Influence of adding 0.5 or 1.0% of benzoic acid on growth performance and urinary parameters of fattening pigs

Abstract

An experiment was conducted to examine the effects of adding benzoic acid to diets on the pH, ammonia and urea of the urine and performance of growing-finishing pigs. The study was carried out with 60 crossbred gilts (32 to 112 kg body weight) distributed among three treatments with each 20 animals (4 pens containing each 5 animals) fed diets differing in addition of benzoic acid: (1) negative control (no addition), (2) 0.5 % benzoic acid, and (3) 1.0% benzoic acid. In the growing period (32 to 70 kg body weight), addition of benzoic acid increased daily weight gain (p<0.05) and daily feed intake. Addition of 1.0% dietary benzoic acid improved the feed conversion rate about 2% points and lowered the duration of the fattening period by about 3.4 days (p<0.05) compared to the control group. In the finisher period (70 to 112 kg body weight), 0.5% benzoic acid showed the highest daily weight gain (893 g) and the shortest duration of fattening (46.4 days). Increasing additions of benzoic acid reduced the mean urinary pH significantly from 7.96 (control) over 7.67 (0.5% benzoic acid) to 7.25 (1.0% benzoic acid). Urinary ammonia, however, was significantly increased by rising additions of benzoic acid from 0.9 up to 1.9 mmol per mmol of creatinine. No significant differences were found between the treatments regarding urinary urea content. In conclusion, benzoic acid improved growth performance and lowered the pH in the urine which may contribute to reduction of ammonia emissions from excrements.