اثرات سطوح مختلف انرژي قابل سوخت و ساز و پروتئين جيره بر عملكرد رشد ، بازده استفاده از انرژي و پروتئين و پاسخ سيستم ايمني جوجه هاي گوشتي سويه راس 308

Effects of different levels of dietary metabolizable energy and protein on growth performance, energy and protein efficiency ratios and immunity system response of Ross 308 broilers

براي ارزيابي اثرات سطوح مختلف انرژي قابل سوخت و ساز و پروتئين جيره بر عملكرد رشد، بازده استفاده از انرژي و پروتئين و پاسخ سيستم ايمني جوجه هاي گوشتي، 640 قطعه جوجه گوشتي سويه راس 308 در قالب آزمايش فاكتوريل 2×2×2 با طرح پايه كاملاً تصادفي شامل 8 تيمار، 4 تكرار 20 قطعه جوجه در هر تكرار مورد استفاده قرار گرفتند. نتايج نشان دادند كه افزايش سطح انرژي و پروتئين جيره تأثير معني داري بر ضريب تبديل غذايي نداشت (0.05< p) ولي موجب كاهش بازده استفاده از پروتئين (0.01>P) در هفته دوم و ششم شد. افزايش انرژي با سطح كمتر پروتئين (22 درصد) تا سن 21 روزگي موجب كاهش مصرف انرژي و پروتئين گرديد و سپس با افزايش سطح پروتئين (24 درصد) تا سن 42 روزگي منجر به افزايش مصرف انرژي و پروتئين شد. ضريب تبديل غذايي در جوجه هاي نر با افزايش سطح انرژي جيره، بهبودي جزئي يافت ولي مصرف انرژي و پروتئين اندكي بيشتر بود و ماده ها در سن 35 روزگي بازده انرژي و پروتئين بالاتري داشتند. با افزايش سطح انرژي جيره، تيتر آنتي بادي بر عليه SRBC افزايش يافت. غلظت HDL و وزن قلب در نرها بيشتر بود. افزايش انرژي موجب دفع بيشتر نيتروژن شد و با سطح بالاتر پروتئين (24 درصد) موجب كاهش وزن روده گرديد. بنابراين افزايش انرژي و پروتئين تا هفته سوم و سپس كاهش پروتئين تا انتهاي دوره جهت مصرف بهينه انرژي و پروتئين و بهبود بازده استفاده از انرژي و پروتئين توصيه مي شود.

In order to investigate the effects of different levels of dietary metabolizable energy (ME) and protein (CP) on growth performance, energy efficiency ratio (EER), protein efficiency ratio (PER) and immunity system response of broilers, a total of 640 Ross 308 broilers were used in a 2×2×2 factorial arrangement with completely randomized design including 8 treatments, 4 replication and 20 chicks in each replication. The factors of interest included 2 levels of ME (3000 and 3100 kcal/kg) and 2 levels of CP (22 and 24 percent) in two sexes. Body weight (BW) and feed intake (FI) were recorded weekly, measurement of antibody titer against sheep red blood cells (SRBC) were performed at 35 day of age and samplings of blood, carcass components and litter were carried out at 42 day of age. The results indicated that increasing of dietary ME and CP levels did not have significant effect (P>0.05) on feed conversion ratio (FCR) but decreased PER in 2nd and 6th weeks (P<0.01). The increasing of ME with lower level of CP (22%) decreased ME and CP intakes up to 21 day of age and then the rising of CP level (24%) increased ME and CP intakes up to 42 day of age. The FCR of males improved inconsiderably by increasing of dietary ME level but the ME and CP intakes were slightly higher and females had higher EER and PER at 35 day of age. The antibody titer against SRBC enhanced by increasing of dietary ME level. The concentration of HDL and heart weight were higher in males. Enhancing of ME led to an increase in nitrogen excretion and higher protein level (24%) caused decrease in intestine weight. Therefore, the increasing of ME and CP up to the 3rd week and then the decreasing of CP up to the end of production period is recommended to optimize ME and CP intakes and improving EER and PER.