Yield and Chemical Composition of Cassava Foliage and Tuber Yield as Influenced by Harvesting Height and Cutting Interval

Duong Nguyen Khang,Hans Wiktorsson,Thomas R. Preston 아세아·태평양축산학회 2005 Animal Bioscience Vol.18 No.7

A 3횞4 factorial field experiment with a complete randomised split-plot design with four replicates was conducted from June 2002 to March 2003 at the experimental farm of the Nong Lam University, Ho Chi Minh City, Vietnam, to determine effects of different harvesting heights (10, 30 and 50 cm above the ground) and cutting intervals (45, 60, 90 and 285 days) on yield of foliage and tubers, and chemical composition of the foliage. Cassava of the variety KM 94 grown in plots of 5 m횞10 m at a planting distance of 30 cm횞50 cm was hand-harvested according to respective treatments, starting 105 days after planting. Foliage from the control treatment (285 days) and all tubers were only harvested at the final harvest 285 days after planting. Dry matter and crude protein foliage yields increased in all treatments compared to the control. Mean foliage dry matter (DM) and crude protein (CP) yields were 4.57, 3.53, 2.49, and 0.64 tonnes DM ha-1 and 939, 684, 495 and 123 kg CP ha-1 with 45, 60, 90 and 285 day cutting intervals, respectively. At harvesting heights of 10, 30 and 50 cm the DM yields were 4.27, 3.67 and 2.65 tonnes ha-1 and the CP yields were 810, 745 and 564 kg ha-1, respectively. The leaf DM proportion was high, ranging from 47 to 65%. The proportion of leaf and petiole increased and the stem decreased with increasing harvesting heights and decreasing cutting intervals. Crude protein content in cassava foliage ranged from 17.7 to 22.6% and was affected by harvesting height and cutting interval. The ADF and NDF contents of foliage varied between 22.6 and 30.2%, and 34.2 and 41.2% of DM, respectively. The fresh tuber yield in the control treatment was 34.5 tonnes ha-1. Cutting interval and harvesting height had significant negative effects on tuber yield. The most extreme effect was for the frequent foliage harvesting at 10 cm harvesting height, which reduced the tuber yield by 72%, while the 90 day cutting intervals and 50 cm harvesting height only reduced the yield by 7%. The mean fresh tuber yield decreased by 56, 45 and 27% in total when the foliage was harvested at 45, 60 and 90 day cutting intervals, respectively. It is concluded that the clear effects on quantity and quality of foliage and the effect on tuber yield allow alternative foliage harvesting principles depending on the need of fodder for animals, value of tubers and harvesting cost. An znitial foliage harvest 105 days after planting and later harvests with 90 days intervals at 50 cm harvesting height increased the foliage DM and CP yield threefold, but showed only marginal negative effect on tuber yield.

Cassava Tops Ensiled With or Without Molasses as Additive Effects on Quality, Feed Intake and Digestibility by Heifers

Van Man, Ngo,Wiktorsson, Hans Asian Australasian Association of Animal Productio 2001 Animal Bioscience Vol.14 No.5

Two experiments on the effects of molasses additive on cassava tops silage quality to its feed intake and digestibility by growing Holstein$\times$local crossbred heifers were carried out. Sixteen plastic bags of one meter diameter and two meters length were allocated in a $2{\times}2$ factorial design with four replicates in the ensiling study, with and without the molasses additive and with two storage times (2 and 3 months). The silage produced in the first experiment was used in the feed intake and digestibility study. Six crossbred Holstein heifers, 160-180 kg live weight, were randomly allocated in a $3{\times}2$ change-over design to three treatments: Guinea grass ad libitum, 70% of grass ad libitum with a supplement of non-molasses cassava silage ad libitum, and 70% of grass ad libitum with a supplement of molasses cassava silage ad libitum. Ensiling was shown to be a satisfactory method for preservation of cassava tops. The HCN content was significantly reduced from $840mg\;kg^{-1}$ to 300 or $130mg\;kg^{-1}$, depending on storage period. The tannin content was not significantly changed. Molasses additive resulted in lower pH, Crude Protein (CP), NDF and higher DM content but did not otherwise affect chemical composition. The voluntary feed intake per 100 kg live weight of the heifers was 2.59, 2.65 and 2.91 kg DM of Guinea grass, non-molasses cassava tops silage and molasses cassava tops silage diet, respectively. Crude protein intake was significantly improved in the cassava tops silage diets. The apparent digestibility of DM, OM, CP, NDF and ADF decreased with the silage supplement diets. No significant difference in digestibility was found between the non-molasses and molasses silage diets. The digestibility coefficient of DM, OM, CP, NDF, ADF in non-molasses cassava tops silage and molasses cassava tops silage was 49.4, 52.1, 45.81, 36.6, 27.7 and 49.7, 51.9, 47.55, 28.1, 19.5, respectively. It is concluded that cassava tops can be preserved successfully by ensiling and that cassava tops silage is a good feed resource for cattle.

The Effect of Replacing Grass with Urea Treated Fresh Rice Straw in Dairy Cow Diet

Van Man, Ngo,Wiktorsson, Hans Asian Australasian Association of Animal Productio 2001 Animal Bioscience Vol.14 No.8

Nine tons of fresh rice straw from early-maturing varieties was ensiled with 50 g urea $kg^{-1}$ DM straw in plastic bags immediately after threshing. Five months after storage, preserved straw was used to partially replace elephant grass (Pennisetum purpureum, Schumach) for lactating cows. Eight crossbred Holstein lactating cows (75% of Holstein blood) in their second to fourth lactation and in mid-lactation were arranged in a balanced design with two squares consisting of $4\;periods{\times}4\;treatments$ (100% grass ad lib. as a control; 75% grass+urea treated fresh rice straw (UTrFRS) ad lib.; 50% grass+UTrFRS ad lib.; 25% grass+UTrFRS ad libitum) in one square. A concentrate supplement was given at a rate of 400 g per day per kg of milk produced. Samples of fresh straw taken in the field and UTrFRS and elephant grass taken at feeding time were evaluated in a degradation trial with 3 fistulated heifers (undefined blood ratio of crossbred of Sindhi and local yellow cattle). Straw preserved for 5-9 months was in nearly all cases of good quality. Crude protein (CP) content was increased 2.1 fold and 48 h dry matter loss (DML) was 20% higher compared to dry straw. Elephant grass cultivated intensively was low in DM content and 10% higher in 48 h DML compared to UTrFRS. Dry matter intake (DMI) was higher for the mixture of UtrFRS and Elephant grass, and highest when one-third of the roughage was UTrFRS. Higher DMI of mixed roughage diets was probably due to the low DM content of elephant grass in the sole grass roughage diet. Increasing substitution of elephant grass with UTrFRS up to 75% of the roughage component increased milk fat content and had no effect on milk yield and other milk composition parameters. Feeding UTrFRS, partially replacing elephant grass in the diets of lactating cows in the dry season can reduce the cost of roughage.

Effect of Molasses on Nutritional Quality of Cassava and Gliricidia Tops Silage

Van Man, Ngo,Wiktorsson, Hans Asian Australasian Association of Animal Productio 2002 Animal Bioscience Vol.15 No.9

The study aimed to evaluate the influence of molasses in ensiling cassava and Gliricidia tops, common crop residues in the farming systems of Vietnam. Four levels of sugarcane molasses: 0, 30, 60 and 90 kg per tonne of fresh material, and two storage periods (2 and 4 months) for each of the two plant species: Cassava (Manihot esculenta, Crantz) and Gliricidia (Gliricidia sepium, Jacq.) were allocated in a 4${\times}$2 factorial completely randomized block design with 3 replicates. A total of 48 plastic bags, each one containing 10 kg herbage were used. Based on the colour, smell and mold appearance, all the silages were considered to be acceptable but with more spoiled silages with higher levels of additives. DM of herbages (25.8% and 22.4% in cassava and Gliricidia tops, respectively) were not changed during ensiling and the molasses additive had no significant effect on the silage DM. Contents of CP and NDF in the cassava tops silage decreased significantly with increased level of molasses and storage period, respectively. The mean pH values of non-molasses silages were 4.39 in cassava tops and 4.60 in Gliricidia tops. Increased additive levels significantly reduced silage pH in Gliricidia (p<0.01) but not in cassava tops silage (p=0.10). Longer storage period significantly reduced pH in both silages. The water soluble carbohydrate (WSC) concentrations of cassava tops and Gliricidia tops were reduced by 90 and 80%, respectively, after ensiling. Molasses addition increased significantly the silage WSC concentrations. HCN contents in the fresh cassava and Gliricidia tops were reduced by 68 and 43%, respectively, after 2 months ensiling, and were continuously reduced during storage. A reduction of 25% and 42% in the tannin content of fresh cassava and Gliricidia tops, respectively was found after ensiling. Storage time and molasses additive had little affect on the tannin content. Silage lactic acid concentrations were around 1,0% of DM in cassava and 1.7% of DM in Gliricidia top silages, and no effect of molasses additive and storage time was found. It is concluded that cassava and Gliricidia tops residues can be preserved successfully by ensiling, and only low levels of molasses additive are needed to improve silage fermentation.

Effects of Ensiled Cassava Tops on Rumen Environment Parameters, Thyroid Gland Hormones and Liver Enzymes of Cows Fed Urea-treated Fresh Rice Straw

Khang, Duong Nguyen,Wiktorsson, Hans Asian Australasian Association of Animal Productio 2004 Animal Bioscience Vol.17 No.7

Four rumen-cannulated cows (330 kg average weight at 4 years) were used to evaluate the supplement of ensiled cassava tops (ECT) (variety KM 94, 39% DM) on rumen functions, thyroid hormones and liver enzymes. The treatments, arranged in a 4 $\times$4 Latin square design, were ECT at 0, 50, 100 and 150 g CP 100 kg$^{-1}$ body weight (BW), and a basal diet of urea-treated fresh rice straw (UFRS) ad libitum and 1.1 kg dry matter (DM) cassava root meal (CRM) in each 30 day study period. The results showed a continuous decrease in dry matter intake (DMI) of UFRS with increasing level of ECT supplement (p<0.001). The highest total DMI was observed for treatment ECT$_{150}$ (2.68 kg DM 100 kg$^{-1}$ BW day$^{-1}$) followed by treatments ECT$_{100}$, ECT$_{50}$ and ECT$_{0}$, with 2.47, 2.24 and 2.06 kg DM 100 kg$^{-1}$ BW⋅day$^{-1}$, respectively. Increasing levels of ECT supplement increased the concentration of total volatile fatty acids (p<0.05) and ammonia nitrogen (p<0.05) and resulted in a decrease in pH (p<0.05). Overall average plasma triiodothyronine and thyroxine concentrations were 0.80, 0.82, 0.85 and 0.69 ng ml$^{-1}$ (p>0.05), and 50.9, 49.5, 50.7 and 42.4 ng ml-1 (p>0.05) for treatments ECT$_{0}$, ECT$_{50}$, ECT$_{100}$ and ECT$_{150}$, respectively. There were non-significant differences in alanine aminotransferase and aspartate aminotransferase among treatments. It is concluded that ECT is a valuable protein-rich feed supplement to cattle, and the highest level of on average 2.48 kg DM ECT per cow and day (28% of total DMI) did not significantly affect thyroid gland hormones and liver enzymes in cows.