Effect of adding graded levels of lablab forages on fermentation characteristics of Brachiaria silage

Abstract

Ensiling as a method of forage feed conservation is the most appropriate in conserving of crude protein (CP) enhanced forages for sustainable dairy production. This is attributed to the fact that with this method, protein dependent lactic acid bacteria (LAB) hydrolyze water soluble carbohydrates (WSC) into short chain volatile fatty acids (VFAs) which are precursors for milk synthesis while the proteins buffers the excessive organic acids to produce more acetate and propionate. The study therefore aimed at assessing the quality of Brachiaria silage which was protein supplemented with graded levels of lablab forage. To achieve this objective, wilted Brachiaria forage (Brachiaria hybrid cv Mulato II) was collected, wilted and ensiled with and Lablab purpureus forages at inclusion levels of 0%, 10%, 20%, 30% Lablab purpureus forage. The resultant 4 treatments were assessed in a completely randomized design in 3 replicates. All silages were prepared using plastic jar mini-silos to laboratory scale and then incubated at room temperature (±30°C) for 45 days. After the 45 days, chemical analysis for quantification of water soluble carbohydrate (WSC), none protein nitrogen (NH3-N), Acid detergent fiber (ADF), Neutral detergent fiber (NDF), pH, in-vitro organic matter digestibility (INVOMD), acetic acid, lactic acid and propionic acid composition were conducted. The results indicated that; none protein nitrogen, acetic acid and propionic acid composition decreased in quadratic trends with increasing legume forage inclusion to minimum values of 5.8, 48.0 and 0.7g/kg at 14.7, 1.8 and 6.0% inclusion levels of lablab forage, respectively. On the other hand, following a quadratic trend, WSC composition decreased with increase in lablab forage, with a maximum of 28.9g/kg obtained at 7.6% inclusion level of lablab forage. Generally, CP, dry matter, INVOMD and metabolizable energy of the silage increased with increase in the inclusion levels of lablab silage. Using regression equations of the response curves, NDF and ADF decreased with increasing legume forage inclusion to minimum values of 349.3 and 172.1g/kg at inclusion levels of 16.1 and 17.1%, respectively. On the other hand in-vitro organic matter digestibility increased with the increase in the lablab forage inclusion to a maximum of 49.4%. However, mineral composition of the silage was not affected by lablab forage inclusion. Since the quality of silage for dairy cows depends on short chain volatile fatty acid, fibre and crude protein composition, inclusion of lablab forage to Brachiaria hybrid cv mulato II silage at a rate of 17.1% potentially yields the best results in lactating cows.