Effect of ensiling on the nutritive value of low quality roughage rice hulls. I. Microbial studies

Abstract

Rice hulls were ensiled in laboratory silos in t w o separate experiments with the same treat. ments. I n the first, sealing was delayed for a period of three days. In the second experiment, silos were sealed immediately after filling. In each experiment, four treatments were applied, namely control, molasses 2% added, urea 0.5% added, and molasses 2% + urea 0.5% added.Lactobacilli, streptococci, and coliforms appear to form the main bulk of the flora characteristic of fresh rice hulls. while the lactic acid bacteria dominate at the commencement of the silage ripening. The characteristics of 30 representative pure strains of both lactic ncid and coliform bacteria isolated from rice hulls laboratory silage are described. On the basis of morphological, cultural, and biochemical characteristics, the isolated cultures were identified as ten strains of Lactobacillus, ten strains of Streptococcus, five strains of Klcbsiclla, and five strains of Escherichia. IntrodiictionOld oil paintings foiind in Egypt dating from the period 10oO to 1500 BC demonstrate that Ancient Egyptians were familiar with ensiling the whole-crop cereals. KIRSTELN [l], and SCHUKKING [2] revealed that ensilage was practiced around 3000 years ago. The first reference af the ensiling process as it is understood today was cited by WATSON and SMITH [3] in which ensilage of fresh grass in pits was described. Ensilage has become an increasingly important method of conservation in the past 50 years. The greater popularity of silage stems largely from: (a) the escalating cost of feed concentrates throughout the world, and (b) the development of a technology which enables material of a more predichble quality to be made than was possible previously. I n general, any material which is unstable in air and has, or is provided with, sufficient fermentable carbohydrate can be ensiled. I n Egypt, renewed efforts were made to establish the means for making consistently good quality silages, particularly from low qcality roughages, e.g., rice hulls. These efforts were prompted by the desire on the production of unconventional fodders for livestock to sttain self-sufficiency, presumably becsuse the conventional silages made from corn, grasses, legumes, etc. were considered insufficient. Approximately 200 thousand tons of rice hulls are produced annually in Egypt& Even though they contain enough cellulose and hemicellulose to make it a source of energy for the ruminants, they are inefficiently utilized by ruminants because of low nitrogen and high content and low digestibility of the fibrous fractions. This low di-3*

Effect of ensiling on the nutritive value of low quality roughage rice hulls. II. Chemical studies

“…This is in accordance with the findings of SHAWKY et al [20], that the four treatments could be arranged according to their efficiency of enhancing the development of lactic acid bacteria as follows: molasses > molasses + urea > urea > control. This discrepancy can be explained by: (a) The pH values of the molasses-treated rice hulls were lower than those of the untreated rice hulls, which molasses tend to improve the conditions whereby the traditional lactic acid fermentation, with a concomitant fall of pH to 4.8 may take place more readly and with greater certainty, i.e., the lactic acid production was stimulated to some extent, with a corresponding effect on the pH drop.…”

“…It seems clear from these results that the supplementa-tion of 2% molasses can have a beneficial effect on fermentation, resulting not only from increasing the levels of total soluble sugars but also from a direct effect on the activities of the microflora, which is in good agreement with the results of lactobacilli counting in the previous paper according to SHAWKY et al [20], who demonstrated that the prevalence of anaerobic conditions in the presence of molasses provides conditions more favourable for lactic acid bacteria, i.e., the counts reaching 25 x lo6 cells/g on the 90-day period, which runs parallel with the maximum production of lactic acid in the present study. Therefore, the existence and the increase of this acid during the ensiling process was due to the accelerated growth of lactic acid bacteria, which ferment sugars to lactic acid.…”

Determining the safety of microbial cultures for consumption by humans and animals

“…Fermented foods and feeds have been consumed by humans and agricultural animals, respectively, for thousands of years (McGovern et al, 2004;Shawky et al, 1990), and the microorganisms that produce them grow in the food (or feed), metabolize nutrients (sugars, amino acids, etc. ), and produce metabolites that humans (or animals) find desirable in terms of flavor, aroma, texture, etc.…”