume varieties suitable for feeding pigs
2. To generate information on the nutritional value for pigs of selected forage legumes
3. To integrate forage legumes in existing pig production systems as part of diets composed of other locally available feed resources

Nutritional Synergisms among Contrasting Forages

The Tropical Forage Project of CIAT is developing new forages options that will complement at the farm level existing forage resources of variable quality. Thus we are studying how the level and frequency of feeding different legume-based supplements affect the nutritional parameters of ruminants being fed low-quality grass diets.

We are also carrying out on farm work in subhumid regions to define if by using improved legume-based supplements in cut-and-carry or direct grazing systems farmers can substitute expensive protein concentrates in the dry season.