Genetic relationships of lamb weight, maternal ability, and mature ewe weight in Swedish finewool sheep.

Näsholm, A.; Danell, Öje

doi:10.2527/1996.742329x

Cited by 121 publications

(92 citation statements)

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“…Selecting for either birth weight or weaning weight without changing ewe weight would be difficult. This is in agreement with other reports (Nasholm & Danell, 1996;Yazdi et al, 1997;Mousa et al, 1999).…”

Section: Resultssupporting

confidence: 83%

Phenotypic and genetic relationships between lamb and ewe traits for the Sabi sheep of Zimbabwe

Matika¹,

Wyk²,

Erasmus³

et al. 2001

SA J. An. Sci.

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Genetic and phenotypic correlations were estimated between lamb and ewe traits in a flock of Sabi sheep reared at the Matopos Research Station. Direct additive estimates of heritability were: 0.28 ± 0.04; 0.17 ± 0.00; 0.25 ± 0.01; 0.39 ± 0.01; 0.59 ± 0.01; 0.50 ± 0.01; 0.68 ± 0.03; 0.12 ± 0.003; 0.25 ± 0.01; 0.11 ± 0.00; 0.12 ± 0.00; for birth weight, weaning weight (120 days), 12 month weight, 18 month weight, ewe mating weight, post partum weight, ewe weight at weaning of lamb, total weight of lamb weaned, slaughter weight, hot and cold carcass weights respectively. Genetic correlations between birth weight and other weights to 18 months were high (0.75-0.85), whilst the relationship between weaning, 12 month and 18 month weight was close to unity. The genetic correlation between birth weight and ewe weights (mating, post-partum and dam weight at weaning of lamb) were moderate viz. 0.51 ± 0.08, 0.40 ± 0.09, 0.49 ± 0.07 respectively and were close to unity at 18 months of age viz. 0.96 ± 0.02, 0.92 ± 0.03, and 0.84 ± 0.03 respectively. Total weight of lamb weaned was moderately correlated to birth weight (r g = 0.46 ± 0.15) but tended to be highly correlated with 18 month weight (0.92 ± 0.10) and ewe weights (0.75 ± 0.09-0.91 ± 0.07). The genetic correlation between birth weight and slaughter and carcass weight was moderate and was high at 18 months. The heritability estimates from a univariate logit transformed analysis for fertility, prolificacy and lamb survival were 0.08 ± 0.04, 0.22 ± 0.03, and 0.01 ± 0.02 respectively. The genetic correlation between fertility and lamb weight and ewe weights was low (-0.08 ± 0.004, to 0.06 ± 0.02) and some estimates had large standard errors. The genetic correlation between prolificacy and birth weight was close to zero. The genetic correlations between prolificacy and weaning weight, 12 month weight, 18 month weight, ewe mating, post-partum and ewe weight at weaning were 0.07 ± 0.02; 0.12 ± 0.00; 0.07 ± 0.02; 0.22 ± 0.00; 0.13 ± 0.00; 0.24 ± 0.00 respectively, and that between fertility and prolificacy was negative (-0.17 ± 0.07). Genetic correlations between lamb survival and birth weight, weaning weight, 12 month weight, 18 month weight and total weight of lamb weaned were 0.18 ± 0.00, 0.26 ± 0.00, 0.15 ± 0.00, 0.15 ± 0.00, 0.13 ± 0.00 respectively. Selection for birth weight and total weight of lamb weaned have possible uses in a selection index for the Sabi flock. _______________________________________________________________________________________

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Section: Resultssupporting

confidence: 83%

Phenotypic and genetic relationships between lamb and ewe traits for the Sabi sheep of Zimbabwe

Matika¹,

Wyk²,

Erasmus³

et al. 2001

SA J. An. Sci.

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“…This result indicates that slow genetic progress appears possible for this trait under the prevalent management conditions. The total heritability for birth weight observed in this study was comparable to the findings of Ekiz et al (2004) (0.14), Nasholm and Danell (1996) (0.24), and Neser et al (2001) (0.21). Higher estimates of total heritability in comparison to this study were obtained by Assan et al (2002) in Sabi sheep (0.77).…”

Section: Birth Weightsupporting

confidence: 80%

“…The low productivity and the poor environment could partially explain low maternal effects at weaning for this breed in this study. These results also suggest that the importance of maternal effects, and particularly additive maternal effects, declined from birth to weaning, which agrees with results of Tosh and Kemp (1994), Snyman et al (1995), Nasholm and Danell (1996), Yazdi et al (1997), El Fadili et al (2000, and Mandal et al (2008).…”

Section: Weaning Weightsupporting

confidence: 80%

“…A number of studies have demonstrated that maternal effects are substantial for growth-related traits in sheep and the inclusion of maternal effects in animal models has an important effect on the estimates of direct heritability (Maria et al 1993;Ozcan et al 2005;Mandal et al 2006;Rashidi et al 2008;Baneh et al 2010). Genetic and environmental relationships between direct and maternal effects for growth have often varied from moderately positive to highly negative in various sheep breeds (Maria et al 1993;Tosh & Kemp 1994;Snyman et al 1995;Nasholm & Danell 1996;Yazdi et al 1997;Notter 1998). Hence, to achieve optimum progress in a selection program, both direct and maternal components should be taken into account, especially if there is an antagonistic relationship between them.…”

Section: Introductionmentioning

confidence: 99%

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Genetic parameter estimates for growth traits in Iran-Black sheep

Kamjoo

Baneh

Yousefi

et al. 2013

Journal of Applied Animal Research

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The present study was conducted to estimate variance components and genetic parameters for growth traits of Iran-Black sheep, maintained at the Abbasabad sheep breeding station, located in northeast of Mashhad, (Razavi Khorasan province of Iran) over a period of 24 years (1981 through 2004). Records of 4607 lambs descended from 155 rams, and 1227 ewes were used in the study. Traits included for the present study were birth weight (BW), weaning weight (WW), weight at 6 months (W6), weight at 9 months (W9), and yearling weight (YW). Analyses were carried out by restricted maximum likelihood (REML) fitting an animal model and ignoring or including maternal genetic or permanent environmental effects. Six different animal models were fitted for all traits. The most appropriate model was chosen after testing the improvement of the log-likelihood values. Heritability estimates for weight at birth; weaning; and 6, 9, and 12 months of age were 0.04, 0.14, 0.16, 0.19, and 0.18, respectively. Maternal heritability of body weight declined from 0.33 at birth to 0.04 at six months of age. The maternal permanent environmental component accounted for 6% to 15% to the total variance for all traits under study. The direct-maternal genetic correlation (r am ) was positive for all traits and ranged from 0.3690.27 for BW to 0.9990.98 for YW, but was never significant. The results showed that modest rates of genetic progress appear possible for all weights. Results also suggest that maternal additive effects were only important in early stages of growth, whereas a permanent environmental maternal effect existed at all ages up to 12 months of age, probably as a carry-over effect of maternal influences present at weaning. Direct genetic correlations (r a1,a2 ) between traits were positive and ranged from 0.82 (BW-WW) to 0.99 (W6-YW). The estimates of correlation between permanent environmental maternal effect among traits were close to those of r a1,a2 . Phenotypic and environmental correlations for all traits were generally lower than direct genetic correlations.

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“…Consequently, for maintenance traits, requirements for dietary energy and protein (equations (3) and (4) in Appendix 1) were always assumed to be positively related, as maintenance processes require both protein and energy [12]. Further, as body weight is generally positively correlated across time [20], it was assumed that the growth trait parameters EBW 0 and P mat , and EBW 0 and L mat , respectively, are weakly positively correlated. For the maturity traits, P mat and L mat , both positive and negative genetic correlations were considered, representing breeds that evolved through different selection procedures (e.g.…”

Section: Test Assumption 1: Introducing Co-variation Between Underlyimentioning

confidence: 99%

Exploring the assumptions underlying genetic variation in host nematode resistance(Open Access publication)

et al. 2008

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-The wide range of genetic parameter estimates for production traits and nematode resistance in sheep obtained from field studies gives rise to much speculation. Using a mathematical model describing host -parasite interactions in a genetically heterogeneous lamb population, we investigated the consequence of: (i) genetic relationships between underlying growth and immunological traits on estimated genetic parameters for performance and nematode resistance, and (ii) alterations in resource allocation on these parameter estimates. Altering genetic correlations between underlying growth and immunological traits had large impacts on estimated genetic parameters for production and resistance traits. Extreme parameter values observed from field studies could only be reproduced by assuming genetic relationships between the underlying input traits. Altering preferences in the resource allocation had less pronounced effects on the genetic parameters for the same traits. Effects were stronger when allocation shifted towards growth, in which case worm burden and faecal egg counts increased and genetic correlations between these resistance traits and body weight became stronger. Our study has implications for the biological interpretation of field data, and for the prediction of selection response from breeding for nematode resistance. It demonstrates the profound impact that moderate levels of pleiotropy and linkage may have on observed genetic parameters, and hence on outcomes of selection for nematode resistance. gastro-intestinal parasites

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Genetic relationships of lamb weight, maternal ability, and mature ewe weight in Swedish finewool sheep.

Cited by 121 publications

References 0 publications

Phenotypic and genetic relationships between lamb and ewe traits for the Sabi sheep of Zimbabwe

Phenotypic and genetic relationships between lamb and ewe traits for the Sabi sheep of Zimbabwe

Genetic parameter estimates for growth traits in Iran-Black sheep

Exploring the assumptions underlying genetic variation in host nematode resistance(Open Access publication)

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