Agriculture Reference
In-Depth Information
with other whey proteins (Danielsen
et al.
, 2011; Yvon
et al.
, 1993). Estimates of gross
energy based on bomb calorimetry may overestimate the energy that the piglet derives
from colostrum. The transient increase in gross energy observed at day 2 and day 3 is
likely associated with the peak in fat content that occurs during that phase of lactation.
9.9
Minerals
Total inorganic components of mammary secretions are typically reported as ash. From
the summary of studies in Table 9.2 and 9.3, ash content of colostrum at parturition is
approximately 0.68%. Ash percentage is increased by day 2 of lactation and then continues
to increase gradually up to about week 2 and then remains at approximately 0.90%. The
ash percentages reported in Table 9.3 for 42 to 60 d are based on a limited number of
studies that have reported on this component during an extended lactation.
Table 9.6 summarizes reported concentrations of individual minerals in sow colostrum
and milk. Concentrations of calcium are relatively low in colostrum, and then increase
throughout lactation, at least up to week 6 or 7 of lactation (Coffey
et al.
, 1982; Gueguen
and Salmon-Legagneur, 1959; Harmon
et al.
, 1974; Miller
et al.
, 1994; Perrin, 1955). Most,
but not all, calcium is bound in the casein micelles. Concentrations of diffusible calcium
are highest in colostrum and then decline as lactation progresses (Kent
et al.
, 1998),
consistent with the concurrent increase in casein content. Phosphate concentrations
follow a similar pattern to that of calcium, increasing in content from colostrum to milk
(Table 9.6). Dietary level of calcium does not affect milk calcium concentration (Miller
et al.
, 1994), and an inorganic source of dietary microminerals results in higher milk
calcium concentrations than an organic source (Peters
et al.
, 2010).
Concentrations of potassium and sodium are greater in colostrum than in milk
(Table 9.6). Synthesis of most milk components occurs in the relatively high potassium
and low sodium environment of the mammary epithelial cell. Therefore, mammary
secretions reflect this potassium/sodium relationship. Chlorine is also found in greater
amounts in colostrum than in milk (Table 9.6). Magnesium does not seem to be
significantly different in concentration between colostrum and milk (Table 9.6). Sulfur
content of colostrum is higher in colostrum than in milk (Table 9.6). Citrate is included
here as an anion often associated with the diffusible calcium component. Concentrations
of citrate decline from the colostrum phase to the milk phase (Holmes and Hartmann,
1993; Kent
et al.
, 1998 Konar
et al.
, 1971), consistent with the progression of lactogenesis
and the increase in lactose as the major osmole in milk (Holmes and Hartmann, 1993;
Peaker and Linzell, 1975).
Concentrations of microminerals in sow colostrum and milk are summarized in Table
9.6. Of particular note are copper, iron, iodine, manganese and zinc, each of which has
a higher concentration in colostrum than in milk. Most studies have found that dietary
level of iron does not affect iron concentration in mammary secretions (Pond and Jones,
1964; Pond
et al.
, 1965; Venn
et al.
1947; Veum
et al.
, 1965), while other studies have
observed an increased iron concentration in milk when sows are supplemented with iron
