Effect of Diet Supplemented with Natural Humic Compounds and Sodium Humate on Performance and Selected Metabolic Variables in Broiler Chickens

The effect of humic substances from different sources on the performance and selected biochemical indicators was studied in 150 one-day-old broiler chickens (Ross 308) divided into control (C) and two tested groups (n = 50). Chickens of tested groups were fed diets supplemented with natural humic compounds (group HS) and sodium humate (group HNa) at amounts of 5 g·kg-1 of feeds in phase 1 and 7 g·kg-1 of feeds in phases 2 and 3 of the fattening period. Higher final body weights (not significant) were observed in both tested groups (2527.6 g for HS; 2481.5 g for HNa) than in the control group (2476.6 g). The feed conversion ratio throughout the whole experiment was lower in the HS group (P < 0.001) and higher in the HNa group (P < 0.001) compared to the control group. The European Efficiency Index reached at the end of the experiment was the highest in the HS group (P < 0.001) and the lowest in the HNa group compared to the control group. Differences in total protein, albumin, total lipids, triglycerides and phosphorus among the tested groups were not significant. Higher values of Ca (P < 0.05) in the HS group and lower cholesterol (P < 0.05) in the HNa group were observed after 14 days; lower AST (P < 0.05) in the HS group and lower calcium (P < 0.05) and higher glucose (P < 0.01) in the HNa group were observed after 35 days of the experiment in comparison with the control group. Humic substances, production, biochemical indices Humic substances are natural, yellow to brown-black coloured organic compounds with a relatively high molecular weight ranging from 2 to 200 kDa, that originate from the decomposition of plant and animal remains (Stevenson 1994). This process of decomposition is called humification. Humic substances can be found in soil, peat, lignites, brown coals, sewage, natural waters and their sediments. The content of humic substances in these materials varies from trace amounts in sands and clays to tens of per cents (310%) in brown coal. Extremely high amount (up to 85%) is present in the lignite, the peat and the oxyhumolite (oxidised brown coal) (Peña-Méndez et al. 2005; Skokanová and Dercová 2008). Humic substances contain humin, humic acid, fulvic acid, ulmic acid and some microelements (Stevenson 1994) such as iron, manganese, copper and zinc (Aiken et al. 1985). Nowadays, humic substances are used in agriculture, industry (building industry, woodworking industry, ceramic industry and paper industry), environmental and bio-medicine. In agriculture they are used mainly as fertilizers in the form of humates to increase soil fertility, to increase transfer of micronutrients from soil to plants, to increase seed germination rates, and to reduce the usage of mineral fertilizers (Peña-Méndez et al. 2005). The main function of humic substances in environmental chemistry is to reduce the toxic effect of residual amounts of heavy metals, herbicides, fungicides, insecticides, nematicides, dioxins and radionuclides and other harmful substances in water and soil (Shin et al. 1999; Loffredo et al. 2000; Kucukersan et al. 2005). In the veterinary medicine they are used in horses, ruminants, swine and poultry for the treatment of diarrhoea, dyspepsia and acute intoxications. They have a protective action on the mucosa of the intestine via a protective film formation (Kucukersan et al. 2005). They can also bind ACTA VET. BRNO 2010, 79: 385–393; doi:10.2754/avb201079030385 Address for correspondence: MVDr. Alena Šamudovská Department of Nutrition, Dietetics and Animal Breeding University of Veterinary Medicine, Komenského 73 041 81 Košice, Slovak Republic Phone: +421 910 460 957 E-mail: [email protected] http://www.vfu.cz/acta-vet/actavet.htm toxic metals and other toxic substances by the formation of insoluble and non-resorbable complexes (Alvarez-Puebla et al. 2004) and have antiphlogistic and antimicrobial properties (EMEA 1999). In recent years the interest in the use of humic substances in animal husbandry has increased. Many authors in their studies observed an improvement in growth and feed conversion, and reduction of animal mortality after addition of humic substances into feedstuff (Eren et al. 2000; Kocabağli et al. 2002; Karaoglu et al. 2004; Ji et al. 2006; El-Husseiny et al. 2008). An improvement in egg production and egg weight was observed in a study of the effect of humic acids in laying hens performed by Kucukersan et al. (2005). Although there is not enough evidence to hypothesize how humates promote growth, it is assumed that humates might increase the uptake of nitrogen, phosphorus and other nutrients due to their chelating properties (Kocabağli et al. 2002). The objective of the present study was to investigate the effect of supplementation of natural humic compounds and sodium humate on the performance and selected biochemical indicators of broilers. Materials and Methods Birds and diets In this study, a total of 150 unsexed one-day-old broiler chickens (Ross 308) obtained from a commercial supplier were used. Chickens were weighed, randomly divided into three groups: one control (C) and two tested groups (HS, HNa) with 50 chicks per group. Birds were housed on deep bedding in agreement with the technological instruction for Ross 308 chickens, with controlled light, temperature, animal hygiene and feeding regime. Birds were fed a complete mixture in the mash form according to the growth phases (phase 1: week 1 to 2; phase 2: week 3 to 5; phase 3: week 6) ad libitum. The composition of feed mixtures is shown in Table 1. The tested group diets were supplemented with natural humic compounds (oxyhumolite total humic acids 68%, free humic acids 48%, minerals 18%; locality Dudar, Hungary) (group HS) and sodium humate (dry matter 84.8%, humic acids 63.2%, ash 36.9% in dry matter) (group HNa) at different amounts: 5 g·kg-1 of diet during first two weeks and 7 g·kg-1 of diet from week 3 to 6. No antibiotic growth promoters or anticoccidials were used in the diets. Birds were individually weighed and the feed consumption was observed weekly. Body weight gain (BWG) and feed conversion ratio (FCR) were calculated. Mortality was recorded as it occurred and percentage of mortality was determined on day 35 and at the end of the study. The following equation was used for the evaluation of results using European Efficiency Index (EEI): EEI = live weight (kg) × liveability × 100 age (days) × feed conversion Blood samples were collected from ten birds in each group on days 14 and 35 of experiment from the jugular vein for biochemical analysis. The experiment was carried out in the barns of the Institute of Animal Nutrition and Dietetics at the University of Veterinary Medicine in Košice in compliance with the EU regulations concerning the protection of experimental animals. The experiment was carried out with the consent of the institutional Animal Care and University Ethics Committee. Analytical methods Diets were analyzed for dry mater, crude protein, ether extract, crude fibre and ash by the AOAC (2001). Total protein, albumin, glucose, total lipids, cholesterol, triglycerides, alkaline phosphatase, aspartate aminotransferase, calcium and phosphorus blood serum concentrations were determined by spectrophotometry using commercial Bio-La-Tests (Pliva-LaChema Brno Ltd., Czech Republic). Statistical analysis Statistical evaluation of the effects of natural humic compounds and sodium humate on body weight, feed conversion ratio, European Efficiency Index and biochemical indices of chickens among the groups was performed by one-way ANOVA (analysis of variance) and significance of mean differences between the groups was tested by Tukey-Kramer multiple comparison test (level of significance set at P < 0.05, P < 0.01, P < 0.001). Results and Discussion Composition, nutrient and metabolizable energy content of diets for the control and tested groups used in experimental periods are shown in Table 1. Diets used in the control and tested groups in respective periods were isoenergetic and isonitrogenous. There were no significant differences in the initial body weights of chicks between 386