ABSTRACT This experiment was conducted to investigate the effect of feeding different concentrations and sources of zinc (Zn) on the growth performance, tissue mineral status, bone morphology and immunity responses in 0-4-week broiler chickens. Four hundred and forty 1-d-old broiler chickens were assigned randomly to 11 dietary treatments with 4 cages per treatment and 10 broiler chickens per cage in a completely randomized design. Dietary treatments were: corn-soybean meal basal diet (negative control), basal diet supplemented with 5 g yeast/kg (yeast), and basal diet supplemented with 20, 50, or 80 mg of added Zn/kg as ZnSO4, Zn-Met, or Zn-yeast in a 3 x 3 factorial arrangement of treatments. The results showed that broilers fed Zn supplemented diets had greater average weight gain and average feed intake than chickens fed the negative control diet (p<0.05). The Zn deposition in tibia, meat (thigh and breast) and excreta increased (p<0.01), regardless of source, in response to increasing dietary Zn concentrations. Zinc level increased dry weight of tibia bone and its large diameter. The strength of tibia bone as judged by Seedor index and breaking strength was improved (p<0.01) with Zn concentration in increased diets. Furthermore, supplemental Zn up to 50 mg/kg improved immunity responses of broiler chickens (p<0.01). It is concluded that supplementation with 50 mg Zn may be sufficient for normal broiler growth up to 28 d of age and the dietary inclusion of organic Zn could be utilized more effectively when compared to inorganic sources.

In this study, one hundred and twenty 40-wk-old White Leghorn laying hens were submitted to two different thermal conditions (24° C vs. 34° C) and were fed three levels (0, 10, or and 20 g/kg of diet)of fennel fruits (Foeniculum vulgare Mill.) as a feed additive in. This study was carried out according to a factorial design consisting of two temperatures and three fennel levels with five 5 replicates each (n = 2 × 3 × 5). Performance, egg production, egg quality, and oxidative product levels (malondialdehyde, MDA, and carbonyl) in the eggs were measured before and after heat exposure. The results showed that the tested temperatures did not affect egg production (p>0.05), but the production of eggs with broken shell and feed intake were affected by heat stress (p<0.05). The different temperatures also affected egg quality (p<0.05), reducing egg weight (EW), eggshell thickness (EST), eggshell strength (ESS), Haugh units (HU), albumen height (AH), and albumen weight (AW). At the high environmental temperature, MDA and carbonyl egg contents increased (p<0.05), while fennel consumption reduced the values of both parameters. Heat stress had no effect on yolk cholesterol levels (p>0.05), but increased yolk triglyceride levels. Hens that consumed fennel presented lower yolk cholesterol and triglyceride levels (p<0.05). In general, fennel fruit influenced egg yolk cholesterol and triglyceride contents, and because of its antioxidant properties, it may alleviate the adverse effects of heat stress on laying hens.