Agriculture Reference
In-Depth Information
litter suckles concomitantly. Even though this technique directly quantifies milk yield,
it can underestimate it because some piglets urinate and defecate between the two
weighings and this must be accounted for with estimates of urine and/or feces loss. In
addition, handling the litter twice each hour disturbs the sow and likely reduces milk
yield. It has been reported that milk yield measured by the weigh-suckle-weigh technique
underestimates milk yield quantified by the DO dilution technique by approximately 20%
(Hansen
et al.
, 2012b).
The DO dilution technique may be regarded as the golden method to measure milk intake
of piglets and milk yield of sows due to its high accuracy (Theil
et al.
, 2007). Yet, its major
drawbacks are the exuberant cost and the fact that it is labour intensive. The technique
is more suitable for quantifying milk than colostrum intake, because the measurement
interval can then be extended to 3 to 4 days, which increases the precision. The technique
is described above (How to measure colostrum yield). The costs of using the technique
can be reduced considerably by using only three piglets per litter to quantify milk intake,
as long as weight gains of all littermates are known (Theil
et al.,
2002).
The third method is a prediction of milk intake based on live weight gain of either
individual piglets or the whole litter, or alternatively, weight gain or weight at weaning
can be used as indicators of milk production without attempts to calculate the actual
production level. If milk yield is calculated from piglet or litter gain, it is important
to note that the efficiencies of converting milk into piglet weight gain increases with
advancing lactation. In a study by Theil
et al.
(2002), it was found that the amount of
milk required per gram of piglet weight gain increased from 3.78 g/g milk at day 3 to
4.58 g/g milk at day 10, and 4.89 g/g milk at day 17. The study also reported a curvilinear
relationship between milk intake and live weight gain of piglets, which reflects that at
low milk intake a proportionally higher amount of milk ingested is used to maintain live
weight, whereas at high milk intake more body fat is retained, which is associated with
low live weight gain (Noblet and Etienne, 1987).
Recently, a prediction model to calculate the lactation curve for sows was developed based
on a meta-analysis of sow experiments carried out since 1980 (Hansen
et al.
, 2012b). he
required inputs to the model are litter size and litter weight gain (kg/d). Based on these
production traits, the developed framework calculates the actual milk yield of a given
sow from days 3 to 30 of lactation. The model takes into account published data on
sow milk yield during the last 30 years where milk yield was measured at least at two
different stages of lactation, and it also takes into account that the weigh-suckle-weigh
method underestimates actual milk yield by 20%. The model is freely available and can
be downloaded as a spreadsheet.
8.4.4
Factors affecting milk yield
Genetics and parity
It is known that sow breed affects milk yield (Grun
et al.
, 1993; Farmer
et al.
, 2001).
Chinese-derived sows produce more milk than sows from typical European breeds (i.e.
