عنوان مقاله [English]
Introduction It is advantageous to include as many ingredients as possible when formulating a diet for broiler chickens, because the supplementary nature of nutrients in different feedstuffs promotes the reduction of nutrient variation. The results of some experiments have shown that diet uniformity, through variance reduction for nutrients, improves broiler performance. In addition, lower variability of nutrients reduces the possibility of nutrient wastage. Also, in practical feed formulation when using of cheaper feed ingredients such as canola meal (CM) or poultry by-product meal (PBM) instead of more expensive ingredients such as soybean meal (SBM) in such a way that inclusion of them didn’t result in a lower production and quality indices thus they may result in a lower feed costs and higher economic benefit for producer. Both CM and PBM are good sources of protein for broilers and less expensive than SBM. Canola meal is a worthful feed ingredient and according to climatic condition and type of processing contains 36-39% crude protein. It may consider as a good source of calcium, phosphorus, magnesium, manganese, zinc, and iron as well as relatively good source of methionine and lysine. Poultry by product meal can be used in poultry ration up to 6% of total feed if sanitary operations is observed. High levels of fat, moisture and feather contents are main drawbacks of PBM in the poultry rations. However, if PBM mixed with CM that has low levels of fat and moisture, a proteinous mixture will result with similar CP level to SBM and longer storage potential. Both CM and PBM have lower nutrient digestibility as crude protein, fats and trace minerals because of phytate and NSP and dietary exogenous enzymes may improve digestibility of nutrients. The results of some researches showed that Kemin multi-enzyme supplementation improved broiler performance or carcass characters. This research is carried out for study effect of different substitution of a proteinous mixture composed of CM and PBM (65%:35%) with SBM with Kemin WP multi-enzyme supplementation on production and economic performances of broiler chickens.
Materials and Methods This experiment was conducted in a factorial arrangement 4×2 (4 levels of proteinous mixture replaced with SBM: 0, 25, 50 and 75%×2 levels of Kemin WP multi-enzyme supplementation: 0 and 250mg/kg diet) with 8 treatments, 4 replicates of 12 pieces of Ross308 strain broiler chicks of either sex reared on 1×1.25m floor pens in a completely randomized design. Proteinous mixture was made by proper mixing of CM and PBM (65%:35). During experimental period chickens were received mash diet according to Ross308 feed specification booklet (2014) for as hatched broilers. Feed and water were prepared for broilers ad-libitum. Body weight, feed intake, feed conversion ratio (FCR), production index, feed cost to gain (Rials/kg), and monetary returns (Rials/bird) were measured or calculated at different phases of growth period. At the end of growth period (42 days of age) one bird similar in body weight to average weight of each replicate was selected and sacrificed for carcass character measurements. Collected data were subjected to analysis of variance by ANOVA procedure of SAS2003Software. Treatment means were separated using Duncan multiple range test at 0.05 significant level.
Results and Discussion At shorter growth period of 1-24 days, there was a significant interaction between dietary multi-enzyme supplementation and different substitution levels of protein mixture and SBM on body weight and FCR. As, in diets without multi-enzyme supplement,75% substitution of protein mixture with SBM significantly resulted in the most decrease in body weight and increase in FCR however, in diets with enzyme supplement 50 and 75% substitution levels of protein mixture with SBM resulted in a non-significant difference in body weight and FCR of chickens. It is reported that commercial multi-enzymes in broiler diets resulted in an increase in body weight and decrease in FCR. Also, there are some evidence that the mean retention time of digesta in different parts as well as whole digestive tracts of broilers in diets with CM was significantly less than SBM diets and this may be the cause of decrease in digestion and absorption of nutrients in diets with CM. It is reported that the use of more than 6% poultry offal meal in broiler diet resulted in a lower production performance and higher FCR and the causes of these phenomena should be searched in lower quality and palatability of poultry offal meal with higher level usage in the diet. Protein mixture substituted with SBM resulted in the lower feed cost to gain. However, diets with 50 and 75% substitution levels resulted in a significant decrease in MR compared with 0 and 25% substitution levels. Different substitution levels of protein mixture with SBM had no significant effect on carcass characters, however, dietary multi-enzyme supplementation resulted in a significant higher abdominal fat percentage. Similar to this results, it is reported that multi-enzyme supplementation resulted in higher abdominal fat percentages in broiler chickens. The lipase content in multi-enzyme may cause increase in digestion, absorption and deposition of fat in the body.
Conclusion To sum up, the results showed that 25% dietary protein mixture substitution with SBM in the broiler diet did not showed significant negative impact on economic performance of broiler chickens and could potentially be used as a substitute for more expensive soybean meal protein. Also, the use of multi-enzyme supplementation in the diet restricted to the age of chickens and the quality of protein source. As considering lower growth period of 24 days and 75% substitution levels of protein mixture with SBM multi enzyme supplement may result in a better FCR. However, for production of broilers with 42 days of age multi-enzyme supplementation in the diet had no significant positive effect on broiler performance and its economic traits.