Agriculture Reference
In-Depth Information
Table 14.2. Arteriovenous differences (mg/100 ml for all variables except volatile fatty acids and free fatty acids
which are in Meq/l) of plasma carbohydrates and lipids in the lactating sow (Farmer
et al
., 2008b).
Linzell
et al.,
1969b
Spincer
et al.,
1969
Spincer and Rook, 1971
19.8
1
Glucose
37.5
28.7
Triglycerides
7.6
7.2
10.2
ND
2
Lactate
7.4
1.4
Phospholipids
0.3
4.1
ND
Β-hydroxybutyrate
0.2
0.2
ND
0.2
1,3
0.6
4
Volatile fatty acids
ND
0.1
3
Free fatty acids
ND
ND
Citrate
ND
0
ND
1
Adjusted from whole blood to plasma using the average hematocrit value of 31.7%.
2
Not determined.
3
Both negative and positive values were observed.
4
Value for acetate only.
(2000) corroborated these earlier reports on the relative uptakes of glucose, triglycerides
and amino acids by the sow mammary glands.
There is some recent information on the uptake of minerals and vitamins across the
mammary glands of lactating sows. Both Nielsen
et al.
(2002a) and Dourmad
et al.
(2000) showed a positive mammary AVD for calcium. Dourmad
et al.
(2000) also noted
a positive uptake of phosphorus, with its AVD across mammary tissue increasing after
a meal, whereas calcium uptake remained constant post-prandially. The extraction
rates of calcium and phosphorus from arterial blood are typically lower (4.1 and 3.1%,
respectively) than that of other major nutrients (ranging from 20 to 35%). In addition,
there was very little to no uptakes of riboflavin (3.4 pmol/ml), vitamin B (0 pg/ml) or folic
acid (-1.2 ng/ml) by the sow mammary glands (Dourmad
et al.
, 2000).
14.3.4
Uptake of energy and energetic efficiency of milk synthesis
The uptake of energy by the mammary glands can be calculated from the uptake of
glucose, amino acids and other milk precursors and their energy content. From the
studies of Linzell
et al.
(1969b) and Renaudeau
et al.
(2003), energy AVD of 9.1 and 8.8
kJ/l plasma, respectively, can be calculated (Figure 14.2). A similar value of 8.9 kJ/l was
measured in postprandial animals (Dourmad
et al.
, 2000), whereas after 16 h of fasting
the AVD of energy tended to decrease (7.6 kJ/l). In fed sows, the contribution of glucose
and lactate to total energy uptake by the mammary glands averaged 45%, whereas in
fasted sows this value dropped to 28% (Dourmad
et al.
, 2000). The contribution of free
fatty acids to energy uptake was highly dependent on nutritional status of the sows.
In fasted sows, free fatty acids contributed approximately 35% of the energy uptake
whereas no uptake was detected after a meal. The situation in restrictively-fed sows was
