Digestibility of dietary proteins and fats from diets with different proportions of beef for minks

An experiment was conducted in the Research Institute of Animal Production at Nitra. Five standard male minks were included in experiments at four mon ths of age. The animals were clinically healthy and were examined for plasm ocytosis. The objective of the experiment was to determine digestibility of dietary proteins and fats from diets for minks with different percentage p roportions of beef and digestibility of these nutrients in the feed itself. The experiment consisted of four separate stages. The animals received con trol diets with the lowest proportion of beef - 31.4% in stage I. Beef cont ents were increased to 40.3% in stage II, to 44.3% in stage III and to 55.2 % of the initial content in stage IV. Every experimental stage had two peri ods - a preparatory one and an experimental one. The stages followed each o ther uninterruptedly during the experiment. The preparatory period lasted f or seven days, when the animals accustomed to a new diet, the experiment la sted for five days. The animals were fed twice a day - at 9.00 and 15.00 ho urs. Parameters necessary to calculate digestibility coefficients for diets were recorded during the experiment, that means feed intake, residues of u nconsumed feed and excrements. Samples to determine the parameters were tak en twice a day, an hour before feeding (i.e. at 8.00 and 14.00 hours) in al l cases, and they were weighed to the nearest of 0.1 g. Basic organic analy sis was carried out in feed and excrement samples in accordance with the st andard STN 46 7092. Protein and fat digestibility of control diet was deter mined by a direct method and that of beef by an indirect method (Schurch, 1 969). Protein digestibility coefficient in the experimental diets for minks with increasing percentage of dietary beef increases from 76.94 to 81.09% and fat digestibility coefficient decreases from 94.22 to 89.88%. Significa nt differences in protein and fat digestibility were established between co ntrol diet and experimental diets with higher beef percentage as well as be tween the separate experimental diets. Digestibility coefficients of proteins and fat for beef were 85.87% and 88. 13%, respectively.