Galinhas poedeiras alimentadas com simbiótico versus bacitracina de zinco : hemato-bioquímica, avaliação de órgãos, morfologia intestinal e isolamento de Clostridium perfringens

Abstract

The aim of this study was to evaluate the effect of replacing zinc bacitracin with a symbiotic on starting in the rearing, growing and production phases on hematological and biochemical parameters, organ development and Clostridium perfringens antibiogram and count in the cecum of layers hens in the late phase. An experiment was conducted with laying hens, 70 to 90 weeks of age, in an entirely randomized design, composed of six treatments, with six repetitions, three repetitions containing 5 birds, and three repetitions containing 6 birds, totaling 198 birds. The treatments consisted of four experimental diets, two base diets, the first composed of corn and soybean meal (RMS) and the second composed of corn, soybean meal and meat and bone meal - without additives (FCO), and two other diets with inclusion of additives to the FCO diet, with 0.05% zinc bacitracin (BAC) and 0.1% of symbiotic additive, The latter was fed to three groups of birds, one with birds that had already been receiving the symbiotic since the rearing phase, i.e., since one day of age (SIMC), another that had already been consuming it since rearing, i.e., starting at 6 weeks of age (SIMR), and another that initiated the consumption of the symbiotic at 17 weeks of age, the beginning of production (SIMP). At 89 and 90 weeks of age, blood samples were collected to perform hematology and serum biochemistry analyses. At the end of the 90th week the birds were euthanized one bird per replicate to measure weight, organ length, and pH of the luminal contents and count and resistance of C. perfringens in the cecal contents. Segments of the small intestine were used to evaluate histomorphometry (duodenum, jejunum and ileum). Variables were analyzed by PROC GLM of the SAS OnDemand program and means were compared by the Orthogonal Contrast test (P≤0.05). The contrasts consisted of C1: RMS vs FCO; C2: FCO vs BAC; C3: BAC vs SIMC; C4: BAC vs SIMR; C5: BAC vs SIMP. For C1 there was significant difference for uric acid (URI) and C.perfringens count, where FCO treatment showed lower URI concentration and higher C.perfringens count. In C2 there was difference for the variables thrombocytes (TROMB), total proteins (PT), aspartate aminotrasnferase (AST), lactate dehydrogenase (LDH), phosphorus (FOS), cholesterol (COL) and caecum length (CEC), where BAC showed higher concentrations of liver enzymes, FOS and COL and lower number of TROMB and smaller size of CEC. In C3 there was a difference for eosinophils (EOS), SIMC treatment obtained a higher mean, liver enzymes activity and FOS had lower concentration in SIMC and higher concentration of high density proteins (HDL) and a lower C.perfringens count in the same treatment. In C4 it obtained significant differences similar to C3, except for the inclusion of difference in lymphocytes (LIN), LDH, liver relative weight and pap pH, where SIMR had higher mean LIN, lower LDH concentration, lower liver proportion and more acidic pap pH compared to BAC. Contrast 5 showed the same behavior for liver enzymes, phosphorus and HDL in C3, the same for pap pH and proportion of FIG in C4 and higher caecal content pH of SIMP treatment compared to BAC. The symbiotic improved the histomorphometry (villus area and height) of the jejunum, duodenum and ileum compared to the other treatments. And it increased the susceptibility of antibiotics to C.perfringens isolates. It is concluded that the symbiotic stands out as a good substitute for zinc bacitracin, as it provides better hemato-biochemical status, organ health, improves histomorphometric conditions of the small intestine and reduces Clostridium perfringens colonization and its resistance to various antibiotics. Considering all the data obtained, the rearing phase would be the best time to introduce the symbiotic to maintain healthy layers up to 90 weeks of age.