Desempeño de corderos en un cruzamiento rotacional entre Corriedale y Merino Dohne

In Uruguay, sheep production has seen a decline in stock numbers, falling from 25 million head in 1990 to 4.75 million in 2025, due to competition from other agricultural sectors. The Corriedale breed is the predominant one in the national flock, accounting for 42 % of the total, whilst the Dohne Merino breed is emerging as a dual-purpose alternative of growing interest. National research has focused on comparing the two breeds as competitors, without proposing sustainable breeding strategies that capitalise on their complementary characteristics. Rotational crossbreeding is presented as an effective tool that makes it possible to capture two-thirds of the potential heterosis and produce more profitable sheep in extensive systems. 

The overall aim of this study was to assess the impact of rotational crossbreeding between the Corriedale and the Dohne Merino breeds on the growth and survival of lambs during the suckling period. The study sought to quantify the differences in birth weight and weaning weight amongst the different genotypes produced by the crossbreeding scheme. It was also proposed to analyse the influence of environmental and maternal factors – such as type of birth and rearing, sex of the lambs, age of the ewes and year – on the performance of the offspring.

The study was carried out at the Bernardo Rossengurtt Experimental Station (Cerro Largo, Uruguay), analysing data collected over 11 consecutive years. A refined database of 4076 lambs from 1402 ewes and 31 rams was used, under an extensive production system on natural pasture, with strategic pre-lambing supplementation and access to winter pastures of oat and ryegrass. The variables assessed were birth weight, weaning weight and lamb survival. Data was analysed using the R software, employing mixed linear models for the growth variables and generalised mixer linear models with a binomial distribution for survival. 

The results, analysed using the aforementioned database, showed an average birth weight (BW) of 4.59 kg and a weaning weight (WW) of 22.63 kg. The fixed effects of genotype, sex, type of birth and dam’s age were highly significant for BW (p < 0.001), whilst for WW, sex, type of birth and rearing, dam’s age, age at weaning and genetic group were significant. All crossbred genotypes outperformed the purebred Corriedale (21.27 kg) in weaning weight, with the ~67MD group standing out with an advantage of 1.11 kg. Average survival rate was 91.5 %, with birth weight being the most influential determinant (p < 0.001; OR = 1.71). 

The results obtained show clear differences in performance in favour of the crossbred animals, which is consistent with the theoretical realisation of heterosis in rotational systems. This approach improves productivity without compromising survival, establishing itself as a sustainable technological alternative for increasing the competitiveness of the Uruguayan sheep sector.