Effect of three different roughages additives on the silage characteristics of fodder beet (Beta vulgaris L.)

Extended Abstract
Introduction
Fodder beet, with its high yield (120 t/h;18-20% DM) and low water demand compared with fodder corn and alfalfa, can provide part of the livestock's nutritional needs during autumn and winter seasons. One of the problems of storing the root of fodder beet, despite its high nutritional value, is its low durability time cocerned with its high moisture content. Due to its high soluble carbohydrate content, the root has a good ability to reach the appropriate pH (3.79-4.33) and produce silage with excellent quality. Therefore, it is necessary to evaluate its storage methods, especially ensiling with a combination of available and inexpensive moisture-absorbing roughages materials such as wheat straw, bean straw, and sugarcane pith, which absorb the beet's leachate (especially soluble carbohydrates) and make them palatable. The present study conducted to evaluate the feature of fodder beet silage mixed with dry roughages to achieve the above objectives.
Material and methods
After harvest, the fodder beet roots were cleaned, crushed, and ensiled with four treatments and five replications including: 1) FB: 100% fodder beet, 2) WSFB: 90% fodder beet+10% wheat straw, 3) BSFB: 90% fodder beet+10% bean straw, 4) PFB: 90% fodder beet+10% sugarcane pith. Ten kg of the material of each treatment were compressed, air-tight and tightly ensiled in plastic bags, and placed at 15 °C. After 45 days, the pH, dry matter, and soluble carbohydrates of the samples were immediately determined, and the rest of the samples were dried at 60°C for 72 hours to measure DM, ASH, ADF, NDF, and CP. To measure DM, ASH was measured according to Van Soest et al. (1991). Crud protein was determined according to AOAC (2010). The method introduced by Lengerken and Zimmermann (1991) used to determine soluble carbohydrates. To measure pH, 100 ml of distilled water added to 10 g of fresh silage sample, shaked for 10 minutes, filtered by passing through a cotton cloth and finally the pH of the obtained solution recorded using a digital pH meter. Aerobic stability measured according to the method of Morgan et al. (1966). The buffering capacity of silages measured according to the method of the American Feed Industry Association (AFIA 2011). To measure volatile fatty acids, a gas chromatography device used. Data were analyzed in a completely randomized design using SAS software (Ver. 9.1). The multiple comparison method was used to compare means. Duncan's range was used at a 5% confidence level.
Result and discussion
The color of the silages in pure FB silage was too dark brown, which could be due to the property of root that tends to darken quickly after being sliced. The color of the other treatments was brown, so that the degree of darkness in WSFB and BSFB silages was less and lighter brown, respectively, however the color was dark brown in PFB treatment due to the brown color of the sugarcane pith. A suitable fermentation odor was noticeable in all experimental treatments. The texture of all silages in different treatments observed without sticking.
The highest pH value was found in fodder beet silage contained b ean straw (4.24) and the lowest pH was 3.85 in the fodder beet silage without additives (P < 0.05). In the current experiment, all silages had an optimal pH range of 3.79 to 4.33. The highest values of DM, NDF and ADF were found in silage with wheat straw and the lowest was in pure fodder beet silage (P < 0.05). Ensiling FB with 10% of dry roughages absorbed silage leachate and prevented the loss of its nutrients. The highest CP and Ammonia-N in pure fodder beet silage was 14.29%, 90.88mmol/l, respectively, and the lowest amounts (7.7% and 58.56 mmol/l) were found in the fodder beet silage with sugarcane pith (P < 0.05). The increase in CP in FB silage is likely due to the growth of beneficial bacteria fermenting the existed carbohydrates. The lower pH of FB silage compared with other treatments, indicating greater fermentation due to more soluble carbohydrates and greater bacterial growth in the silage. The concentration of ammonia nitrogen in silage is an indication of the degree of protein breakdown, perhaps because the more acidic environment of silage was the reason for the breakdown of proteins. The highest (22.74%) and the lowest (8.25%) soluble carbohydrates were in the pure fodder beet silage andwas  in fodder beet silage with bean straw, respectively (P < 0.05). The highest acetic acid (13.01) was observed in fodder beet silage with bean straw. The lactic acid was not significant among treatments. The highest amounts of buffering capacity were obtained in fodder beet silage with bean straw and pith (P < 0.05). The aerobic stability was lower in pure fodder beet silage than other treatments.
Conclusion
Due to the characteristics of fodder beet, which is rich in soluble carbohydrates, ensiling fodder beet is possible, and adding 10% of dry roughages such as wheat straw, bean straw, and sugarcane pith, which prevents leachate loss and play a positive role in increasing the durability of this silage is recommended.