Genetic and environmental parameters for ewe productivity in Merinos

Duguma, G.; Schoeman, S.J.; Cloete, S.W.P.; Jordaan, G.F.

doi:10.4314/sajas.v32i3.3740

Cited by 31 publications

(36 citation statements)

References 19 publications

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“…The model with only direct additive random effects best fits the data for all ewe reproduction traits, and was therefore used to analyse these traits. This is consistent with the majority of studies on sheep for corresponding ewe reproduction traits (Olivier et al, 2001;Duguma et al, 2002;Zishiri et al, 2013). The results from the current study also indicated that only the direct additive effect had a significant contribution to variation in CY, SL, SS, and CVFD.…”

Section: Resultssupporting

confidence: 92%

Genetic parameters for ewe reproduction with objectively measured wool traits in Elsenburg Merino flock

Matebesi-Ranthimo¹,

Cloete²,

Wyk³

et al. 2017

SA J. An. Sci.

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Reproduction is important for sustainable lamb production in Merino sheep. Data from a Merino flock maintained at Elsenburg Research Farm in the Western Cape, South Africa, were used to investigate the genetic parameters for ewe reproduction traits and their relationship with objectively measured wool traits. Traits included number of lambs born during the first lambing opportunity (NLB1), number of lambs weaned during the first lambing opportunity (NLW1), total weight of lamb weaned during the first lambing opportunity (TWW1), number of lambs born during a ewe's lifetime (NLB3), number of lambs weaned during a ewe's lifetime (NLW3), and total weight weaned per ewe's reproductive life (TWW3) Fixed effects of selection line, birth type, sex, age of the dam in years, year of birth, and the sex*birth year interaction had significant effects on all bodyweight and objectively measured wool traits. Only year of birth and selection line affected ewe reproduction traits. Heritability estimates amounted to 0.10 ± 0.03 for NLB1, 0.07 ± 0.02 for NLW1, 0.10 ± 0.04 for TWW1, 0.25 ± 0.04 for NLB3, 0.12 ± 0.03 for NLW3, and 0.18 ± 0.04 for TWW3. Wool traits were moderately heritable at 0.28 ± 0.05 (staple strength) to 0.60 ± 0.03 (clean yield (CY)) and coefficient of variation of fibre diameter (CVFD). Relationships among ewe reproduction traits were high, ranging from 0.74 between TWW1 and NLB3 to 1.00 between NLW1 and TWW1. The genetic relationships of ewe reproduction traits with wool weights and staple length were positive. Fibre diameter (FD) and CY were unfavourably related to ewe reproduction traits. It seems possible to improve ewe reproduction when selecting on NLB, NLW, and TWW in Merino sheep without unwanted correlated response to selection in wool traits, with the exception of FD and CY.______________________________________________________________________________

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Section: Resultssupporting

confidence: 92%

Genetic parameters for ewe reproduction with objectively measured wool traits in Elsenburg Merino flock

Matebesi-Ranthimo¹,

Cloete²,

Wyk³

et al. 2017

SA J. An. Sci.

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“…Therefore, ewe productivity could be improved by increasing the number and weight of lambs weaned per ewe within a specific year (Duguma et al 2002).…”

Section: Introductionmentioning

confidence: 99%

Estimation of genetic parameters for reproductive traits in Mehraban sheep

Yavarifard¹,

Hossein-Zadeh²,

Shadparvar³

2015

CZECH J ANIM SCI

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Genetic parameters for basic and composite reproductive traits in Mehraban sheep were estimated. Data included 10 257 records on reproductive performances of 5813 lambs from 69 sires and 603 dams which were collected from 1994 to 2011 in the Mehraban breeding station in Hamedan province, western Iran. Studied traits were litter size at birth (LSB), litter size at weaning (LSW), litter mean weight per lamb born (LMWLB), litter mean weight per lamb weaned (LMWLW), total litter weight at birth (TLWB), and total litter weight at weaning (TLWW). Test of significance to include fixed effects in the statistical model was performed using the GLM procedure of SAS. Genetic parameters were estimated with univariate and bivariate repeatability animal models using WOMBAT program. Direct heritability estimates were 0.16, 0.14, 0.03, 0.16, 0.06, and 0.18 for LSB, LSW, LMWLB, LMWLW, TLWB, and TLWW, respectively, and corresponding repeatabilities were 0.02, 0.01, 0.73, 0.41, 0.27, and 0.03. The estimate for animal-dependent permanent environmental variance ranged from 0.01 ± 0.04 for LMWLW to 0.23 ± 0.04 for LSB. Genetic correlation estimates between traits ranged from −0.98 for LSB-LMWLW to 0.99 for LSB-TLWB. Phenotypic and environmental correlations were generally lower than genetic correlations. Phenotypic correlations ranged from −0.50 for LSB-LMWLB to 0.85 for LMWLW-TLWW. Environmental correlations ranged from −0.45 for LSB-LMWLB to 0.87 for LMWLW-TLWW. The results suggested that indirect selection based on TLWW could improve the reproductive performance in Mehraban ewes more effectively than if based on the other traits.

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“…Reproductive characteristics have been recognized as main factors affecting profitability of sheep breeding systems (Matos et al, 1997). Therefore, improvement in ewe productivity is a key target in sheep breeding and could be attained to some extent by increasing the number of lambs weaned and weight of lambs weaned per ewe within a specific year (Duguma et al, 2002). The major part of the income in any sheep production system is supplied through lamb production (Ekiz et al, 2005).…”

Section: Introductionmentioning

confidence: 99%