Effects of Different Mechanical Preparation Methods on Drying Rate and Nutrient Composition of Forage Sweet Potatoes Hay

Abstract

Many forage sweet potatoes (Ipomoea batatas (L) Lam) cultivars have not been adequately evaluated for their hay making potential in Eastern Africa. The objective of the study was to evaluate three nutritionally superior cultivars to determine the effects of forage mechanical preparation on their drying rate and nutrient composition. The experiment was a split-plot design where the three cultivars (K158, Marooko and Wagabolige) and the three mechanical treatments (un-chopped, chopped and shredded forage) were the main plots and the five sampling times during drying (0, 24, 48, 72 and 96 hr) formed the sub-plots. The DM increase during drying was used to indicate the drying rate as high DM reflected faster moisture loss. The hay had similar DM at 0 and 24 hr but the DM significantly increased at 48, 72 and 92 hr. Mechanical treatments and drying time caused shredded cultivars to increase in DM at all the five drying durations. Chopped cultivars maintained their DM between 0 and 24 hr and again between 48 and 72 hr. The cultivars, however, recorded increased DM at 96 hr that was significantly higher than at all other times. Cultivars left whole recorded similar DM at 0 and 24 hr although they had higher DM at 48, 72 and 96 hr respectively. At 0 hr chopped and shredded cultivars; whole and chopped cultivars respectively recorded similar DM although shredded cultivars had lower DM compared to the whole cultivar treatment. However, the three mechanical treatments maintained similar DM in cultivars at 24, 48 and 72 hr of drying. Chopped cultivars and those left whole had similar DM at 96 hr although the DM was lower than that of shredded cultivars. Shredded cultivars tended to dry faster although this difference did not reach significance until the cultivars were dried for 96 hours. The three mechanical treatments did not influence the nutrient composition in the three cultivars. However, cultivars differed in nutrient composition as, although, K158 and Wagabolige recorded similar DM, OM and ADF but they differed in CP, NDF and ADL. Marooko contained the highest CP and the lowest DM and fibre. The three cultivars contained similar gross energy and mechanical treatments and drying durations did not affect their gross energy.

Keywords: Sweet potato, hay, drying rate, mechanical treatment, nutrient composition.