Discussion
In contrast to effects in human beings lac ingestion in
pigs did not result in laxation although comparable
amounts were supplemented. In further feeding experiments
with pregnant sows (Kamphues, unpublished) even
amounts of more than 300 g per sow and day did not lead
to laxation. In human beings lac is fermented and
absorbed predominantly in the hindgut (Schumann
1997), whereas the lac concentrations in ileum contents
of sacrificed piglets as well as of fattening pigs indicate
that already high amounts of lac disappear in the prececal
part of the gastrointestinal tract. Assuming a prececal
digestibility rate of about 0.75 of the diet lac concentrations
of around 100 g/kg DM of chyme should be
achieved but the values were much lower (all values
b50 g/kgDM). Lac entering the hindgut is fermented very
fast in pigs as indicated by the lac concentrations in the
cecumand colon contents. Also themissing differences of
lac concentrations between cecum and colon support this
hypothesis. According to Harju (1986) mucosa of small
intestine in pigs has a lac splitting capacity. Murray et al.
(1996) observed in piglets (7 days old) lac absorption by
colonic mucosa without prior microbial digestion. These
observations combined with findings of the present study
concerning the lac concentration in chyme might explain
why lac ingestion did not cause fermentative diarrhoea.
Recent experiments on nutritional measures concerning
Salmonella prophylaxis in pigs