Investigating the effects of bile salts on performance, carcass characteristics and blood parameters in broilers

Lipids (fat and oil) are the most concentrated sources of energy for animals, which are usually added to poultry diets to meet energy requirements for better performance (Abudabos 2014). However, there are problems with dietary lipid levels and digestibility in poultry, especially in young birds due to low bile secretion (Ravindran et al 2016). This physiological limitation of the poultry digestive system can be solved by using exogenous emulsifiers. Emulsifier can help increase the active level of lipids, stimulate the formation of micelles, and then increase the digestibility of dietary lipids and other nutrients in broilers (Siyal et al 2017). Upadhaya et al (2017) showed that 1, 3-diacylglycerol as an exogenous emulsifier can improve growth performance and increase nutrient digestibility in broilers. In addition, a large number of studies have also shown that exogenous emulsifier can improve meat quality and regulate fat metabolism of broilers (Zhao and Kim 2017). Bile acids are the main pathway of cholesterol catabolism in mammals. Cholesterol is converted into bile acids by changes in ring structure, oxidation and side chain shortening (Li and Chiang 2019). The chemistry of bile acids is complex due to the large variety of chemical structures in natural compounds such as cholic acid, kenodeoxycholic acid, deoxycholic acid, and lithocholic acid. Bile acids of birds are mainly composed of kenodeoxycholic acid and cholic acid (Hoffman and Hagee 2018). Recently, bile acids have been considered as an emulsifier to increase digestibility (Upadhaya et al 2019) and improve the performance of broiler chickens (Parsai et al 2007). Supplementation of bile acids in the diet of broilers significantly improves fat digestibility (Lammasak et al 2019). The effect of bile salts on performance, carcass characteristics and blood parameters of broiler chickens were investaigeted.

Three hundered one-day-old broilers (Ross 308) were divided into 5 treatments and 6 replications with 10 birds in each replication. Five experimental treatments included the control diet (corn soybean based diet), emulsifier (added to control diet) and three levels of 0.05%, 0.1% and 0.2% of poultry bile salts (added to control diet). All the dietary treatment were fed to the birds from day one to day 42 of age. The experiment lasted for 42 days and were performed during the starter (1-10 days), grower (11-24 days) and finisher (25-42 days). Performnce indices were measured during the difeferned periods and carcass characteristics and blood parameters were determined on day 42 of age. The data obtained from the present study were statistically analyzed using SAS statistical software and GLM procedure. To compare the means, Tukey's test was used.

The results showed that consumption of different levels of bile salts had no significant effect on feed consumption (P<0.05). However, consumption of 0.1% bile salts improved body weight gain and feed conversion ratio during the starter period (P<0.05). Previous studies have shown that the consumption of 0.05% commercial emulsifier can improve the growth performance of broiler chickens (Wang et al 2016). In addition, in the present study, 0.05% poultry bile acids supplement significantly improved daily weight gain and feed conversion ratio during 1 to 10 days, which is consistent with the results of Alzawqari et al (2011) regarding bile. These researchers observed improvement in daily weight gain with 0.05% bovine bile acid supplementation. Arshad et al (2020) reported that feed intake was not affected by bile acid supplementation in the initial, growth, finisher and overall periods. In the newly hatched chick, the ability to digest and absorb dietary fat is poor as a result of limited bile secretion (Tancharonrat et al 2013). For this reason, artificial bile acid and bile salts have shown the greatest effect in young broiler chickens to improve fat digestion, and the improvement in the performance of birds receiving bile in the initial period of recent research was for this reason. The results of Maisonnier et al (2016) showed that 0.5% of pig bile acids can increase fat digestibility and body weight in broilers. These results may imply that the supplementation of bile acids in diets improved the growth performance of broiler chickens by increasing the solubility and digestibility of dietary fat and fat-soluble nutrients in this study. Abdominal fat decreased significantly by consumption of 0.1% bile salts (P<0.05). Subcutaneous fat and abdominal fat are considered as the main factors influencing the performance of poultry carcasses (Tůmová and Teimouri 2010). In agreement with our results, many researchers have pointed out the positive effects of emulsifier on reducing fat status and improving carcass quality in broiler chickens (Zhao and Kim 2017). Blood triglyceride concentration was decreased in 0.05% bile salts fed birds wherease cholesterol and uric acid concentrations decreased in the birds fed emulsifier (P<0.05). Triglyceride, cholesterol, HDL and LDL blood are key indicators of lipid metabolism balance (Helkin et al 2017). In agreement with our results, researchers reported that bile acids increased hepatic AST and ALT activity in broilers and reduced serum triglyceride levels, which could be due to the participation of these enzymes in the lipogenesis process (Ge et al 2019). In addition, Siyal et al (2017) showed that feed emulsifier can reduce serum triglyceride concentration in broilers. It can also be stated that bile acids may enhance fat catabolism and inhibit fat synthesis by regulating the expression of genes related to lipid metabolism which may play a pivotal role in improving serum lipid profile and reducing fat deposition in broiler chickens (Ge et al 2019).

Totally, it was found that dietary bile salts supplementation improves the performance of, carcass characteristics and blood lipids in broiler chcikens.