of age, at 24 months of age and at maturity to create a model to predict the growth rate of Holstein, Ayrshire, Jersey and Brown Swiss heifers. The data included numerous records of body weight and wither height from dairy herds across Quebec. Body weight was determined by heart girth circumference with a measuring tape, and wither height was determined by a height measuring stick and included records from 1995 to 2012 (Duplessis et al., 2014). Mature body weight According to Duplessis et al., 2014, researchers were able to assess the mature body weight of multiparious cows for Holstein, Ayrshire, Jersey and Brown Swiss breeds. This data is unique in the sense there is little information on the mature weight of cows from various breeds. Overall, mature cows’ body weight ranged from 470 kilograms for the Jerseys to 710 kg for the Holsteins, indicating breed and individual animal differences in mature body weight, which is important for determining when to breed heifers as shown in Figure 1 (adapted from Duplessis et al., 2014). The mature body weight reported in this study was higher than those reported in NRC, 2001, due to the relationship between body weight and selection for milk production. Body weight (kg) at breeding, 24 months and mature weights for Holstein, Ayrshire, Jersey and Brown Swiss breeds from dairy farms from Valacta in Quebec. Recommended weight (kg) at breeding based on 55 per cent of average mature weight of Holstein, Ayrshire, Jersey and Brown 50 Promotional Supplement Focus On Dairy | June/July 2024 Figure 1 FOCUS ON DAIRY
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