Agriculture Reference
In-Depth Information
made concerning the environment in the pen, it can be suggested that sows develop some
form of 'subgroup identity' as is described by other authors (see also Moore
et al.
, 1993).
Competition over access to feed, particularly in sequential feeding systems such as
Electronic Sow Feeding, is regulated in so-called feeding orders. These are closely related
to the dominance hierarchy in that the most dominant animals will generally be the
first to feed following the feeder start (Csermely, 1989; Hunter
et al.
, 1988). Recently,
Kirchner
et al.
(2012) reported on a study in which they supported the development of a
feeding order by training sows to respond to an acoustic signal (Call Feeding). In Normal
Feeding, more sows were involved in agonistic interactions compared with Call Feeding
(83.1 vs. 61.5%). The number of severe lesions was greater at the head and the flank but
not at the shoulders and the hindquarter in Normal Feeding compared with Call Feeding.
Kirchner
et al.
(2012) suggested that signalling the feeding time individually increases the
predictability for access to the feeding station, thus reducing competition between sows.
The level of sow aggression is influenced by aspects related to: (1) the management of the
animals; (2) the feeding system; (3) the design of the pen and building; and (4) the skills
and attitude of the stock person. For the latter aspect we refer to Chapter 12 (Prunier and
Tallet, 2015). The other three will be addressed in the following paragraphs.
3.2.2
Management of groups
Timing of mixing
It has been argued that stress negatively affects embryo survival in particular during early
pregnancy, around the period of attachment of the embryos to the uterine wall (d 11-16),
and the period shortly thereafter. In this period, the so-called 'maternal recognition of
pregnancy' takes place with many associated hormonal changes. Whether this is relevant
to the timing of introducing sows to a group has received much debate.
Dutch work in the late eighties suggested that grouping of sows during the first week
of pregnancy resulted in 20% return rate whereas grouping during the fourth week of
pregnancy led to a significantly lower return rate of 10% (Bokma, 1990). In this study,
sows were fed with an electronic sow feeder and kept in dynamic groups of 40 sows. Every
week, 5 to 6 new sows were introduced in the group, which of course may have contributed
to the poor results. Kirkwood and Zanella (2005) suggested that the critical period for
grouping may be more limited: they found in floor-fed groups of 15 sows that regrouping
soon after insemination (d 2) gave the highest farrowing rate and regrouping around d 14
gave the lowest farrowing rate, but litter size (of those that conceived to service) was not
significantly affected by the time at grouping. Van der Mheen
et al.
(2003), who looked at
375 sows during 800 pregnancies, also found the lowest level of regular returns to estrus
and the highest litter size in sows that were grouped immediately after insemination. Knox
et al.
(2014) appeared to find the opposite. In their study, they compared mixing of sows on
d 3 to 7 (D3), d 13-17 (D14), after d 35 (D35), and stall housing throughout. They observed
the poorest reproductive results when sows were mixed 3 to 7 d after breeding. There were
few differences between the D14 and D35 treatments in reproduction or welfare, but D14
