The Optimum Energy Density in Diets for Lori-Bakhtiari Lambs during a Fattening Program
محورهای موضوعی : Camelم. کاظمی بن چناری 1 , م.ر. جوانمرد 2 , م. اسلامی‌زاد 3
1 - Department of Animal Science, Faculty of Agriculture and Natural Resources, Arak University, Arak, Iran
2 - Department of Veterinary and Food Hygiene, University of Scientific-Applied, Arak, Iran
3 - Department of Animal Science, Faculty of Agriculture and Natural Resources, University of Tehran, Karaj, Iran
کلید واژه: lamb, fattening, lean mass, optimum energy density,
چکیده مقاله :
Forty growing ram lambs (Lori-Bakhtiari breed) averaging 28 kg (±1.5) were allocated in this study to evaluate the optimal dietary energy density in a lamb fattening enterprise in Iran. The feed intake (FI), body weight (BW), gain to feed ratio (G:F) and carcass characteristics were studied. Four treatments differed in metabolizable energy content (ME) as follow; 2, 2.3, 2.6 and 2.9 Mcal/kg for treatments 1 to 4, respectively. The study lasted 120 days and all the experimental lambs were slaughtered and carcass composition was compared among treatments. Average daily gains were 230, 252, 267 and 259 g/d for treatments 1 to 4, respectively (P<0.01). Moreover, lower energy density resulted in up to 19% greater FI (P<0.01) and higher F:G ratio (P<0.01) and therefore lower carcass growth efficiency (P<0.05). Higher energy density improved G:F ratio; but caused fatter carcasses compared to lower dietary energy levels. In addition to fatter carcasses for higher energy diets, the greatest tail-fat weight was observed for treatment 4 (2.9 Mcal/kg) and may explain the lower feed efficiency in this treatment. The values for lean mass weights were 12.7, 14.1, 14.7 and 12.7 kg for treatments 1 to 4, respectively. Overall, the best carcass efficiency was found with treatment 3. Based on these results, energy density of 2.6 Mcal/kg may be recommended for growing Lori-Bakhtiari male lambs in a fattening enterprise under the conditions of this trial.
در مطالعه حاضر تعداد 40 رأس بره نر (نژاد لری-بختیاری) با متوسط وزن 28 کیلوگرم (با انحراف معیار 5/1 کیلوگرم) جهت ارزیابی انرژی بهینه مورد نیاز برای پرواربندی در سیستم پرورشی ایران مورد استفاده قرار گرفتند. خوراک مصرفی، وزن بدن، و ضریب تبدیل خوراک به وزن و همچنین ویژگی‌های کیفیت لاشه مورد بررسی قرار گرفتند. چهار تیمار از نظر انرژی قابل متابولیسم متفاوت در نظر گرفته شدند که شامل 0/2، 3/2، 6/2 و 9/2 مگاکالری در کیلوگرم بودند. طول دوره مطالعه 120 روز بوده و تمام بره‌ها کشتار شده و ترکیبات لاشه مورد مقایسه قرار گرفت. میانگین افزایش وزن روزانه به ترتیب 230، 252، 267 و 259 گرم در روز به ترتیب برای تیمارهای 1 تا 4 حاصل شد (01/0P<). علاوه بر این سطح انرژی پایین‌تر سبب افزایش ضریب تبدیل تا 19 درصد (01/0P<) و سبب افزایش نسبت خوراک به افزایش وزن گردید (01/0P<) و همچنین سبب کاهش کیفیت لاشه گردید (05/0P<). افزایش غلظت انرژی سبب بهبود بازدهی انرژی گردید اما سبب افزایش چربی موجود در لاشه گردید. علاوه بر چرب‌تر شدن لاشه در جیره‌های با انرژی بالا، دنبه بیشتری نیز در تیمار 4 به دست آمد که نشان دهنده انرژی پایین‌تر در این تیمار بوده است. مقادیر وزن لاشه خالص برای تیمارهای 1 تا 4 برابر 7/12، 1/14، 7/14 و 7/12 کیلوگرم بود. در نهایت بهترین بازدهی برای تیمار سوم حاصل گردید. بر اساس نتایج به دست آمده با توجه به شرایط موجود در این آزمایش سطح انرژی 6/2 مگاکالری قابلیت توصیه به بره‌های نر لری بختیاری بود.
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