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Estimation of genetic progress and profitability of dairy herds using varying proportions of in-vitro produced sexed embryos
The objective of the study was to estimate the genetic and economic performance of a dairy herd in which varying proportions of animals were impregnated with in-vitro produced sexed embryos (IVP-ET) obtained from the genetically best heifers. A daily dynamic stochastic model that includes the 12 genetic traits in the lifetime Net Merit index (NM$) was used. Phenotypic performance depended on genetic values. A herd of 1,000 milking dairy cows, heifers and embryos were simulated over time. Genetic progress came from selecting superior donors and external sires. Eleven scenarios were evaluated, from 0% IVP-ET conceptions to 100% IVP-ET conceptions, with increments of 10 percentage points. Each scenario was run 20 times. Animals with the greatest Estimated Breeding Value (EBV) for NM$ were selected as donors. Recipients were selected from heifers first, and from cows with the greatest EBV for fertility traits second. Sexed semen was used on the genetically better heifers for 2 inseminations. All other non-recipients were inseminated with conventional semen. To maintain a 33% annual cow cull rate, surplus heifer calves were sold based on the lowest EBV of NM$ and received a premium price based on their EBV of NM$. Results were measured by the true breeding values (TBV) of NM$ of all cows and profit per cow per year in year 15 after the start of the IVP-ET program, and cumulative profit in the 15 years after the start of the program. The mean ± SE of TBV of NM$ of all cows was $608 ± 7 greater for 100% IVP-ET compared 0% IVP-ET in year 15. The maximum increase in profit per cow per year (and optimum IVP-ET program) in year 15 when embryo costs were $120 and $160 was $125 (100% IVP-ET) and $75 (42% IVP-ET), respectively, compared to a 0% IVP-ET program. Because return on investment in an IVP-ET program is not immediate, the 15 year cumulative discounted profits per cow in comparison to the 0% IVP-ET program at embryo costs of $80, $120 and $160 were obtained at 72% IVP-ET, 21% IVP-ET, and 0% IVP-ET, respectively. The optimal proportions of IVP-ET depended greatly on the costs of embryos and the sale price of surplus calves. In conclusion, the use of IVP-ET at current prices was profitable but the optimal amount of IVP-ET was sensitive to realistic variations in prices of embryos and surplus heifer calves.
Keywords:
In-vitro production, embryo, profit