Reproduction performances and conditions of group-housed non ...

- Paper I -
Gilts
Moderate energy supply (29.4 MJ ME day -1 ) compared to low energy supply (17.6 MJ ME
day -1 ) both from mating until 30/35 days after mating and from mating until ten days after
mating increased the embryonic mortality and reduced the number of embryos in gilts
(Dyck & Strain, 1983). Some authors argue that a lower embryo survival in gilts fed moderate
energy intake could be due to the ovulation rate being increased and hence, the embryo
mortality as a result of the moderate energy intake immediately after mating (Toplis et
al., 1983). However, in the present study, the ovulation rate did not differ between the treatments.
Therefore, this could probably not be the explanation. Jindal et al. (1996) also found
that moderate energy supply in gilts the first 15 days after mating resulted in a significant
lower embryo survival and a non-significant lower number of viable embryos at day 25-30
compared to low energy supply. These authors also found an inverse relationship between
plane of nutrition and circulating progesterone concentrations. Furthermore they observed
that the group of gilts with the greatest average plasma progesterone concentration had the
greatest embryonal survival. Similarly, Pharazyn et al. (1991) observed that overall plasma
progesterone concentrations on day three after oestrus were positively related to embryo
survival. Perhaps increases in energy intake leading to rapid gains will result in reduced
embryo survival because of an increase in metabolic clearance of progesterone as a
consequence of increased hepatic blood flow (Einarsson & Rojkittikhun, 1993)
Reduced levels of energy from day three to day 15 of gestation did not have an effect on the
number of embryos in the uterus at day 28 (Pharazyn et al., 1991). Similarly, Jindal et al.
(1996) found that low energy supply from day three after mating until day 15 does not effect
embryo survival. Therefore, these authors suggest that a reduction in feed intake has a
positive effect but only if it occurs in the first days after onset of oestrus. This is in agreement
with other studies beginning treatment three days after mating and finding no effect
(Liao & Veum, 1994) or even a negative effect (Liao & Veum, 1994) of low compared to
moderate energy supply.
In the light of the above-mentioned results, it seems that a low feed intake (17.6/22.8 MJ
ME day -1 ) the first days after mating has a positive effect on reproduction performance
compared to moderate feed intake (29.4/31.3 MJ ME day -1 ). However, in other studies with
treatment beginning immediately after mating, no positive effect of low energy supply
(15.7/21.4 MJ ME day -1 ) was found compared to moderate energy supply (31.4/34.6 MJ
ME day -1 ) on embryo survival (Dyck, 1991; Cassar & King, 1992) or number of foetuses
(Dyck, 1991). So, the results are inconsistent. Foxcroft (1997) argues that the inconsistency
in much of the literature regarding effect of energy intake on embryo survival could be due
to differences in number of animals used and level of embryo survival in the control group.
32