Fig. 4

Parental generation intervals I₁ (in months). I₁ were defined as the difference between the birthdate of an individual and its parents’ (in months). The yellow line represents the mean for each birth year and the error bars the standard deviation. Generation intervals I₁ were computed for progeny-tested bulls born between 2005 and 2010 and for marketed bulls born between 2012 and 2015, for Montbéliarde (a), Normande (b) and Holstein (c)