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With the objective to determine the best mathematical model that could demonstrate the relationship between body weight and age in crossbred sheep, and to evaluate its applicability in different farms, 9985 live weight records of 837 crossbred lambs of Texel, Ile de France, Suffolk, and Hampshire Down breeds were used. Brody, von Bertalanffy, Richards, Logistic, and Gompertz models were fitted to the weight data, which were compared based on adjusted R 2 , Syx%, chi-square, and Kolmogorov-Smirnov tests, as well as residual analysis. After selecting the model, lambs whose weights at different ages fell within, below, or above ±20% of the values predicted by the model were classified as medium, low, or high performance, respectively. To validate the model, we used a validation dataset comprising 2898 weights of lambs from 6 different farms. Based on statistical analysis and biological characteristics (sigmoid trend of weight over time, weight at birth, and standard deviation), the model that best represented the growth of the lambs was the Richards model. The percentage of lambs classified as below, within, and above the predicted values based on the model was highly similar for the original and validation data, which indicates that this model could be used in different farms. It was concluded that the Richards model best described the live weight growth of crossbred lambs and aided in classifying the lambs as high, medium, or low performance, thereby providing a complementary tool in management decision-making.

The study evaluated the reproductive performance of Ile de France, Texel, Suffolk and crossbred ewes in different seasons, considering season of mating, age, body condition score and breed. The herd was located at geographic coordinates −25.66114429 S, −49.27262198 W, in Fazenda Rio Grande, Paraná State, southern Brazil, in a semi‐intensive system. 643 mating were evaluated, under natural oestrous conditions in 10 consecutive breeding seasons (2015–2019), under a body condition score between 2.5 and 3.5 in 93.9%. Data were analysed using Chi‐square tests, binary logistic regression, ANOVA and t‐test. Considering the breeds and crossbred animals, a pregnancy rate (PR) of 83% (winter), 91% (autumn) and 89% (summer) with no differences between them was obtained, except for 77% PR in spring (p < .05). Ile de France and crossbred ewes showed similar PR in all four seasons. Suffolk ewes showed similar fertility rates in summer, autumn and winter, but reduced in spring (p < .05); Texel ewes showed lower PR in summer and spring compared to autumn and winter (p < .05). The twin PR (TPR) in autumn, winter and spring showed no differences, except for summer (p < .05). Age did not influence the PR of ewes <2 years, 2–8 years and >8 years in the seasons, except in summer. It was concluded that the reproduction of European ewes breeds under medium latitude, combined with the use of constant management and feeding conditions, resulted in a fertility rate above 77% in all seasons, resulting in constant production of lambs.