Genetic Comparison of Breeding Schemes Based on Semen Importation and Local Breeding Schemes: Framework and Application to Costa Rica

Abstract

Local breeding schemes for Holstein cattle of Costa Rica were compared with the current practice based on continuous semen importation (SI) by deterministic simulation. Comparison was made on the basis of genetic response and correlation between breeding goals. A local breeding goal was defined on the basis of prevailing production circumstances and compared against a typical breeding goal for an exporting country. Differences in genetic response were <3%, and the correlation between breeding goals was 0.99. Therefore, difference between breeding objectives proved negligible. For the evaluation of genetic response, the current scheme based on SI was evaluated against a progeny testing (PT) scheme and a closed nucleus (CN) breeding scheme, both local. Selection intensities and accuracy of selection were defined according to current population size and reproduction efficiency parameters. When genotype x environment interaction (G x E) was ignored, SI was the strategy with the highest genetic response: 5.0% above the CN breeding scheme and 33.2% above PT. A correlation between breeding values in both countries lower than one was assumed to assess the effect of G x E. This resulted in permanent effects on the relative efficiencies of breeding strategies because of the reduction in the rate of genetic response when SI was used. When the genetic correlation was assumed equal to 0.75, the genetic response achieved with SI was reduced at the same level as local PT. When an initial difference in average genetic merit of the populations was assumed, this only had a temporal effect on the relative ranking of strategies, which is reverted after some years of selection because the rate of change in genetic responses remains unchanged. Given that the actual levels of genetic correlation between countries may be around 0.60, it was concluded that a local breeding scheme based on a nucleus herd could provide better results than the current strategy based on SI.

Economic evaluation of progeny-testing and genomic selection schemes for small-sized nucleus dairy cattle breeding programs in developing countries

“…Genetic improvement can be realized by importation of exotic germplasm or by local breeding programs. Local breeding programs for developing dairy cattle industries provide a means to address unfavorable genotype by environment interactions resulting from importation of exotic germplasm (Ojango and Pollot, 2002;Vargas and van Arendonk, 2004;Okeno et al, 2010a). However, minimal routine pedigree and performance recording impede the implementation of large-sized breeding programs in many developing countries (Wasike et al, 2011).…”

“…Such an approach considers a national breeding program in which revenue is generated from sale of end products such as milk or meat (Brascamp et al, 1993;König et al, 2009). For small-sized nucleus schemes in developing countries economic appraisal from a national perspective seems more suitable because the aim of such schemes is to address challenges posed by importation of germplasm (Ojango and Pollot, 2002;Vargas and van Arendonk, 2004;Okeno et al, 2010a). We recently illustrated the feasibility of small-sized GS or PT programs (Kariuki et al, 2014).…”

Selection for pure- and crossbred performance in Charolais

“…However, the benefit from combining breeding programs decreases as the breeding objectives in the two breeding programs differ. Studies found that when the correlation between breeding objectives was lower than a threshold ranging from 0.75 to 0.90, running a combined breeding program resulted in lower genetic gain than two separate breeding programs Vargas and van Arendonk, 2004;. Below this threshold, the two breeding programs tend to select more of their own bulls and stop selecting bulls from the other breeding program after a few generations .…”

“…As expected based on the genetic correlations, the sire with the lowest breeding value for birth weight in purebred also had the lowest breeding value in crossbred. The genetic correlation (0.95) estimated for birth weight is higher than the threshold (from 0.75 to 0.90) suggested in some studies for splitting up breeding programs Vargas and van Arendonk, 2004;. Thus, if selection of bulls was based on birth weight only, the purebred and the crossbred breeding programs should be combined.…”

“…The population with the lowest genetic merit benefits most from a combined breeding program. The high genetic merit population still benefits from combined breeding program, but initially less, when the low genetic merit population contributes little and gradually more as the two populations equalize Vargas and van Arendonk, 2004). Genetic means for birth weight in purebreds and crossbreds were assessed by the mean EBVs of the sires from the purebred and the crossbred breeding programs.…”