Crossbreeding parameters in a rotational scheme between Corriedale and Dohne Merino sheep: effects on wool production and live weight in ewe hoggets

Abstract

Rotational crossbreeding is a simple and scalable alternative that combines the advantages of two breeds and captures up to two-thirds of the potential heterosis. With the aim of promoting the complementary use of Corriedale (C) and Dohne Merino (DM) sheep breeds in Uruguay, we have conducted a rotational crossbreeding experiment since 2015 at Estación Experimental Bernardo Rosengurtt (Cerro Largo) of Facultad de Agronomía. In this study, we estimated the effects of individual heterosis (h^I) and of direct breed proportion (k^I_C) using 1,107 records taken at one year of age from ewe hoggets born between 2015 and 2022. We fitted mixed linear models in R (lme4 package), including year of birth, age of the dam, type of rearing, h^I and k^I_C as fixed effects, and sire as a random effect. Heterosis showed a positive and significant effect (p < 0.0001) on greasy fleece weight (GFW) and post-shearing live weight (PSLW) of 0.217 and 2.23 kg, equivalent to 5.7 % and 5.2 % with respect to C, respectively. No heterosis was detected on fibre diameter (D, p = 0.88). Breed differences favoured C in GFW (+0.654 kg) and DM in D (–4.25 µm; p < 0.0001). We did not observe significant differences between breeds for PSLW (p = 0.94). These results confirm the complementarity between C and DM: C contributes to the quantity of wool, DM to fibre fineness, and their crossbred progeny benefit from heterosis in live weight, enhancing sheep meat production. This study provides quantitative evidence on the usefulness of the rotational crossbreeding scheme between C and DM to improve the productivity of extensive sheep farming systems in the north-east of the country. Its results offer valuable inputs for designing alternatives for the sustainable use of genetic resources for dual-purpose sheep farming systems.