Assessment of morphological characteristics, dry matter yield and effect of harvesting stage and additives on fermentation characteristics and nutritional value of silages from Andropogon gayanus and Desho (Pennisetum pedicellatum) grasses

Abstract

The objectives of the study was to assess the effect of harvesting stage/height on morphological characteristics and dry matter yield of grasses and determine the effect of harvesting stage/height and additives on silage quality, preference, feed intake and digestibility of silages made from Andropogon gayanus (A.gayanus) and P.pedicellatum (desho) grasses. Two separate experiments were carried out using A.gayanus and desho (Kulumsa ecotype). The experimental plot (402.5 m2) was prepared for each grass and divided into six blocks (11.5 x 5 m2) and three plots (3.5 x 5 m2) with a total of 18 plots for each grass for morphological evaluation, laboratory silage making and chemical analysis. Six random plots from the 18 plots (one replicate in each block) were used for morphological data collection and silage preparation at each harvesting stage/height with 3 x 4 factorial arrangement for each grass (3 harvesting stage/height), 4 additive type (without, T1, 4% molasses, T2, 0.6% urea, T3 and 0.6% urea + 4% molasses, T4) and 3 replications). For morphological data collection and laboratory silage making the grasses were harvested at vegetative, boot and full bloom for A. gayanus and a height of 70,90 and 110 cm for desho grass For preference test and digestibility experiment an additional area of 450 m2 (12 m x 36 m) was prepared in a similar manner to harvest A.gayanus at boot stage and desho grass at 90 cm height. The grasses were ensiled in triplicates for each treatment. The number of leaves per plant, NTPP (number of tiller per plant) and leaf length per plant were the highest (p<0.05) at boot stage for A.gayanus and the highest (P<0.05) leaf to stem ratio was recorded during vegetative stage. Dry matter yield (DMY) increased (P<0.05) with increasing grass maturity/height for both grasses. Desho grass harvested at 70 cm resulted in the lowest (P<0.05) NTPP A.gayanus silages score for smell, color and moldiness decreased (P<0.05) with increasing (P<0.05) stage of harvest. Better (P<0.05) score for smell and texture was recorded for silage produced for T2 and T4 for desho grass. The highest (P<0.05) pH was observed at full bloom while the lowest (P<0.05) was at boot stage of A. gayanus. The neutral detergent fiber (NDF) content of A.gayanus silage for T1 was greater (P<0.05) than that of T3 and T4 while the highest (P<0.05) acid detergent fiber (ADF) content was for T1 and T4. A.gayanus silage in T1 was lower (P<0.05) in crude protein (CP) content compared with the other treatments. The CP content of desho grass harvested at 90 cm and for T2 and T4 was the highest (P<0.05). The highest (P<0.05) DM intake and relative palatability index was for T2 followed by T4 while the lowest (P<0.05) was for T1 and T3 during preference study for A.gayanus silage. In Desho grass silage, the highest (P<0.05) DM intake was for T2 while T3 resulted in the lowest DM intake. In A.gayanus silages, goats in T2 and T3 digested more (P<0.05) dry matter (DM), organic matter (OM) and CP compared with the other treatments while the least (P<0.05) was for T1.The digestibility DM and OM of desho silage for T2 was greater (P<0.05) than T1 and T4. The highest (P<0.05) digestibility of CP in desho grass silage was for T3 and T4. For desho grass silage the lowest (P<0.05) digestibility of NDF and ADF was for T1. In conclusion, A.gayanus and desho grass could be harvested at boot stage and 90 cm, respectively, for achieving optimum DMY. Ensiling A.gayanus with 4% molasses and desho with 4% molasses plus 0.6% urea are recommended to produce good quality silage.