Diverse effects of linseed oil and fish oil in diets for sows on reproductive performance and pre-weaning growth of piglets

Perinatal mortality of piglets means a serious loss for the pig industry. Therefore, finding strategies to decrease stillbirths and increase piglet vitality is crucial. Supplementing the gestation and lactation diets with n−3 polyunsaturated fatty acids (PUFA), and especially docosahexaenoic acid (DHA), can be beneficial, as these PUFA are essential for the development of the foetus. Docosahexaenoic acid can be directly supplied from the maternal diet through addition of fish oil, or it may result from the conversion of dietary precursors such as alpha-linolenic acid, e.g. by addition of linseed oil. Until now, studies assessing the effects of n−3 PUFA on sow reproduction give equivocal results. Therefore, this study aimed to examine the effects of linseed oil and fish oil in the maternal diet of a large number of sows (734 sows in total) on their reproductive performance in the current and subsequent gestation. Furthermore, the effect of diet on the farrowing process, piglet weight and vitality was analysed. From day 45 of gestation and during lactation, sows were fed a palm oil diet or one of the six n−3 PUFA diets, each containing different concentrations (0.5%, 1% or 2%) of linseed oil, fish oil or their combination. Sows fed linseed oil had 0.9 more live born piglets (P=0.02) and 0.5 more weaned piglets (P=0.02) compared to fish oil fed sows. In the subsequent gestation, linseed oil fed sows had 1.3 and 1.5 more live born piglets compared to sows fed fish oil (P=0.006) or palm oil (P<0.001), respectively. No dietary effects were observed on piglet birth weight and litter weight, but linseed oil supplementation resulted in a higher piglet weight and litter weight at 5 days of age, compared to piglets from sows fed fish oil (P=0.04 and P=0.02, respectively) or palm oil (P=0.02 and P=0.002, respectively). Adding n−3 PUFA to the maternal diet had no effect on piglet vitality, but it increased the duration of farrowing (P=0.05).