Supplementation of pressed sugar-beet pulp silage with molasses and urea, laying hen excreta or soybean meal in ruminant nutrition

Abstract

The feasibility of ensiling pressed sugar-beet pulp alone or supplemented with molasses and urea or laying hen excreta (LHE) was evaluated by measuring fermentation characteristics of the silages. The volatile fatty acids, lactic acid and NH 3 contents were significantly higher ( P < 0.05) for pulp supplemented with LHE. All pathogens (coliforms, Streptococci, Staphylococci, yeasts and moulds) were eliminated after ensiling, except Clostridia but these germs were present in very small quantities (less than 100 germs g −1). A second experiment was carried out with 12 adult wethers in a complete random block scheme in order to determine the apparent digestibility of the main constituents of three diets consisting of pressed pulp supplemented with molasses and urea (P-MU), LHE (P-LHE) or soybean meal (P-SM). The diets were supplemented with 10% hay of known digestibility and this latter value was deducted from the measured digestibilities in order to obtain those of the studied diets alone. The crude protein digestibility was significantly higher for P-MU ( P < 0.05), and that of organic matter significantly lower for P-LHE ( P < 0.05). Crude fibre digestibilities significantly differed for the three diets ( P < 0.05) in the following order: P-LHE < P-SM < P-MU. In a third experiment, three wethers fitted with rumen and duodenal cannulas were given, in a Latin-square design, one of the three studied diets. The NH 3 contents and pH of the rumen fluids were significantly higher ( P< 0.05) for P-LHE whereas the volatile fatty acid profile was the same for the three diets. The yield in bacterial N synthesis, estimated with the diaminopimelic acid method, was significantly higher ( P < 0.01) for P-MU: 45.3 g bacterial N kg −1 organic matter digested in the rumen versus 36.5 g and 33.9 g for P-SM and P-LHE, respectively. The proportion of bacterial N at the duodenal level was significantly lower ( P < 0.01) for P-SM (58% versus 75% and 73%, respectively for P-MU and P-LHE). The duodenal flow of amino acids was significantly lower ( P < 0.001) for P-LHE: 113 g day −1 versus 147 g day −1 and 148 g day −1 for P-SM and P-MU, respectively. It was concluded that pulp is very easy to conserve by ensiling, even when mixed with LHE and, thanks to the high degradability of its fibre in the rumen, it is a very good energy source that may be supplemented by non-protein nitrogen. The bacterial protein synthesis is optimised by supplementation with urea and molasses.