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Zinc is an essential trace mineral for birds, functioning elaborately in enzyme systems and being involved in protein synthesis, carbohydrate metabolism, and many other biochemical reactions. Zinc is required for normal growth, reproduction, and glandular development of birds. A severe zinc deficiency causes numerous physical and pathological changes including skin lesions, decreased growth, general disability of bones and joints, very poor feathering, reproductive failure, and reduced immunity to infection of several diseases. In skin, it is five to six times more concentrated in the epidermis than the dermis. In addition, zinc is associated with wound healing because of its role in collagen and keratin syntheses. All proliferating cells, including inflammatory cells, epithelial cells, and fibroblast, require zinc. Furthermore, zinc is an essential element of more than 200 metalloenzymes and affects their conformity, stability, and activity. The superoxide dismutase, one of the zinc-containing antioxidant enzyme, has a critical role in keeping broiler skin healthy and increasing the shelf-life of broiler meat. However, a clear appreciation of the role of this element in broiler production is still limited. This article provides an overview on the role of zinc in broiler feeding and nutrition, immunity, reproduction, and meat quality in particular.

A rapid increase in corn use in ethanol plants, and subsequent creation of distillers dried grains with solubles (DDGS) by-products, has led to an increase in the use of DDGS in the diets of livestock. DDGS has been used all over the world as a dietary ingredient and this has necessitated more research to be conducted on its quality, nutritive values, and recommendations for feeding to poultry. Currently, there have been a limited number of research publications regarding corn DDGS as an ingredient of diets for poultry. Approximately 100 scientific papers can be found which cover a variety of topics, with various degrees of depth into each. The purpose of this review is to collate the available information to date on the application of corn DDGS as an ingredient of poultry diets that can be easily accessed by researchers and nutritionists. This review presents the current state of knowledge of nutritive values of various corn DDGS ingredients, summarizes recommendations for using DDGS in diets for laying hens, broilers and turkeys, and reports the environmental ramifications when utilizing corn DDGS in poultry feed. In spite of the great amount of variation in nutritional properties of corn DDGS originating from various sources, it has been concluded that good quality corn DDGS, especially when derived from new generation plants, can be a viable ingredient in poultry diets.Corn distillers dried grains with solubles (DDGS) is a by-product of ethanol production plants that use corn for manufacturing (Aines et al., 1986). During yeast fermentation in ethanol plants, corn is ground, mixed with water, cooked and the liquefied starch from this process is hydrolysed and fermented to produce ethanol and CO 2 (Rosentrater,

1. An experiment was conducted to evaluate the effect of dietary zinc proteinate (ZP) supplementation on growth performance and on skin and meat quality of male and female broiler chicks. 2. A total of 240 1-d-old male and 240 1-d-old female broiler chicks were randomly distributed into 24 floor pens (12 replicate pens/sex; 20 birds/pen) and were given either 0 (Control diet) or 40 mg/kg ZP (ZP 40), resulting in a 2 × 2 factorial arrangement of treatments. 3. The growth performance of male and female broiler chicks was not affected by the ZP supplementation, but the males showed significantly higher growth performance than did females. 4. ZP supplementation increased the total thickness of skin in both sexes, and males had thicker skin than females. It also increased the collagen content of skin, but not that of meat. Males had higher skin collagen contents than did females, but no sex difference was found in the meat collagen contents. 5. ZP supplementation did not affect the shear force values of skin and meat; however, males had higher shear force values of back skin than females. ZP supplementation increased the zinc contents of thigh meat and plasma in both sexes. Males had higher zinc contents in back skin than females. 6. It is concluded that dietary ZP supplementation could increase the skin quality of broiler chicks in both sexes, particularly in female broilers, without any effect on growth performance. Male broilers have better growth performance and skin quality than females.

A 10-wk layer feeding trial was conducted to investigate the effects of high quality corn distiller's dried grains with solubles (DDGS) on performance, egg qualities, and yolk fatty acid composition. The economics of using DDGS in the Korean situation was also analyzed. A total of 216 Hy-line Brown layers, 23-wk of age, were employed in this trial consisting of three dietary treatments (0%, 10%, and 20% DDGS), and six replicates per treatment. All experimental diets were prepared as iso-protein (17%) and iso-calorie (2,780 kcal/kg). The use of DDGS up to 20% in layer diets did not affect the feed intake, laying rate, egg weight, and feed conversion ratio (P>0.05). At 5th and 10th wk of the trial, the eggshell color, albumen height, and Haugh unit were not influenced by the DDGS supplementation. At 5th wk of the trial, the eggshell qualities, like eggshell weight, eggshell thickness, and eggshell strength, were not affected by the DDGS feeding; however, these eggshell qualities were decreased at 10th wk due to the 20% DDGS feeding (P<0.05). Yolk color of DDGS 20% increased compared to DDGS 0% at 5th and 10th wk of the trial (P<0.05). At 10th wk, yolk/egg ratio of DDGS 20% decreased compared to DDGS 0% (P<0.05). The yolk fat content was not changed due to DDGS feeding. The monounsaturated fatty acid content of yolk decreased linearly by feeding DDGS (P<0.05). The yolk polyunsaturated fatty acid content of DDGS 20% increased significantly compared to DDGS 0%. The DDGS feeding was not found to affect the degree of yolk fat unsaturation. The cost of feed (\/kg feed) decreased as the level of DDGS increased. The production costs of egg (\/kg egg) were cheap in the order of DDGS 10%, DDGS 20%, and DDGS 0%, indicating that DDGS is a viable alternative feed ingredient to corn and soybean meal. In conclusion, high quality DDGS (L * 61.72) could be used economically up to 20% level without any harmful effect on laying performance: however, the use of DDGS up to 10% is more economical than DDGS 20%. (Key words : corn distiller's dried grains with solubles, layer, laying rate, egg quality, yolk fatty acid composition, economics) † To whom correspondence should be addressed : leebd@cnu.ac.kr