Isabel Cristina Ferreira

Análise da pele de três espécies de peixes: histologia, morfometria e testes de resistência

This study was carried out to analyse the skin of three species of fish (piavucu Leporinus macrocephalus, pacu prata Mylossoma sp e piraputanga Brycon hilarii) through histological and morphometrical analysis and resistance tests after hardening. Skin samples from the dorsal region were taken and fixed in Bouin solution for 24 hours. They were embedded in paraffin, cut 5 µm thick and stained by Hematoxylin-eosin technique. The cuts were analyzed by light microscopy. A EMIC dynamometer was used for the physical mechanical analysis of the skin in 10 samples, longitudinally oriented from the dorsal region of each specie of fish. The dermis of those fishes has a structural pattern common to teleosts, but the setting and distribution of collagen fibers was different among the analyzed species. The skin dermis thickness differed among the three species by the morphometrical analysis. No difference was observed for the resistance test to traction in piraputanga leather (16.88 N/mm2) as well as in piavucu leather (18.50 N/mm2). The results for the skin of both fish species were higher than those for pacu (11.83 N/mm2). The value of stretching as to the point of rupture was higher for piavucu (52.83%) and piraputanga (60.45%), showing no difference among them, but it was lower for pacu (33.83%). The progressive tearing was greater in pacu skin (36.51 N/mm). The skin of the three analyzed species can be turned into leather for the manufacture of several artifacts.

Estimates of covariance functions for growth of Anglo-Nubian goats

It was used 4,313 weight records from birth to 196 days of age from 946 Anglo-nubiana breed goats, progenies from 43 sires and 279 dams, controlled in the period from 1980 to 2005, with the objective of estimating covariance functions and genetic parameters of animals by using random regression models. It was evaluated 12 random regression models, with degrees ranging from 1 to 7 for direct additive genetic and maternal and animal permanent environment effect and residual variance adjusted by using animal age ordinary polynomial of third order. Models were compared by using likelihood ratio test and by Bayesian information criterion of Schwarz and Akaike information criterion. The model selected based on Bayesian information criterion was the one that considered the maternal and direct additive genetic effect adjusted by a quadratic polynomial and the animal permanent environmental effect adjusted by a cubic polynomial (M334). Heritability estimates for direct effect were lower in the beginning and at the end of the studied period and maternal heritability estimates were higher at 196 days of age in comparison to the other growth phases. Genetic correlation ranged from moderate to high and they decreased as the distance between ages increased. Higher efficiency in selection for weight can be obtained by considering weights close to weaning, which is a period when the highest estimates of genetic variance and heritability are obtained.

Avaliação econômica da aplicação de fertilizantes nitrogenados em pastagens destinadas a vacas em lactação

O crescimento da renda e da populacao mundial tem demandado um aumento de alimentos e de insumos. Essas questoes afetam diretamente a pecuaria leiteira explorada em pastagens intensivas. Por meio deste estudo, buscou-se avaliar economicamente a estrategia da fertilizacao nitrogenada em pastagens destinadas a atividade leiteira, em distintos cenarios economicos e produtivos. Utilizou-se a margem bruta como indicador economico. Ficou evidenciada a importância da eficiencia da utilizacao de insumos e de forragem. No cenario atual de precos de fertilizante e de leite, a fertilizacao com nitrogenio (N) foi viavel economicamente, principalmente em doses de, aproximadamente, 200 kg de N/ha/ano, quando houve fornecimento de concentrados e 400 kg de N/ha/ano, quando nao ocorreu essa suplementacao. Neste trabalho, a ureia apresentou melhor resultado economico em relacao ao sulfato de amonio.

Composição química da silagem de milho com aditivos

Corn silage is one of the most conserved feed used in animal production during drought. The objective of this study was to evaluate the chemical composition of corn silage with different additives. The design was randomized, in a 3x3 factorial scheme (three values of the addition of wet corn gluten feed and two additives + one without additive), with three replications, totaling 27 experimental units. We used analysis of variance with 5% significance and Scott-Knotts test for the data obtained. The values of total digestible nutrients and dry matter increased proportionally to the co-product inclusions in the silages with additives. The crude protein and neutral detergent fiber presented the same behavior, while the values of acid detergent fiber were reduced in the silages with 30% of the co-product. Silages treated with benzoate showed higher ash content. Lower values for ethereal extract content were found in the silages without inclusion of the co-product. The use of 15 and 30% of wet corn gluten feed had no effect on the chemical composition of the silage.