Gastrointestinal changes during lactation are further altered by litter size in Wistar rats

Johnson, Michelle; Saffrey, Jill and Taylor, Victoria (2013). Gastrointestinal changes during lactation are further altered by litter size in Wistar rats. In: The Society for Reproduction and Fertility Annual Meeting 2013, 11-13 Jul 2013, Fitzwilliam College, University of Cambridge.



Food intake increases of up to 300% during lactation in rats have been documented, alongside hypertrophy in gastrointestinal (GI) tissues. This study further elucidates changes in dam GI-anatomy during lactation, and also examines the effects of varying litter sizes on dam GI changes for the first time. Detailed measurements were made of gut areas implicated in appetite regulation by gut-peptides including ghrelin, peptide-YY and glucagon-like peptide-1.

Nulliparous female Wistar rats were kept under a reverse-lighting schedule (lights-off 11.00-23.00 hr) and bred in-house, using the oestrous dance for accurate time-mating. Rats were mated for the defined time-points of days 4, 12 and 18 of pregnancy, and days 0, 5, 10 and 25 of lactation. Litters were standardised to 8 pups each by day-3 post-partum; pups remained with dams throughout. Additional groups of dams culled at day-25 of lactation (d25L) had their litters manipulated to 4 or 12 pups to determine effects of litter size on dam GI-anatomy. Dams were fasted from 08.00 hr on the day of dissection and gut samples obtained following culling after 12.00 hr. Multiple gut measurements were taken and standardised by relaxation of free-floating gut using nicardipine.

Both small (F(7,49)=20.5, P<0.001) and large (F(7,47)=11.1, P<0.001) intestine lengths were observed to peak late in lactation. Dams with small litters of 4 pups had significantly shorter small (F(2,17)=6.2, P=0.009) and large (F(2,17)=10, P=0.001) intestines than other d25L groups. Although dams with large litters of 12 pups had similar small intestine lengths to d25L controls with 8 pups, their duodenum circumference was significantly larger (F(2,17)=6.9, P=0.006). Dams whose litters died shortly after birth did not have any GI changes by day-25 post-partum compared with proestrus controls.

Lactation results in substantial changes to gut structure. Detailed measurements from this study have found these changes to be additionally influenced by increased or decreased litter size.

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