20 th European Symposium on Poultry Nutrition | 24–27 August 2015 | Prague, Czech Republic P-188 (ID 119) THE IMPACT OF SODIUM AND CHLORIDE LEVELS AND RATIOS ON THE PERFORMANCE OF BROILERS FED DIETS CONTAINING LASALOCID AT TWO DIETARY LEVELS V. Stanev 1 , M. LaVorgna 2 , T. Barbosa 3 , M. Quiroz 3 , J. Dickson 3 , D. Vancraeynest 1 1 Zoetis International Services, Paris, France 2 Devenish Nutrition, Fairmont, MN, USA 3 Zoetis Global Poultry, Durham, NC, USA Abstract The objective of the study was to evaluate the performance parameters of broilers fed with two different levels of a diva- lent ionophore (lasalocid) in combination with 12 different sodium:chloride (Na:Cl) ratios at moderate to low field coc- cidiosis infection pressure. A total of 4224 Cobb 500 male broilers were divided among 192 pens across 24 treatments. Results indicated that there was an interaction between electrolytes (Na & Cl), thus the ratios of these key nutrients can be as important as the actual levels. Best performance was achieved when the Cl level in the diet was 20% higher than the Na level. Water consumption was not statistically affected by the lasalocid dose, but it was in respect to dietary Na treatments. Also, broilers receiving a moderate (90 ppm) level of lasalocid during the latter stages of the growing cycle had higher body weights and lower feed conversions than those receiving a high (125 ppm) level. However, since there is a clear dose – anticoccidial efficacy response in ionophores, it could be that the situation would look differently under high coccidiosis infection pressure: there, the merits of a higher inclusion rate in preventing coccidiosis might become more important than a possible drawback. For this reason infection pressure should be taken into account in determin- ing the actual anticoccidial dose in feed, when dose range is available. Introduction In feed anticoccidials are largely used as a prevention tool in control of coccidiosis in poultry under modern production practices. In its commission report 233/2008, the European Commission recognizes their use as “essential”. Ionophores are the most commonly used anticoccidial drugs in the modern poultry production. They are lipid-soluble molecules that bind to and transport ions - mainly mono- and divalent cations, across the bipolar lipid layer of biological membranes, which is normally non permeable for such ions. This leads to disruption of transmembrane ion concentration gradients of microorganisms which suppresses their proliferation. Due to this ion binding and transporting mode of action of iono- phores, it has been speculated that different levels of electrolytes may affect performance of broilers fed with ionopho- res (Frigg & Broz, 1983; Cervantes and all., 1982; Christmas & Harms, 1988). It is known that levels of sodium (Na) and chloride (Cl) vary among commercial broiler diets, giving great variability to dietary electrolyte balance (DEB) levels. The study design evaluated the performance parameters of broilers fed with two different levels of a divalent ionophore (lasalocid) in combination with 12 different sodium:chloride (Na:Cl) ratios, under moderate to low field coccidiosis infec- tion pressure. Materials and Methods Animals. 4224 Cobb 500 males were divided into 192 pens at 1d of age. Birds were housed in an environmentally con- trolled building in 0.9m x 1.5m concrete floor pens at the stocking density of 16 birds per m 2 . Birds were vaccinated for Marek’s disease in ovo and for Newcastle and infectious bronchitis by spray application at day of hatch. Experimental design. Table 1 describes the group distribution for the study. The study had 24 different groups divided into two different levels of a divalent ionophore (lasalocid) in combination with 12 different Na:Cl ratios. No phytase has been used in order not to deviate the available levels from the analytical ones. For each Na level, there were three relative percentage levels of Cl (approximately 80%, 100% and 120% of the Na levels, respectively). Each treatment had eight replicates distributed in a randomized complete block design, with the pen as the experimental unit. Birds were kept for 42 d with feed ad libitum. Feed schedule consisted of 3 different diets: Starter (0-18 d), Grower (19-28 d) and Finisher (29-42 d).