Page 424 - Anatomy and Physiology of Farm Animals, 8th Edition

Physiology of Digestion / 409

Micelles containing bile salts, triglycerides,
cholesterol, monoglycerides, and fatty acids
VetBooks.ir

Synthesis of
Monoglyceride triglycerides and
Cholesterol Fatty acid formation of
chylomicrons

Chylomicron

Secretion of chylomicrons

Chylomicron
Sites of transport
by diffusion
Lacteal

Figure 21-10. Absorption of lipids and cholesterol by intestinal cell and subsequent formation and
secretion of chylomicrons.

increases calcium absorption by increasing approximately 1 day in the horse and pig
calcium transport proteins in enterocytes. and up to 3 days in the ruminant.
Calcitriol formation by the kidneys is
increased when blood calcium is low. To be
absorbed, minerals such as calcium and Physiology of the Cecum
phosphate must be in their ionized state. and Colon
If the ratio of cations to anions is too high
or too low, absorption can be reduced. In carnivores the cecum and colon primar-
For example, if the dietary content of the ily absorb water and some electrolytes to
phosphate (an anion) is too high relative to reduce the volume and fluidity of the
calcium (a cation), the excess phosphate digesta in the formation of feces. Feces are
binds the available calcium to form cal- also stored in the terminal portions of the
cium phosphate, and calcium absorption is colon prior to their movement into the rec-
impaired. tum for defecation. In omnivores (e.g., pig)
The small intestine of some neonatal and some herbivores (e.g., cattle and sheep)
(newborn) animals can absorb macromol- the cecum and colon are also sites of some
ecules, including intact protein molecules limited fermentation and microbial diges-
from the colostrum. Colostrum, the first tion. In cattle and sheep the cecum and
milk of the horse, pig, and ruminants, colon are proportionally larger and more
contains the γ‐globulins needed to pro- complex than in carnivores, but the fores-
duce passive immunity in the newborns of tomach is the much more important site of
these animals. This receptive period lasts fermentative digestion in these herbivores.