نوع مقاله : مقاله پژوهشی
نویسندگان
1 گروه علوم دامی دانشکده کشاورزی و منابع طبیعی دانشگاه محقق اردبیلی، اردبیل ، ایران
2 گروه علوم دامی دانشکده کشاورزی و منابع طبیعی دانشگاه محقق اردبیلی، اردبیل ، ایران.
چکیده
کلیدواژه‌ها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
Introduction: When forage amount and height decrease in the pastures,forage grazing becomes difficult for sheep. Moreever, sheeps donot like to graze dead forages and avoid grazing them unless they be forced for supplying their reqired nutrients. In this conditions, the amount of dietary metabolizable energy decreases and it will be a limiting factor for sheep growth and production. Conventional sheep grazing programs does not provide enough and sustainable nutrients to achieve optimal growth and most of grazing animals experience malnutrition periods and lack of supplying the required nutrients and thereafter they will start to reduce production and growth rate. A pasture-based lamb rearing system can provide better growth rates when the animals were supplemented with concentrate feeds to compensate the pature deficiencies. Supplementation of concentrate feeds in addition to free grazing in pastures has significantly improved sheep production and increased growth performance in lambs. Identifying the genetic potential of Iranian sheep ecotypes and creating appropriate mixtures in integrated rearing systems (combining pasture grazing and concentrate feeds) can lead to higher efficiency. Therefore, the aim of the present study was to investigate the effect of different levels of concentrate on the growth performance of weaned Moghani and Romanov-Moghani crossbreed lambs under grazing conditions.
Material and Methods: This study was conducted using 32 weaned Moghani and Romanov-Moghani cross-bred lambs with an average weight of 24±7 kg in a completely randomized design with 4 treatments as a 2×2 factorial experiment. The experiment was conducted in two stages over 8 months. The first stage was carried out for 3 months (feeding period) and the experimental treatments included 1) Moghani lambs without concentrate supplement feeding, 2) Moghani lambs fed with 250 grams per day of concentrate supplement per lamb, 3) Romanov-Moghani cross-breed lambs without concentrate supplement feeding and 4) Romanov-Moghani cross-breed lambs fed with 250 grams per day of concentrate supplement per lamb. The second stage was carried out for 5 months and all experimental groups were deprived of receiving concentrate supplement (non-feeding period). Lambs were weighed every two weeks and monthly for up to 3 months after the end of the feeding period to determine weight gain and biometric parameters. A 25×25 cm wooden plots were used to measure pasture phytomass production. Plants in the plots were cut from about one centimeter above the ground and collected in a bag. After air drying in the shadow, they were used to analyze and identify the type of plant species.. To determine diet digestibility, a fecal collection bag was used that was tied to the animal's rump for 2 consecutive days and done for two occasions (days 45 and 90 of rearing). Blood samles were taken from the jugular vein after the lambs returned from the pasture and 3 hours after hand-feeding the concentrate suplement, and analyzed for blood metabolites including glucose, urea, total protein, albumin, cholesterol, and triglycerides by using commercial kits.
Results and discussion: The results of the present study showed that feeding concentrate supplement improved the growth status of lambs compared to the group without concentrate supplement, which had a significant effect in the first month, the third month and the entire of feeding period, but genotype had no effect on growth performance. The effect of adding concentrate supplement to the diet of lambs grazing on pasture was also effective during the period without feeding, so that the effect of feeding had a significant effect on the growth of lambs in all months without feeding. In addition, the effect of genotype had a significant effect in the fourth, fifth, seventh months and for the entire of the without feeding period. Concentrate supplement feeding increased significantly the concentration of blood urea and glucose. However, it had no significant effect on the concentrations of blood total protein, triglyceride and cholesterol. The genotype factor had a significant effect on urea concentration. Among the different biometric traits, the animal height showed a significant increase by the effect of feeding concentrate supplement and the interaction effect of genotype by feeding. Chest circumference was affected by the interaction effect of genotype on feeding. Supplemental feeding of concentrate had a significant effect on body length, chest circumference, height and pin width during the period without feeding.
Conclusion: Based on the results obtained, daily feeding of 250 grams of concentrate supplement is recommended when raising lambs in pasture grazing conditions. In addition, based on the results obtained, lambs of Moghani breed performed better than Moghani-Romanov cross-bred lambs under pasture rearing systems.
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