Agriculture Reference
In-Depth Information
improve sow milk yield and a better understanding of the mechanisms involved in the
control of milk production is needed to achieve that goal. Nutrients available to mammary
tissue may be enhanced by increasing the concentrations of nutrients in blood and the
blood flow to the glands (Renaudeau
et al.
, 2002). The present chapter therefore focusses
on mammary blood flow and the uptake of nutrients and hormones by mammary tissue in
swine. The direct and indirect methods of estimating blood flow will be described and an
update on the current knowledge of the factors involved in its regulation will be provided.
Mammary uptake of major nutrients, such as glucose and amino acids, and of other
energetic precursors will be covered, with some emphasis on novel findings pertaining
to glucose and amino acid transporters. Finally, the limited information available on
mammary uptake of hormones will be summarized and the potential involvement of
specific hormones for nutrient uptake by the sow's udder discussed.
14.2
Blood flow
14.2.1
Anatomy of the mammary circulatory system
The arterial, venous and lymphatic circulation of the sow mammary glands are provided
on each side of the ventral midline by a network that extends longitudinally from the
axillary to the inguinal regions (Schummer
et al.
, 1981), as depicted in Figure 14.1. In
contrast to ruminants where only one artery (pudendal artery) supplies blood to both
sides of the udder (Barone, 1996), several arteries supply each side of the sow's udder
(Trottier
et al.
, 1995a). The external pudendal artery descends through the inguinal
canal where it divides into the lateral cranial, middle cranial and medial cranial branches
Internal iliac vein
Caudal vena cava
Internal pudendal
vein
Cranial vena cava
External iliac vein
External iliac artery
External pudendal vein
Caudal epigastric vein
Superior epigastric artery
External pudendal artery
Inferior epigastric artery
Internal
thoracic vein
External thoracic vein
Caudal mammary
vein
Cranial mammary
vein
Internal thoracic artery
Caudal super
cial
epigastric veins
Cranial super
cial
epigastric veins
Lateral thoracic or
mammary artery
Figure 14.1. Illustration of the lactating sow mammary circulatory system. The oval line represents the inguinal
canal. Single dash arrows indicate direction of venous blood flow and double dash arrows indicate direction
of arterial blood flow. Arteries are opened and veins are filled. Drawing not to scale.
