Małgorzata Kwiecień
The effect of form and level of copper and iron in feed on performance and some metabolic indices of broiler chickens
Introduction. Recent years have brought an increased interest in the chelates of new generation in which one to three particles of glycine are binding with microelements, such as copper, iron, zinc or manganese. Such a form guarantees even higher stability, as well as chemical and physical homogeneity, compared to previously used chelates with lysine or methionine.

Aim of study. The research aimed at comparing the influence of two different chemical forms (sulphates and glycine chelates) of copper and iron administered at different amounts in feed mixtures, on rearing efficiency indices, the quality of carcass and metabolic processes in Ross 308 broiler chickens.

Material and methods. Two growth experiments were performed on cockerels, reared in cages, placed in a room with regulated temperature and humidity, with free access to feed and water. In each of the experiments 300 chickens were divided into 6 groups, each consisting of 10 cockerels, in 5 replications. Mineral elements, Cu or Fe, were added to the feeds at three levels: 100%, 50% or 25% of their requirements, in the form of sulphates or chelates. During the experiments the body weight of all the birds was monitored and feed intake, body weight gains and survivability were determined. The tissues taken during slaughter were used to determine the content of basic components, as well as Cu, Fe, Zn and Ca. Also, the weight, length, strength, geometrical parameters and cortical indices of the femoral bone shaft, and the content of crude ash, Ca, P, Mg, Cu, Fe and Zn were determined. Blood samples were used to determine the value of biochemical and hematological indices, as well as the content of Cu, Fe, Zn and Ca.
Results  and  discusion. Replacing copper sulphate with the chelate resulted in a significant increase in chickens’ body weight in the 10th, 21st, 35th and 42nd day of their life, as well as in lower feed intake per 1 kg of body weight increase in the particular rearing periods. Also, higher dressing percentage and a higher share of leg muscles in the carcass were noted. Breast muscles revealed a higher content of crude ash and crude protein, while leg muscles had more crude ash. Breast muscles of the chickens fed Cu in the chelate form revealed a higher content of Fe, compared to the birds receiving the sulphate. A positive effect of replacing the inorganic form with the chelate on some blood indicators – lipid indices, activity of some emzymes (ALT, AST and LDH) and WBC count was proved. Analyzed physical features (weigt, length and perimeter), cortical (Ix) characteristic and selected strength parameters (Wy, dy and BI) of chicken femur were significantly higher with Cu added to the feed in the chelate form. Comparing different levels of Cu used in the form of the chelate, it was demonstrated that using a Cu additive in amount of 25% of chicken requirements did not lead to decreased body weight of the chickens in the 21st and 42nd day of their lives, while it significantly reduced feed intake during the starter period.
Replacing iron sulphate with the chelate resulted in increased body weight of the chickens in the 10th, 21st, and 35th day of their lives, as well as in reduced feed intake during the starter period. The addition of Fe in the form of the chelate increased the content of crude protein and reduced the share of crude fat in breast and leg muscles. Chickens’ breast muscles revealed a higher concentration of Fe, Cu and Zn, whereas leg muscles contained more Fe, Zn and Ca. Replacing the sulphate with the chelate increased the content of glucose, total protein, Fe, Cu, CHOL and its HDL fraction, WBC, RBC and Hb in chickens’ blood. On the other hand, the bones revealed higher bone density and a positive increase in bone strength parameters (Wy, dy, Wf, Wf/A and BI) and minerals (Ca, Mg and Zn). Comparing different levels of Fe used in the form of a chelate, it may be concluded that the addition of 25% of Fe resulted in an increased share of leg muscles and their higher share of crude ash. A positive increase in HDL fraction was noted with using the chelate at the level of 50% and 25%. 

Conclusions. The requirements of broiler chickens of Ross 308 line, established by manufacturers – 8 mg·kg-1 complete mixture for Cu and 80 mg·kg-1 for Fe are too high.
Introduction of 2 mg copper and 20 mg iron in the glycine chelates form to 1 kg of complete mixture had a positive effect on the performance, slaughter parameters and the content of minerals in the tissues, without compromising the biochemical and hematological blood parameters, and mechanical parameters of femur bone. 
The study confirmed the hypothesis about the legitimacy of the new generation of glycine chelates in broiler chicken nutrition.