In piglets, benzoic acid (BAc) has been shown to improve growth performance and N retention, and it is also capable to reduce pH levels in urine and emissions of ammonia and odour. BAc is approved in the European Union in concentrations up to 0.5%. BAc Na salts, used as food preservatives, has not been investigated till now as a feed additive in piglets. It is known that organic acids are capable to influence the absorption of minerals. Then, the objective of this study was to compare the effects of sodium-benzoate (NaB) with those of benzoic acid (BAc) on growth performance of piglets as well as nutrient digestibility, nitrogen and mineral balance, urinary pH, and the urinary excretion of BAc and hippuric acid (HAc). The study was conducted with 120 weaning piglets (6.5 kg body weight) [(German Landrace x German Edelschwein) x Pietrain], divided in four groups (15 replicates of two piglets each), which received (1) a basal diet (Control), or the basal diet supplemented with (2) 4 g NaB per kg (Group 4NaB), (3) 3.5 g BAc per kg (Group 3.5BAc) or (4) 5 g BAc per kg (Group 5BAc). Performance data were monitored over a 42-day period. Urine and faeces were collected from day 28–33 in metabolic cages with five piglets per treatment.
Piglets of Groups 3.5BAc and 5BAc had similarly a considerably improved average daily gain and feed intake (P < 0.05). Performance of Group 4NaB was not significantly different from the other groups. Compared to the Control, the nitrogen retention was only improved in Group 5BAc (P < 0.05); the other groups showed intermediate values. In the supplemented groups, most of the BAc was excreted as HAc in urine, but only Groups 3.5BAc and 5BAc had reduced urinary pH (P < 0.05). Daily intake and faecal and urinary excretion of P and Ca were not affected by the treatment. The molar excess of Na in Group 4NaBA was reflected by higher renal excretion of Na compared to the other groups (P < 0.05).
In conclusion, BAc is more effective than NaB in improving the performance of piglets. Variations found in ammonia, hippuric acid, pH and minerals seem likely that further unidentified factors could contribute to this phenomenon.
T Gräber, H Kluge, F Hirche, J Broz, GI Stangl. Effects of dietary benzoic acid and sodium-benzoate on performance, nitrogen and mineral balance and hippuric acid excretion of piglets. 2012. Archives of Animal Nutrition. 66(3):227-236. http://dx.doi.org/10.1080/1745039X.2012.676812