Two experiments were conducted to investigate the efficacy of benzoic acid on the growth performance of nursery and grower-finisher pigs. A randomized complete block design was used in both experiments with the initial body weight as the blocking factor. There were 3 treatments corresponding to 3 dietary levels of benzoic acid: 0, 0.3%, and 0.5%. In experiment 1, a total of 144 PIC L1050 barrows (initial body weight 7.1 ± 0.6 kg) were used with each treatment replicated 8 times. In experiment 2, a total of 288 PIC L1050 barrows (initial body weight 36.1 ± 3.6 kg) were used with each treatment replicated 16 times. There were 6 barrows in each replicate pen for both experiments. Experiments 1 and 2 lasted 28 and 70 days, respectively. In experiment 1, average daily gain (ADG) of all growth phases increased linearly (P < 0.05) with increasing supplementation of benzoic acid, which led to a linear improvement in average body weight on d 28 (P < 0.05). There was also an improvement in feed conversion ratio (FCR) of d 0 to 14 (linear effect: P < 0.05) and in average daily feed intake (ADFI) of d 14 to 28 and d 0 to 28 (linear effect: P < 0.01). In experiment 2, ADG during d 0 to 35 and d 35 to 70 and average body weight on d 35 improved linearly (P < 0.05) with increasing supplementation of benzoic acid. Average daily gain of d 0 to 70 and average body weight on d 70 increased significantly in a both linear and quadratic manner. There was a linear improvement in FCR in all growth phases (P < 0.05). In conclusion, the dietary inclusion of benzoic acid at the supplementation levels of 0.3% and 0.5% significantly improved the growth performance of nursery and grower-finisher pigs in the current study; the nursery pigs responded to the dietary supplementation of benzoic acid up to 0.5% linearly while the grower-finisher pigs achieved the optimal ADG at the calculated supplementation level of 0.36%.
Keywords: Average daily feed intake; Average daily gain; Benzoic acid; Feed conversion ratio; Grower-finisher pig; Nursery pig.