Effect of dietary electrolyte balance on rearing performance of broiler chickens under farm conditions

the aim of the study was to determine the efficiency of adding sodium and chlorine to commercial cereal-soybean starter and grower diets with increased potassium content in broiler chickens raised under farm conditions. a total of 4800 day-old hubbard flex broilers were divided into 4 groups with 6 replicates of 200 chickens each and kept in boxes on straw litter. basal starter and grower diets contained in 1 kg (as analysed): 8.37 and 8.27 g potassium; 1.79 and 1.66 g sodium; and 3.17 and 2.76 g chlorine, respectively. the dietary electrolyte balance (dEb) values were 203 and 206 mEq/kg, respectively. basal experimental diets were supplemented with 0.3 g na and/or 0.5 g cl/kg of diet in the form of sodium carbonate, sodium chloride or ammonium chloride. the dietary supplements had no effect on production parameters during the starter period. in the grower period, the sodium (nahco3) supplement increased dEb value to 219 mEq/kg, significantly (p<0.05) increasing chickens’ body weight gain and feed intake. sodium added together with chloride as nacl tended to improve production parameters (non-significantly) without any effect on dEb values. throughout rearing, the positive effect of sodium supplementation was only observed for increased feed intake (p<0.05). supplementation of chlorine (nh4cl) to the starter and grower diets reduced dEb values to 188 and 192 mEq/kg, respectively, without a positive effect on rearing performance, and decreased feed intake (p<0.05). the analysed sodium and chlorine supplements had no effect on dressing percentage, abdominal fat content of the carcass and litter moisture. key words: broiler chickens, electrolyte balance, sodium, chlorine, performance. Relatively high potassium levels in plant-based diets may increase the sum of both cations (K+ and Na+) while creating a special need for chlorine supplementation to reach the optimum dietary electrolyte balance (DEB) (Mongin, 1981). Dietary potassium may increase chickens’ water intake and litter moisture (Vieira and Lima, 2005). In our previous experiment with caged chickens kept on wire floor the starter Support by the Ministry of Science and Higher Education, Project No. N 311 0347 34 (2261.5). J. Koreleski et al. 406 diets with high potassium levels (10.7, 12.2 and 12.7 g/kg) and a higher content of sodium (2.0 g) and chloride (3.1 g/kg) increased performance indices (Koreleski et al., 2011 a). The performance also improved at high potassium and chloride (1.73 g) levels when dietary sodium was elevated from very low to 1.61 g/kg (Koreleski et al., 2010). During the starter period, body weight gains and feed conversion ratio were positively affected by the dietary chloride content increased from 2.11 to 2.95 g or 3.16 g Cl per kg (Koreleski et al., 2011 b). At high dietary potassium level excreta moisture was increased (Koreleski et al., 2011 a). As a result of potassium level elevated from 7.8 g to 11.9 g/kg, the dry matter content of excreta decreased and the proportion of breast meat in the carcass increased (Koreleski et al., 2011 b). In this study performance, litter moisture and carcass indices were investigated in farmed broiler chickens kept on straw floor and fed commercial diets supplemented or not with sodium and chloride added together or separately. material and methods A total of 4800 day-old Hubbard Flex broilers of both sexes were divided into four nutritional groups with 6 replicates of 200 chickens each and kept on straw floor at a stocking density of 14 birds/m2. Chickens were provided with tap drinking water and feed ad libitum. The basal feed mixtures (cereal-soybean starter and grower diets) were bought from the market and their composition was guaranteed. The experimental diets were the basal feeds supplemented with sodium (0.3 g/kg) and chlorine (0.5 g/kg) added together as sodium chloride (NaCl) or separately as sodium bicarbonate (NaHCO3) or ammonium chloride (NH4Cl). The body weight (BW) and feed intake (FI) of the chickens were measured and mortality was recorded. The body weight gain (BWG) and feed conversion ratio (FCR) were calculated for the first (1–14 days) and second period of feeding (15–42 days) and for the entire feeding experiment (1–42 days of age). The production index (PI) was calculated for the entire period from the equation: PI = [BW (kg) × × liveability (%) / age (42 days) × FCR] × 100. At 21 and 35 days of age each box was awarded a subjective litter score in points, where 1 means dry litter, 2 normal litter, 3 wet litter and 4 very damp litter. Moisture, as average percent of measurements made at 5 locations of each floor was determined using a moisture meter for hay and straw (Draminski, Olsztyn). At the end of the experiment, after 12 hours of starvation, 5 representative cockerels and 5 pullets with body weight close to the respective treatment mean were chosen from each group and decapitated. The live weight and weight of the cooled carcasses with edible giblets were estimated and carcass yield and relative weights of abdominal fat were calculated (Ziołecki and Doruchowski, 1989). The Local Kraków Ethics Committee for Experiments with Animals approved all experimental procedures relating to the use of live animals. The potassium and sodium content of the diets was analysed by atomic absorption spectrometry (ISO 6869.2000). The chloride content was calculated from waDietary electrolyte balance and broiler performance 407 ter soluble chloride (as NaCl), and analysed by the silver nitrate titration method (Volhard, 1874). Basal feed nutrient content was analysed using standard methods (AOAC, 1990) for dry matter (method 930.15), crude protein (984.13, by means of the Kjeldahl method, using Kjeltec Auto 1030, Tecator), crude fat (920.39) and ash (942.05). Crude fibre was estimated with Tecator Fibertec System M. The data were subjected to a one-way factorial analysis of variance. The significance of differences between means was determined by Duncan’s multiple range test and differences were considered significant at P≤0.05. Statistical analyses were performed using Statistica 5.0 PL software (Statsoft Inc.).