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The present study aimed to evaluate acid-insoluble ash (AIA) as an internal marker for the measurement the coefficient of total tract apparent digestibility (CTTAD) in rabbits through two experiments (E1 and E2). In E1, 48 rabbits were used to calculate the CTTAD of the same basal diet according to the European reference method (ERM), the AIA and the titanium dioxide (TiO2 with 1 g of TiO2/kg diet) techniques (n=16 rabbits/method). The effect of feed sample quantity on dietary AIA content was investigated and total collection of faeces was carried out to calculate marker recovery. In E2, 48 rabbits were allotted to three groups fed diets with no sugar beet pulp (SBP0) or with 100 (SBP100) and 200 (SBP200) g sugar beet pulp/kg (n=16 rabbits/group). Each group was divided into two subgroups, ERM and AIA (n=8 rabbits/subgroup), in which CTTAD was measured using the European reference and AIA method, respectively. In AIA subgroups, only 10% of the total daily faecal output was sampled from 9:00 to 9:30 am. Feed analysis in E1 showed that increasing sample quantity from 5 to 9 g did not affect the dietary AIA content; however, the analytical error was 7 and 5 times lower (P<0.05) for 9 g, when compared to 5 and 7 g samples. Feed analysis also showed 1.030±0.003 g TiO2/kg diet. Faecal marker recovery was 99.80±0.03 and 96.89±0.16% for AIA and TiO2, respectively. The CTTAD of dry matter (DM), did not differ between methods in E1, but a 5-fold higher variability (P<0.05) was observed for the TiO2 technique in comparison with the ERM and AIA methods. Also, no differences in the CTTAD of DM between the ERM and AIA methods were found in E2. In conclusion, AIA is a reliable internal marker in rabbits and offers the possibility of measuring the CTTAD of diets with precision, when complete faecal collection or feed intake measurement is not possible. [ABSTRACT FROM AUTHOR]

The suitability of blood and hair as non-invasive tools to monitor trace element contents was studied in 48 Hyla male growing rabbits. Three diets with increasing organic selenium (Se) addition (0.1, 0.5 and 2.5 mg/kg) were used to induce alterations in the concentrations of trace elements vs. an unsupplemented diet. In blood, a linear decrease in Co (P<0.001), Cu (P<0.001), Mn (P<0.05), Zn (P<0.05), Sb (P<0.001), As (P<0.001), Cr (P<0.001), Mo (P<0.001), Ni (P<0.001) and Cd (P<0.001) concentrations with increasing dietary Se was observed. In hair, a cubic effect of dietary Se on Co (P<0.01), Cu (P<0.05), Mn (P<0.001), Pb (P<0.05), Mo (P<0.05) and Cd (P<0.05) concentrations was found, while As, Cr and Ni concentrations decreased linearly (P<0.01, P<0.01 and P<0.001, respectively) with increasing dietary Se. Selenium was negatively correlated to Sb, As, Cr, Mo, Ni and Cd, (P<0.001) in blood, and to As (P<0.05), Cr, Ni (P<0.01) and Pb (P<0.05) in hair. The contents of Se, As, Cr and Ni in blood were highly correlated (P<0.001) to those in hair. Blood appeared to be more sensitive than hair in detecting small changes in the trace element profile in rabbits, as was indicated by the discriminant analysis. In conclusion, blood and hair can be suitable biological indicators of essential, toxic and potentially toxic trace element status in rabbits, particularly when used complementarily. [ABSTRACT FROM AUTHOR]