Cássio Xavier de Mendonça

Effect of vitamin E and selenium on resistance to oxidative stress in chicken superficial pectoralis muscle.

One-day-old chicks were reared using diets that differed in their vitamin E and/or selenium content. In chicks depleted of both selenium and vitamin E, signs of exudative diathesis on the superficial pectoralis muscle were observed. The purpose of this research was to determine the defective points of the antioxidant defense system, which made this tissue highly susceptible to nutritionally-induced oxidative stress. Vitamin E, and selenium in lower magnitude, were the factors that strikingly affected the course of mitochondrial lipid peroxidation. Animals fed diets deficient in vitamin E and selenium displayed the lowest reduced glutathione level and glutathione peroxidase activity. The decreased levels of reduced glutathione were not due to a defective activity of glutathione reductase, which was increased in both mitochondria and cytosol. The absence of vitamin E was linked to lowering of mitochondrial thiol levels. The Glutathione peroxidase/Cu,Zn-superoxide dismutase ratio was 2.8 in animals fed selenium and vitamin E, and decreased to 0.13 in animals deficient in both nutrients. This change was indicative of oxidant-induced damage mediated by hydrogen peroxide. Catalase activity increased in an attempt to counteract the decrease in glutathione peroxidase activity. The results obtained showed that alpha-tocopherol and Se deficiencies caused multiple alterations in the antioxidant system and adversely affected the redox state of chicken superficial pectoralis muscle.

Effect of Dietary Lipid-Lowering Drugs upon Plasma Lipids and Egg Yolk Cholesterol Levels of Laying Hens

To evaluate the effect of lipid-lowering agents upon egg quality, reproductive performance, plasma lipids, and egg yolk cholesterol levels, 30-week-old Shaver laying hens were fed a basal diet (commercial ration) supplemented with 0.1% probucol (PROB), 0.025% gemfibrozil (GEMF), or lovastatin at 0.0005% (LOV1), 0.001% (LOV2), or 0.0015% (LOV3) for a 12-week experimental period. It was observed that the supplementation of the drugs did not impair albumen and shell quality. Hen performance was not adversely affected. The depression in triglyceride concentrations approached statistical significance only in LOV2 (38.5%), and total cholesterol was significantly depressed in LOV2 (36.0%), LOV3 (36.8%), PROB (29.6%), and GEMF (30.4%) treatments. Egg cholesterol content, expressed per gram of yolk, was significant lowered in LOV1 (7.5%) and LOV3 (12. 7%).

Efeito da adição de óleo de peixe à dieta sobre o desempenho e níveis de lípides plasmáticos e de colesterol no ovo de galinhas poedeiras

The purpose of this study was to evaluate the effect of fish oil upon egg quality, production, plasma lipids and egg yolk cholesterol levels of laying hens. 89-week-old hens were fed diets containing 0.5%, 1%, 2%, 3% and 4% fish oil for 5 weeks. It was observed that the addition of 1% to 4% fish oil to the diet reduced egg weight, but did not affect feed conversion. Albumen and shell quality was not impaired by the supplementation of fish oil to the diet. No significant changes were observed on plasma triglyceride and cholesterol levels, and egg yolk cholesterol content was not affected by the addition of fish oil.

Efeito dos níveis de proteína e de metionina da dieta sobre o desempenho de galinhas poedeiras após a muda forçada

This experiment was conducted to evaluate the effect of diets with two protein levels (16.5% and 14.5%) and 5 supplemental methionine levels (0%, 0.025%, 0.050%, 0.075% and 0.100%) on postmolt layer performance. Two hundred forty commercial laying hens at 67 wk of age were induced to molt by zinc oxide and fed ten molt experimental diets for 6 wk. At the end of the experiment body weight, feed consumption and feed conversion were significantly higher for the birds fed the 16.5% crude protein diet. Hens fed higher protein level diet returned to egg production faster than those birds fed lower protein diet. Rations with 16.5% of protein determined a significant better egg production until the fifth experimental week, without affecting the egg weight. The methionine supplementation significantly increased egg weight, however did not statistically influence the egg production. Birds fed approximately 300 mg methionine daily (0.050% and 0.075% supplemental methionine levels) produced eggs significantly heavier, however resulting in a low egg shell quality measured by egg specific gravity, shell thickness and shell weight.

Efeito de diferentes métodos de descanso forçado sobre o desempenho de poedeiras

One experiment was conducted to compare productive performance of laying hens of two strains: Babcock (light) and Hisex Brown (semi-heavy), exposed to forced molt according to the following treatments: A- Feed restriction (11 days), B- Salt restriction (42 days), C- high dietary zinc (2.0% of ZnO during 11 days) and D- High dietary iodine (0.6852% de KI during 42 days). The experimental design was a random block design. The birds (128 by strain) were 66 weeks old at the beginning of the molt phase. Birds on treatments A and C had better production in the second cycle and better feed conversion. Birds on treatment A produced the heaviest eggs with lowest quality (both internal and external). Percentage of production was not different among the strains tested, even though the lightweight birds showed a significantly better feed conversion and lower feed consumption. The semi-heavy strain produced significantly heavier eggs, with better internal quality but lower shell quality.

Efeitos de níveis de cobre suplementar na dieta sobre o desempenho produtivo, colesterol na gema e lípides no plasma sangüíneo de poedeiras comerciais

No presente estudo, foi verificado o efeito da suplementacao de elevados niveis de cobre alimentar sobre o desempenho de galinhas poedeiras, niveis de colesterol na gema do ovo e de lipides plasmaticos. Foram utilizadas 160 galinhas poedeiras comerciais, perfazendo 5 tratamentos com 4 repeticoes de 8 aves, alimentadas por 6 semanas com dieta comercial (controle) ou suplementada com sulfato de cobre de modo a fornecer 200, 400, 600 e 800 mg de cobre/kg de dieta. A suplementacao de cobre em niveis de ate 400 ppm nao afetou significativamente o peso e a producao dos ovos, o consumo e a conversao alimentar, no entanto, quando em teores de 600 e 800 mg/kg, determinou reducao significativa no peso dos ovos, postura e consumo de alimento. A qualidade da casca, avaliada em termos de peso (gramas e % do peso do ovo) e espessura da casca, foi significativamente reduzida apenas com 800 ppm na racao. As concentracoes plasmaticas de triglicerides e de colesterol HDL mostraram comportamento inverso em relacao ao excesso de cobre suplementar. Em nivel de 800 ppm, o cobre determinou, de forma significativa, diminuicao dos triglicerides (705 mg/dL) e aumento do colesterol HDL (9,7 mg/dL) sanguineos em relacao ao grupo controle (1.643 e 4,5 mg/dL, respectivamente). Quando administrado na concentracao de 800 ppm, o cobre determinou aumento significativo dos valores de colesterol no ovo, tanto expressos em relacao a gema original (14,83 mg/g) como a gema seca (27,70 mg/d) comparado ao controle (12,35 e 23,08 mg/g, respectivamente). O efeito de elevados niveis de cobre alimentar na reducao do colesterol na gema do ovo nao foi confirmado no presente estudo. Futuras pesquisas sao recomendadas.

Effects of cholestyramine and lovastatin upon plasma lipids and egg yolk cholesterol levels of laying hens

O presente trabalho teve por objetivo avaliar os efeitos da colestiramina e da lovastatina, drogas hipolipemizantes, sobre a qualidade do ovo, desempenho das aves, teores de lipides plasmaticos e de colesterol na gema do ovo de galinhas poedeiras Shaver. Aves com 26 semanas de idade receberam como alimentacao dieta formulada sem ingredientes de origem animal (COM) acrescida de colestiramina a 0,2% (COL1) e 0,3% (COL2) e lovastatina a 0,005% (LOV) durante 6 semanas. A adicao das drogas nao prejudicou a qualidade da casca e do albumen dos ovos. De um modo geral, o desempenho produtivo das aves nao foi afetado, com excecao da reducao observada no peso medio dos ovos. Nao foram observadas mudancas nos teores de lipides plasmaticos das aves e a concentracao de colesterol na gema permaneceu inalterada mediante a adicao das drogas.