Effect of Season on Dry Matter Intake and Reproductive Activity of Merghoz Buck Goats in West of Iran
محورهای موضوعی : Camel
1 - Department of Animal Science, Faculty of Agriculture, Razi University, Kermanshah, Iran
2 - Department of Animal Science, Faculty of Agriculture, University of Jiroft, Jiroft, Iran
کلید واژه: dry matter intake, Merghoz buck, natural photoperiod, reproductive activity, Sexual behavior,
چکیده مقاله :
Ten male Merghoz goats with initial live weights of 29.2 ± 1.2 kg (Mean±SE) were used to investigate the effect of natural changes in photoperiod on dry matter intake (DMI) and reproductive activity during a 365 day study. The bucks were housed in individual pens, under natural daylength condition at west of Iran, Kermanshah (34˚ 18¢N and 47˚ 3¢E and 1420 m above sea level). A diet was offered with an estimated concentration of metabolizable energy and crude protein of 7.9 MJ and 98.8 g per kg dry matter (DM) respectively. Live weight, DMI, and additive daily gain (ADG) of individual animals were recorded weekly. The serum testosterone concentrations were determined in blood samples collected at monthly intervals. During the observation period, semen was collected monthly with the aid of an electro-ejaculator and examined microscopically immediately after collection. The physical parameters of semen and the semen index were recorded. The sexual behavior and testicular size of goats were assessed monthly throughout the study period. The highest DMI was observed during summer (64.3±0.9 g/kg BW0.75) and spring (62.2±2.9 g/kg BW0.75) however, the lowest was recorded in the winter season (54.0±0.9 g/kg BW0.75). The seasonal values of ADG (g/d) ranked spring > summer > winter > autumn. Bucks demonstrated the highest sexual behavior in late summer and, thereafter during autumn, using the lower (P<0.05) number of mounts per ejaculation and a higher frequency (P<0.05) to sniff, approach, and vocalize a doe with estrous status. This was coincided with a higher (P<0.05) level of plasma testosterone (8-10.1 ng/mL) and the best semen quality (semen index: 744-989×106/mL) and quantity (semen volume: 1.1-1.2 mL per ejaculate), higher testis length (13.3-14.7 cm) and width (6.0-6.1 cm) and scrotal circumference (32.2-35.5 cm). It is concluded that, in Merghoz bucks, the seasonal pattern of DMI and reproductive activity may be attributed to each other as well as photoperiod.
در این آزمایش از 10 رأس بز نر نژاد مرغز (میانگین وزن 2/1±2/29 کیلوگرم) برای مطالعه اثر فصل بر مصرف ماده خشک و فعالیت تولید‌مثلی استفاده شد. دام‌ها در در قفس‌های انفرادی و تحت نور طبیعی در مزرعه تحقیقاتی دانشکده کشاورزی دانشگاه رازی کرمانشاه واقع در غرب ایران به مدت یک سال نگهداری شدند. جیره غذایی با 9/7 مگاژول انرژی متابولیسمی و 8/98 گرم در کیلوگرم ماده خشک پروتئین خام در طول دوره آزمایش به دام‌ها داده شد. وزن زنده، مصرف ماده خشک و افزایش وزن روزانه هر کدام از دام‌ها به طور هفتگی اندازه‌گیری شد. غلظت هورمون تستسترون در سرم نمونه‌های خون ماهانه اندازه‌گیری شد. نمونه‌های منی به طور ماهانه از دام‌ها توسط دستگاه الکترواجاکیولیتور جمع‌آوری گردید و بلافاصله بعد از آن توسط میکروسکوپ نوری بررسی شد. در طی آزمایش، رفتارهای جنسی دام‌ها و اندازه بیضه‌ها به طور ماهانه ثبت گردید. حداکثر مصرف ماده خشک در فصول تابستان (9/0±3/64 گرم بر کیلوگرم وزن متابولیکی) و بهار (9/2±2/62 گرم بر کیلوگرم وزن متابولیکی) و حداقل آن در فصل زمستان (9/0±0/54 گرم بر کیلوگرم وزن متابولیکی) ثبت گردید. ارزش افزایش وزن روزانه به صورت بهار > تابستان > زمستان > پاییز ثبت شد. بیشترین رفتارهای جنسی در اواخر تابستان و سپس در طی پاییز که مصادف بود با حداکثر غلظت هورمون تستسترون (1/10-8 نانوگرم بر میلی‌لیتر) ثبت گردید. علاوه بر این، بهترین شاخص و حجم منی (2/1-1/1 میلی‌لیتر)، طول بیضه (7/14-3/13 سانتی‌متر)، عرض بیضه (1/6-0/6 سانتی‌متر) و محیط بیضه (5/35-2/32 سانتی‌متر) در اواخر تابستان و در فصل پاییز مشاهده شد. نتایج این آزمایش نشان می‌دهد که مصرف ماده خشک و فعالیت تولید‌مثلی بزهای نر مرغز با یکدیگر مرتبط بوده و ناشی از تغییرات فصلی فتوپریود می‌باشد.
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