Composition of sow colostrum and milk - The Gestating and Lactating Sow - page 190

9.6 Lipids

The fat content of mammary secretions is considered as the most variable of the
components. This is particularly apparent in considering the effects of stage of lactation,
diet and other factors on fat content of colostrum and milk.

9.6.1 Stage of lactation

Averaging the fat, or lipid concentrations of mammary secretions that have been reported
in the various studies listed in Table 9.1 gives a profile of that component through
lactation (Table 9.2 and 9.3). Among the studies summarized in Table 9.2, fat percentage
of colostrum at parturition ranges from 4.9 to 10.9%, with an average of 6.4%. Average fat
content remains at the 5.9 to 6.4% level until 18 h postpartum and then increases to about
8% by 24 h. A transient peak of fat content is seen in most studies, occurring typically
between 24 h and day 3 postpartum, although some studies report continued elevated
fat percentages even at day 7. Fat concentrations as high as 13% have been reported at
day 3 (Csapo et al. , 1996). This elevation of fat in mammary secretions coincides with
a phase of transient milk identified as occurring in the period between the colostrum
phase (parturition to 24 h postpartum) and about day 4 of lactation (Theil et al. , 2014).
Average fat percentage is relatively stable at 7.0 to 7.6% from day 7 through 6 to 8 weeks
of lactation (Table 9.3), a period when mature milk is present (Theil et al. , 2014).

Average concentrations of the major fatty acids in sow milk are indicated in Table 9.4.
Concentrations of fatty acids in sow colostrum have been reported by Csapo et al. (1996).
When comparing fatty acid proportions in colostrum (at parturition) and day 20 of
lactation, the increases in proportions of C16:0, C16:1 and C18:3 during lactation are
partially offset by decreases in proportions of C18:1 and C18:2. Sow mammary secretions
contain only trace amounts of short and medium chain fatty acids up to C12:0 (Csapo et
al. , 1996; Hartog et al. , 1987; Lauridsen and Danielsen, 2004). Csapo et al. (1996) found
that less than 0.25% of total fatty acids were composed of the short and medium chain
fatty acids C4:0 through C12:0. Others have reported proportions of C10:0 and C12:0 of
up to 0.36 and 0.49% of total fatty acids, respectively (Lauridsen and Danielsen, 2004).

9.6.2 Diet

The primary impact of diet on colostrum or milk composition occurs through an effect
on milk fat content. Gestation diets might be expected to impact colostrum composition
and perhaps have a carry-over effect into lactation. On the other hand, lactation diets
might be expected to impact colostrum composition only if feeding of the diet was
initiated prepartum. Lactation diets would be expected to impact sow milk composition.
Some studies have found that supplemental dietary fat increases milk fat percentage in
sow mammary secretions (Boyd et al. , 1982; Pettigrew, 1981; Shurson and Irvin, 1992;
Shurson et al. , 1986), while other studies have not found a significant effect of feeding
supplemental dietary fat during late gestation and lactation on the percentage of milk
fat (De Quelen et al. , 2010, 2013; Farmer et al. , 2010; Jackson et al. , 1995; Lauridsen and
Danielsen, 2004; Leonard et al. , 2010; Miller et al. , 1971; Schieck et al. , 2010; Seerley et