The nuclear stage at which oocytes are cryopreserved influences further development ability and cryopreservation affects ultrastructure of both cumulus cells and the oocyte. In this work, we analyze the effects of vitrification at different nuclear and cytoplasmic maturation stages on the oocyte ultrastructure and developmental ability. Culture in TCM199 + PVA with roscovitine 25 M during 24 h led to meiotic arrest (MA) in cumulus-oocyte complexes (COCs), while permissive in vitro maturation (IVM) was performed in TCM199, 10% FCS, FSH-LH and 17b-estradiol for 24 h. Oocytes were vitrified using the open pulled straw method (OPS) with minor modifications. Fresh and vitrified/warmed COCs were fixed as immature, after IVM, after meiotic arrest (MA) and after MA + IVM.Vitrification combined with MA followed by IVM produced the highest rates of degeneration, regardless of the vitrification time. As a consequence, lower proportions of embryos cleaved in these groups, although differences were eliminated at the five-eight cell stage. Development rates up to day 8 were similar in all experimental groups, being significantly lower than those in fresh controls. Only oocytes vitrified after IVM were able to give blastociysts. The morphological alterations observed can be responsible for compromised development. More research is needed to explain the low survival rates of the bovine oocyte after vitrification and warming. #

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Thermally assisted mechanical dewatering (TAMD) is a new process for energy efficient liquid/solids separation which enhances conventional device efficiency. The main idea of this process is to supply a flow of heat in mechanical dewatering processes to favour the reduction of the liquid content. This is not a new idea but the proposed combination, especially the chosen operating conditions (T < 100 C and P < 3000 kPa) constitutes an original approach and a significant energy saving since the liquid is kept in liquid state. Response surface methodology was used to evaluate the effects of the processing parameters of TAMD on the final dry solids content, which is a fundamental dewatering parameter and an excellent indicator of the extent of TAMD. In this study, a two factor central composite design was used to establish the optimum conditions for the TAMD of alfalfa biomass. Experiments were carried out on a laboratory compression cell. Experi ments showed that the dewatering enhancement results only from thermal effects. With a moderate heat supply (T piston ¼ 80 C), the dry solid content of the press cake can reach 66%, compared to 36% at ambient temperature. A significant regression model, describing changes on final dry solids content with respect to independent variables, was established with determination coefficient, R 2 , greater than 88%. With an energy consumption of less than 150 kWh/m 3 , the use of the TAMD process before a thermal drying process leads to an energy saving of at least 30% on the overall separation chain.