Treatment of Rice Stubble with Pleurotus ostreatus and Urea Improves the Growth Performance in Slow-Growing Goats

SIMPLE SUMMARY: Fungi treatment is well established as a promising approach to upgrade the nutritional value of lignocellulosic biomass. This potency of fungi treatment is, however, primarily based on in vitro experiments, and extrapolation to practice is currently hindered, owing to a dearth of studies addressing the practical relevance of fungal treatment of high-fiber feed, such as rice straw and rice stubble. These potential biomasses are rife in Southeast Asian countries, coinciding with increasing rice production; however, it remains a big challenge to utilize rice stubble as a potential feed for ruminants. Similar to rice straw, rice stubble is traditionally eliminated through controlled burning, which is harmful to the environment. The aim of this study was to convert rice stubble into a new animal feed capable of increasing environmental friendliness. Using urea, it is well known to modify the lignification or silicification of lignocellulosic biomass. However, it remains scanty in combination with fungi treatment. Therefore, we treated rice stubble with either urea or oyster fungus (Pleurotus ostreatus) or a combination of these two treatments and offered these treated rice stubbles to slow-growing goats with the objective to study their effect on feed intake, digestibility, and fermentation end-products. ABSTRACT: The objective of this study was to evaluate the efficacy of the fungal treatment (Pleurotus ostreatus) of urea-treated rice stubble on growth performance in slow-growing goats. Eighteen crossbred Thai-native x Anglo-Nubian male goats (average body weight: 20.4 ± 2.0 kg) were randomly assigned to three experimental total mixed rations containing 35% rice stubble (RS) that were either untreated (URS), urea treated (UTRS), or treated with urea and fungi (UFTRS). URS and UTRS were cultivated and harvested from an aseptically fungal spawn, incubated at 25–30 °C for 25 days. Indicators of growth performance were monitored, and feces were collected quantitatively to assess nutrient digestibility, during a 12-week feeding trial. All goats remained healthy throughout the experiment. The goats fed UFTRS had a lower feed conversion ratio (kg feed/kg growth) compared to goats fed URS or UTRS. Compared to URS, dietary UFTRS increased the nutrient digestibility of slow-growing goats, such as organic matter (OM) (+8.5%), crude protein (CP) (+5.5%), neutral detergent fiber (NDF) (+39.2%), and acid detergent fiber (ADF) (+27.4%). Likewise, dietary UFTRS tended to increase rumen ammonia concentrations, but rumen pH and volatile fatty acids were not affected by UFTRS. In conclusion, the present study indicates that the fungal treatment of RS is an effective tool to improve the growth performance of slow-growing goats.