Performance, and thyroid gland, liver and kidney functions in broilers fed diets containing expeller-extracted canola meal

Information on the effect of including expeller-extracted canola meal (EECM) in broiler diets on performance, and thyroid gland, liver and kidney functions and anaemia is limited. Thus, a study was conducted to determine the effect of including EECM in diets for broilers on performance; thyroid gland, liver and kidney sizes; and haemoglobin content in blood and haematocrit. Two hundred one-day-old male broiler chicks were divided into 40 groups of 5 birds balanced for body weight and fed 5 diets in a completely randomised design (8 groups per diet) from day 1 to day 21 of age. The diets were a complete corn-soybean meal-based basal diet with 0, 10, 20, 30 or 40% of EECM. The diets were formulated to be the same in metabolizable energy, crude protein, calcium, non-phytate phosphorus, and standardized ileal digestible methionine, lysine and threonine contents. The EECM contained (% of dry matter) 37.8% crude protein, 0.74% methionine, 2.14% lysine, 1.62% threonine, 1.61% valine, 1.23% isoleucine, 2.57% leucine, 1.41% phenylalanine, 2.12% arginine, 0.97% histidine and 8.03 μmol/g of glucosinolates. An increase in dietary level of EECM from 0 to 40% resulted in a linear decrease in feed intake (P < 0.001) by 4.8 g per 21-day period for each 1% increase in EECM and body weight gain (P < 0.001) by 6.0 g per 21-day period for each 1% increase in EECM. An increase in dietary level of EECM also resulted in a linear depression in feed conversion ratio (P < 0.001) by 0.004 g/g per 1% of EECM inclusion. However, an increase in dietary level of EECM from 0 to 40% resulted in a linear increase (P < 0.001) in the liver weight and a quadratic increase in kidney weight relative to live body weight. An increase in dietary level of EECM also tended to linearly increase the heart (P = 0.069). There was no effect of dietary treatment on thyroid gland size relative to live body weight, and on the blood haemoglobin content, and haematocrit. In conclusion, an increase in dietary level of EECM resulted in reduced growth performance and may interfere with liver and kidney functions likely due to increased dietary concentration of glucosinolates. Thus, the amount of EECM included in broiler diets should be based on the desired growth performance and the cost of the EECM.