ارزیابی اثرات حذف یونجه و کاهش میزان علوفه بر عملکرد بره‌های پرواری نژاد افشاری

به منظور بررسی اثرات کاهش میزان علوفه و همچنین حذف یونجه بر عملکرد بره های پرواری نژاد افشاری، آزمایشی با استفاده از تعداد 36 راس بره نر نژاد افشار با میانگین وزن زنده 1.9± 32.53 کیلوگرم و میانگین سن 6.63 ± 93 روزگی  به‌مدت 90 روز، بر اساس آزمایش فاکتوریل بر پایه طرح کاملاً تصادفی انجام شد. جیره های آزمایشی شامل: تیمار 1) 80 درصد کنسانتره و 20 درصد علوفه (10 درصد کاه گندم و 10 درصد یونجه)، تیمار 2) 80 درصد کنسانتره و 20 درصد علوفه (20 درصد کاه گندم و صفر درصد یونجه)، تیمار 3) 90 درصد کنسانتره و 10 درصد علوفه (پنچ درصد کاه گندم و پنج درصد یونجه) و تیمار 4) 90 درصد کنسانتره و 10 درصد علوفه (10 درصد کاه گندم و صفر درصد یونجه) بود. جیره های آزمایشی بر اساس جداول استاندارد غذایی (2007) nrc تنظیم شده و مواد خوراکی تشکیل‌دهنده جیره ها و ارزش غذایی آن‌ها مشابه بود. ترکیب شیمیایی جیره‌ها با تغییر نسبت علوفه به کنسانتره تغییر یافت و با افزایش کنسانتره در جیره‌ها میزان nfc افزایش و در مقابل درصد ndf کاهش یافت. ماده خشک مصرفی و افزایش وزن روزانه برای تیمار چهار به‌طور معنی داری بیشتر از تیمارهای دیگر بود. تیمار چهار  به ‌لحاظ عددی ضریب تبدیل غذایی کمتری (6.1) در مقایسه با سه تیمار دیگر داشت. نتایج مربوط به مقایسه اقتصادی نشان داد که بره های تغذیه شده با 90 درصد کنسانتره و 10 درصد کاه گندم سوددهی بیشتری در مقایسه با سایر گروه ها داشتند. به طور کلی، از نتایج این مطالعه می‌توان گزارش کرد که افزایش کنسانتره و حذف یونجه در جیره باعث بالا رفتن مصرف خوراک و افزایش وزن روزانه و در مجموع، وزن نهایی بالاتر در بره های پرواری می‌شود و همچنین بالاترین تاثیر را روی سوددهی پروار دارد.

evaluation of the effects of alfalfa removal and forage reduction on performance of afshari breeding lambs

introduction: stall-fed lambs, which account for the bulk of mutton production, are one of the main sources of red meat supply in the country. in order to achieve optimal and economical production, sheep breeders must take into account the nutritional needs, food quality and dietary intake time in the diet plan of livestock. however, due to the shortage of forage and pastures in iran, stockbreeders are forced to include more concentrate in the animals’ diet, while trying to carefully observe the concentrate proportions as well as the necessary points associated with concentrate feeding. therefore, the purpose of this project is to evaluate the effects of alfalfa removal and reducing forage on the profitability of afshari fattening lambs.materials and methods: in order to investigate the effects of reducing the amount of forage and also removing alfalfa on performance of afshari breeding lambs, based on a factorial experiment with a completely randomized design, was done on 36 afshari male lambs, with a mean live weight of 32.53 ± 1.9 kg and a mean age of 93 ± 6.63 days for 90 days. experimental diets included: 1) 80 percentage concentrate and 20 percentage forage (10 percentage wheat straw and 10 percentage dry alfalfa), 2) 80 percentage concentrate and 20 percentage forage (20 percentage wheat straw, 0 percentage dry alfalfa), 3) 90 percentage concentrate and 10 percentage forage (5 percentage wheat straw and 5 percentage dry alfalfa), and 4) 90 percentage concentrate and 10 percentage forage (10 percentage wheat straw and 0 percentage dry alfalfa). experimental diets were adjusted according to nrc (2007) standard diet tables and the constituents of the diets and their nutritional value were similar. the data were analyzed using spss21.results and discussion: the chemical composition of diets was changed with altering of the forage to concentrate ratio, and with increasing the concentrate in the diet, the amount of nfc increased and the percentage of ndf decreased. increasing the concentrate and removing of alfalfa increased feed intake and daily weight gain throughout the period (p <0.05). increasing of feed consumption seeks higher concentrate intake is due to faster consumption by animal compared to forage intake. on the other hand, the retention time of the concentrate in the abdominal area is less than the fodder. therefore, the effect of filling after using of forage, limits the consumption of feed. result indicated no significant differences in digestibility and feed conversion ratio between experimental treatments. the results of this study showed that the dry matter consumption and daily weight gain for treatment four was significantly higher than other treatments. the fourth treatment had a numerically lower food conversion coefficient (6.1) compared to the other three treatments. accordingly, increasing the concentrate and removing of alfalfa has caused a significant increase in weight throughout the period. regarding the interaction effects of concentrate and forage on daily weight gain, it also was shown that the most of the daily weight gain obtained followed by increasing of the concentrate level and then the removal of alfalfa. the most important factor affecting daily weight gain is feed consumption. regarding to the effect of alfalfa reduction on feed intake, it can be stated that by reducing alfalfa, despite not reducing dietary fiber (treatments two and four), other dietary nutrients supplied through alfalfa were supplied through concentrate, which itself increased the digestibility of the ration. the feed conversion ratio of the four treatments was in the same range. the results of economic comparison showed that lambs fed with 90% concentrate, 10% wheat straw and 0% alfalfa had higher yields compared to other groups.conclusion: the results of the present study showed that with increasing the percentage of concentrate and removal of alfalfa from the feed, feed intake increases accordingly. concentrate is palatable and contains more energy and nutrients than forage. therefore, lambs fed with diets containing higher concentrate levels and no alfalfa experienced faster growth and higher growth efficiency and produced heavier carcasses. thanks to this diet, stock breeders can save feeding and breeding costs during seasons when feed is more expensive or insufficient. according to the results, diets containing 90% concentrate, 10% wheat straw and no alfalfa can be suggested for optimal yield in stall-fed lambs.