Scientists at the National Genetic Research Institute in France compared two statistical models, fixed threshold (FT) and fixed linear (FL) to estimate genetic parameters for calving difficulty in the French Charolais cattle population. Calving records were analyzed on 246,576 Charolais calves born from 1985 to 1999. Interestingly, most calvings (93%) were either unassisted (score=1) or required only minor assistance (score=2) (56 and 37%, respectively). The remaining 7% are either mechanically assisted (score=3) or were caesarian births (score=4).

• Heritabilities of direct calving ease were 0.27 and 0.14 for the FT and FL models, respectively.
• Heritabilities of maternal calving ease were 0.18 and 0.13, respectively.
• The genetic correlations between direct and maternal were -0.36 and -0.34, respectively, indicating that the two traits are somewhat antagonistic.