Effect of dietary sodium on digestibility of nutrients and performance in growing rabbits

The effects of a reduction in the sodium content from 2.6 to 1.6 g/kg DM in diets with similar electrolyte balance on fattening performances and ileal apparent digestibility of nutrients were investigated in early weaned rabbits. Two diets containing 17.9% DM of crude protein, with the same composition and only differing in sodium chloride content (0.5 and 0.2%) were given to rabbits weaned at 25 days to measure fattening performance (46 rabbits per diet), and apparent ileal digestibility (AID, 14 rabbits per diet) of DM, crude protein (CP) and amino acids (AA). Neither AID of DM nor AID of CP, which amounted 47.4 and 60.9% as average respectively, were affected by the dietary sodium content. The effect of a decrease in dietary sodium concentration on the AID differed among amino acids, as a reduction was observed for cystine (by 11%; P < 0.01), methionine, arginine, tyrosine and phenylalanine (by 4.9, 5.6, 7.4 and 10.3%; respectively P < 0.05), glutamic acid, leucine and isoleucine (by 4.1, 6.1 and 7.1%, respectively P < 0.1),,whereas no differences (P > 0.10) were detected for the other amino acids. A reduction of dietary sodium content did not affect daily weight gain, feed intake and feed efficiency (46.7 g/d, 76.7 g/d and 0.609 as average, respectively) neither during the first two weeks after weaning when the experimental diets were used, nor when the whole fattening period was regarded. The results of this experiment indicate that is possible to reduce the current dietary sodium recommendations for fattening rabbits to 1.6 g/kg DM during the first two weeks after weaning, without impairing either the fattening performances or the ileal digestibility of DM and CR In addition, this study indicate that the level of sodium in the diet affects the gut absorption of methionine and cystine and several non-essential AA.