Los resultados de las primeras evaluaciones del Proyecto Ovejas Prolíficas de INIA (2008-2011) muestran que la cruza Frisona Milchschaf x Corriedale o Finnish Landrace x Corriedale desteta 60 % más corderos que la Corriedale pura y, por otro lado, la cruza Finnish Landrace x Frisona Milchschaf desteta 85 % más que la Corriedale pura. Sin embargo y bajo las mismas condiciones productivas, no se conoce el comportamiento al parto y la producción de calostro de estos nuevos biotipos. Para recabar información, se realizó un experimento en INIA La Estanzuela, Colonia, Uruguay (34ºS; 57ºO) donde se utilizaron 61 borregas de 4-6 dientes nacidas en la primavera del año 2010. Se utilizaron dos razas puras: Corriedale (C.C) y Frisona Milchschaf (M.M) y las cruzas Finnish Landrace x Corriedale (F.C), Frisona Milchschaf x Corriedale (M.C), 3/4 Frisona Milchschaf - 1/4 Finnish Landrace (M.(F.M)) y 7/8 Finnish Landrace - 1/8 Corriedale (F.(FxF.C)), apareadas con carneros Texel. El incremento de sangre Finnish en la cruza redundó en un aumento en la prolificidad (2,2; 2,3 y 2,4 para 1/4; 1/2 y 7/8 Finnish) con corderos más livianos y menor asistencia al parto. Tanto la media sangre Milchschaf como la pura tuvieron una prolificidad similar e intermedia (1,8 M.C y 1,7 M.M) mientras que la asistencia al parto fue alta. La producción y composición de calostro fue similar entre biotipos a excepción de M.M que produjo más. No existió diferencia en eficiencia placentaria entre biotipos. El peso vivo al nacimiento de los corderos influyó sobre el comportamiento de los mismos en su primera hora de vida, precisamente en el tiempo desde el nacimiento hasta que lograron pararse y mamar.

The results of the first evaluation of the Prolific Sheep Project of INIA (2008-2011) demonstrated that the crossbred biotypes Corriedale by East Friesian or Corriedale by Finnish Landrace weaned 60 % more lambs than pure Corriedale and, on the other hand, the crossbred East Friesian by Finnish Landrace weaned 85 % more than pure Corriedale. However, and under the same productive conditions, the behavior at lambing and colostrum production of these new biotypes are unknown. In order to find out, an experiment was conducted at INIA La Estanzuela, Colonia, Uruguay (34ºS; 57ºO) where 61 female lambs 4-6 teeth born in the spring of 2010 were evaluated. Two pure breeds were used: Corriedale (C.C) and East Friesian (M.M), and the crosses Finnish Landrace x Corriedale (F.C), East Friesian x Corriedale (M.C), 3/4 East Friesian - 1/4 Finnish Landrace (M.(F.M)), 7/8 Finnish Landrace - 1/8 Corriedale (F.(FxF.C)), mated with Texel rams. The increase in Finnish blood resulted in more prolificacy (2.2; 2.3 and 2.4 for 1/4; 1/2 and 7/8 Finnish with lighter lambs and less lambing assistance. Both half and pure East Friesian had similar and moderate prolificacy (1.8 M.C and 1.7 M.M) whereas lambing assistance was high. Colostrum production and composition was similar between biotypes, with the exception of M.M, that produced more. There were no differences in placental efficiency between biotypes. Birth weight of lambs affected their behavior in the first hour of life, specifically the time from birth to first stand up to suckle.

Las primeras evaluaciones del Proyecto Ovejas Prolíficas del Instituto Nacional de Investigación Agropecuaria (INIA, 2008-2011) muestran que las madres cruza Frisona Milchschaf x Corriedale y Finnish Landrace x Corriedale destetan 60 % más corderos que la madre Corriedale pura, mientras que la madre cruza Finnish Landrace x Frisona Milchschaf desteta 85 % más que la madre Corriedale pura. Para recabar información respecto a la edad con que se inicia la pubertad, la estación de cría y tasa ovulatoria de estos nuevos biotipos se realizó un experimento con 87 corderas nacidas en la primavera 2010. Se utilizaron dos razas puras: Corriedale (C.C) y Frisona Milchschaf (M.M) y las siguientes cruzas: Finnish Landrace x Corriedale (F.C), Frisona Milchschaf x Corriedale (M.C), ³/4 Frisona Milchschaf - ¹/4 Finnish Landrace (M.(F.M)), 7/8 Finnish Landrace -¹/8 Corriedale (F.(FxF.C)). Las corderas con más de 75 % de sangre Frisona Milchschaf (M.M y M.(F.M)) presentaron los mayores porcentajes de inicio de pubertad en su primer año de vida (>90 %). La estación de cría de estos dos biotipos fue la más amplia con una tasa ovulatoria de 1,0. Las corderas F.(FxF.C) siguieron a las anteriores en el porcentaje que alcanzó la pubertad y en la amplitud de la estacionalidad con una tasa ovulatoria 1,5. La estación de cría como borregas fue similar para todos los biotipos destacándose la alta tasa ovulatoria de las cruzas Finn (1,9-2,8) seguidas de Frisona Milchschaf (1,5-1,8) y de Corriedale (1.3).

First evaluations of the Prolific Sheep Project of Instituto Nacional de Investigación Agropecuaria (INIA, 2008-2011) demonstrated that the crossbred mothers Corriedale by East Frisian or Corriedale by Finnish Landrace weaned 60 % more lambs than pure Corriedale, and the crossbred mothers East Friesian by Finnish Landrace weaned 85 % more than pure Corriedale. To obtain information regarding the age when puberty begins, the breeding season, and the ovulation rate of these new biotypes, an experiment was carried out with 87 female lambs born the Spring of 2010. Two pure breeds: Corriedale (C.C) and East Friesian (M.M) and the following crosses: Finnish Landrace x Corriedale (F.C), East Friesian x Corriedale (M.C), ¾ East Friesian - ¼ Finnish Landrace (M.(F.M)), 7/8 Finnish Landrace -¹/8 Corriedale (F.(FxF.C)) were used. Female lambs with more than 75 % of East Friesian blood (M.M and M.(F.M)) had the highests percentages of puberty onset in their first year of life (> 90 %). Their breeding season was the widest with an average ovulation rate of 1.0. F.(FxF.C) lambs followed the previous ones in the percentage reaching puberty and the width of the breeding season with an average ovulation rate of 1.5. Breeding season of hoggets was similar for all biotypes, however, hoggets with Finn blood were outstanding by their high ovulation rate (1.9-2.8) followed by East Friesian (1.5-1.8) and Corriedale (1.3).

The aim of this study was to investigate the genetic diversity within and among three breeds of sheep: Corriedale, Merino and Creole. Sheep from the three breeds (Merino n = 110, Corriedale n = 108 and Creole n = 10) were genotyped using the Illumina Ovine SNP50 beadchip®. Genetic diversity was evaluated by comparing the minor allele frequency (MAF) among breeds. Population structure and genetic differentiation were assessed using STRUCTURE software, principal component analysis (PCA) and fixation index (F ST). Fixed markers (MAF = 0) that were different among breeds were identified as specific breed markers. Using a subset of 18,181 single nucleotide polymorphisms (SNPs), PCA and STUCTURE analysis were able to explain population stratification within breeds. Merino and Corriedale divergent lines showed high levels of polymorphism (89.4% and 86% of polymorphic SNPs, respectively) and moderate genetic differentiation (F ST = 0.08) between them. In contrast, Creole had only 69% polymorphic SNPs and showed greater genetic differentiation from the other two breeds (F ST = 0.17 for both breeds). Hence, a subset of molecular markers present in the OvineSNP50 is informative enough for breed assignment and population structure analysis of commercial and Creole breeds.