Effect of controlled alterations in maternal dietary retinol on foetal and neonatal retinol status and pregnancy outcome in pigs

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The objective of this experiment was to examine the effects of feeding a vitamin A deficient diet (VAF) to pigs at different times on day 100 of foetal and days 0, 1 and 2 of neonatal development. Three treatments included a control ( n = 12), VAF for 100 days before mating and during the first month of pregnancy ( n = 13; VAF–control), and VAF during the oestrous cycle before mating and throughout pregnancy ( n = 13; control–VAF). On day 100 of pregnancy, maternal liver and plasma retinol concentrations were reduced in both groups of gilts fed a vitamin A free diet compared to controls ( P < 0.001 and P < 0.01, respectively). Day 100 foetal liver retinol concentrations were not affected by dietary treatment, whereas foetal plasma concentrations were higher in foetuses carried by gilts fed the VAF–control diet ( P < 0.05). Piglets born to mothers fed the control–VAF, but not the VAF–control diet had consistently lower hepatic and plasma liver retinol concentrations ( P < 0.05). Moderate reductions in maternal vitamin A at either stage of pregnancy did not affect pregnancy rate, litter size, progesterone secretion or the allometric relationships between foetal or neonatal organ and total body size. Reduced vitamin A during conception and early pregnancy, but not during later pregnancy, was associated with increased within-litter uniformity in birth weight ( P < 0.05) and a tendency for fewer low birth weight piglets, but this needs to be confirmed in a greater number of sows. The mechanism underlying this effect is not known, but appears to not involve an alteration in progesterone production.