Interaction of dietary calcium and zinc with coccidiosis in relation to broiler performance

Abstract

The effect of excess dietary calcium and zinc levels on growth and feed conversion efficiency was studied in broilers artificially illfeced with mixed Eimeria species. Dietary treatments using 2 levels of calcium (Cal-1.03% and Ca2-1.98%) and 3 levels of zinc (Zn1-63, Zn 2-93 and Zn2 -123 ppm) were formulated in a factorial design. Day-old broiler chicks (306) were randomly divided into 24 groups of 12 to 13 chicks in each and 4 replicated groups were offered each dietary treatment. At fourth week of age, birds of 2 groups in each treatment were artificially infected with 60 000 sporulated oocysts of Eimeria spp. (E.tenella, E.necatrix and E.acervulina) per bird through crop intubation, while the other 2 groups (uninfected control) received tap water. The broiler performance was assessed by feed intake, body weight gain and feed conversion efficiency at sixth (market age), and sevcnth (convalescent stage of coccidiosis) week of age. Zinc levels and the infection did not influence the feed intake, while it was reduced (P<0.01) by high calcium diet. The infection and high calcium diet significantly reduced (P<0.05) the body weight gain. Relative growth rate was higher (P<0.01) in high calcium diet and it improved in high calcium diet with 93 or 123 ppm zinc during 1-21 days post infection period. The interaction between calcium level and infection status was also significant (P<0.05). The calcium and zinc levels had little effects on feed conversion efficiency but efficiency offeed utilization for'unit gain decreased in infected groups at both the stages. Mortality of birds was highest in the dietary treatment Ca Zn and on fifth day post infection. The diets containing 1.98% calcium and 93 or 123 ppm zinc reduced the growth depression and improved conversion efficieny of birds artificially induced with coccidiosis.