Factors that affect oocyte vitrification in small ruminants / Fatores que afetam a vitrificação de oócitos em pequenos ruminantes

At the end of its growth, the mammalian oocyte, include in preovulatory follicle, is the largest cell of the organism, with about 120 µmin diameter. The size of oocyte, together with the specific arrangement of its organels and cytoskeleton, makes a real challenge forcryopreservation techniques. For such large cell, methods that do not require equilibrium to cryopreservation, such as vitrification,are more promising. It is important to highlight that the cryopreservation of oocytes is more difficult than zygotes or later stageembryos and this technique is a challenging task because of oocyte sensitive nature to chilling and toxic effects of cryoprotectants.However, the development of a reliable method for oocyte cryopreservation would be an important advance in the field of reproductivebiology for the preservation of genetic resources. The vitrification of mammalian oocytes is influenced by many variables, such asdifferent cryoprotectants, vitrification techniques, presence or absence of cumulus cells, the oocyte structure, metabolism (such aslevel of lipid storage) and meiotic stage. Thus, all these factors should be considered to optimize the techniques and adapt them tooocytes from each species. Therefore, the present review aims to describe the main factors that affect oocyte vitrification in sheepand goats, reporting the main findings in both species, as well as perspectives of future improvements.

No fim do seu crescimento, o oócito mamífero é a maior célula do organismo, com cerca de 120 µm de diâmetro. O tamanhodo oócito em conjunto com a disposição específica das organelas e do citoesqueleto faz com que ele represente um verdadeirodesafio para as técnicas de criopreservação. Para grandes células, métodos que não exigem equilíbrio para criopreservação,como a vitrificação, são mais promissores. É importante ressaltar que a criopreservação de oócitos é mais difícil que de zigotosou embriões em estádios mais tardios e esta técnica representa um desafio devido à natureza sensível do oócito ao resfriamentoe aos efeitos tóxicos de crioprotetores. Entretanto, o desenvolvimento de uma técnica confiável para a criopreservação oocitáriarepresentaria um avanço importante para a preservação de recursos genéticos. A vitrificação de oócitos em mamíferos é influenciadapor muitas variáveis, tais como diferentes crioprotetores, técnicas de vitrificação, presença ou ausência de células do cumulus,estrutura do oócito, metabolismo (como o nível de armazenamento de lipídios) e estágio meiótico. Assim, todos esses fatoresdevem ser considerados quando o objetivo é otimizar as técnicas e adaptá-las para oócitos de cada espécie. Assim, a presenterevisão tem como objetivo descrever os principais fatores que afetam a vitrificação de oócitos em ovinos e caprinos, relatando osprincipais resultados em ambas as espécies, bem como as perspectivas de melhorias futuras.

Clinical, haematological and biochemical responses of sheep undergoing autologous blood transfusion.

BACKGROUND: This study aimed to evaluate the clinical, haematological and biochemical responses to autologous blood transfusion and the feasibility of this practice in sheep. Thus, we used eight male, 8 months old sheep, weighing on average 30 kg, from which 15 mL/kg of whole blood was collected and stored in CPDA-1 bags. Blood samples were refrigerated for 8 days and subsequently re-infused. The clinical, haematological and biochemical parameters were evaluated before blood collection and reinfusion, after 10 minutes of collection and reinfusion, after 3, 6, 12, 24, 48, 96 and 192 hours after collection and reinfusion. RESULTS: With respect to clinical parameters, we observed a decrease in heart rate after 24, 48 and 196 hours from reinfusion compared to basal values (p < 0.05). Haematological variables including globular volume and erythrocyte counts showed a significant decrease (p < 0.01) at all time points after collection and increased (p < 0.01) at all time points after reinfusion. There was a significant increase in total protein and calcium at all time points after reinfusion (p < 0.05). CONCLUSION: Autologous transfusion in sheep slightly altered the physiological, biochemical and haematological responses of sheep, indicating that the technique proposed is safe and can be applied in the clinical practice of this species. The 8 d period was not sufficient for complete recovery of the haematological parameters after blood collection.

Copper deficiency in sheep with high liver iron accumulation.

An outbreak of enzootic ataxia among sheep raised in the northeastern region of Brazil is described. Copper (Cu) deficiency was diagnosed in a herd of 56 sheep, among which five presented characteristic clinical symptoms of enzootic ataxia. The symptoms began 30 days after birth, with a clinical condition that included locomotion difficulty, limb ataxia, tremors, and continual falls. Liver biopsies were performed and blood was collected to determine hepatic and plasmatic Cu, iron (Fe), and zinc (Zn) concentration, respectively. The laboratory results showed that the animals presented low copper concentrations in the plasma and liver, without difference between the clinically healthy animals and those affected by enzootic ataxia. Even after supplementation with adequate Cu levels had been recommended, it was found on a new visit to the farm four months later that one animal still presented a clinical condition and that the hepatic Cu levels of the herd had not risen. Despite the low copper content of the diet, the high hepatic Fe levels found suggest that antagonism due to this element may have been an important factor in triggering copper deficiency in these animals, and thus, additional copper supplementation may be necessary for these animals.