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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

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.

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.

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.

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.