Abstract
The aims of the study were to investigate the fixed effects which are considered to influence ewe productivity and to estimate the genetic parameters for ewe productivity traits of Lohi sheep. Genetic parameters were estimated by restricted maximum likelihood (REML) procedure using the GENSTAT program. The effects of year and age of ewe were significant for fertility, litter size at birth (LSB), litter size at weaning (LSW), litter weight at birth (LWB) and litter weight at weaning (LWW). The least squares means of fertility, LSB, LSW, LWB and LWW were 0.904, 1.422, 1.358, 6.689 kg and 41.577 kg, respectively. The means of total number of lambs born (TLB), total number of lambs weaned (TLW), total birth weight of lambs (TWB) and total weight of lambs weaned (TWW) per ewe over four lambing opportunities were 5.48, 5.25, 25.61 kg and 162.47 kg, respectively. Estimates of heritability for fertility, LSB, LSW, LWB and LWW were 0.0250, 0.0533, 0.0430, 0.0462 and 0.0255, respectively; and estimates of repeatability for these traits were 0.1242, 0.0787, 0.0772, 0.0882 and 0.0715, respectively. The low estimates of heritability and repeatability obtained in the current study for ewe productivity traits indicate that selection based on the ewe's own performance may result in slow genetic improvement. Key words: Genetic parameter, litter size, ewe productivity.
Highlights
The Lohi breed is the biggest and most productive of all the breeds of sheep in Pakistan
The first four lambing opportunities of a ewe were used to indicate lifetime reproduction, and total number of lambs born (TLB), total number of lambs weaned (TLW), total birth weight of lambs (TWB) and total weight of lambs weaned (TWW) per ewe; over four lambing opportunities were used as lifetime productivity traits
The least squares means and standard errors of fertility, litter size at birth (LSB) and litter size at weaning (LSW), and litter weight at birth (LWB) and litter weight at weaning (LWW) of Lohi sheep are presented in Tables 1 and 2, respectively
Summary
The Lohi breed is the biggest and most productive of all the breeds of sheep in Pakistan. It comprises some 40% of the Punjab and 15% of the national sheep production (Government of Pakistan, 2009). The Lohi breed belongs to the irrigated areas of the central Punjab but is widespread in other regions of the province . There is a wide diversity in various production traits of this breed which suggests that there is a great scope for improvement of performance traits. This diversity in performance traits could be due to several genetic and environmental influences. Efficiency of lamb production is controlled by reproduction, mothering ability and milk production of the ewe, as well as growth rate and survival of the lamb (Rao and Notter., 2000)
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