Abstract
The data set for estimation of genetic and phenotypic parameters of reproductive traits in Kordi sheep were collected from 1996 to 2013. The reproductive traits included age at first lambing (AFL), number of lambs born (NLB/EL) and weaned (NLW/EL) per ewe in each lambing, total weight of lambs born (TWLB/EL) and weaned (TWLW/EL) per ewe in each lambing, total number of lambs born (TNLB) and weaned (TNLW) per ewe, total weight of lambs born (TWLB) and weaned (TWLW) per ewe. The genetic parameters were estimated through restricted maximum likelihood method using WOMBAT. The effects of environmental factors (year of lambing, type of birth, maternal age at lambing) on all reproductive traits were significant (p < 0.01). Direct heritability, maternal heritability and the ratio of maternal permanent environmental variance to phenotypic variance for reproductive traits were estimated in the range from 0.07 to 0.18, 0.03 to 0.08 and 0.01 to 0.03, respectively. Genetic and phenotypic correlations between reproductive traits were estimated to be positive and within the range of 0.09 to 0.96 and 0.02 to 0.29, respectively. The results suggest that selection based on number of lambs born per ewe can be more effective than other traits in improving reproductive performance in Kordi ewes.
Highlights
Kordi sheep is an Iranian fat-tailed native breed which develop to produce meat
The increase of reproductive performance compared with faster growth rate or decrease of body fat is far more effective in Maringá, v. 39, n. 3, p. 323-328, July-Sept., 2017 reduction of economic costs of meat production which could result from an increase in the number and weight of reared lambs reared per productive ewes due to the increase of conception rate, number of born lambs per lambing, survival of lambs until weaning and their growth (Fogarty, 1995)
The results of this study showed that the effects of fixed factors such as lambing year, type of birth, and age of dam at lambing on all reproductive traits were significant (p < 0.01)
Summary
Kordi sheep is an Iranian fat-tailed native breed which develop to produce meat. The main distribution area of this breed is North Khorasan Province of Iran with a population of over 325,350 head which are mainly grown traditionally by nomadic people in pastures (Saghi et al, 2014). The main source of protein in Iran is mutton because of the special taste of people, so that 42% of total red meat production comes from the sheep. Since this amount of produced meat does not meet the needs of the growing population, increased efficiency in its production is of great importance that can be influenced by sheep reproductive function. Economic efficiency of sheep breeding is significantly influenced by the ewes' reproductive performance. The increase of reproductive performance compared with faster growth rate or decrease of body fat is far more effective in Maringá, v. The increase of reproductive performance compared with faster growth rate or decrease of body fat is far more effective in Maringá, v. 39, n. 3, p. 323-328, July-Sept., 2017 reduction of economic costs of meat production which could result from an increase in the number and weight of reared lambs reared per productive ewes due to the increase of conception rate, number of born lambs per lambing, survival of lambs until weaning and their growth (Fogarty, 1995)
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