Aluminossilicatos em dietas de bovinos de corte e indicadores na estimativa de consumo total, diferenciado e digestibilidade da matéria seca | ALUMINOSILICATES IN BEEF CATTLE DIETS AND MARKERS FOR ESTIMATING TOTAL AND DIFFERENTIATED INTAKE AND DRY MATTER DIGESTIBILITY

The first study aimed to investigate the effect of different contents of a product elaborated from the aluminosilicate glauconite, of trade name Beefplus, on nutrient intake and digestibility, the metabolism of nitrogen compounds, pH, ammonia nitrogen (N-NH3), purine derivatives, efficiency, and production of microbial protein in the diets of beef cattle. Five Nelore bulls, fistulated in the rumen, were distributed in a 5 × 5 Latin Square, composed of five treatments (inclusions of 0.0, 0.5, 1.0, 1.5, and 2.0% aluminosilicates, based on the diet DM) and five experimental periods of 15 days, totaling 75 days of experimentation. The base diet consisted of 40% corn silage and 60% concentrate based on cornmeal and soybean meal. Adaptation to the diet occurred from day 1 to 10 of each period. Total feces was collected in the five subsequent (from 11 to 15) and, on the last day (15), samples of ruminal fluid were collected for pH and ammonia nitrogen analysis and urine was "spot" collected to determine the concentrations of allantoin, uric acid, and creatinine. The forage and concentrates, as well as the leftovers, were sampled during the collection period for further analysis. There was no effect of aluminosilicate content (P>0.05) on nutrient intake and digestibility. There was no effect (p>0.05) of the addition of aluminosilicates on the metabolism of nitrogen compounds. Interaction was observed (p<0.05) between the content of aluminosilicate and pH. The pH of the 2.0% aluminosilicate inclusion treatment was significantly higher than the control treatment at 4 and 6 hours after feeding and in the general average. There was interaction (p<0.05) between the content of aluminosilicate and the concentration of N-NH₃. However, there was no difference between the control treatment and the treatments with aluminosilicate inclusions. There was no statistical difference in the efficiency of microbial protein synthesis (P>0.05), possibly due to the high coefficient of variation. In conclusion, the addition of aluminosilicates in the diet improves the pH but does not change nutrient intake and digestibility or the ruminal concentration of ammonia nitrogen. The second study aimed to evaluate fecal output (FO ) and recovery (FR), dry matter intake (DMI), and dry matter apparent digestibility (DMAD) estimated by the markers titanium dioxide (TiO₂) and NANOLIPE® in diets containing different levels of aluminosilicates (0, 0.5, 1.0, 1.5, and 2.0% inclusion in the diet DM). Five Nelore bovines were used in a 5 × 5 Latin Square experimental design in a split-plot scheme. The plots were the aluminosilicate contents and the split-plots were the markers. The experiment consisted of five periods of 15 days, totaling 75 days. There was no statistical difference (P>0.05) between the real FO and the FO estimated by markers. There was an interaction between diet and markers in FR. The markers differed among themselves (p>0.05) in the FR of the diet with no addition of aluminosilicates, but were similar to total collection. The other diets presented no significant difference between the estimates of FR between markers and between the real FR. The DMI and DMAD estimated by markers were similar (p>0.05) to the values obtained by the total collection of feces in all treatments. In conclusion, the markers estimated the parameters evaluated satisfactorily and can be used in intake and digestibility assays with beef cattle. The third study consisted of three experiments. The first experiment aimed to evaluate the involuntary intake (provided directly in the rumen) of mineral supplement using the double marker method in diets containing different levels of aluminosilicates (0, 0.5, 1.0, 1.5, and 2.0% in the diet DM). The second and third experiments aimed to evaluate the voluntary intake of mineral supplement (the animal consumed the supplement from the trough ad libtum) using the double marker method. The first experiment employed five Nelore bovines in a 5 × 5 Latin Square in a split-plot scheme. The plots were the inclusions of aluminosilicates and the subplots were the markers. The second experiment employed eight Nelore bovines. The first and second experiments were conducted in Brazil, at the UFV-Florestal campus. The third experiment, conducted at the Experimental Station of the University of Florida in the United States, employed eight Aberdeen Angus heifers. The statistical design used in the second and third experiments was entirely randomized. The real mineral mixture intake was similar to that estimated by the markers in experiments 1 and 2. However, the technique overestimated the intake of the mineral mixture in experiment 3 by 145%. In conclusion, the markers estimated the intake of the mineral supplement successfully.

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