The effect of different levels of diet total volatile nitrogen on performance, carcass characteristics and meat total volatile nitrogen in broiler chickens

This study was conducted to determine the effect of different levels of diet total volatile nitrogen (TVN) on performance, carcass characteristics and meat TVN in broiler chickens. A total of 400 one-day-old Ross 308 broiler chicks was used in this study. On the first day, male and female chicks were separated by feather sexing. In the first week, all chicks were reared together and fed with a basal diet without urea. At the beginning of the second week, the male and female chicks were weighed so that the average body weight of chicks was approximately equal in each cage. Then the male and female chicks were allocated to 25 floor pens in a completely randomized design with five treatments, five replicates and 16 chicks in each replicate (eight males and eight females) throughout the experimental period, which lasted for 42 days. Dietary treatments consisted of zero (control), 0.5, 1, 1.5 and 2 % of urea in the diets. Before starting the experiment, the TVN levels in all diets were measured after adding different levels of urea, and TVN levels were 13.30, 14.95, 17.26, 23.26 and 27.47 mg 100 g^&minus;1 and 16.66, 15.02, 17.81, 24.66 and 26.25 mg 100 g^&minus;1 in starter and grower diets, respectively. Feed intake (FI), body weight gain (BWG) and the feed conversion ratio (FCR) were measured. Carcass characteristics as well as TVN in breast meat, thigh meat and the whole carcass and in left tibia and toe ash were measured. The results showed that FI levels were significantly different between the groups at different weeks except for the second week (<i>P</i> &lt; 0.05). The BWG significantly differed among treatments (<i>P</i> &lt; 0.05). In the second and sixth weeks, FCR was affected by increasing TVN in the diet (<i>P</i> &lt; 0.05). Increasing TVN in broiler diets had a significant effect on the carcass characteristics (<i>P</i> &lt; 0.05). Increasing TVN to more than 15 mg 100 g^&minus;1 linearly reduced left tibia and toe ash (<i>P</i> &lt; 0.05). In addition, increasing TVN in the broiler diets affected the TVN of breast meat, thigh meat and the whole carcass of broilers (<i>P</i> &lt; 0.05). These results suggest that increasing diet TVN to more than 15 mg 100 g^&minus;1 reduces performance traits, carcass characteristics, and left tibia and toe ash and increases the TVN amount of breast meat, thigh meat and the whole carcass.