FODDER PRODUCTION AND CHEMICAL COMPOSITION OF PIGEON PEA [Cajanus cajan (L.) MILLSPAUGH] VARIETIES GROWN IN THE SUBTROPICAL REGION OF SOUTH AFRICA

Abstract

Background. Pigeon peas (Cajanus cajan) produce large amounts of high protein leaves that make it suitable for cultivation in arid and semiarid regions. Objective. To evaluate the biomass production and chemical composition of three pigeon pea varieties (ICEAP 00557, ICEAP 01514 and CIMMYT 100/01). Methodology. A completely randomized design was used. In two growing seasons, the plots were harvested at flowering and biomass yields were measured for fresh forage and dry matter (DM). Harvested leaves were either shade or oven-dried to a constant weight before being milled for chemical analyses. The proximate composition, mineral content, phenolic, tannin and saponnin contents were determined. Results. Varieties ICEAP 01514 and CIMMYT 100/01 yielded the highest fodder of 2620.6 and 4458.3 kg DM/ha in 2016 and 2017, respectively. Variety ICEAP 00557 produced the lowest amount of fodder in both 2016 and 2017 at 1997.6 and 2933.3 kg DM/ha, respectively. There were interactions among varieties, seasons and drying methods on proximate composition. The DM, organic matter (OM) and neutral detergent fibre (NDF) were higher for ICEAP 01514 at 96.0, 88.0 and 55.3 %, respectively and digestible dry matter (DDM) (67.8 %) and metabolizable energy (ME) (9.8 MJ/kg DM) were higher for variety ICEAP 00557 in 2017.  Shade drying recorded higher crude protein (CP) values (24.2-27.0 %) across all varieties with higher values occurring in 2017 compared to 2016. The interactive effect of season, pigeon peas varieties and drying method had little effect on both macro and micro- minerals except for copper (Cu) values. The ranges in macro-minerals were: calcium (Ca) (1.21-2.35), magnesium (Mg) (0.33-0.89), sodium (Na) (0.1-0.7) and phosphorus (P) (0.13-0.31 %). The ranges in micro-minerals were: iron (Fe) (206.7-283.4) and Cu (5.94-7.95 mg/kg DM). The tannins, phenolic and saponin contents were different (P< 0.05) among varieties and between drying methods. Their ranges were: 2.7-8.0 mg catechin equivalent (CE)/g, 13.6-15.9 mg gallic acid equivalent (GAE)/g and 3.4-6.1 %, respectively. Implications. Pigeon peas are suitable for farming systems in the drylands and these varieties are suitable diets for ruminants in the subtropics, where CP in the diets are low. Conclusions. Air-drying under a shade was recommended to preserve the nutritional quality of pigeon peas fodder. The macro and micro-nutrients in the pigeon peas satisfied the animal requirements, except for the deficiency in Na and Cu. The concentration of the anti-nutritive compounds in the pigeon peas will not limit animal performance.