Effect of Heat Processing on Nutrient Digestibility and Metabolizable Energy of Canola Seed in Broiler Chickens

During the past decades, rapeseed production, including canola varieties, has surpassed peanut, sunflower, and even cottonseed in production, and ranks second among oilseed crops worldwide. Due to its drought endurance, canola may be the preferable grain for cultivation in several locations of Iran. Canola seed (CS) is an economic feed ingredient containing well-balanced protein (19 to 22%) and a high oil content, up to 45% in some cases. Apart from the oil content of CS, its concentration of dietary fiber, glucosinolates, and tannins are of concern. Canola has less glucosinolates and erucic acid than rapeseed. It, resulting in a higher level of vital nutrients and higher nutrient density. The nutrient composition and presence of anti-nutritional factors in CS may also affect its quality and feeding value for poultry. However, the presence of some glucosinolates, erucic acid, and other undesirable compounds such as phytates, polyphenols, and soluble non-starch polysaccharides (NSPs) may reduce nutrient digestibility and performance of the chickens. Heat process affects the rate of protein denaturation, starch gelatinization, digestive enzymes accessibility, bacterial counts and toxin degradation of feed. On the other hand, starch gelatinization by heat processing may increase amylase effects to break the chains of amylose and amylopectin, which in turn increases the digestibility of less digestible carbohydrates, improves metabolizable energy and digestibility of amino acids in beans, soybeans, peas and canola. Some concerns have been raised about the inclusion levels of CS in broiler diets. This experiment was carried out to investigate the effect of processing method on apparent metabolizable energy (AME), apparent metabolizable energy corrected for nitrogen (AMEn), apparent dry matter digestibility (ADMD), and apparent nutrients digestibility (and) of CS (Nafis variety) in broiler chickens.
This study was designed to determine the nutrient digestibility and, AMEn value of crud and heat processed CS. The CS used in this research was of the Nafis variety, which was sourced from the Astan Quds Razavi farm, Mashhad, Iran. The obtained CS sample was divided to three equal subsamples. One part was unprocessed, second part was micronized; one hour before processing CS was moistened by 20% of the weight, and then placed in a single layer on a vibrating conveyor belt under the infrared emission source at a speed of 6.25 cm/s until the surface temperature of the grain should reach 130○C, and third part super-conditioned under humidity of 16% and temperature of 75-85○C for 3-4 minutes. A total of 48, day-old Ross 308 male broiler chicks was obtained from a commercial hatchery. Chicks were reared and housed in battery brooders in a room. From day one to 10 and 11 to 15, chicks had ad libitum access to conventional corn-soybean meal starter and grower diets, respectively, to meet the nutrient specification of the strain as recommended by Ross 308 manual. A common corn-soybean meal diet was formulated to serve as the reference diet to meet or exceed the nutrient requirements of broiler chicks as described for the Ross 308. The CS samples (row, micronized, and super-conditioning) were incorporated into the reference diet at a 40% inclusion rate (60% reference diet and 40% CS). The digestion trial included a 4-day preliminary period in 16–19d of age, followed by 4 days of recorded total feed consumption and excreta collection. The feed was provided ad libitum during the preliminary and the collection period. During the collection period (20-23d of age) total feed intake was measured, and excreta from each cage were collected twice a day, pooled, and kept frozen at -20oC until subsequent analyses. The excreta samples were oven-dried at 60○C for 72 hours to determine dry matter content. The dried excreta and diet samples were ground through 20 mesh screens, and nutrient content was determined according to (AOAC, 2000). The gross energy of the dried excreta and diet samples was measured with Bomb-calorimeter (Model 1266, PARR). The apparent nutrients digestibility, AME and AMEn of the reference and test diets were determined. Accordingly, apparent nutrients digestibility, AME and AMEn of the CS was calculated as: ”.
The average of dry matter, crude protein, ether extract, fiber, ash, and gross energy for CS were 96.20, 17.70, 46.60, 6.00, 4.11%, and 7137 kcal/kg, respectively. The apparent digestibility of dry matter, crude protein, crude fat and AMEn for raw CS in broiler chickens were 54.28±1.19%, 69.42±1.13%, 77.1±1.32%, and 4673±268 kcal/kg of dry matter. Processing of canola by micronization and super-conditioning method numerically increased the dry matter content of CS by 2.46% and 0.88%, respectively. Crude fat and crude protein content also changed with a similar trend to dry matter content. The effect of canola processing on AME and AMEn in broilers was not significantly (P> 0.05). Micronizing process of CS increased ADMD and AMEn values of 7.47% and 117 kcal/kg than non-processed seed, respectively. Super-conditioning process was less effective than micronization on improving CS nutrient digestibility and AMEn values.
The outcomes of the present study showed that spit non-significant effect of heat processing on energy value and nutrients digestibility of CS (Nafis variety) that might be due to better tolerance of chickens fed recent varieties of CS. However, the change in nutrients digestibility and AMEn values of CS with processing by super- conditioning method was poor, a trend of improving nutrient digestibility and AMEn values were seen in micronize process. More research is needed to clarify the response of the chickens when CS in the raw, micronized or conditioned forms.