Fetal programming is a phenomenon by which a significant or constant stimulus in the sow's uterus establishes a permanent response in the fetus that impacts physiologic function later in life.

It has been reported that pregnancy rate was 15% higher for gilts kept in individual stalls compared with those kept in groups. However, blood serum concentrations of cortisol, a classical “stress” hormone, tended to be greater in gilts housed in stalls.

The working hypothesis is that if there is indeed a difference between accommodations (individual stalls vs. group pens) in terms of stress and well-being of sows, then fetal programming may affect the growth and reproductive performance of their offspring.

The objective of this experiment was to determine the effects of sow gestation accommodations on various characteristics of female offspring, including growth and age at puberty.

The experiment included Yorkshire × Landrace gilts farrowed by females that were kept in one of three types of gestation accommodations:

Treatment #1 — Individual stalls throughout gestation;

Treatment #2 — Group pens throughout gestation (5 to 6 females/pen); or

Treatment #3 — Individual stalls for 30 days, post-mating, then group pens for the remainder of gestation.

At weaning, gilts farrowed exclusively by females exposed to one of the three treatments were placed in nursery pens containing three gilts each.

Average daily gain, feed consumption and feed conversion efficiency were recorded during the five-week nursery trial and the subsequent grow-finish period. Gilts were then checked for estrus, once daily, in the presence of a boar to determine age at puberty.

During the nursery phase, there was no effect of treatment on growth rate, feed consumption or feed conversion efficiency.

Overall, average daily gain during the grow-finish period was not affected by treatment (Table 1). However, the pattern of pig growth was affected by gestation accommodation. Figure 1 shows a significant accommodation-by-time interaction, with gilts farrowed by females housed in stalls throughout gestation weighing more during the last four weeks of the grow-finish period.

Housing type did not affect feed consumption of the offspring. However, feed conversion efficiency was significantly enhanced in gilts farrowed by females in Treatments 1 and 3 compared to those farrowed by females in Treatment 2.

Gilts farrowed by females kept in stalls throughout gestation tended to have less backfat than those farrowed by females kept in group pens throughout gestation. Gilts from females in Treatment 2 had an intermediate value that was not different from the other two treatments.

The average age at puberty did not differ among groups; however, fewer gilts farrowed by Treatment 1 females reached puberty by 165 days of age compared with the other two groups (Figure 2).

The implications of this study are:

  • Keeping pregnant females in individual stalls results in certain production advantages, but this method of sow accommodation remains as one of the most contentious welfare issues facing pork producers.

  • Results of this project suggest that the type of accommodation in which pregnant sows are kept affects the performance of gilt offspring.

  • During the late-finishing phase, body weights were greater for gilts farrowed by sows gestated in stalls compared with the other groups. Moreover, gilts farrowed by females kept in stalls throughout pregnancy were more feed efficient and leaner at market weight.

  • Gilts farrowed by females that gestated in group pens tended to reach puberty earlier than gilts farrowed by sows kept in stalls.

Researchers: Mark J. Estienne and Allen F. Harper, Virginia Tech, Blacksburg, VA; contact Estienne by e-mail: mestienn@vt.edu.