Developing breeding schemes for pasture based dairy production systems in Kenya

Kahi, A.K.; Nitter, G.; Gall, C.

doi:10.1016/j.livprodsci.2003.07.015

Cited by 62 publications

(51 citation statements)

References 21 publications

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“…This procedure was used by Munoz-Luna et al (1988) and by Bekman and van Arendonk (1993) when calculating the EVs for growth rate or carcass traits during fattening; only bulls were included because very few heifers are fattened in production systems with dairy cattle. Kahi and Nitter (2004) considered only heifers when estimating the EVs for pre-weaning and post-weaning daily gain and survival rate in dairy cattle, because their model did not involve fattening of male calves.…”

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

confidence: 99%

“…This procedure was used by Munoz-Luna et al (1988) and by Bekman and van Arendonk (1993) when calculating the EVs for growth rate or carcass traits during fattening; only bulls were included because very few heifers are fattened in production systems with dairy cattle. Kahi and Nitter (2004) , 2006). Using this approach, the authors assumed that a change in the genetic potential for a trait would result in the same changes in the phenotypic means in both sexes and in all animal groups.…”

mentioning

confidence: 99%

“…However, there are practical problems in acquiring data for EV and breeding value estimation for these components of female reproductive ability. Therefore, calving (lambing, farrowing) interval as a composite trait was chosen by several authors (Albera et al, 2004;Kahi and Nitter, 2004).The calving interval is influenced by the interval from calving to first mating, the conception rate and the length of pregnancy. These three components have distinct patterns of inheritance and different impacts on the economics of the evaluated production system.…”

mentioning

confidence: 99%

“…This trait can also serve as an easily recorded proxy for conception rate, but again it is a composite trait of age of replacement females at first service, conception rate and length of pregnancy. Therefore, a clear description of the assumptions made when calculating the EV of age at first parturition as a reproductive trait should be given (González-Recio et al, 2004;Kahi and Nitter, 2004;Roughsedge et al 2005).Some authors have assumed that replacement females are first mated at the optimal weight for the evaluated breed and have expressed age at first service as a function of the growth rate. The economic impact of the change in age at first mating (and therefore also in the age at first parturition) is then included in the EV of growth rate (Wolfová et al, 2007 and2009).…”

mentioning

confidence: 99%

“…Then fat and protein contents should be always the primary traits for which levels are to be changed, when calculating EVs for fat and protein production and the levels of which are to be held constant when calculating EV for milk yield. Then, the transformation of the EVs for fat and protein contents to EVs for fat and protein yields is straightforward (Kahi and Nitter, 2004;Pä rna et al, 2007; see also discussion on this topic by Dekkers and Gibson, 1998). …”

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confidence: 99%

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

confidence: 99%

“…This procedure was used by Munoz-Luna et al (1988) and by Bekman and van Arendonk (1993) when calculating the EVs for growth rate or carcass traits during fattening; only bulls were included because very few heifers are fattened in production systems with dairy cattle. Kahi and Nitter (2004) , 2006). Using this approach, the authors assumed that a change in the genetic potential for a trait would result in the same changes in the phenotypic means in both sexes and in all animal groups.…”

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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

Wolfová

Wolf

2013

Animal

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Genetic improvement of the Kenya Dual Purpose Goat: Influence of economic values and prospects for a practical breeding programme

et al. 2007

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This study determined the influence of economic values on genetic gain and explored the prospects for a practical breeding programme for the Kenya Dual Purpose Goat. The economic values for production traits (live weight (direct), live eight (maternal), milk yield and consumable meat) and functional traits (doe weight, number of kids weaned, kidding frequency and rate, doe weaning and survival rate, pre‐ and post‐weaning survival rate, and residual feed intake for yearlings and does) in the breeding goal addressed the smallholder production system. There was a potential for genetic progress in the breeding‐goal traits even by using simple selection criteria. In the breeding programme, the predicted genetic gains per year for milk yield were 0.737 and 0.047 kg for the sires of sires and dams of dams pathways, respectively. The required population size of 2500 does in the nucleus would be attained within ten years after the start of the breeding programme. The availability of a simple breeding programme for the Kenya Dual Purpose Goat offers enormous opportunities for private large‐scale flocks or for flocks owned by parastatal or research organisations to exploit genetic and economic benefits from the breeding programme. Copyright © 2007 John Wiley & Sons, Ltd

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Milk production and reproductive performance of Sahiwal cattle in semi‐arid Kenya

et al. 2007

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The aim of this study was to evaluate milk production and reproductive performance of Sahiwal cattle in semi‐arid Kenya. Milk production traits considered were lactation milk yield, lactation length and test‐day milk yield, while reproductive traits included age at first calving, calving interval and number of services per conception. Various fixed effects affected performance of milk production and reproductive traits to varying significance levels. The mean estimates for milk production traits were 1368 kg, 282 days and 4.9 kg for lactation milk yield, lactation length and test‐day milk yield, respectively. For reproductive traits, mean estimates were 468 days, 2.2 and 1345 days for calving interval, number of services per conception and age at first calving, respectively. There was a decline in lactation milk yield and lactation length, and an increase in calving interval and age at first calving over the years. Satisfactory management and appropriate genetic improvement strategies would result in improved performance. Implications of the results for genetic improvement of the breed in Kenya are discussed. Copyright © 2007 John Wiley & Sons, Ltd

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Developing breeding schemes for pasture based dairy production systems in Kenya

Cited by 62 publications

References 21 publications

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

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

Genetic improvement of the Kenya Dual Purpose Goat: Influence of economic values and prospects for a practical breeding programme

Milk production and reproductive performance of Sahiwal cattle in semi‐arid Kenya

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