The effects of high levels of L-arginine on performance, morphology of small intestine and immune system organs of broilers during the growth period

The objective of the present study was to investigate the effects of using 24 days high dietary levels of L-arginine on growth, intestine morphology and immune system of female Ross broiler chicks. In this experiment, 192 day old chicks were fed with 4 dietary treatments, 4 replications and 12 observations in each replication in a completely randomized design. Dietary treatments included 100%, 153%, 168% and 183% of digestible arginine, based on the Ross catalogue recommendation, and were fed from day 1 to 24. On 10th and 24th days of experiment, chicks were weighed and feed consumption was recorded. At the end of experiment, three chicks per replication were selected randomly and were slaughtered in order to determine weight, length and histology of small intestine, and to measure immune system tissues’ weight. The results showed that high dietary levels of arginine had a significant increasing effect (P<0.05) on body weight, average daily weight gain, feed efficiency, thymus and spleen relative weight, and skin reaction to phytohemagglutinin P, relative weight and length of small intestine, and villous height and crypt depth of duodenum and jejunum; while it decreased (P<0.05) villous height/crypt depth ratio, goblet cell number, and epithelium thickness of duodenum and jejunum. According to the results of this study, consumption level of 168% digestible arginine, based on the Ross catalogue recommendation, had the best results on growth improvement of broiler chicks and it also improved weight, length and histology of small intestine, and immune characteristics. Therefore, it is advised to use 168% digestible arginine in broiler chicks’ feeding from day one to 24 in order to improve growth and viability.