Effects of Different Levels of Dietary Zinc-Threonine and Zinc Oxide on the Zinc Bioavailability, Biological Characteristics and Performance of Honey Bees (Apis mellifera L.).

The experiment was conducted to investigate the effect of supplementary different levels of zinc-threonine (Zn-Thr) and zinc oxide (ZnO) on the Zn bioavailability, biological characteristics and performance of honey bees (Apis mellifera L.). The experiments were carried out with seven treatments in a completely randomized design with five replicates for each treatment. During the experiment, groups were fed a basal diet without extra zinc (10.4 mg Zn/kg diet), and it was used as the control diet and 3 levels of 20, 40, and 60 mg Zn/kg were added to the diet by ZnO and Zn-Thr sources. The results showed that different levels of organic Zn significantly increased Zn and Fe content in the carcass of caged bees compared to different levels of inorganic Zn and control groups. Also, honey bees fed with levels of 40 and 60 mg Zn/kg Zn-Thr supplementation significantly had lower Malondialdehyde (MDA) concentration and higher ash content, protein content, superoxide dismutase (SOD) activity in their tissues. In addition, they showed more life span, feed intake, population, brood rearing, and hive weight gain (p < 0.05). Totally, the results of the present experiments revealed that diets supplied with organic Zn compared to inorganic Zn play significant roles in the improvement of Zn bioavailability, biological characteristics, and performance in honey bees.

Comparison the Zn-Threonine, Zn-Methionine, and Zn Oxide on Performance, Egg Quality, Zn Bioavailability, and Zn Content in Egg and Excreta of Laying Hens.

The experiment was conducted to investigate the effect of supplementary zinc-threonine (Zn-Thr), zinc-methionine (Zn-Met), and zinc oxide (ZnO) on the laying performance, egg quality, Zn content in egg and excreta. One hundred and sixty hens (Hy-Line W36) were randomly divided into 10 treatments with 4 replications of 4 hens each. During the first 4 weeks, groups were fed a corn-soy basal diet without extra zinc (30.3 mg Zn/kg diet) to depletion storage zinc from the body and it was used as the control diet. During the ensuing 10 weeks from 36 to 45 weeks of age, 3 levels of 30, 60, and 90 mg Zn/kg were added to the diet by ZnO, Zn-Met, and Zn-Thr sources. Results showed that there were no significant differences between the experimental treatments in terms of egg weight, feed intake, eggshell weight, eggshell percentage, and albumen weight. In total experimental period, the supplementation of Zn-Met and Zn-Thr decreased feed conversion ratio and increased egg mass and egg production compared with ZnO 30 and 60 mg Zn/kg and control treatments (P < 0.05). The results showed that treatment effect on Zn content in egg and excreta was significant (P < 0.05). It is concluded that diets supplied with lower levels of organic Zn can maintain egg production performance, improve egg quality, enrich eggs, increase bioavailability, and reduce the negative effects of age on egg quality characteristics in laying hens compared with their oxide form.