Genetic improvement in growth traits of first generation hybrid lambs due to crossbreeding of Romanov ram with native sheep of Lori breed

Background and Aim: In order to compare the growth traits of hybrid lambs resulting from crossbreeding of Romanov rams with native sheep of Lori breed, ۱۹۵ ewes of Lori breed that were at least two months old were selected.Methods: To induce estrus synchronization in Lori lactating ewes, flushing diets were given to them ۱۴ days before laparoscopic surgery and then estrus synchronization was performed. On the fourteenth day of the experiment, the ewes received a dose of ۴۰۰ international units of PMSG (Hispanic) at the same time as removing the sponge. The ewes were inoculated with frozen sperm of four Romanov rams, ۴۸ hours after sponge removal. At birth, items such as ewe number, lamb number, birth weight of lambs, sex of lambs, and birth type of lambs were recorded. Also, pregnancy rate, fertility rate and twinning were recorded. The lambs were then weighed at birth to ۲۷۰ days of age. Pedigree and production performance data of crossed Lori lambs were entered in Excel software and analyzed using R software.Results: Gestational length, birth weight, three-month weight, six-month weight, nine-month weight in F۱ lambs were ۱۵۶.۶۱±۰.۵۵, ۳.۸۳±۰.۰۷۴, ۲۶.۲۹±۰.۴۴, ۴۴.۲۷±۰.۵۶, ۵۱.۳۲±۰.۶۵ respectively. The results showed that the birth weight, three months, six months and nine months weight in Lori-Romanov crosses incressed comparing to local breed.Conclusion: Twinning rates have also increased in mixed ewes. Therefore, controlled crossbreeding with respect to the preservation of indigenous genetic resources can help increase production efficiency in sheep breeding raring centers.

Keywords:

Lori Sheep , Genetic improvement , crossbreeding , Laparoscopy