Agronomic characteristics and nutritive value of pigeon pea [Cajanus cajan (L.) Millsp.] harvested at different stages of maturity

Abstract

This study was divided into three parts. The first evaluated the effects of five stages of plant maturity (60, 75, 90,120 and 180 d) on the agronomic characteristics, chemical composition and in vitro degradability (IVDMD) of pigeon pea [Cajanus cajan (L.) Millsp.] 'Kaki' and its anatomical fractions, leaves and stems. In the second part, the selective consumption of this legume was studied. In the third part, the effects of the inclusion of pigeon pea in diets based on tropical grass hay for goats on voluntary intake, and digestibility of dry matter (DM), crude protein (CP) and neutral detergent fiber (NDF) were determined. Plant height increased and leaf :stem ratio decreased, as the plants grew. In the whole plant, DM and NDF content increased (P < 0.05) by 13.9 and 19.2 percentage units, but CP content numerically decreased by 4.8 units as plant maturity progressed from 60 to 120 d. At the five successive stages evaluated, CP content in the leaves exceeded that of the stems, whereas NDF content showed the opposite trend. The IVDMD values were 69.6% in the whole plant, 73.9% in the leaves, and 50.4% in the stems. Whole plant IVDMD decreased (P < 0.05), with advancing plant maturity, from 71.2% at 60 d to 55.8% at 180 d. In the selective consumption trial, intake of fresh pigeon pea was compared with that of fresh native tropical grass (NTG) or NTG hay. A high selection of pigeon pea was observed for the first 10 minutes, but during the following 20 minutes this selection decreased. In the voluntary intake and digestibility trial that utilized six goats (26.4 kg live weight) to evaluate the inclusion of 25% of pigeon pea in a NTG-based diet, CP intake was markedly higher (P < 0.05) with legume supplementation. Dietary inclusion of the legume also tended to improve the digestibility of DM and CP but not at the P < 0.05 level of significance (56.7% vs. 51.4% and 58.7 vs. 51.2%); however, it did not affect NDF digestibility. As the pigeon pea plant increased in height, changes occurred in leafistem proportions and chemical composition. The IVDMD results suggest that the interval from 75 to 120 d of growth is favorable for possible utilization of pigeon pea as fresh forage in diets for small ruminants.