Automatically-guided farm tractors are conventional tractors equipped with geo-positioning systems, sensors and actuators that allow programing their trajectory. Automatic steering systems eliminate the need of having a driver as they are able to make accurate trajectories and also allow carrying out farm work during the night or when there is low visibility. In order to evaluate lateral error, the ideal trajectory of a tractor, regarding it as a point mass, was plotted. For this purpose, a Trimble® EZ-Guide 250 automatic guidance system was installed on a Massey Ferguson 592T tractor. Using vector equations, the ideal trajectory was obtained; it was also observed that in straight line travel, when the speed was increased from 5 to 9 km∙h-1, the mean trajectory error increased from 2.0 to 7.0 cm. In the case of center pivot travel, with the same increase in speed, the mean error increased from 6.1 to 7.8 cm, with significant differences among treatments (P ≤ 0.05).

A growing trend in the meat industry is to produce more with less, which can lead to higher yields without losing the chemical properties of the meat, which determine the price. The aim of this study was to determine the effect of tannin-supplemented diets on the compositional quality of beef. Sixteen male calves were subjected to a productive response test in a feedlot over a 40-day period, with a 30-day adaptation phase prior to the finishing stage of the experiment. Treatments consisted of: a typical cattle finishing diet (control) and a similar diet with 0.3 % extract of condensed and soluble tannins added, providing 1 g of tannin extract per 10 kg of bodyweight. After slaughter, meat samples were taken by cutting transversely between the 12th and 13th rib; the cuts consisted of four 2.5-cm thick chops from each carcass. Samples were analyzed for protein, ash, moisture, fat and dry matter contents using AOAC methods. Results showed that the average content levels were 20.18 % for protein, 5.47 % for fat, 74.35 % for moisture, 2.01 % for ash and 25.65 % for dry matter, for both groups. No significant differences (P ≤ 0.01) compared to the control group were observed; only the fat content was higher than previously reported. Therefore, the tannin concentration used in the cattle diets does not affect the chemical composition of the meat.

Two mixing devices used for stirred yogurt production were evaluated. One system had two coaxial impellers, an anchor and a modified anchor; the other had a double helical ribbon agitator. The performance of the mixing systems was evaluated using cooling time, syneresis, and sensory analysis. Cooling time results for both mixing systems showed that the double helical ribbon system needed shorter cooling times than the coaxial anchor-modified anchor one. There were no statistical differences in syneresis of the yogurts made in the different mixing vessels. Sensory analysis was evaluated considering difference-from-control test, quantitative descriptive analysis, and preference test. These experiments showed that the best quality was obtained using a double helical ribbon device at 45 rpm. In light of the findings, it is possible to suggest stirred yogurt production in small tanks with a double helical ribbon mixing system at 45 rpm.