Interrelações entre minerais no solo, plantas forrageiras e tecido animal no norte de Mato Grosso 4. Zinco, magnésio, sódio e potássio

An experiment was conducted with samples from six farms in northearn Mato Grosso, Brazil, to study the interrelationships among levels of minerals in soil, forage, and animal tissues during the wet and dry seasons of the year. Soil extractable Zn levels were low in three out of six farms. Forage Zn levels were defficient in five farms. Levels of Zn in the liver were defficient in all six farms, being much lower (68 ppm) during the wet season than during the dry season (113 ppm). Magnesium levels in soil were low in one farm and adequated in five. Forage and animal tissue Mg levels were adequated in all six farms. Soil extractable sodium was normal and the salinity in all six farms was considered negligible. Forage sodium was highly defficient, being able to meet only between 14 to 30% of the animal requirements. Soil potassium levels were low in two out of six farms, but forage levels were adequate in all six farms to meet the requirement of grazing beef cattle.Levantamento das deficiências minerais de seis fazendas localizadas ao norte do Estado de Mato Grosso, tendo sido amostrados os solos, plantas forrageiras e tecido animal, nas estações seca e chuvosa. Foram constatadas deficiências de Zn no solo em três das seis fazendas estudadas. Cinco das seis fazendas apresentaram deficiência de zinco nas forrageiras. Os níveis de Zn no fígado dos animais foram deficientes em todas as seis fazendas, mas sendo muito mais deficientes ainda no período chuvoso (68 ppm) do que no período seco, (113 ppm). Os níveis de Mg nos solos foram mais baixos em apenas uma fazenda. Nas forrageiras e no tecido dos animais amostrados, os níveis de Mg foram normais. Os níveis de Na nos solos foram considerados normais, e a salinidade nas regiões estudadas foi considerada insignificante. Em todas as fazendas, as forrageiras mostraram-se altamente deficientes em Na, satisfazendo apenas entre 14 a 30% das exigências nutricionais dos bovinos. Os níveis de K nos solos mostraram-se deficientes em duas das seis fazendas estudadas. As forrageiras apresentaram níveis médios adequados às exigências nutricionais dos bovinos em todas as fazendas

Sperm selection in natural conception:what can we learn from Mother Nature to improve assisted reproduction outcomes?

BACKGROUND: In natural conception only a few sperm cells reach the ampulla or the site of fertilization. This population is a selected group of cells since only motile cells can pass through cervical mucus and gain initial entry into the female reproductive tract. In animals, some studies indicate that the sperm selected by the reproductive tract and recovered from the uterus and the oviducts have higher fertilization rates but this is not a universal finding. Some species show less discrimination in sperm selection and abnormal sperm do arrive at the oviduct. In contrast, assisted reproductive technologies (ART) utilize a more random sperm population. In this review we contrast the journey of the spermatozoon in vivo and in vitro and discuss this in the context of developing new sperm preparation and selection techniques for ART. METHODS: A review of the literature examining characteristics of the spermatozoa selected in vivo is compared with recent developments in in vitro selection and preparation methods. Contrasts and similarities are presented. RESULTS AND CONCLUSIONS: New technologies are being developed to aid in the diagnosis, preparation and selection of spermatozoa in ART. To date progress has been frustrating and these methods have provided variable benefits in improving outcomes after ART. It is more likely that examining the mechanisms enforced by nature will provide valuable information in regard to sperm selection and preparation techniques in vitro. Identifying the properties of those spermatozoa which do reach the oviduct will also be important for the development of more effective tests of semen quality. In this review we examine the value of sperm selection to see how much guidance for ART can be gleaned from the natural selection processes in vivo