Agriculture Reference
In-Depth Information
Sow colostrum and milk contain several steroid hormones. The mammary gland of the
sow produces estradiol, a function that seems to be under the control of progesterone
(Staszkiewicz
et al.
, 2004). Estradiol concentrations in the sow's plasma are elevated prior
to parturition and decline rapidly during the initial day postpartum (Devillers
et al.
,
2004a; Osterlundh
et al.
, 1998). Concentrations of estradiol in whole colostrum collected
just prior to parturition are 3 to 4 fold greater than in plasma at the same period (Devillers
et al.
, 2004a). In another study using fat-free colostrum, concentrations of estradiol were
about half the plasma concentrations (Osterlundh
et al.
, 1998). Estradiol concentrations
decline rapidly during the first day postpartum from about 1.5 ng/ml at parturition to 0.5
ng/ml by 24 h postpartum (Devillers
et al.
, 2004a). Concentrations of estrone in whole
sow colostrum are highest immediately after parturition (13.8 ng/ml) and rapidly decline
over the first 24 h, reaching 0.5 ng/ml by 48 h postpartum (Farmer
et al.
, 1987). Estrone
concentrations in whole sow mammary secretions are not affected by gland location
(Farmer
et al.
, 1987). Concentrations of progesterone in sow mammary secretions follow
a similar pattern to that of estrogens, with concentrations being highest in colostrum and
then rapidly declining during the initial day postpartum (Devillers
et al.
, 2004a). Cortisol
is also present in sow mammary secretions, with highest concentrations approximately 2
to 2.5 fold greater shortly after parturition compared with milk concentrations (measured
in fat-free secretion; Osterlundh
et al.
, 1998).
Concentrations of insulin and neurotensin are elevated in colostrum at parturition and
then decline over the initial 3 d of lactation, while concentrations of bombesin remain
relatively constant through the same period (Westrom
et al.
, 1987). Concentrations of
thyroid hormones in milk do not appear to be different between colostrum and milk during
early lactation (Mostyn
et al.
, 2006). A breed effect has been noted for triiodothyronine
concentrations in sow mammary secretions, but not for thyroxine (Mostyn
et al.
, 2006).
Several growth factors and growth-factor activities have been identified in sow milk.
Concentrations of insulin-like growth factor-I (IGF-I) are highest in colostrum collected
during the first day postpartum (ranging from 14 to 70 ng/ml), then decline by more
than 50% by the second day postpartum, and continue declining through about day
10 of lactation (ranging from 3 to 14 ng/ml; Monaco
et al.
, 2005). The effect of stage
of lactation is significant on IGF-I concentrations in sow mammary secretions, while
there is no significant difference between first and second parities (Monaco
et al.
, 2005).
Simmen
et al.
(1990) also observed an effect of stage of lactation on IGF-I concentrations
in mammary secretions, as well as a breed effect. An epidermal growth factor-like peptide
has been identified in sow milk (Tan
et al.
, 1990). Epidermal growth factor concentrations,
estimated by radioreceptor assay, are highest in mammary secretions collected in the
first 24 h postpartum, decline by ~90% by day 9 of lactation, and then remain relatively
constant at least through day 27 (Jaeger
et al.
, 1987). Prostaglandin-like activity declines
approximately 2.5 fold from the high levels in colostrum to day 5 of lactation and remains
constant at least through day 20 of lactation (Maffeo
et al.
, 1987). A number of cytokines
have been identified in sow colostrum and milk, including IL-4, IL-6, IL-10, IL-12,
IFN-γ, TNF-α, and TGF-β (Nguyen
et al.
, 2007). Each cytokine identified has the highest
concentrations in colostrum and early lactation milk, followed by declining concentrations
as lactation progresses, although declining at differing rates (Nguyen
et al.
, 2007).
