Agriculture Reference
In-Depth Information
80
70
60
50
40
11-14
14-17
17-20
20-23
23-26
Backfat depth at
rst breeding (mm)
Figure 1.3. Relationship between backfat depth at first breeding and total piglets born in the sow's lifetime
(Bussières, 2013).
not clear how this recommendation was drawn from data suggesting that a range of 20
to 26 mm was superior in terms of prolificacy.
1.3.4
Body protein
In recent years it was suggested that body protein stores and metabolism may be more
important than body fat for lifetime sow productivity. Jagger
et al.
(2008) stated that
gilt appear to have an innate need to reach a certain protein mass to achieve optimum
reproductive performance. With respect to body protein reserves of sows, Clowes
et al.
(2003b) reported that if the young sow mobilizes 9 to 12% of her protein stores during
lactation, the growth of her litter after the 20
th
day of lactation is decreased. Additionally,
the authors suggested that body protein mass and (or) the rate of protein mobilization
reach thresholds that are necessary to provide amino acid precursors for the biosynthesis
of proteins associated with ovarian functions. Consequently, parity-two conception rate
and litter size may decrease if those thresholds are not reached.
Most of the support for the importance of greater body protein was an outcome of studies
showing a relationship between body weight and lifetime born and sow longevity (The
British Pig Executive, 2010a; Williams
et al.
, 2005). Body weight is interpreted as an
effect of protein mass. Schenkel
et al.
(2010) studied the effect of body tissue mobilization
during parity one on parity two reproductive performance. Body protein mass estimates
were based on body weight and backfat depth. The percentages of body fat and body
protein were estimated according to the equations of Whittemore and Yang (1989). A
reduction in parity-two litter size was associated with the following thresholds of bodily
losses in parity-one lactation: >10% body weight, >10% body protein, or >20% body fat.
Yet the authors also stated that absolute amounts of weight, body protein and body fat at
parity-one parturition were important because sows of greater body weights had more
piglets born in parity two than lighter sows at parity-one parturition, regardless of the
percentage of body weight or body protein loss.
Most fascinating about the results of Schenkel
et al.
(2010) is that most of parity-one
females (97%) weighed more than 135 kg at breeding and more than 180 kg at parity-one