Effects of molasses-enhanced fermentation and exogenous enzymes on the nutritive value of castor bean (Ricinus Communis L) oil cake for growing pigs

Abstract

Castor bean (Ricinus communis L) is highly valued for its oil, which has diverse applications in the pharmaceutical industry. Castor bean oil cake (CBOC) contains high levels of protein, but contains highly toxic compounds that require proper processing before feeding to livestock. The aim of the study was to evaluate optimum solid fermentation for CBOC, and the effects on nutrient digestibility, nitrogen balance, or plasma metabolites of 10% of the optimally fermented CBOC (FCBOC) in a diet fortified with exogenous fibrolytic enzymes. In experiment 1, a micro-fermentation study was conducted to evaluate the optimum level of supplementary Voermol (Product V10257; molasses containing 33 g/kg CP, 300 g/kg moisture, 6-9.2 g/kg Ca, 0.8 g/kg P and, 9.5 MJ ME/kg), 75% BRIX 75) in relation to the period of anaerobic solid fermentation of the CBOC. The experiment followed a completely randomized, 4 (molasses level; 0%, 5%, 10%, and 15%) x 4 (fermentation days; 0, 4, 7, and 10-day) factorial design, replicated three times. The change in proximate and detergent fibre composition was evaluated, and the pH of the fermented CBOC (FCBOC) measured as an indicator of fermentation intensity and extent, which are key determinants of silage quality and anerobic stability. Highest (P<0.05) OM was observed in 5% Voermol, 4- day FCBOC, similarly (P>0.05) followed by 10% Voermol, 4% fermented FCBOC, and least (P<0.05) OM in 15% Voermol, 7- day FCBOC, followed in the increasing (P<0.05) order 10% Voermol, 4-day fermented FCBOC>15% Voermol, 4-day fermented FCBOC. Treatment effects on ash were inverse to the OM (P<0.05) The fat content decreased (P<0.05) with 7, and 10-day fermentation, while 15% Voermol inclusion decreased (P<0.05) the fat content. The lowest pH (3.89) was achieved with 5% Voermol inclusion and 7-day fermentation. In experiment 2, the effects of including 10% inclusion of the optimally (5% Voermol, 7-day fermentation) fermented FCBOC in the pig's diet, and the efficacy of fibrolytic enzymes were investigated. Experimental diets were a standard maizesoybean diet (0% FCBOC), and an iso-nutrient, 10% FCBOC diet, each with (+) and without (-) 500g/tonne of Ronozyme® WX CT (EC-3.2.1.8, 1000 FXU/g endo-1,4-β-xylanase). Eight growing (31.88 ± 1.63 kg live weight) male Large White x Landrace pigs in metabolic cages were assigned to diets in a randomized 2 (diet) x 2 (enzyme) factorial arrangement within a two balanced 4 (period) X 4 (diet) Latin squares. Each feeding period consisted of 9 days dietary adaptation, plus five days of feed intake measurement, and the total collection of faeces and urine, from which nutrient digestibility, and parameters of N balance (Nitrogen intake, Urine Nitrogen Output, Feacal Nitrogen Output, Total Nitrogen Excretion, Absorbed Nitrogen, Nitrogen Retention, Nitrogen Utilization, Biological Value Feed Protein , and Apparent N digestibility were calculated. Blood was collected by jugular venepuncture into 10ml serum vacutainers on the last day of each period, from which Glucose, Urea, Creatinine, total protein, albumin, globulin, alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, bilirubin, cholesterol and triglyceride were analysed. In conclusion, based on the depletion of organic substrates, intensity and extent of CBOC fermentation, optimum fermentation was considered to be through 5% supplementary Voermol and 7-day ensilage. The 10% dietary inclusion of the optimally fermented FCBOC was not detrimental to nutrient digestibility, nitrogen balance, or plasma metabolites, which were not affected by the fibrolytic enzymes.