Genetic parameter estimates of early growth traits in the Tygerhoek Merino flock

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

doi:10.4314/sajas.v32i2.3747

Cited by 43 publications

(41 citation statements)

References 31 publications

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“…For four sheep breeds, Bromley et al (2001) reported direct heritability estimates of total weaning weight, ranging from 0.02 to 0.11 fitting the same model as in the present study, while Snyman et al (1997) (Cloete et al, 2002a;b;Matika et al, 2003). Estimates from other studies (Duguma et al, 2002;Rosati et al, 2002;Matika et al, 2003) are higher than the estimate in this study. The distribution of data for total weaning weight in the current study is highly skewed due to the inclusion of a large number of zero values for those ewes which failed to wean a lamb.…”

Section: Resultssupporting

confidence: 59%

“…These results suggest that selection on direct breeding values for increased weaning weight will not detrimentally affect reproduction. Although live weights at joining or at hogget age are genetically positively related to total weight of lamb weaned in Merinos (Cloete et al, 2002;3003b), it has not been studied in dual-purpose or meat sheep. In the previous study of Van der Merwe (1976) on the Elsenburg Dormer stud, reproduction was not phenotypically related to live weight.…”

Section: Resultsmentioning

confidence: 99%

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Revised models and genetic parameter estimates for production and reproduction traits in the Elsenburg Dormer sheep stud

Wyk¹,

Fair²,

Cloete³

2004

SA J. An. Sci.

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Genetic parameters for production and reproduction traits in the Elsenburg Dormer sheep stud were estimated using records of 11743 lambs born between 1943 and 2002. An animal model with direct and maternal additive, maternal permanent and temporary environmental effects was fitted for traits considered traits of the lamb (birth and weaning weight and survival). Fixed effects were sex, birth status, year and age of dam. Weaning weights were pre-adjusted to a 100-day equivalent. For reproduction traits (considered as traits of the ewe), which included number and weight of lambs born and weaned, repeatability models were fitted. The random part consisted of direct additive and ewe and sire permanent environmental effects. Direct and maternal heritability estimates were 0.13 and 0.23 for birth weight and 0.07 and 0.09 for weaning weight. Corresponding proportions of total phenotypic variance due to maternal permanent and temporary environment were 0.09 and 0.28 and 0.06 and 0.22 respectively. The genetic correlation between animal effects was -0.23 in the case of birth weight. The results showed that temporary environment (full sibs within a year) generally has a major effect on all pre-weaning traits. The direct heritability estimate of survival was 0.02 while the temporary maternal environmental variance as a proportion of phenotypic variance was 0.10. The estimates obtained for number and weight of lambs born and weaned were generally low, ranging from 0.03 for number of lambs born to 0.11 for total weight at birth. The permanent environmental effect of the ewe accounted for 6-7% of the total phenotypic variance. Genetic correlations of total weight of lamb weaned with the other reproduction traits were generally high (0.64 to 0.92) with low standard errors. The corresponding phenotypic, environmental and ewe permanent environmental correlations were all medium to high and estimated with a fair deal of accuracy according to low standard errors. The genetic relationship between weaning weight of the ewe and her lifetime reproduction (accumulated over four lambing chances) ranged between 0.40 and 0.67. Correlations between number of lambs weaned per ewe and weight of lamb weaned per ewe were particularly high (0.8 -0.9). It was concluded that the maternal environmental effect should be partitioned into two components (permanent and temporary) when data sets involving multiple births over many generations are considered.

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Section: Resultssupporting

confidence: 59%

Section: Resultsmentioning

confidence: 99%

Revised models and genetic parameter estimates for production and reproduction traits in the Elsenburg Dormer sheep stud

Wyk¹,

Fair²,

Cloete³

2004

SA J. An. Sci.

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“…No caso de ovinos de corte, os resultados observados são de certo modo contraditórios. Maria et al (1993) encontraram correlações altas e negativas entre esses efeitos para vários pesos, Neser et al (2001) estimaram correlação positiva e moderada para PN e de moderada a alta, mas negativa para peso à desmama, Duguma et al (2002) obtiveram estimativas negativas e moderadas para PN e baixas e positivas para peso à desmama e Boujenane e Kansari (2002) verificaram correlações moderadas e negativas para características do nascimento aos 90 dias de idade.…”

Section: Resultsunclassified

Estimação de parâmetros genéticos para características de crescimento de ovinos Santa Inês utilizando modelos uni e multicaracterísticas

Sarmento¹,

Torres²,

Sousa³

et al. 2006

Arq. Bras. Med. Vet. Zootec.

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RESUMOUtilizaram-se registros de pesos do nascimento aos 196 dias de idade de 927 cordeiros, filhos de 45 reprodutores e 323 matrizes de ovinos da raça Santa Inês, controlados de 1983 a 2000, com o objetivo de avaliar três modelos que consideraram ou não o efeito genético materno e a (co)variância entre os efeitos genéticos direto e materno, para estimar componentes de variância e parâmetros genéticos por meio de modelos uni e bicaracterísticas. Os componentes de (co)variâncias e os parâmetros genéticos direto e materno para os pesos foram estimados pelo método da máxima verossimilhança restrita, sob modelo animal. De acordo com o teste de razão de verossimilhança, o modelo que incluiu o efeito aditivo direto mais o efeito materno foi o indicado para todas as características estudadas. A não-inclusão do efeito materno no modelo de análise superestimou as variâncias e as herdabilidades para o efeito direto (0,56 a 0,23). A importância do efeito materno diminuiu ao longo da trajetória de crescimento, à medida que a idade dos cordeiros aumentava. As variâncias e as herdabilidades estimadas por meio dos modelos bicaracterísticas para os efeitos genéticos diretos foram superiores às obtidas pelos modelos unicaracterísticas. As correlações genéticas entre as características foram altas e positivas. O efeito materno foi importante para todas as características estudadas, devendo, portanto, ser considerado nos estudos de crescimento. Os modelos bicaracterísticas possibilitaram resgatar parte da variância aditiva direta, levando a estimativas maiores de herdabilidade.

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“…The program was mainly focused on indigenous genetic resources of sheep and traditional breeders were total involved in all steps of breeding program [10][11][12]. Southern Region Agricultural Research Institute (SRARI) was an active implementing partner of the community-based sheep improvement program and launched community based sheep breeding programs at different Zones in the region following the same approach.…”

Section: Introductionmentioning

confidence: 99%

Effect of Non-Genetic Factors on Reproductive and Growth Performance of Abera Sheep under Community Based Breeding Program in SNNPRS Ethiopia

Marufa¹,

Taye²,

Abebe³

et al. 2017

J Adv Dairy Res

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The study was conducted in Sidama Zone, Dara District Southern Ethiopia. The intention was to investigate the effect of non-genetic factors on reproductive and growth performance of Abera sheep in the District. For this study three years (2013)(2014)(2015) performance data were obtained from Hawassa research center, Dara sub-site. Study identified age at first lambing (AFL) and lambing interval (LI) of the sheep were 9.6 and 12.9 months, respectively; while annual reproductive rate and litter size of the ewes were 1.9 and 1.5 heads. Average birth weight, weaning weight and 6 month weight of Abera sheep were 2.8, 12.3 and 18.5 kg, respectively; while pre and post weaning average daily weight gains were 106 and 40 g/day, respectively. Birth type, sex and year had significant (p<0.05) effect on birth weight (BWT), weaning weight (WWT) and six-months weight; whereas season and parity had significant (P<0.05) effect on BWT and WWT only. Sex and birth type had significant (p<0.01) effect on pre-weaning average daily gain whereas year, season and parity had significant effect on both pre and post-weaning average daily gain. There was within breed variability in growth traits, which were significantly influenced by non-genetic factors like birth type, sex, year, season and parity. Selection for further improvement to achieve higher lamb crop with superior growth performance should be prioritized as within population variability is raw material for improvement through selection. Molecular characterization should also be carried out to identify uniqueness of Abera sheep.

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Genetic parameter estimates of early growth traits in the Tygerhoek Merino flock

Cited by 43 publications

References 31 publications

Revised models and genetic parameter estimates for production and reproduction traits in the Elsenburg Dormer sheep stud

Revised models and genetic parameter estimates for production and reproduction traits in the Elsenburg Dormer sheep stud

Estimação de parâmetros genéticos para características de crescimento de ovinos Santa Inês utilizando modelos uni e multicaracterísticas

Effect of Non-Genetic Factors on Reproductive and Growth Performance of Abera Sheep under Community Based Breeding Program in SNNPRS Ethiopia

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