Effect of chelated trace-elements (zinc, manganese, iron) administered in dairy cows feed ration on productivity, milk composition and bioavailability

Trace elements are essential elements despite their name and quantity that is required by the animal organism, as they have many important effects on well-being and performance of cows. These elements, naturally present in cattle feed ration in an inorganic form, are not well assimilated by the animal and therefore the majority of them will be present in the feces; leading to a toxicity to the environment and human. Knowing that the organic form of trace elements is more absorbed than the inorganic one; for this reason, this study aimed to evaluate the influence of organic trace elements supplementation on their absorption, milk yield and composition, by adding Zinc (0.026%), Manganese (0.016%) and Iron (0.04%) to the basic feed ration.16 dairy cows were divided randomly into 4 groups: control, zinc, manganese and iron. Milk yield data was collected weekly for a period of 3 months. Milk composition (fat, protein, Solid-Non-Fat percentages and density) were measured monthly using Milkana. In order to assess the quantities of the studied trace elements in cattles diet and feces, Atomic Absorption Spectrometer was used. The obtained results showed that milk yield data in the second month of the study has decreased, while a significant (P<0.05) decrease was seen for iron and manganese treatment; meanwhile for the third month, it increased in all groups except the control. Zinc treatment had the best effect on milk yield. Concerning milk fat, the treated groups showed a higher fat yield than control with iron treated group have a significantly (P<0.05) higher fat yield. For milk protein, treatment has no significant (P>0.05) effect on this factor. For milk density, for the first two months of the study, no significant difference (P>0.05) was seen among groups; meanwhile for the last month, milk density was significantly lower for manganese and iron groups when compared to control group; we concluded that zinc group has the best effect on milk density between treatments. For milk Solid Non Fat, for the first two months there was no significant difference (P>0.05) among all groups but for the last month, manganese group has a significantly (P<0.05) lower Solid Non Fat. The amount of trace elements absorbed by the cows was significantly (P<0.05) higher in treatment group when compared to each corresponding element in control one, while zinc was the best assimilated element. We can conclude that zinc has the best effect and absorption on dairy cows.