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Pigs fitted with ileal T-cannula in the terminal ileum were used to study the effect of synthetic amino acids (AA) added to a nitrogen-free diet on endogenous losses. We compared the obtained data with data from other research centres in the world that are focusing on these problems. In the present experiment, we used three synthetic diets - a nitrogen-free (NF) diet, a diet with added essential AA (E), a diet with the same amounts of essential AA and a mixture of non-essential AA (E+N) added. The diets, apart from the amount of AA, had the same composition. Chromium oxide was used as an indigestible marker. The supplementation of the NF diet with sulphur AA, threonine and tryptophan resulted in a reduction of the endogenous flow of all AA except for cysteine. However, the difference between the NF and E diet was significant only in the case of proline. The effect of the non-essential AA addition to diet E was negligible, even though the endogenous flow of most AA tended to decrease. In comparison with NF diet, the endogenous flow of total N in diets E and E+N was reduced by about 30%. This reduction was mainly due to the decreased endogenous flow of proline, which accounted for 59% in diet E and 55% in diet E+N. Proline was the most abundant AA in all diets, followed by glycine and glutamic acid. The sum of proline and glycine in diets NF, E and E+N amounted to 59, 44, and 46% of total AA flow, respectively. In contrast, the proportion of the sum of essential AA of total AA flow in diets NF, E and E+N was 21, 28 and 27%, respectively. Our data on the endogenous AA and N flow are in the range of previously published values.

A digestibility experiment using six ileally cannulated growing gilts (initial BW 31.6 kg) was carried out to study the effect of microbial phytase and diet form on apparent ileal and total tract digestibilities of dry matter (DM), nitrogen (N), phosphorus (P), calcium (Ca) and energy and on apparent ileal digestibility of amino acids. The basal P-deficient diet was fed either dry or mixed with water (feed:water ratio 1:2.5) and fermented in a laboratory setup. The enzyme was added to the dry diet at four levels (0, 1 000, 1 500 and 3 000 U/kg) and to the liquid fermented diet at two levels (0 and 1 000 U/kg) using a 6 × 6 Latin square design. The supplementation of microbial phytase to the basal diets significantly (P < 0.05) improved ileal and total tract digestibility of P and tended to improve the digestibility of Ca. Phytase supplementation at 3 000 U/kg to the dry diet improved ileal and total tract P digestibility by approximately 30 and 60%, respectively. A similar effect was found in the liquid fermented diet supplemented with phytase at 1 000 U/kg. As a result of improved P digestibility, faecal P excretion was reduced by 20-40%. There was no significant effect of phytase addition or diet fermentation on the digestibility of DM, N, energy or amino acids. The response in amino acid digestibility to phytase calculated with acid insoluble ash as a marker was slightly higher than that calculated with Cr2O3.

Six female pigs of approximately 50 kg BW, fitted with simple T-cannula in the terminal ileum, were used to study the effect of microbial phytase on apparent total tract digestibility and retention of P and N. Three P-adequate diets (digestible P concentration 2.3 g/kg) containing barley (B), soybean meal (S) or their mixture (BS) with or without phytase supplement (1 000 FTU/kg) were fed to pigs using a 6 × 6 Latin square design. The addition of phytase increased (P < 0.05) apparent total P digestibility of diets S and BS from 56.5 and 57.2% to 69.0 and 65.2%, respectively, and apparent plant P digestibility of the same diets from 41.3 and 50.0% to 60.5 and 60.0%, respectively. An insignificant improvement in total and plant P digestibilities was found in diet B. Phytase supplementation reduced (P < 0.05) P excretion in pigs fed diets S and BS by 25 and 14%, respectively. As compared with diets S and BS, urinary P excretion in pigs fed diet B was much higher, which suggests a lower requirement for available P due to the lower protein deposition and growth rate. Phytase supplementation had no effect on digestibility or retention of N. In all three diets, total tract P digestibility was lower (P < 0.05) than ileal digestibility thus indicating a net flux of P into the large intestine.