اثرات افزودن دارچين و آويشن به جيره بر عملكرد و ابقاء نيتروژن جوجه‌هاي گوشتي تغذيه شده با سطوح مختلف پروتئين

Effects of dietary inclusion of cinnamon and thyme on performance and nitrogen retention of broilers fed with different levels of protein

زمينه مطالعاتي: با توجه اثرات سودمند گياهان دارچين و آويشن بر قابليت هضم و استفاده پروتئين جيره، انتظار مي‌رود استفاده از اين گياهان بتواند اثرات نامطلوب جيره‌هاي كم پروتئين را كاهش دهد. هدف: اين پژوهش به منظور بررسي تأثير پودر دارچين و آويشن بر عملكرد و ابقاء نيتروژن جوجه ­هاي گوشتي تغذيه شده با دو سطح پروتئين جيره انجام شد. روش كار: شمار 480 قطعه جوجه گوشتي يك روزه در قالب يك آزمايش فاكتوريل 4×2 بر پايه طرح كاملاً تصادفي به هشت تيمار‌ آزمايشي با 3 تكرار و 20 قطعه جوجه در هر تكرار اختصاص يافتند. دو فاكتور مورد بررسي شامل سطح پروتئين جيره (توصيه NRC و 85 درصد توصيه NRC) و افزودني (بدون افزودني، ۰/۵ درصد پودر آويشن، ۰/۵ درصد پودر دارچين و مخلوط ۰/۵ درصد آويشن و ۰/۵ درصد دارچين) بودند. نتايج: عملكرد جوجه­ ها (افزايش وزن بدن، مصرف خوراك و ضريب تبديل خوراك) در طول دوره آزمايش تحت تأثير افزودني­ها و اثر متقابل آن‌ها با سطح پروتئين جيره قرار نگرفت. جوجه ­هاي تغذيه شده با جيره ­هاي كم پروتئين نسبت به جوجه‌هاي تغذيه شده با سطح توصيه شده پروتئين، افزايش وزن كم‌تر و ضريب تبديل خوراك بالاتري داشتند (۰/۰۵

Introduction: Protein sources are high cost feedstuffs in poultry diets. Additionally, nitrogen excretion is an important challenge in intensive animal production systems (Abd El - Hakim et al. 2009). Hence, application of low protein diets (LPD) in poultry nutrition has been received more attention in recent years. Dietary level of crude protein in starter, grower and finisher phases of the rearing period of broilers could be reduced by 10% from the NRC (1994) recommendation levels, without adverse effects on their perfor mance. Although, LPD have some advantages, they may negatively influence broilers performance (Aftab et al. 2005). On the other hand, dietary inclusion of antibiotic growth promoters has been banned in many countries of the worlds. Thus, different organic feed additives including herbs have been proposed as alternatives to antibiotics. Herbal plants have positive effects on immunity, gut microflora and performance of broilers (Gou et al.2004a, b; Franco - Jimenez et al 2007). Different studies have been condu cted on the effects of thyme ( Thymus vulgaris) and cinnamon (Cinnamon zeylanicum) on broilers. Due to high levels of active compounds such as thymol and carvacrol in thyme (Mikaili et al. 2010) and c innamaldehyde and ugenol in cinnamon (Gruenwald et al. 2010) they can beneficially influence broilers (Hernandez et al. 2004; Al - Kassie 2009; Shirzadegan 2014). Positive effects of thyme (Hernandez et al. 2004) and cinnamon (Al - Kassie 2009) on protein digestibility and utilization have been reported. Considering these beneficial consequences, it could be hypothesized that dietary inclusion of those herbs can reduce the negative effect of LPD in broilers.Material and m ethod s : A total of 480 1 - d - old male and female Cobb 500 broiler chicks wer e obtained from a commercial hatchery and transferred to rearing place. The experiment was conducted as a completely randomized design in a 2×4 factorial arrangement with two levels of dietary crude protein (NRC recommendation and 85% of NRC recommendation ) and four feed additives (without additive, 0.5% thyme powder. 0.5% cinnamon powder and a mixture of 0.5% thyme and 0.5% cinnamon). Each experimental treatment had 3 replicates with 20 birds each. All birds had free access to feed and water and reared und er same management conditions on floor pens until 42 days of age. Isocaloric starter (d 1 - 21) and finisher (d 22 - 42) diets were formulated to meet or exceed the NRC (1994) nutrients requirements (except for crude protein and essential amino acids). At the end of the experiment, 6 birds (3 males, 3 females) from each treatment were transferred to separate cages and given diets containing 0.3 % Cr 2 O 3 as an indigestible marker for 5 days and excreta were collected. Feed samples and excreta were analyzed (AOAC 1990) to determine nitrogen retention (Woodworth et al. 2011). Results and d iscussion : The results indicate d that dietary protein level had no significant effect on starter (d 1 - 21), finisher (d 22 - 42) and overall (d 1 - 42) feed intake (P> 0.05). From 22 to 42 d of age, birds fed diets containing 85% of NRC had less body weight gain than those fed recommended level (P< 0.05). Also, feeding birds with 85% of NRC resulted in a lower overall body weight gain (1731 g) compared to the NRC (1912 g) (P< 0.05). Du ring d 22 - 42 and d1 - 42, birds fed diets containing 85% of NRC had higher feed conversion ratio (FCR) than the NRC which means that they converted feed with less efficiency compared to those fed NRC (P< 0.05). In brief, the results suggested that reduction in dietary protein level by 15% impaired performance. The findings of some previous studies indicated that more than 10% reduction in dietary protein level had negative consequences on broiler performance (Aftab et al. 2005; Kamran et al., 2008). As adequ ate levels of dietary protein and amino acids are needed for optimum performance (NRC 1994) , these results are not unexpected. Our results indicated that body weight gain, feed intake and FCR were significantly not influenced by additives throughout the re aring period (P> 0.05). Similarly, other previous researchers (Amozmehr and Dastar 2009; Sadeghi et al. 2012; Salimian et al. 2016) did not find positive effect of herbs on broilers performance. Numerous factors such as additive dose, type, delivery method , duration, feedstuffs quality, birds characteristics (age, sex and production), rearing condition particularly farm hygiene status and stress level can affect broilers response to feed additives. Moreover, herb species, harvest time, plant maturity, dryin g method, storage time, chemical and physical condition of the soil influence the level of active compounds in herbs and thus play important role in this case (Burt 2004; Bakkali et al. 2008; Amozmehr and Dastar 2009; Salimian et al. 2016). Taking together , inconsistent results could be related to all stated factors. There was no significant interaction between dietary protein level and additives for performance traits. It means that broiler’s response to feed additives was not influenced by dietary protein level. Nitrogen retention was higher in birds fed NRC recommended level of protein than those fed 85% of NRC recommended level. This result is in line with Malomo et al (2013) who reported that lowering protein level reduced nitrogen retention in broiler chickens. A significant interaction between dietary protein level and feed additives was observed for nitrogen retention. Nitrogen retention was significantly improved in birds fed low protein diets supplemented with a mixture of cinnamon and thyme and was similar to birds fed recommended levels of protein (P< 0.05). In fact, it seems that addition of a mixture of 2 herbs has a synergistic effect on nitrogen retention in broilers fed low protein diets. In a previous study (Abd El - Hakim et al. 2009), supplem entation of low protein diets with a mixture of thyme and Curcuma longa improved nitrogen retention by 13.25%. This improvement was attributed to the synergistic effect between 2 herbs. Feeding birds with 85% NRC caused in a significant increase in abdomin al fat and liver weight (P< 0.05) which is in agreement with other results (Swennen et al. 2006; Kamran 2010). Conclusion : A significant reduction in broilers performance was observed when dietary protein level was reduced by 15%. Dietary supplementation with thyme and cinnamon had no significant effect on broilers performance but addition of their mixture to low protein diet significantly improved nitrogen retention.