Effect of stage of growth on nutritional value of dual purpose sorghum
The study was conducted to evaluate the effect of stage of growth on the quality of improved dual purpose sorghum (Sorghum bicolor) fodder and silage (IDPS). Six treatments based on physiological stage of growth of sorghum were assigned randomly in plots within a block and replicated three times. Treatments were bloom stage (PS1), soft dough stage (PS2), hard dough stage (PS3), physiological maturity stage (stalks with grains), (PS4), physiological maturity stage (stalks without grains) (PS5), and 1 month post grain harvest (PS6). The parameters determined were dry matter yield, nutrient composition, plant height, tiller count and effect of protein (cotton seed cake) supplementation on silage digestibility at different physiological stages of growth. Highest (P< 0.05) DM yield (18.01 ton/ha) was obtained at PS4 compared with 8.69, 12.75, 16.27 17.04 and 13.04 ton/ha for PS1, PS2, PS3, PS5 and PS6, respectively. CP declined (P<0.05) with maturity from 8.6 at PS1 to 7.98, 7.96, 7.61, and 6.77 to 6.72 at PS2, PS3, PS4, PS5 and PS6 respectively. NDF and ADF at PS1, PS2, PS3, PS4, PS5 and PS6 were 54.4, 60.8, 65.71, 65.93, 66.73 70.3 and 27.93, 35.96, 41.98, 41.97, 42.04, 46.05 respectively. ADL was 3.44, 5.03, 7.38, 7.39, 7.42, and 8.3 for PS1, PS2, PS3, PS4, PS5 and PS6 respectively. Highest (P<0.05) silage IVDMD of 60.72 was at PS1 compared with 54.73, 53.82, 53.56, and 45.75 obtained at PS2, PS3, PS4, PS5 and PS6 respectively. Inclusion of cotton seed cake in silage increased (P<0.05) IVDMD at various growth stages. PS3 growth stage provided fodder material with higher (P< 0.05) nutritive for silage making while highest (P< 0.05) fodder yields were obtained at PS4. Harvesting at PS5 provided both fodder and grains for livestock and human consumption respectively. It was evident that yields and quality of IDPS was affected by age at harvesting.
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