Desempeño durante la lactancia de corderos Highlander, Milchschaf y sus cruzas con Corriedale

Sheep meat production has gained economic and social importance among small-scale farmers in southern Uruguay. The use of prolific breeds with maternal ability and early growth is presented as a tool to maximize productive results. The aim of this study was to investigate the possibility of improving the productivity of intensive sheep production systems by upgrading a Corriedale (C) flock by Highlander (H) or Milchschaf (M) breeds. Records from lambs born between 2015 and 2021 at Centro Regional Sur, in Progreso (Canelones) were used. The variables analyzed were:  birth, lamb marking, and weaning weight; daily and total weight gain during lactation and lamb survival. Genotypes evaluated were purebred Highlander and Milchschaf, and crossbred lambs of these two breeds with Corriedale, generated during the upgrading process. The statistical models fitted included genotype, sex, year of birth, age of dam, type of birth and/or rearing as fixed effects, and marking and weaning ages were fitted as covariables. The results of purebred H and M genotypes were thought to have special significance over the crossbred C genotypes due to the absorptions tendency towards H and M purebreds genotypes. Significant differences were found for birth weight between H and M genotypes, with M showing higher weights. Non-significant differences between H and M genotypes were found in marking or weaning weight. It was concluded that there are no differences in weaning weight between Highlander and Milchschaf, although Highlander could produce heavier lambs at weaning during the upgrading period.