Dairy cows fitted with ruminal, duodenal and ileal cannulas were
utilized
to investigate the effects of feeding with Ca soaps (CaS) of
palm fatty acids (FA) and
rapeseed FA. Diets compared were control diet based on maize silage and
concentrate, and two diets with 40 g CaS of palm oil FA or rapeseed
oil FA/kg diet,
replacing part of the concentrates of the control diet. Total
digestibilities of dry
matter, fibre and fat, and ruminal fermentation were not significantly
altered by
giving CaS; the extent of ruminal biohydrogenation of total unsaturated
C18 FA was
significantly reduced by both CaS diets. Apparent intestinal digestibility
of FA was
not different among diets, although the amount of FA absorbed with the
CaS diets
was twice that with the control diet. No difference among diets
was observed for milk
production, or fat and protein contents. Giving CaS diets decreased the
proportions
of 4[ratio ]0 to 14[ratio ]0 FA in milk fat, and increased
cis-18[ratio ]1n−9, compared with control diet.
The rapeseed diet lowered the content of 16[ratio ]0, and increased the
contents of 18[ratio ]0
and trans-18[ratio ]1n−7. CaS diets did not
result in a marked increase of polyunsaturated
FA content in milk fat. Butter from cows fed on the CaS diets contained
more liquid
fat at 6 and 14°C than butter from the cows fed on the control diet.
Incorporating
CaS, particularly those from rapeseed, in dairy cows'
diets increased C18 FA in milk and improved butter spreadability.