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Using 12 gilts (initial body weight: 38.4±1.1 kg), we investigated an effect of early dietary amino acid (AA) restrictions on daily changes in urinary N excretion and growth performance during the following re-alimentation period. After the 10-d preliminary period of using a high-protein diet, we estimated protein deposition rate (PD) of pigs, two 14-d experimental periods followed. Pigs were allotted to 2 groups so as the mean PD of both groups was similar. During the first 14-d restriction period, the control group was fed an AA adequate diet, while the restricted group was fed an AA deficient diet. During the following 14-d re-alimentation period, both groups were fed AA adequate diet. Starting on d 12 of the restricted period, samples of urine were collected from both groups using permanent bladder catheters to monitor daily N excretion. Pigs were weighed weekly, the remaining feed were collected daily, and average daily feed intake (ADFI), average daily gain (ADG), gain:feed (G:F) were calculated for each period separately and overall for the restriction and re-alimentation periods. For the same periods, urinary N excretion rate was determined. During the re-alimentation period, pigs that were previously fed the AA deficient diet tended ( P =0.060) to have greater ADFI (2297 vs. 2171 g/d), and greater ( P P

Standardized ileal digestibilities of amino acids and nitrogen in rye, barley, soybean meal, malt sprouts, sorghum, wheat germ and broken rice fed to growing pigs were determined. Seven cannulated gilts (initial BW 34.8 ± 0.7 kg) fitted with T-cannula in terminal ileum were housed in metabolism cages in an air-conditioned room. The tested feeds were used in the diets as sole sources of N. The diets were fed to pigs according to a 7 × 7 Latin square design. A nitrogen-free diet was used to estimate basal endogenous losses of amino acids and N. The highest standardized ileal digestibility of amino acids was observed in broken rice (0.96) and wheat germ (0.84) while the lowest value was found in malt sprouts (0.61). Digestibility values estimated in soybean meal, barley, sorghum and rye were 0.91, 0.83, 0.82 and 0.77, respectively. The first-limiting ileal digestible amino acids were lysine (rye, barley, sorghum, rice) or sulphur-containing amino acids (soybean meal, malt sprouts, wheat germ). Taking into consideration crude protein and digestible amino acid contents, the best sources of available protein were soybean meal and wheat germ.

Nitrogen (N) balance experiment was carried out to study the individual and group response of growing pigs to lysine (Lys) intake. A series of 15 purified diets limiting in Lys were fed sequentially to nine pigs (initial body weight, 39 kg) during a 15-day experiment. Lysine concentration ranged from 50% to 140% of its assumed requirement. N retention in individual pigs was related to Lys intake using linear-plateau (LP) and quadratic-plateau (QP) models. No difference in the closeness of fit between the models was found (p = 0.72). There were significant differences between the slopes of individual regression lines in the LP model (p = 0.018) and between the individual plateau values in both models (p < 0.0001). The breakpoint values in the QP model were greater than those of the LP model (p = 0.027), while the plateau values estimated by both models were similar (p = 0.32). In the LP model, no relationship was found between the slopes and plateau values (p = 0.67, r = 0.17) or between the slopes and breakpoint values (p = 0.55, r = -0.23), thus suggesting that pigs with higher protein deposition rate do not utilize lysine more efficiently. However, there was a close positive correlation between breakpoint and plateau values (p = 0.0005, r = 0.92). Based on LP and QP models, the mean daily requirement of Lys for a 47-kg gilt was estimated to be 20.8 and 24.2 g (0.79 and 0.92 g/MJ metabolizable energy), respectively, with coefficients of variation of approximately 10%. Marginal efficiency of Lys utilization derived from the LP model was 0.67 and was dependent on the range of input data selected. Lysine disappearance was a curvilinear function of Lys intake, indicating that Lys catabolism is not directly related to Lys intake. The closeness of fit of exponential, saturation kinetics or four-parameter logistic models applied to data set of all pigs was similar to that of LP or QP models.

Summary The results of three experiments, focused on the determination of endogenous ileal flow (EIF) of amino acids (AA) and nitrogen (N) (Exp. 1), apparent ileal digestibility (AID) of AA and N (Exp. 2), and apparent total tract digestibility (ATTD) of dry matter (DM), organic matter (OM), N, calcium (Ca) and phosphorus (P) (Exps. 2 and 3), were used to compare chromic oxide (Cr2O3) and acid-insoluble ash (AIA) as digestibility markers. In Exps. 1 and 2, a total of six gilts fitted with T-cannula in terminal ileum, and in Exp. 3, a total of 24 pregnant sows were used. In Exps. 1 and 2, the pigs were assigned into four dietary treatments according to 4 × 6 crossover design (Exp. 1; diets with 0%, 4%, 8% and 12% of casein; Exp. 2 basal diet with different levels of phytase). In Exp. 3, the sows were assigned to four dietary treatments (basal diet with different levels of phytase) of six sows. In Exps. 1 and 2 ileal digesta and in Exps. 2 and 3 faeces were collected for the determination of EIF, AID and ATTD. Differences in EIF of AA determined by Cr2O3 and AIA ranged (p ˃ 0.05) from −4.62 to 4.54%. The lowest EIF was for methionine and the greatest one for proline, determined by both markers. Apparent ileal digestibility determined by Cr2O3 was slightly greater (p ˃ 0.05) in comparison with AIA. Differences ranged from 1.88% (Arg) to 7.08% (Gly). The greatest AID was for arginine and the lowest one for glycine, determined by both Cr2O3 and AIA. Similarly for ATTD of DM, OM, N, Ca and P, there were no differences in digestibility determined by Cr2O3 and AIA. Both, Cr2O3 and AIA, are suitable and comparable markers for digestibility studies in pigs.

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 digest - ibility thus indicating a net flux of P into the large intestine.

The effect of dietary essential:total (E/T) N ratio on endogenous amino acid losses (EAAL), endogenous losses of total N (ENL) and N retention (NR) was studied in ileally cannulated pigs. The treatments were a protein-free (PF) diet and four isonitrogenous (1.2% N) purified diets with E/T ratios of 0, 0.33, 0.66 and 1.0 (diets ET0, ET33, ET66 and ET100). The highest ENL (g per kg dry matter intake) were found in diet ET0 (2.56) followed by diets PF, ET33, ET66 and ET100 (2.24, 1.43, 1.33 and 1.25, respectively). A similar response was found for EAAL. In most cases, EAAL in pigs fed diets ET33, ET66 and ET100 were significantly lower than those in pigs fed diet ET0. The high ENL in diets PF and ET0 were largely due to the high endogenous losses of proline and glycine, the sum of which accounted for 36–42% of total EAAL. The proportion of diaminopimelic acid of total AA in ileal digesta was low, suggesting that the contribution of intestinal microflora to EAAL was negligible. N retention increased curvilinearly as the E/T ratio increased and reached the maximum at E/T value of 0.74.

A digestibility trial on piglets was conducted to study the effect of an enzyme complex derived from Trichoderma longibrachiatum (Roxazyme G2) supplemented to a rye-based diet on apparent ileal digestibility of amino acids and NSP-constituting sugars. Enzyme supplementation at 200 mg kg − 1 increased ( P P P