Abstract

MUELLER, Joaquin P.  and  ARANGUREN, E.m.. Implementación y resultados de un programa de mejora genética en ovinos. RIA. Rev. investig. agropecu. [online]. 2022, vol.48, n.1, pp.16-23.  Epub Apr 06, 2022. ISSN 1669-2314.

The Ideal or Polwarth sheep breed originated in Australia, is raised in the centre of the argentine Litoral, providing income to producers through wool and meat. Breeders from the region, interested in refining the wool, increasing or at least maintaining the fleece weight and increasing the body weights of their Ideal sheep, formed the association “Cabañas Integradas” and started a genetic improvement program in 2003. The aim of this study was to evaluate the results of this program after completing fifteen years in operation. The program was based on a nucleus herd with the best ewes available in order to produce rams for the individual herds. After the initial introduction of rams all replacements of rams and ewes were based on candidates born in the nucleus or in the individual herds. For the selection of replacements, selection indexes were used based on an objective function with breeding values ​​of traits of interest weighted by their economic importance. The goal traits were weaning weight (PCD) and shearing weight, fleece weight and mean fibre diameter at first (PCE1, PVS1 and PDF1) and second shearing (PCE2, PVS2 and PDF2). The economic importance was determined as marginal benefit, price minus cost, per unit of change in each trait. The breeding values expressed as expected progeny differences (DEPs) were obtained from mixed multivariate analyses with BLUP properties using “Provino Avanzado” the national sheep genetic evaluation service operated by INTA. For its calculation, genetic and phenotypic parameters calculated from the population itself were used. The genetic trends were similar for the three body weights (PCD, PCE1 and PCE2) with rates of 0.12 to 0.14 kg per year. The accumulated genetic gains in the 15 years reached 2.5 kg. No genetic improvement was achieved in the fleece weights (PVS1 and PVS2), but it was possible to refine the wool (PDF1 and PDF2) by close to one micron. The genetic trends in the seven traits are summarized in the increase in economic income of approximately 1% per year. The phenotypic trends resulted with a low coefficient of determination, but in the desired directions. Taking the average of the first and last three years of the program, the body weight at the first shearing increased 3.1 kg and the mean fibre diameter decreased by 1.5 µm. It would be desirable for more Ideal breeders to start their own improvement programs based on Provino Avanzado evaluations, eventually linking to Cabañas Integradas for a joint genetic evaluation and thus take better advantage of the existing genetic variability in the breed.

Keywords : Polwarth; Ideal; wool; breeding value; selection index; breeding goal.

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