Estimation of genetic and environmental parameters of milk production traits in Slovak purebred sheep using test-day model

Oravcová, M.; Groeneveld, Eildert; Kovač, Milena; Peškovičová, D.; Margetín, M.

doi:10.1016/j.smallrumres.2004.03.002

Cited by 33 publications

(40 citation statements)

References 13 publications

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“…Due to the large variation in flock size, the flock-test month effect was included in the random part of the model as previ-ously done by Brežnik (1999), Komprej et al (2003) and Oravcová et al (2005), causing the enlargement of phenotypic variance. Exact quantification of this enlargement is difficult, since it is not possible to obtain reliable estimates of variance components with flock-test month effect in the fixed part of the model.…”

Section: Discussionmentioning

confidence: 99%

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Covariance components by a repeatability model in Slovenian dairy sheep using test-day records

Komprej¹,

Kompan²,

Kovač³

2009

CZECH J ANIM SCI

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ABSTRACT:The estimation of covariance components for daily milk yield, fat and protein content was performed in three Slovenian dairy sheep breeds (Bovec, Improved Bovec, and Istrian Pramenka). In the period 1994-2002, 38 983 test-day records of 3 068 ewes were collected according to ICAR regulations (method A4). All the available relationships between animals were considered. For that reason, information on 3 534 animals was included. Test-day records were analysed by a multiple-trait repeatability animal model. In its fixed part, the model contained breed and season of lambing as classes. Days after lambing, parity, and litter size were treated as covariates. Days after lambing were modelled with modified Ali-Schaeffer's lactation curve, parity with quadratic, and litter size with linear regression. The random part of the model consisted of flock-test month effect, additive genetic effect, permanent environment effect over lactations, and permanent environment effect within lactation. Covariance components were estimated using the restricted maximum likelihood method (REML). The estimated heritabilities were 0.11 for daily milk yield, 0.08 for fat content, and 0.10 for protein content. A relatively high variance ratio for all milk traits was explained by the flock-test month effect (from 0.27 for daily milk yield to 0.57 for protein content), while ratios explained by both permanent environment effects were lower (up to 0.13). Additive genetic correlations between daily milk yield and fat content, and daily milk yield and protein content were negative and similar (-0.36 and -0.37). A high and positive (0.67) additive genetic correlation between fat and protein content was found. Correlations for environmental effects showed a pattern similar to additive genetic correlations. Genetic parameters estimated in Slovenian dairy sheep showed that genetic progress in milk traits could be achieved using test-day milk records.

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Section: Discussionmentioning

confidence: 99%

“…The model was applied several times to Spanish Churra ewes by Baro et al (1994), El-Saied et al (1998a,b,c) and also to Latxa and Manchega sheep by Serrano et al (2001). It was also used in Slovenian dairy sheep breeds by Brežnik (1999) and in Improved Walachian and Tsigai breeds from Slovakia by Oravcová et al (2005).…”

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confidence: 99%

Covariance components by a repeatability model in Slovenian dairy sheep using test-day records

Komprej¹,

Kompan²,

Kovač³

2009

CZECH J ANIM SCI

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“…Covariance components were estimated using the REML (Restricted Maximum Likelihood) method as applied in VCE 6 (Groeneveld et al, 2010). The main effects were described in previous studies of Oravcová et al (2005Oravcová et al ( , 2006Oravcová et al ( , 2007Oravcová et al ( and 2008. The model used here was aimed to estimated only one lactation curve for each trait in each breed (i.e.…”

Section: • E Is the Vector Of Residualsmentioning

confidence: 99%

“…The first study aimed at quantification of direct additive genetic effect and permanent environmental effect of ewe (Oravcová et al, 2005(Oravcová et al, , 2008 showed that these effects are important sources of variability of milk traits and should be taken into account when fitting lactation curves to milk traits data. Heritabilities of milk traits were estimated between 0.12 and 0.19, and between 0.06 and 0.10 in Tsigai and Improved Valachian breeds, respectively.…”

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The effect of stage of lactation on daily milk yield, and milk fat and protein content in Tsigai and Improved Valachian ewes

2015

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“…Means and genetic standard deviations of all traits and their MEVs and REVs calculated for typical production circumstances (base production conditions) are summarised in Table 1. Genetic standard deviations of the traits were derived from Oravcová et al (2005) and from the Breeding Services of the Slovak Republic, s.e. (not published) when available.…”

Section: Methodsmentioning

confidence: 99%

Impact of production strategies and animal performance on economic values of dairy sheep traits

Krupová

Wolfová

Krupa

et al. 2012

Animal

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The objective of this study was to carry out a sensitivity analysis on the impact of various production strategies and performance levels on the relative economic values (REVs) of traits in dairy sheep. A bio-economic model implemented in the program package ECOWEIGHT was used to simulate the profit function for a semi-extensive production system with the Slovak multi-purpose breed Improved Valachian and to calculate the REV of 14 production and functional traits. The following production strategies were analysed: differing proportions of milk processed to cheese, customary weaning and early weaning of lambs with immediate sale or sale after artificial rearing, seasonal lambing in winter and aseasonal lambing in autumn. Results of the sensitivity analysis are presented in detail for the four economically most important traits: 150 days milk yield, conception rate of ewes, litter size and ewe productive lifetime. Impacts of the differences in the mean value of each of these four traits on REVs of all other traits were also examined. Simulated changes in the production circumstances had a higher impact on the REV for milk yield than on REVs of the other traits investigated. The proportion of milk processed to cheese, weaning management strategy for lambs and level of milk yield were the main factors influencing the REV of milk yield. The REVs for conception rate of ewes were highly sensitive to the current mean level of the trait. The REV of ewe productive lifetime was most sensitive to variation in ewe conception rate, and the REV of litter size was most affected by weaning strategy for lambs. On the basis of the results of sensitivity analyses, it is recommended that economic values of traits for the overall breeding objective for dairy sheep be calculated as the weighted average of the economic values obtained for the most common production strategies of Slovak dairy sheep farms and that economic values be adjusted after substantial changes in performance levels of the traits.

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Estimation of genetic and environmental parameters of milk production traits in Slovak purebred sheep using test-day model

Cited by 33 publications

References 13 publications

Covariance components by a repeatability model in Slovenian dairy sheep using test-day records

Covariance components by a repeatability model in Slovenian dairy sheep using test-day records

The effect of stage of lactation on daily milk yield, and milk fat and protein content in Tsigai and Improved Valachian ewes

Impact of production strategies and animal performance on economic values of dairy sheep traits

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