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The purpose of the study was to observe the effect of feeding extruded feed that contained rapeseed (that was extruded using the standard methods for large-scale production of extruded feed) on retention and coefficient of total tract apparent digestibility (CTTAD) in hens. The laying hens were divided into two groups NEX and EXT. The composition of the diets was the same in both groups (wheat 39%, rapeseed 13.5%, pea 13.5%, soya bean meal 6%, maize 14%, fish meal 3%, limestone 1%, premix 10%). But 0.45 kg of 1 kg of the diets EXT (wheat, pea, and rapeseed) was extruded by dry extrusion at temperature 137 °C and at moisture from 12 to 18% for 16 s. A balance assay was conducted with four laying hens from group NEX and eight from group EXT when they were 61 weeks old. The CTTAD of fat, calcium and amino-acids, and the retention of the nitrogen were estimated using the indicator method. The significance between the means was evaluated by a t-test. The average egg mass production during the assay was for group NEX 45 ± 3.9 g/hen/day and for group EXT 50 ± 5.0 g/hen/day. The extrusion process significantly increased (P < 0.001) the CTTAD of fat from 0.807 (NEX) to 0.937 (EXT). The coefficient of nitrogen retention was higher in group EXT (0.629) than in group NEX (0.584). The extrusion significantly increased the CTTAD of arginine (P < 0.05, NEX: 0.929, EXT: 0.944) and isoleucine (P < 0.05, NEX: 0.870, EXT: 0.904). The extrusion had a tendency to increase the CTTAD of leucine (P < 0.1, NEX: 0.885, EXT: 0.907), glutamic acid (P < 0.1, NEX: 0.931, EXT: 0.945), glycine (P < 0.06, NEX: 0.823, EXT: 0.859) and alanine (P < 0.1, NEX: 0.806, EXT: 0.844). CTTAD of lysine was almost the same in both groups (NEX: 0.950 and EXT: 0.949). The extrusion process had a tendency to decrease the CTTAD of histidine (P < 0.06, NEX: 0.906, EXT: 0.859) and tyrosine (P < 0.07, NEX: 0.974, EXT: 0.921). The extrusion had a positive effect on the fat CTTAD, nitrogen retention and on the CTTAD of the essential amino-acids (except lysine and histidine). The decrease in the digestibility of these two amino-acids was not significant.

Whole tract and post ruminal digestibility of crude protein (CP) and dry matter (DM) in ryegrass, alfalfa hay (high and medium quality) and maize silage were determined by means of a rumen in situ nylon bag, a mobile nylon bag and a nylon capsule method as well as by calculations that combined the methods. Calculation of whole tract digestibility was from results of rumen in situ nylon bag and mobile nylon bag methods and calculation of post ruminal digestibility was from results of the nylon capsule and rumen in situ nylon bag methods. Three dry cows (Red Holstein × Black Friesian) fitted with ruminal and duodenal cannulas were used for testing the nylon bag and mobile bag methods, whereas the nylon capsule method utilised three dairy cows (Red Holstein × Black Friesian). Differences between determined and calculated values for whole tract digestibility of CP and DM ranged from −3.3 to +2.9%, and from −0.1 to −8.5%, respectively. Differences between determined and calculated values of intestinal digestibility of undegraded CP were higher and ranged from −10.6 to +13.8%, and from +0.4 to +17.5% for CP and DM, respectively.