**2.2.2 Biochemical analysis**

After the collection, 1 g of digesta (jejunum, ileum, colon) was diluted in 50 ml of deionized H2O and applied at a volume of 30 µl for analysis of SCFAs. The concentration of formic, acetoacetic, lactic, succinic, acetic, propionic, butyric and valeric acids in the intestinal content was determined by capillary isotachophoresis (ITP). The measurements were done on an "Isotachophoretic analyser ZKI 01" (SR). In the pre-separation capillary, a leading electrolyte of the following composition was used: 10-2 M HCl + 2.2. 10-2 M ε-aminocaproic acid + 0.1% methylhydroxyethylcellulosic acid, pH 4.3. As finishing electrolyte, a solution of 5.10-3 M caproic acid + histidine was used. This electrolytic system worked at 250µA in preseparation and 50 µA in the analytic capillary. pH was measured by a pH meter (LP Prague, Czech Republic).

Differences in the Development of the Small Intestine

7.64 and the pH of the colonic content ranged from 6.24 to 7.53.

**gnotobiotic and conventionally bred piglets** 

**3.3.1 Conventional suckled piglets (natural feeding)** 

concentration at 2 weeks post-weaning (p < 0.001).

**3.3.2 Conventional replacer-fed piglets (artificial feeding)** 

**3.3 Effect of age and weaning on production of SCFAs in the intestinal tract of** 

Concentration of both acetoacetic and acetic acid in the jejunal content of suckled piglets (Table 2) within the period of milk nutrition was the highest at 7 days of age (p < 0.001 and p < 0.01, respectively). Subsequently the values declined at 2 weeks of age to 14.76 mmol/l of acetoacetic and to 28.02 mmol/l of acetic acid. This decline continued in acetoacetic acid by day 35 of age to 6.10 mmol/l and in acetic acid by week 4 of life to 7.71 mmol/l (p < 0.01). The concentration of lactic acid in jejunal contents was comparable to that of both acetoacetic and acetic acid, with a mean decline of 11.85 mmol lactic acid/l between day 2 and day 21. But a pronounced increase in the concentration of lactic acid was recorded at 1st week post-weaning - i.e. 53.91 mmol/l. The course of the concentration of both acetoacetic and lactic acid in the ileal content (Table 3) was largely similar to that recorded in the jejunal content. Under the influence of more diverse populations of microorganisms, the conditions in the colonic content changed. Propionic acid concentration (Table 4) increased gradually up to weaning (28 days) and then markedly after weaning (day 35: p < 0.01 and on day 42: p < 0.05). The most pronounced production of acids in the colonic content was observed in acetoacetic acid with highest concentrations at day 14 and 28 of age (p < 0.001 and p < 0.001) and a sudden 4-fold decline at 1st week post-weaning (p < 0.01). In acetic acid, a gradual increase in values was recorded from 7 days of age (11.91 mmol/l), with its highest

In both acetoacetic and lactic acid, the highest levels in the jejunal content in replacer-fed piglets (Table 2) were recorded at 7 days of age (19.89 mmol/l and 24.92 mmol/l, p < 0.01,

**3.2 Acidity** 

Between Gnotobiotic and Conventionally Bred Piglets 381

petechial bleeding on seroses and mucoses of the gastrointestinal tract. Transudate in the abdominal cavity was of a deep-red colour, and the blood was uncoagulated. In the groups of suckled piglets (natural feeding) and gnotobiotic piglets the health status was good.

The actual acidity of stomach digesta in replacer-fed piglets ranged more widely - i.e. from pH 1.7 to 3.8. During the period of observation, only on day 2 of age the pH of stomach contents of these piglets was significantly lower (p<0.01, p<0.05) than in suckled piglets with pH ranging from 2.9 to 3.7 and gnotobiotic piglets with 2.7 - 4.1 pH range (Table 1). In the proximal segment of GIT (content of duodenum and jejunum) of gnotobiotic piglets we recorded between days 7 and 28 days of age the lowest levels of pH which differed significantly on day 14 of age (p<0.001) in duodenum and on day 21 of age (p<0.01) in jejunum in comparison with replacer-fed piglets. The pH level in the caudal segment of GIT (ileal content) of suckled piglets was lower in comparison with replacer-fed piglets and significantly lower on days 2 (p<0.05) and 21 (p<0.01) of age. The ileal and colonic pH were on average lower by 0.08 to 0.5 in the group of suckled piglets and the pH values ranged from 6.27 to 7.17 and from 6.50 to 7.21 compared to replacer-fed piglets in which the pH of the ileal content ranged from 6.93 to
