Agronomic indices and nutritional values of plant parts of three varieties of sorghum (Sorghum bicolor (L.) Moench) fodder at late stages of growth

Résumé

The study was conducted to assess the agronomic indices and nutritional values of plant parts fractions of three varieties of sorghum fodder in late stages of growth in humid tropics. The experiment was 2 x 3 factorial scheme fitted into a completely randomize design, comprising of two (2) plant fractions (stem and leaf) and three (3) varieties of sorghum (Samsorg-17, 44 and 45). Agronomic parameters (plant height, leaf length, leaf width, stem circumference, fresh leaf number and dried leaf number) were monitored from 10 – 16 weeks after planting (WAP), 16 WAP leaf and stem were sampled for proximate composition, fibre fractions, mineral profile, anti-nutritional factors and in-vitro digestibility. Results obtained showed a significant difference (P<0.05) in all the agronomic indices across the weeks of growth. Plant height was higher (P<0.05) for Sarmsorg-45 (131.25 cm) and lower (P<0.05) for Samsorg-17 (107.25 cm). There were no significant differences (P>0.05) in dry matter, crude protein (CP), ether extract, ash, neutral detergent fibre and non-fibre carbohydrate among the varieties. Leaf fraction had higher (P<0.05) contents of CP (17.53%). Stem had higher (P<0.05) values of all fibre fractions except acid detergent fibre. There was a significant (P<0.05) influence of varieties on the Ca, P, Fe, Cu and Mn. Leaf fraction had higher (P<0.05) contents of P (1.06%), K (0.37%), Na (1.75%), Cu (13.01 mg/kg) and Zn (17.53 mg/kg). Plant fractions were significantly (P<0.05) influenced by the anti-nutritional factors. Leaf fraction had higher (P<0.05) contents of phytate (0.79%), oxalate (0.60%), tannins (0.60%), trypsin inhibitor (15.98 mg/g) and dhurrin (6.97 ìg/g). Post in-vitro characteristics were not significantly (P>0.05) influenced by varieties. Leaf fractions had higher (P<0.05) in-vitro organic matter digestibility (47.39%) IOMD compared to stem (39.65%). Conclusively, all the varieties of sorghum exhibited a good agronomic indices and nutritional value that characterized sorghum as a fodder in humid tropic. Farmers should be encouraged to use leaf fractions of sorghum than stem. Samsorg-17 is recommended because of height.