A total of 104 sows (1 to 6 parities) were evaluated over two reproductive cycles. During the gestation sows received one of four experimental diets: low P diet (LP-, 3.7 g P/kg feed), low P diet with phytase (LP+, containing 765 FTU/kg feed), medium P diet (4.5 g P/kg feed) and high P diet (6.0 g P/kg feed), the last representing the Swedish feeding recommendations for pregnant sows. The source of P in medium and high P diets was monocalcium phosphate. Gestation diets presented a relatively high phytase activity. During the lactations sows were fed the same diet. It was evaluated the farrowing performance of the sows, sow and piglet performance during lactation, and the mineral concentration in sows milk, and on blood serum of sows and piglets.
Low dietary levels of P, without or with phytase (LP- and LP+) presented a higher number of total born piglets at farrowing, being the mortality at birth the highest in LP- diet. Therefore no modifications in the number of live-born piglets were found between diets. No differences were found between experimental diets in terms of sow and piglet performance during the lactation. Mineral levels were only modified in milk samples, being the P level in milk higher in the medium P diet.
From the results it may be concluded that reducing by 25% the Swedish recommendations on P may not affect the performance of the sows. However, it must be taken into account that the experiment was done only over two parities and therefore long-period effects of a lowered P supply should be further studied. Moreover, it should be kept in mind that during the lactation sows received diets with a high supply of P, and that the experimental diets had a relatively high phytase activity.
Lyberg, K., Andersson, H.K., Simonsson, A., Linberg, J.E. (2007) Journal of Animal Physiology and Animal Nutrition, 91: 304-311