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Short chain fatty acids (SCFAs) are intermediates from microbial fermentation of proteins or saccharides. Little is known about their production in different parts of intestine and therefore the aim of the present study was to examine, using 7 double-cannulated gilts (initial BW: 25 ± 0.5 kg), the production of the SCFAs in a jejunal digesta, caecal digesta and faeces. After a 25-d recovery period, a 70-d experimental period followed. On days 28; 42; 56 and 70, samples of jejunal, caecal digesta and faeces were collected. In the samples of jejunal and caecal digesta and in faeces, the content of dry matter (DM), crude protein (CP) and SCFAs was determined. The highest content of DM ( P P P P P P P P P P P

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.

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 experi - ment, 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 endog - enous 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.

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 aim of the present study was to examine the effect of the dietary protein restriction on the plasma concentrations of leptin, insulin-like growth factor (IGF-I), blood urea nitrogen (BUN) and growth performance in growing pigs. A total of 12 gilts were divided into experimental (ET) and control (CT) treatments. After the 14-day dietary restriction period during which the ET fed a low-protein diet (LPD, 5% of crude protein) and the CT fed a standard diet (SD, 16% of crude protein) the second 14-day re-feeding period followed, in which LPD was replaced by a SD that was fed by the both treatments. During the dietary protein restriction reduced (P < 0.05) N intake, average daily gain (ADG), concentration of BUN and tendency (P = 0.084) to the lower IGF-I in ET compared with CT were observed. Feed to gain ratio was greater (P < 0.05) in ET. During the subsequent re-feeding period, there was a tendency to the greater daily feed intake (P = 0.068) and N intake (P = 0.070), greater (P < 0.05) ADG, BUN and plasma leptin but no IGF-I in ET. These observations suggest that dietary protein restriction promotes body growth in pigs, which is associated with increase in blood leptin and BUN level in ET during the re-feeding, indicating that the increased ADG can be due to increased fat deposition but not of protein synthesis.

Eight gilts (29.9 ± 1.7 kg initial BW) were used to evaluate effects of dietary (crude) fiber on N excretion via feces and urine at 2 levels of dietary CP. Pigs were fed 4 dietary treatments according to a double 4 × 4 Latin square. Treatments were low (14%) CP and low (3.25%) (crude) fiber (LPAA), low CP and high (4.46%) fiber (LPAABP), high (18.8%) CP and low fiber (HP), and high CP and high fiber (HPBP). Diets were based on soybean (Glycine max) meal, wheat (Triticum aestivum), and maize (Zea mays) and were supplemented with crystalline AA. High fiber diets contained 15% dried beet (Beta vulgaris) pulp. Pigs were housed in metabolic cages and fed 2 equal meals at 0700 and 1700 h at a daily rate of 90 g/kg BW(0.75). Water was offered ad libitum. Each experimental period consisted of a 6-d adaptation followed by a 4-d collection of feces and urine (bladder catheters). Data were analyzed using ANOVA. Differences between means (P < 0.05) were assessed using Fisher's LSD procedure. The N intake, fecal N excretion and absorption, and N retention increased (P < 0.05) in pigs fed high-CP diets with added fiber (HP vs. HPBR). With added fiber, urinary N excretion (g/d) was reduced (P < 0.02) only for the low-CP diet. Urinary N as a percentage of N intake was reduced (P < 0.01) in both groups fed high-fiber diets irrespective of dietary CP content. Dietary fiber level did not affect DMI. Fecal DM excretion (g/d) was higher (P < 0.02) in pigs fed diets with high CP and high fiber content than in pigs fed diets with high CP and low fiber content. In conclusion, beet pulp fiber added to diets increased fecal N and reduced urinary N and in diets with higher CP content increased overall N retention.

The effect of environmental heat stress on N metabolism was studied using 7 gilts (50.5 ± 1.7 kg initial BW). Pigs were housed in metabolism cages in a climate-controlled room. After a 4-d adaptation, two 14-d experimental periods followed during which the animals were exposed to thermo-neutral temperature (NT; 20.61 ± 0.1°C) or high environmental temperature (HT; 30.41 ± 0.4°C). In each experimental period, two 24-h balance periods were carried out to collect feces and urine (via bladder catheters) for N analysis. Based on N intake and N excretion, N balance was calculated. At HT conditions, N intake was lower (P = 0.028), urinary N excretion increased (P = 0.040), and N retention decreased (P = 0.001) in comparison with NT conditions. Exposure of pigs to HT tended to reduce (P = 0.070) digestibility of N as compared to NT conditions. When pigs are exposed long term to continuous HT, N retention decreases presumably due to decreased use of ME during respiration.

Chemical composition and nutrient and energy digestibilities were determined in 4 samples of dried distillers grains with solubles (DDGS) and 1 sample of wet distillers grains (WDG) from 4 ethanol fuel manufacturers. The cereal sources used for ethanol production were wheat (Triticum aestivum; 1 sample), wheat + barley (Hordeum vulgare; 2 samples), and maize (Zea mays; 2 samples). The nutrient contents (expressed as % of DM) were variable, ranging from 30.5 to 39.5 CP, 4.4 to 12.3 fat, 7.5 to 12.9 crude fiber, 2.7 to 7.8 ash, and 0.4 to 0.9 total P. The concentration of Lys ranged from 2.05 to 5.20 g/kg DM. The diets were fed to 6 gilts (39.9 ± 1.9 kg BW) fitted with ileal T-cannulas using a 5 × 6 Youden square. Each experimental period comprised a 5-d adaptation followed by a 2-d collection of urine and feces and 1-d (24 h) collection of ileal digesta. Using acid-insoluble ash as a marker, apparent ileal digestibility (AID) and apparent total tract digestibility (ATTD) of nutrients and energy and AID of AA were calculated. The ATTD of N ranged from 55.7 to 83.7%. The N retention expressed as percentage of N intake ranged from 10.2 to 32.0. Except for wheat-based DDGS, the AID of N was 66.8%. The ATTD and AID values of NDF were 52.8 and 24.4%, respectively. The concentration of total P in WDG was half of values in DDGS, which likely caused its very low ATTD (1.4%). The ATTD and AID of energy ranged from 58.8 to 73.9% and from 40.6 to 54.1%, respectively. The AID of AA was greatest (P < 0.001) in WDG (71.8%) and lowest (P < 0.001) in DDGS from wheat (44.8%). In conclusion, nutrient variability among DDGS samples varies greatly, and source of origin is an important determinant of quality.

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

The effect of environmental heat stress on N metabolism was studied using 7 gilts (50.5 ± 1.7 kg initial BW). Pigs were housed in metabolism cages in a climate-controlled room. After a 4-d adaptation, two 14-d experimental periods followed during which the animals were exposed to thermo-neutral temperature (NT; 20.61 ± 0.1°C) or high environmental temperature (HT; 30.41 ± 0.4°C). In each experimental period, two 24-h balance periods were carried out to collect feces and urine (via bladder catheters) for N analysis. Based on N intake and N excretion, N balance was calculated. At HT conditions, N intake was lower (P = 0.028), urinary N excretion increased (P = 0.040), and N retention decreased (P = 0.001) in comparison with NT conditions. Exposure of pigs to HT tended to reduce (P = 0.070) digestibility of N as compared to NT conditions. When pigs are exposed long term to continuous HT, N retention decreases presumably due to decreased use of ME during respiration.

Eight gilts (29.9 ± 1.7 kg initial BW) were used to evaluate effects of dietary (crude) fiber on N excretion via feces and urine at 2 levels of dietary CP. Pigs were fed 4 dietary treatments according to a double 4 × 4 Latin square. Treatments were low (14%) CP and low (3.25%) (crude) fiber (LPAA), low CP and high (4.46%) fiber (LPAABP), high (18.8%) CP and low fiber (HP), and high CP and high fiber (HPBP). Diets were based on soybean (Glycine max) meal, wheat (Triticum aestivum), and maize (Zea mays) and were supplemented with crystalline AA. High fiber diets contained 15% dried beet (Beta vulgaris) pulp. Pigs were housed in metabolic cages and fed 2 equal meals at 0700 and 1700 h at a daily rate of 90 g/kg BW(0.75). Water was offered ad libitum. Each experimental period consisted of a 6-d adaptation followed by a 4-d collection of feces and urine (bladder catheters). Data were analyzed using ANOVA. Differences between means (P0.05) were assessed using Fisher's LSD procedure. The N intake, fecal N excretion and absorption, and N retention increased (P0.05) in pigs fed high-CP diets with added fiber (HP vs. HPBR). With added fiber, urinary N excretion (g/d) was reduced (P0.02) only for the low-CP diet. Urinary N as a percentage of N intake was reduced (P0.01) in both groups fed high-fiber diets irrespective of dietary CP content. Dietary fiber level did not affect DMI. Fecal DM excretion (g/d) was higher (P0.02) in pigs fed diets with high CP and high fiber content than in pigs fed diets with high CP and low fiber content. In conclusion, beet pulp fiber added to diets increased fecal N and reduced urinary N and in diets with higher CP content increased overall N retention.

Chemical composition and nutrient and energy digestibilities were determined in 4 samples of dried distillers grains with solubles (DDGS) and 1 sample of wet distillers grains (WDG) from 4 ethanol fuel manufacturers. The cereal sources used for ethanol production were wheat (Triticum aestivum; 1 sample), wheat + barley (Hordeum vulgare; 2 samples), and maize (Zea mays; 2 samples). The nutrient contents (expressed as % of DM) were variable, ranging from 30.5 to 39.5 CP, 4.4 to 12.3 fat, 7.5 to 12.9 crude fiber, 2.7 to 7.8 ash, and 0.4 to 0.9 total P. The concentration of Lys ranged from 2.05 to 5.20 g/kg DM. The diets were fed to 6 gilts (39.9 ± 1.9 kg BW) fitted with ileal T-cannulas using a 5 × 6 Youden square. Each experimental period comprised a 5-d adaptation followed by a 2-d collection of urine and feces and 1-d (24 h) collection of ileal digesta. Using acid-insoluble ash as a marker, apparent ileal digestibility (AID) and apparent total tract digestibility (ATTD) of nutrients and energy and AID of AA were calculated. The ATTD of N ranged from 55.7 to 83.7%. The N retention expressed as percentage of N intake ranged from 10.2 to 32.0. Except for wheat-based DDGS, the AID of N was 66.8%. The ATTD and AID values of NDF were 52.8 and 24.4%, respectively. The concentration of total P in WDG was half of values in DDGS, which likely caused its very low ATTD (1.4%). The ATTD and AID of energy ranged from 58.8 to 73.9% and from 40.6 to 54.1%, respectively. The AID of AA was greatest (P0.001) in WDG (71.8%) and lowest (P0.001) in DDGS from wheat (44.8%). In conclusion, nutrient variability among DDGS samples varies greatly, and source of origin is an important determinant of quality.

Summary Two N balance experiments were conducted to study the individual response of growing pigs to limiting amino acid (AA) intake. Series of fifteen diets with increasing concentration of sulphur amino acids (SAA, Expt 1) or methionine in the presence of excess cystine (Expt 2) were fed sequentially to nine pigs during a 15-day experimental period. The concentration of the AA under test ranged from 50% to 140% of the requirement while other essential AA were given in a 25% excess relative to the limiting AA. N retention was related to the limiting AA intake using rectilinear and curvilinear models. In Expt 1, the quadratic-plateau model fitted the individual data significantly better (p = 0.01) than the linear-plateau model. No difference was found between the two models in Expt. 2, presumably due to the sparing effect of excess cystine on methionine utilization. Exponential, saturation kinetics or four-parameter logistic models fitted to data for all pigs showed that their goodness of fit was similar to those of quadratic-plateau or linear-plateau models. Significant differences (p

A nitrogen balance experiment was conducted to study the individual and group response of growing pigs to threonine (Thr) intake. A series of fifteen purified diets with increasing concentration of Thr was fed sequentially to nine pigs during a 15-d experimental period. The concentration of Thr ranged from 50 to 140% of its assumed requirement while other essential amino acids were given in a 25 % excess. N retention was related to Thr intake using rectilinear and curvilinear models. The quadratic-plateau model fitted the individual data significantly better (P=0.02) than the linear-plateau model. The R 2 statistic indicated that the group response of pigs to Thr intake was better described by the linear-plateau and quadratic-plateau models than by exponential, saturation kinetics or four-parameter logistic models. Significant differences (P=0.004) were found between individual plateau values in the linear-plateau model while the slopes of the regression lines did not differ. No significant correlation was found between the slope and plateau or breakpoint values of the linear-plateau model. Marginal efficiency of Thr utilization derived from the linear-plateau model was 0.67. In the quadratic-plateau model, marginal efficiency of Thr utilization was dependent on Thr intake and ranged from 0.77 (50% of requirement) to 0.42 (100% of requirement). Based on linear-plateau and quadratic-plateau models, daily requirement of Thr for a 45 kg pig was calculated to be 11.5 and 12.1 g, respectively.