Deterministic genetic analysis of open nucleus breeding schemes for dairy cattle in developing countries

Bondoc, Orville L.; Smith, C.

doi:10.1111/j.1439-0388.1993.tb00732.x

Cited by 16 publications

(19 citation statements)

References 9 publications

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“…Open nucleus systems have been shown to be superior to closed nucleus systems in terms of genetic and economic efficiencies (Kinghorn 2000). An open nucleus breeding system is superior to a closed nucleus of the same size because of a higher expected mean genetic value of nucleus replacements and because such a system will integrate farmers’ resources, reduce overhead costs and encourage more farmer participation (Bondoc & Smith 1993). Returns and profit per ewe in the population were highest in CNyre (a system that allowed for downward movement of dams from the nucleus to the commercial sector to breed sires and dams in this sector) under FEED and TR.…”

Section: Resultsmentioning

confidence: 99%

Evaluation of the efficiency of alternative two‐tier nucleus breeding systems designed to improve meat sheep in Kenya

Gicheha¹,

Kosgey²,

Bebe³

et al. 2006

J Animal Breeding Genetics

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A deterministic approach was used to genetically and economically evaluate the efficiency of five two-tier nucleus breeding systems for meat sheep in Kenya. The nucleus breeding systems differed in terms of whether the system was closed or open, in the type of animals that were involved in the movement of genetic superiority and in the number of selection pathways in each system. These systems were compared under four alternative breeding objectives based on monetary genetic gain and profit per ewe. The first objective simulated a situation where the flock size cannot be increased due to non-feed related constraints (FLOCK). The second specifically assumed that the flock size is restricted due to limited amount of feed resources (FEED). The third and fourth objectives assumed that sheep performed only tangible roles (TR) and both tangible and intangible roles (IR) in the production system respectively. Monetary genetic gains were highest for all objectives in an open nucleus system with a certain proportion of commercial-born ewes being introduced in the nucleus while at the same time utilizing young rams from the nucleus to breed sires and dams for the nucleus and commercial sector (ONyre). Utilizing young rams in a closed nucleus system for the dissemination of superior genes resulted in higher annual monetary genetic gain than utilization of old rams. Profit per ewe was significantly higher for FLOCK and IR in ONyre. In a closed system that allowed for downward movement of dams from the nucleus to the commercial sector to breed sires and dams, profit per ewe was highest for FEED and TR. The success of a nucleus breeding system should also focus on the profitability and logistics of establishing it. The implication of these results on the choice of two-tier nucleus breeding systems for the improvement of meat sheep is discussed.

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Section: Resultsmentioning

confidence: 99%

Evaluation of the efficiency of alternative two‐tier nucleus breeding systems designed to improve meat sheep in Kenya

Gicheha¹,

Kosgey²,

Bebe³

et al. 2006

J Animal Breeding Genetics

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“…The genetic theory in dairy cattle open nucleus breeding schemes (see B ondoc and S mith 1993b) is extended to include genotype by environment interactions. Optimized nucleus progeny testing, adult MOET sib testing, or juvenile MOET pedigree testing (from B ondoc and S mith 1993a) are used in the nucleus, while females in the base are field recorded.…”

Section: Methodsmentioning

confidence: 99%

“…where x, v, w, and y are the transfer rates between the nucleus and base and ΔG ijk are the selection differentials of the i th parent born in the j th place to be used in the k th breeding tier (B ondoc and S mith 1993b). Since all males used are born in the nucleus, v = w = 0.…”

Section: Methodsmentioning

confidence: 99%

“…Open nucleus schemes may provide an operational procedure for achieving greater genetic progress than closed nucleus schemes. However, in a two‐tier open nucleus breeding system (B ondoc and S mith 1993b), G × E interactions in different tiers (nucleus and base) may lower the overall efficiency of selection for improvement in the lower tier. Differences in environmental factors such as rainfall, temperature, feeding management, and exposure to diseases with poor health control are most likely to lead to interactions.…”

Section: Introductionmentioning

confidence: 99%

“…The purpose of this study is to determine the consequence of genotype by environment interactions between the nucleus and base herds on the average genetic selection differentials of animals used in the nucleus and in the base, evaluated for their performance in the base environment; the asymptotic response to selection and the asymptotic genetic lag with regard to genetic improvement in the base herds; and the mean genetic level in the base of various dairy cattle open nucleus breeding schemes such as those proposed for developing countries (B ondoc and S mith 1993b).…”

Section: Introductionmentioning

confidence: 99%

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The effects of genotype by environment interactions in dairy cattle open nucleus breeding schemes

Bondoc

Smith

1993

J Animal Breeding Genetics

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The evaluation of open nucleus breeding systems using progeny testing or adult or juvenile embryo transfer in the nucleus is extended to include genotype by environment interactions. Knowledge of the extent of such interactions can be used to design breeding schemes and to predict realistic rates of genetic gain in the commercial environment. Interactions between the nucleus and base (commercial) herds are assumed to be more important than those interactions within tiers (e. g., among base herds). The genetic selection differentials of animals born in the nucleus and evaluated for their performance under the base conditions are reduced by a factor equivalent to the genetic correlation for economic merit between the nucleus and base test environment. This leads to a lower asymptotic genetic gain per year and longer asymptotic genetic lag with regard to the genetic improvement in the base herds. The mean genetic merit in the commercial population at a given planning horizon (20 years) is also increased as the genetic correlation for economic merit between the nucleus and base environment decreases. The applies to all the breeding systems and so the genetic correlation is a critical parameter in evaluating open nucleus breeding schemes. ZUSAMMENFASSUNG: Wirkungen von Genotyp-Umweltinteraktionen in offenen Nukleuszuchtsystemen von Milchrindern Die Bewertung offener Nukleuszuchtsysteme mit Nachkommenschaftsprüfung oder adultem oder juvenilem Embryotransfer im Nukleus wird mit Berücksichtigung von Genotyp-Umweltinteraktionen erweitert. Kenntnis solcher Interaktionen sollen bei der Zuchtplanung und zur Vorausschätzung realistischer genetischer Fortschrittsraten in praxisnahen Situationen Anwendung finden. Interaktionen zwischen Nukleus und Basis (kommerziell) Herden werden als wichtiger angenommen als Interaktionen innerhalb der Schichten (z.B. zwischen Basisherden). Genetische Selektionsdifferentiale von nukleusgeborenen Tieren, die ihre Leistung unter Bedingung der Praxis erbringen, werden proportional der genetischen Korrelation für Wirtschaftswert zwischen Nukleus und Basismilieu vermindert. Dies führt zum geringeren asymptotischen genetischen Fortschritt pro Jahr und einem längeren asymptotischen, mit genetischer Verzögerung in bezug auf genetische Verbesserung der Basisherden. Der mittlere Zuchtwert der kommerziellen Population bei gegebenem Planungshorizont (20 Jahre) wird ebenfalls proportional der genetischen Korrelation kleiner. Das bezieht sich auf alle Zuchtsysteme, so daß die genetische Korrelation ein kritischer Parameter zur Bewertung offener Nukleuszuchtsysteme ist.

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Developing breeding schemes for pasture based dairy production systems in Kenya

Kahi

Nitter

Gall

2004

Livestock Production Science

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Deterministic genetic analysis of open nucleus breeding schemes for dairy cattle in developing countries

Cited by 16 publications

References 9 publications

Evaluation of the efficiency of alternative two‐tier nucleus breeding systems designed to improve meat sheep in Kenya

Evaluation of the efficiency of alternative two‐tier nucleus breeding systems designed to improve meat sheep in Kenya

The effects of genotype by environment interactions in dairy cattle open nucleus breeding schemes

Developing breeding schemes for pasture based dairy production systems in Kenya

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