Breeding objectives for Targhee sheep1

Borg, Randy; Notter, D. R.; Kuehn, L. A.; Kott, R. W.

doi:10.2527/jas.2006-064

Cited by 35 publications

(28 citation statements)

References 31 publications

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“…The traits of economic importance found here are in agreement with Borg et al (2007), Kosgey et al (2004) and Wolfová et al (2009) except for wool traits which are not important in this region of Brazil as generally sheep are not sheared. Most sheep selection indices involve wool traits, which make them difficult for comparison with data here.…”

Section: Resultssupporting

confidence: 91%

Selection objectives and criteria for sheep in Central Brazil

et al. 2011

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-Three production systems for sheep (Low -L, Medium -M and High -H technology), with increasing technological levels, were studied under conditions in the Center-west of Brazil, to determine economic weights and selection indices of important traits. Receipts and costs were simulated using an economic simulator to calculate the structure of the operational costs. Only characteristics that were responsible for more than 10% of the profit were studied, which included: number of weaned lambs, food consumption (ewe and lamb), weight of carcass and weight of female lambs sold for reproduction.Regardless of the index used (profitability or yield) or system (L, M or H), the economic weights are larger for the number of lambs weaned per ewe. With improvement in the technology used within the production system (H to L) the importance of this trait becomes less important. Lamb growth increased and weight of female for slaughter decreased in importance in higher technology systems. Changes in herd structure had little influence on economic values, whereas (co)variances were important sources of change in selection indices.

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Section: Resultssupporting

confidence: 91%

Selection objectives and criteria for sheep in Central Brazil

et al. 2011

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“…Other than Australia, New Zealand, and the United States (Borg et al, 2007), wool traits are of low importance in European countries (Conington et al, 2006;Krupová et al, 2009), which was also confirmed in our investigation. Therefore, these traits are often ignored in breeding goals.…”

Section: Economic Weights Of Traits For Suffolk Sires In Different Brsupporting

confidence: 91%

Calculating economic weights for sheep sire breeds used in different breeding systems1

Wolfová

Wolf

Milerski

2011

Journal of Animal Science

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The objective of this paper was to adapt gene-flow methodology for the calculation of economic weights (EW) for direct and maternal traits and trait components in sheep and to apply this methodology to the Suffolk breed in the Czech Republic. Computer programs were developed in which annual-lambing sheep production systems with purebreeding or partial terminal crossing were simulated. Using these programs, the EW for 12 production and functional traits were estimated for i) Suffolk sires whose sons were used both in purebreeding and in terminal crossing with the 4 dual-purpose breeds, Romanov, Sumavska, Romney, and Merinolandschaf; and ii) Suffolk sires used only for terminal crossing. For case (i), the EW were at first calculated separately for the purebreeding system and for the crossing systems with the 4 dual-purpose breeds in dam position. Compound EW for the general breeding goal for Suffolk were then estimated as weighted averages from the EW in the 5 subsystems. Standardized EW were calculated by multiplying the marginal EW with the genetic SD of the trait, and relative EW were defined as absolute values of the standardized EW expressed as percentage of the sum of the absolute values of the standardized EW over all traits. The 5 most important trait components for Suffolk sires whose sons were used both in purebreeding and in terminal crossing were (relative EW given in parentheses): the direct components of survival rate until weaning (21.0%), daily BW gain until weaning (14.1%), survival rate at birth (14.0%), the maternal component of survival rate until weaning (10.7%), and litter size at lambing (7.6%). There were only small differences between the relative EW calculated for the whole system with pure- and crossbreeding and the relative EW for the purebred system within the Suffolk breed. Therefore, selection of Suffolk rams using a selection index based on the compound EW is expected to be of high efficiency in all of the simulated breeding systems. Only direct traits were relevant for Suffolk sires used only for terminal crossing; the most important (range of relative EW calculated for the 4 crossing systems given in parentheses) were survival rate until weaning (35.2 to 36.5%), daily BW gain until weaning (24.2 to 26.3%), and survival rate at birth (23.7 to 24.8%).

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“…Krupová et al (2009) expressed the EV for growth rate of lambs till weaning per daily gain of female lambs born as singles. Borg et al (2007) chose ewe lambs born as singles and weaned at an age of 120 days as the reference category for the calculation of the EVs for birth and weaning weight. Groen (1988) defined a female calf born in a cow's first parturition as the reference category for the calculation of the EV for birth weight; cows were the reference category for mature weight.…”

Section: Definition Of Traits Expressed In Different Sexes or Animal mentioning

confidence: 99%

Strategies for defining traits when calculating economic values for livestock breeding: a review

Wolfová

Wolf

2013

Animal

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The objective of the present review was (i) to survey different approaches for choosing the complex of traits for which economic values (EVs) are calculated, (ii) to call attention to the proper definition of traits and (iii) to discuss the manner and extent to which relationships among traits have been considered in the calculation of EVs. For this purpose, papers dealing with the estimation of EVs of traits in livestock were reviewed. The most important reasons for incompatibility of EVs for similar traits estimated in different countries and by different authors were found to be inconsistencies in trait definitions and in assumptions being made about relationships among traits. An important problem identified was how to choose the most appropriate criterion to characterise production or functional ability for a particular class of animals. Accordingly, the review covered the following three topics: (i) which trait(s) would best characterise the growth ability of an animal; (ii) how to define traits expressed repeatedly in subsequent reproductive cycles of breeding females and (iii) how to deal with traits that differ in average value between sexes or among animal groups. Various approaches that have been used to solve these problems were discussed. Furthermore, the manner in which diverse authors chose one or more traits from a group of alternatives for describing a specific biological potential were reviewed and commented on. The consequences of including or excluding relationships among economically important traits when estimating the EV for a specific trait were also examined. An important conclusion of the review is that, for a better comparability and interpretability of estimated EVs in the literature, it is desirable that clear and unique definitions of the traits, complete information on assumptions used in analytical models and details on interrelationships between traits are documented. Furthermore, the method and the model used for the genetic evaluation of specific traits in a certain breeding organisation are important for the exact definition of traits, for which the economic values will be calculated, and for the inclusion or exclusion of relationships among traits in the calculation of the EVs in livestock breeding. Keywords: livestock, economic values, definition of traits, relationships among traits ImplicationsA literature review was conducted on different ways of defining traits and considering relationships among them in the calculation of economic values (EVs) in livestock breeding. Diversity among trait definitions makes it difficult to compare EVs from different investigations and individual authors. It was shown that, for the EV of a trait to be correctly interpreted, it is necessary to know exactly how the trait was defined, how its relationships with other traits were accounted for and what assumptions were made in the model for the calculation of EVs. IntroductionHazel (1943) proposed the breeding objective or aggregate genotype of an animal to be defined as 'the sum of its sever...

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Breeding objectives for Targhee sheep1

Cited by 35 publications

References 31 publications

Selection objectives and criteria for sheep in Central Brazil

Selection objectives and criteria for sheep in Central Brazil

Calculating economic weights for sheep sire breeds used in different breeding systems1

Strategies for defining traits when calculating economic values for livestock breeding: a review

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