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ResearchersShow Benefits Of Zinc Supplementation In Broilers

By Douglas P. Smith, Ph.D.
Department of Poultry Science


Red discoloration of fully cooked poultry products is a sporadic yet chronic problem. Zinc has been reported to replace iron in myoglobin in an irreversible reaction that creates a red pigment. Many poultry producers add Zn and Cu to feed, sometimes over supplementing 50-200 percent because these minerals are important for broiler performance. Therefore, this project evaluated whether Zn or Cu in broiler feed at normal or high levels caused an increase of red discoloration in cooked product.

Two studies were conducted on broilers to determine: 1) the effect of feeding different levels of inorganic dietary zinc (Zn), copper (Cu) and roxarsone (As) on growth performance, carcass and meat quality, and blood zinc protoporphyrin/heme ratio (ZPP/H); and 2) the effect of adding high levels of inorganic dietary zinc (Zn) on growth performance, carcass and meat quality, and blood ZPP/H ratio.

In the first study 1,152 broilers were sexed and grown in 72 pens by sex and treatment (varied dietary levels of Zn, Cu, and As) to 56 d on litter. Results of the first study showed that males in comparison to females had increased body weight, body weight gain, feed intake and AdjFCR; however, females had lower mortality. Supplementation of 240 mg/kg Zn improved AdjFCR in the starter period in males and grower period in females. Supplementation of 100 mg/kg Cu was beneficial for both males and females in the grower and finisher periods. Roxarsone supplementation improved AdjFCR only in the finisher period. Minerals did not increase muscle redness.

In the second study, 288 broilers were sexed and raised in battery cages (to minimize availability of minerals from litter) to 42 d. Dietary Zn had no effect on feed intake of males, however, body weight gain and AdjFCR measured from 1-42 d was better in males fed diets supplemented with 120 mg Zn/kg. Dietary Zn had no effect on body weight, feed intake, body weight gain or AdjFCR of females. Dietary Zn had no effect on carcass weight and parts yield, however, breast fillet weights were improved in males when Zn was added to the diets.

Breast fillet cook yield and tenderness were not influenced by either sex or Zn. Raw breast fillet color was influenced by sex. Breast fillets from males were darker, redder and contained less yellow color. Raw thigh color was also lighter and less yellow compared to females. Raw marrow color measured immediately after harvest was more red and yellow in females. Lightness (L*) and redness (a*) of raw and cooked bone marrow collected from males was influenced by Zn. L* was higher at 120 mg Zn/kg for both raw and cooked marrow, while a* of cooked marrow was higher at 240 mg Zn/kg


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