اثر مکمل بتائین و تراکم‌ گله بر عملکرد رشد، ویژگی ‌های لاشه و کیفیت گوشت جوجه‌های گوشتی

زمینه مطالعاتی: تراکم گله یکی از مسائل مهم در صنعت پرورش طیور است که تولید پرنده را تحت تاثیر قرار می دهد. بتائین یا تری متیل گلایسین یک افزودنی سننتیک است که با حفظ فشار اسمزی، تامین گروه‌های متیل و خواص آنتی اکسیدان می‌تواند در جلوگیری از اثرات منفی تنش در جوجه‌های گوشتی موثر واقع شود. هدف: این آزمایش به منظور بررسی تاثیر مکمل بتائین بر عملکرد رشد، کیفیت لاشه و گوشت جوجه‌های گوشتی در تراکم‌های مختلف پرورش، انجام شد. روش کار: این آزمایش به صورت یک آزمایش فاکتوریل 2 در 2 بر پایه طرح کاملا تصادفی شامل دو تراکم گله (9 و 18 جوجه در هر واحد آزمایشی) و دو سطح بتائین ( صفر و 0.1 درصد) در چهار تکرار با استفاده از 216 قطعه جوجه گوشتی نر یک روزه سویه راس 308 انجام شد. نتایج: در تراکم بالا، مقدار خوراک مصرفی و افزایش وزن در دوره‌های رشد، پایانی و کل دوره پرورش به‌طور معنی‌داری کاهش یافتند (0.05>p). افزودن 0.1 درصد بتائین، میزان اضافه وزن را افزایش و ضریب تبدیل خوراک را کاهش داد (0.05>p). با افزایش تراکم گله، وزن نسبی لاشه و سینه جوجه‌های گوشتی کاهش معنی‌داری یافت (0.05>p)، اما اثر تراکم گله بر وزن نسبی ران، کبد، بورس فابریسیوس، طحال و چربی محوطه بطنی معنی‌دار نبود (0.05p). با افزایش تراکم گله، افت پخت افزایش و ظرفیت نگهداری آب گوشت کاهش یافت، درحالیکه افزودن بتائین منجر به افزایش ظرفیت نگهداری آب گوشت و کاهش افت خونابه و پخت گردید (0.05>p). نتیجه گیری نهایی: بر طبق نتایج این مطالعه، افزودن مکمل بتائین به جیره می‌تواند از طریق بهبود عملکرد رشد، خصوصیات لاشه و کیفیت گوشت راهکار مناسبی جهت رفع اثرات منفی افزایش تراکم گله در پرورش جوجه‌های گوشتی باشد.

effect of betaine supplementation and stocking densities on growth performance, carcass characteristics and meat quality of broilers

introduction: stocking density is one of the important concern in the poultry industry and it is related to the poultry productivity and animal welfare. stocking density for broiler chickens is defined as the number of birds or the total live weight of birds in a fixed space. increasing broiler number in breeding environment increases led to a higher production of chicken meat, but, if stocking density exceeds over the proper range, the productivity is rather decreased because of increased health problems and decreased growth performance of broiler chickens. natural betaine is found in several plants and organisms and it is commonly extracted and purified from beetroot. it is classified as a methyl-ammonia due to three chemically-active methyl groups bound to the nitrogen atom of a glycine molecule), and it is considered the only readily active methyl-group donor the biosynthesis of betaine is made by the oxidation of choline in the cell mitochondrion. however, this reaction is not interesting because choline deviated from its essential role in the transmission of nerve impulses, and in addition, choline content in typical corn- and soybean-based broiler diets is not sufficient supply their cell requirements for methylated compounds. another positive aspect obtained with the dietary inclusion of betaine is the methionine-saving effect, that is, betaine donates methyl groups instead of methionine in a reaction with homocysteine.material and methods: this experiment was performed to evaluate the effect of betaine supplement utilization on growth performance and carcass and meat quality of broilers at different stocking density. for this reason, 216 one-day-old male ross 308 broilers were used in a 2×2 factorial arrangements with four treatments including two stocking density (7 and 15 chicks per m2) and two betaine levels (0 and 0.1 percent) and four replications. during the starter (0-10 days), grower (11-25 days), and finisher (26-42 days) phases, the birds were fed according to the ross 308 recommendations. the diet and water were provided ad libitum during the trial. the body weight gain (bwg), feed intake (fi) and feed conversion ratio (fcr) were measured for each phases. at the end of the experiment, two birds per replicate with body weight close to the average of each cage were slaughtered to determine the carcass characteristics after removal of head, feathers and feet. carcass yields were calculated relative to the live body weight. after slaughter, the right thigh and breast of broiler chickens were separated and kept at 4°c for measuring meat quality traits including water holding capacity, cooking loss, ph and drip loss. to determine the whc, 4 g of breast muscle were placed in a filter paper and centrifuged at 1500×g for 4 min, then the samples were placed in an oven at 70°c for 24 h to be dried (castellini et al., 2002). in the case of cook loss, a piece of 1 cm3 of breast muscle was weighed and kept at 4°c for 24 h, then placed in a water bath at 85°c for 10 min and finally cleaned and re-weighed with a linen cloth (bertram et al., 2003). for the measurement of drip loss, a piece of breast muscle was weighed and placed in a plastic bag and kept at 4°c for 24 h. the meat was then gently rubbed into the cloth and weighed again (christensen, 2003). all data were analyzed by anova utilizing glm procedure of sas. means were compared for significant differences utilizing the tukey multiple range test (p˂0.05).results and discussion: the results showed that feed intake and weight gain decreased significantly during the grower, finisher and whole production periods at high stocking density (p<0.05).