Identification and control effects of mycotoxins in nellore bulls finished in feedlot

• Ano de defesa: 2018
• Autor(a) principal: Custódio, Letícia
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Universidade Estadual Paulista (Unesp)
• Palavras-chave em Português: Adsorbent; Carcass gain; Meat quality; Performance; Survey
• Link de acesso: http://hdl.handle.net/11449/166363

The study was divided into two phases. The first phase was designed to identify which mycotoxin was present in Brazillian feedlot diets, and the second phase was designed to evaluate the performance of Nellore bulls finished in feedlot fed mycotoxins, and the effects of mycotoxin adsorbent (ADS). Thus, the objective of the first phase was to identify which mycotoxins were present in ingredients used in diets fed to feedlot cattle and its concentrations. The survey covered 30 Brazillian feedlots located in the 5 largest beef-producing states. Samples of total mixed ration (TMR) and ingredients were collected on-site and sent to the 37+® Analytical Services Laboratory (KY, USA) for analysis of mycotoxins. The quantification of 38 different mycotoxins was performed using ultra-performance liquid chromatography coupled to tandem mass spectrometry. The mycotoxin concentrations were further interpreted according to known species- specific sensitivities and normalized according to the principles of toxic equivalent factors, determining the Risk Equivalent Quantities (REQ) expressed in µg/kg of aflatoxin B1-equivalent. Descriptive statistics were obtained using the UNIVARIATE procedure of SAS and multivariate statistics were obtained using STATISTICA. The toxins identified in TMR were: fumonisins, trichothecenes A, trichothecenes B, fusaric acid, aflatoxins and ergot (means of 2,330, 104.3, 79.5, 105, 10.5, and 5.5 µg/kg, respectively). Fumonisins were the primary mycotoxins found and at highest concentrations in TMR samples. Peanut meal was the most contaminated ingredient. The objective of the second phase was to evaluate the effect of mycotoxins and ADS on performance and meat quality of Nellore cattle finished in feedlot. One-hundred 24-mo-old Nellore bulls (430 ± 13 kg of body weight (BW)) were used in a randomized block design with a 2 × 2 factorial arrangement of treatments. The factors consisted of two diets (Factor 1) with natural contamination (NC) or exogenous contamination (EC) and presence (10g/d/animal; ADS) or absence of ADS (Factor 2). The NC and EC diets had, respectively, the following contaminations: aflatoxin 0 and 10 µg/kg, fumonisin 5114 and 5754 µg/kg, trichothecenes A 0 and 22.1 µg/kg, trichotecenes B 0 and 42.1 µg/kg and fusaric acid 42.9 and 42.9 µg/kg. At the beginning of the experiment, all animals were weighed, and 4 were randomly selected to be slaughtered to evaluate initial carcass weight. After 97 days of experiment, all animals were weighed and slaughtered. Steaks from Longissumus thoracics harvested between 11th to 13th ribs, in which three steaks were randomly assigned to aging times of 7, 14 and 28 days at 4°C. The meat quality was analyzed. There was no interaction among factors for DMI (P = 0.92), however there was a tendency for EC- diets decrease DMI by 650 g/d (P = 0.09). The ADG was greater for NC- when compared to EC- fed cattle (P = 0.04) and there was a tendency for interaction among factors (P = 0.08) being 1.77, 1.65, 1.51 and 1.63 kg for NC-, NC+ADS, EC- and EC+ADS, respectively. There was a tendency for interaction among factors for carcass gain (P = 0.08). Daily carcass gain was 1.20, 1.14, 1.05 and 1.12 kg/d, respectively, for cattle receiving NC-, NC+ADS, EC- and EC+ADS. Then, the NC had greater carcass gain compared to EC- and the addition of ADS recovered part of the gain when used in EC diets. The chemical composition, color, cooking loss and shear force of meat were not affected (P ≥ 0.38) by the factors. In conclusion, mycotoxin affects the performance of beef cattle, and the ADS may alleviate part of this damage when animals were fed diets containing higher contamination. However, these factors did not negatively affect meat quality.