Agriculture Reference
In-Depth Information
Table 14.1. Mammary plasma flow through the entire mammary gland, milk yield and amount of plasma
required to produce 1 kg of milk estimated from data of various studies in sows fed diets providing the
minimum nutrient requirements (Farmer
et al
., 2008b).
Study
Method
Litter size
Plasma flow (l/min)
Milk yield (l/d)
Plasma (l per l milk)
Fick (phe + tyr)
1
Guan
et al.
(2002)
12
4.9
12.1
581
Guan
et al.
(2004a)
Fick (lysine)
11
4.5
11.4
560
Guan
et al.
(2004b)
Fick (lysine)
11
3.6
10.7
490
Linzell
et al.
(1969a)
2
Fick (
3
HO)
1.9
3
441
3
6
6.2
Nielsen
et al.
(2002b)
Fick (lysine)
8
3.2
10
550
Nielsen
et al.
(2002a)
Fick (lysine)
12
5.5
7.4
1,050
Nielsen
et al.
(2002a)
Fick (methionine)
12
4.4
7.4
858
Nielsen
et al.
(2002a)
Fick (calcium)
12
2.8
7.4
548
3.6
3
471
3
Renaudeau
et al.
(2002)
Flow probe
12
11
3.9
4
Renaudeau
et al.
(2002)
Fick (lysine)
12
11
511
Trottier
et al.
(1997)
Fick (lysine)
11
3.0
8.1
541
1
Phenylalanine + tyrosine.
2
A weight of 770 g for the gland subjected to blood flow measurement was derived from the reported milk yield of 43 ml/h or 134 ml/d per
100 g of tissue, and blood flow of 41 ml/min per 100 g of tissue. Blood flow through that gland was recalculated as l/gland/day where 41 ml/
min/100 g tissue represents 316 ml/min/gland or 455 l/day/gland. The number of functional glands was based on the number of suckling piglets,
to calculate mammary blood flow through all functional glands. This value was verified by dividing the total mammary tissue weight of 4.62 kg
by the single gland weight of 770 g (as estimated above). Thus, total mammary blood flow was estimated as 2,728 l/day (455 l/day/gland × 6
glands) and total milk yield as 6.19 l/day (1,032 ml/day × 6 glands). Milk yield per gland was estimated as 1,032 ml/day where 134 ml/100 g
tissue per day × 770 g/gland.
3
Values are for blood flow and liter of blood per liter of milk.
4
Estimated from reported blood to milk ratio of 511 and average milk yield of 11 l/d.
synthesis in lactating dairy cows. Also, the NRC (2012) recently estimated dietary lysine
efficiency of utilization into milk protein synthesis to be 67% in sows; albeit this value
appears to be overestimated, the findings of Lapierre
et al.
(2009) in dairy cows together
with this NRC (2012) estimate suggest that lysine utilization by the porcine mammary
gland may be of greater significance than previously suggested.
Most of the reported plasma flow values from studies using Fick's principle range from
1.9 to 4.9 l/min with corresponding plasma:milk (vol:vol) and milk yield, respectively
ranging from 441 to 581 and 6.2 to 12.1 l/d (Table 14.1). Plasma:milk values as high as
1,050 and 858 were also reported when lysine and methionine, respectively, were used
as internal markers (Nielsen
et al.
, 2002a, Table 14.1). These values raise questions when
considering the reported low average daily milk production of 7.4 kg for a litter size of 12
(Nielsen
et al.
, 2002a). In that same study, when calcium was used as marker, the average
plasma flow was 2.8 l/min, a value falling within the reported range. Because no other
studies are available to compare the plasma flow estimated with calcium, it is unknown
whether calcium is a valid marker. Unlike amino acids, calcium is not metabolized hence
