نوع مقاله : مقاله پژوهشی
گروه علوم دامی، دانشکده کشاورزی، دانشگاه بیرجند، بیرجند، ایران.
عنوان مقاله [English]
Introduction The increase in the cost of the diet, especially the protein part, has caused the desire of producer and researchers to use by-products. The use of animal waste not only reduces the cost of feed but also reduces the entry of contaminants into the environment. Hydrolyzed feathers, meat meal, bone meal, poultry by-product meal (PBM) and fish oil are some of the by-products used in poultry, dairy cattle and other livestock diet. Also, the use of pelleted feed in broiler chicken is increasing, because it produces less dust, improves digestibility, reduces transportation costs, and improves performance indicators such as feed consumption and decrease feed conversion ratio. Sodium bentonite (SB) is one of the substances that has been used as pellet binder in feed. Several studies have evaluated the effects of the addition of SB and had beneficial results on pelleting physical properties such as pellet durability index (PDI) and pellet hardness. Addition of active SB as a pellet binder in wheat-soybean meal-based diets has increased the relative electrical energy usage (REEU) and decreased the feed conversion ratio. However, studies on the use of different levels of PBM and SB as a pellet binder in broiler chicken diets are very limited, the aim of the present study was to investigate the effects of pellet binder levels of SB in diets containing different amounts of PBM on performance, carcass traits and blood metabolites of Ross 308 broiler chickens in finisher period.
Materials and Methods Treatments were assigned in a completely randomized design based on a factorial arrangement of 3 levels of SB conditioning time (0, 1.5 and 3%) × 3 levels of PBM (0, 5 and 10%). Experimental diets were balanced based on Ross 308 recommendations for finisher period (24-42 d) by using UFFDA software. In the present experiment PBM and pellet binder of SB samples were prepared from MegaFaravar Co., Iran. Ingredients of diets were ground through a 2-mm screen size in a hammer mill. All diets mixed in a double-shaft mixer and transferred to super conditioner with 82◦C for 10s, and then pelleted through a 3-mm die. After pelleting of feed produced, 3 replications of each treatment with 3-minute intervals were sampled from the cooler part of the pellet machine. The PDI, hardness test and REEU related to experimental diets was measured. Also, a total of 360 24-day-old male chicks were individually weighted and allocated to 9 treatments of 4 replicates (10 birds in each replication). Feed intake (FI), average daily gain (ADG) and feed conversion ratio (FCR) were recorded. On 42 day, 2 birds per pen were randomly euthanized by cervical dislocation. Carcass characteristics and relative weight of small intestinal segments were measured. Total protein, glucose, albumin, lipoproteins (HDL, LDL) were determined by using autoanalyzer device and commercial kits.
Results and Discussion Addition of 1.5% SB improved and the use of PBM due to its high fat content reduced the quality characteristics of the pellet that due to their strong colloidal properties and giving rise to a thixotropic gelatinous substance. Likewise, different levels of SB as a pellet binder and PBM did not change the ADG and FCR (P <0.05). However, the use of different levels of PBM with and without SB reduced FI (P<0.05). Also, the relative weight of carcass, breast and thigh was not affected by experimental treatments (P <0.05). Abdominal fat increased significantly in the groups receiving PBM (P <0.05). Amino acid imbalances in PBM probably increase deamination and conversion of amino acids to fat. Significant reduction in duodenum and ileum length was observed in the group containing 3% SB and 10% PBM (P <0.05). Also, the level of 10% PBM with and without SB increased the concentration of blood lipids. Blood lipids concentration have a positive correlation with weight and feed as an environmental factor affects its amount.
Conclusion In general, the results of this experiment showed that application of PBM as a source of protein with adequate nutritional value up to 5% without negative effects on performance for use in pelleted diet of broilers at high levels when soybean meal is expensive and or not available, it is possible and useable. Also, commercial sodium bentonite can be used as a pellet binder to increase the quality of pellets up to 1.5%. The need for further studies on the simultaneous use of sodium bentonite as a pellet binder and PBM are recommended to ensure the results obtained in other broiler chicken breeding periods.
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