Introduction: In the poultry industry, feed possess the largest share of production costs, with soybean meal utilizing as the primary protein source. Given that a significant portion of this feedstuff is imported and subject to price fluctuations, identifying native alternatives is essential. Camelina (Camelina sativa), due to its low water requirements, high resistance, and adaptability to low-fertility soils, is considered as a suitable candidate for native protein meal production. Camelina meal (CM) is rich in protein, essential fatty acids, and balanced amino acids, making it a potential substitute for soybean meal. However, the presence of anti-nutritional compounds such as high fiber and non-starch polysaccharides (NSPs) limits its inclusion in poultry diets. These compounds increase gastrointestinal countian viscosity and reduce nutrient digestion and absorption ability. The addition of exogenous enzymes such as xylanase, β-glucanase, pectinase, and protease can mitigate the adverse effects of NSPs and enhance growth performance and poultry health. Accordingly, the current study was designed to evaluate the feasibility of using CM as an alternative protein source with and without multi-enzyme (xylanase, beta-glucanase, cellulase, pectinase, protease, mannanase) supplementation in the finisher diet of broiler chickens.
Materials and Methods: A total of 500, 26-day broiler chickens mixed sex were allocated in a completely randomized design (CRD) with a 5×2 factorial arrangement, ten experimental treatments combining five levels of CM (0, 6, 12, 18, and 24%) and two levels of multi-enzyme supplementation (0 and 50 mg/kg). The CM used in this study, obtained from the Agricultural and Natural Resources Research and Education Center of Fars Province, contained 95.12% dry matter, 4671 kcal/kg gross energy, 37% crude protein, 6.3% ether extract, 11% crude fiber, and 7.01% ash dray mater basis. Birds were fed experimental diets based on corn-soybean meal, formulated using UFFDA software, from 26 to 46 days of age. During this period, various parameters were precisely evaluated, including growth performance indices (live body weight, weight gain, feed intake, and feed conversion ratio), quantitative carcass traits, small intestinal histomorphology indices (villus height and width, crypt depth, and muscular thickness), bone quality indices (ash percentage, calcium and phosphorus content, and bone characteristic), humoral immune responses measured by antibody titers against sheep red blood cells (SRBC), and serum metabolite levels (lipid profile, liver functional enzymes, and thyroid hormones). All collected data were statistically analyzed using SAS software with General Linear Model (GLM) procedure.
Results and Discussion: The results showed that with increasing the level of CM in the diet, abdominal fat decreased (P<0.05), which could be due to the high content of polyunsaturated fatty acids (PUFA) in Camelina oil and its role in inhibiting lipid synthesis. Also, increasing the level of CM in the diet increased the relative weight of the small intestine (P<0.05). This could be due to changes in physicochemical conditions and increased mechanical activities of the intestine in the presence of non-starch polysaccharides. On the other hand, bone quality indices showed a significant decrease in ash and calcium content of the femur with increasing the level of CM (P<0.05), which indicates that the phytic acid in this meal can cause impaired mineral absorption. Also, the pH of the small intestinal contents and the strength of the tibia changed as a quadratic equation (P<0.05); decreasing the pH of the intestinal contents increases mineral absorption and improves bone strength. The immune response against sheep red blood cell injection also decreased with increasing CM in the diet (P<0.05). The reduced immune response in birds may be attributed to its anti-nutritional components such as glucosinolates and tannins. Multi-enzyme supplementation improved feed conversion ratio (P<0.05), which may be due to the degradation of non-starch polysaccharides, reduced viscosity of digesta, and increased nutrient digestion and absorption. Multi-enzyme supplementation also increased triglyceride levels and reduced liver enzyme ALT and thyroid hormone T3 (P<0.05), indicating improved energy status and reduced metabolic stress on the liver. Other studied parameters were not affected by the main effects of CM level, multi-enzyme addition, and interactions between them.
Conclusion: The current study results showed that replacing CM in the finisher diet of broiler chickens (Arian strain) up to 24%; 1) had no adverse effect on growth performance, 2) significantly reduced abdominal fat, 3) adding a multi enzyme (xylanase, beta-glucanase, cellulase, pectinase, protease, mannanase) improved feed conversion ratio, 4) however, by increasing CM levels in the finisher diet due to the presence of anti-nutritional compounds, negative effects were observed in bone quality and immune response against SRBC, therefore, the use of CM in the broiler chickens diet requires management of its side effects on bird health.