Variability
As wet beet pulp and pressed beet pulp result from processes depending on sugar factory management, they may have variable composition and quality. It is thus important for farmers to get as much information as possible from the sugar factory (see below information about pressing adjuvants) (Legrand, 2015; CNC, 2002).
Pectin breakdown
If pressed sugar beet pulp silage does not cool down quickly enough after the fermentation process, a part of the pectin can be cooked by high temperature and result in a pectin breakdown that makes sugar beet pulp yellow, fatty and sticky. This condition is detrimental to storage as the sticky pulp can undergo undesirable secondary fermentations and may raise problems of silo stability. In order to prevent pectin breakdown it is recommended to favour quick cooling. This can be achieved by using silage bags rather than trench silo, by storing pulp in underground silo or exposing the silo to the wind, using black plastic sheets, avoiding to put the beet pulp in a side by side silo or next to a heated building (Norell et al., 2007).
Microbial, fungal and mycotoxin contamination
If the cleaning of the beet roots is not well done, soil residues may bring butyric bacteria in the pulp and result in poor silage quality if the pulp has to be ensiled. In addition, soil residues subsequently reduce the organic matter of the beet pulp (CNC, 2002). If not properly preserved, pressed beet pulp silage is prone to molds and subsequent mycotoxins. In 2009 in France, a study assessing 40 samples of pressed beet pulp silage samples collected in 5 different regions reported that 34 samples contained molds, 27 samples were contaminated with yeasts and 8 samples were positive for mycotoxins (ochratoxin A, zearalenone, mycophenolic acid and roquefortine C). Two samples were found to contain zearalenone at levels exceeding the recommended level of 2000 µg/kg set by European regulations, and could have deleterious effects on reproductive performance (Boudra et al., 2015; European Commission, 2006). In Poland, the number of microorganisms found in pressed sugar beet pulp intended for direct feeding or silage in the majority of cases was reported to be within the range recommended by national regulation (Kowalska et al., 2013).
Additives
Chemicals can be added to the sugarbeet pulp during two steps of processing:
during diffusion, it may be useful to add antiseptic solution in order to prevent further microorganism development. At high level, the antiseptic may hinder silage process.
during pressing of the beet pulp, calcium sulfate or aluminium sulfate adjuvants are required to rigidify the beet pulp cell wall and increase pressing yield, but they can result in a S content too high for ruminants. S excess may have deleterious effects on animals. It results in loss of appetite, digestive troubles, reduced growth performance and it also causes secundary deficiencies in P, Zn, Cu, Se, and vitamin B1.
In order to prevent sulfate toxicity, the inclusion of H2SO4 should be limited to 1300 g/t beet roots. When aluminium sulfate is used for beet pulp pressing, farmers should increase P supplementation in the diet. It is thus important for them to be properly informed by the sugar factory (Legrand, 2015; CNC, 2002).