عنوان مقاله [English]
Background and objectives: Sheep breeding in Iran has been relied heavily on rangeland, but in the current situation, this breeding method needs to investigate again. In order to preserve this profession, it was necessary to seek new methods and solutions in order to make it a professionally dynamic and economical job. One of the effective methods for increasing the growth rate of lambs and improving the quantitative and qualitative efficiency of carcasses is the use of crossbreeding and produce of commercial breed for lamb production systems. Therefore, this research done for producing, promoting and developing livestock production in intensive breeding system.
Material and methods: Two hundreds heads of 2-4 year old ZEL ewes purchased from the flocks of the GOLESTAN province (according to ZEL breed characteristics) and transferred to the shirang experimental station. Ewes randomly assigned to two groups of 100 heads with regard to age groups. They were breed in two different reproductive methods: 1- pure zel (zel x zel) breeding, synchronization, multiplicity (with Hormone therapy), and multiplicity (three times in two years), 2- Crossbreeding (shale x zel), synchronization, multiplicity (with hormone therapy), and multiplicity (three times in two years). The experimental animals flushed for 14 days before mating with flushing diets. The reproductive characteristics of ewes, including: Apparent fertility, Prolificacy, Ewe reproduction performance, and Ewe production performance, investigated.
Results: Under traditional (conventional) breeding conditions of zel breed on average for 100 heads ewe, with 55 to 60% parturition only 70 lambs or about 2030 kilograms live weight of lambs obtained at the end of the 100 days of fattening period. However, under industrial (intensive) conditions in the ZEL pure breed, this factor is 5382 kilograms live weight (increased by 165%) and in the crossbred lambs (shale x zel) increase to 6774 kilograms live weight (with an increase of 234%). It is evident; of course, production costs in the industrial breeding system were up to 30% higher than the current breeding method in the region. The average lambing rate under triditional conditions of the Zel breeding system was 70 lambs per 100 ewes per year but in this experiment with the ZEL pure breed, during two years, from 207 ewes 624 lambs was borne. That is, each year, 151 lambs per 100 ewe have produced, which has almost doubled than usual.
Conclusions: In the industrial breeding method, during breeding in two years, the average lambs per ewe was 1.55, while in the usual breeding method in the region, each lamb is produced at 0.7 lamb per year. At the end of the breeding period, the lambs of pure zeal 165% and crossbred lambs (shale x zel) yielded (234%) more lamb weight than the usual breeding in the region.