Longitudinal analysis of the effects of IGF1-SnaBI genotypes on the growth curve of Angus bull calves

Abstract

The Insulin Growth Factor 1 (IGF1) has been proposed as a candidate gene for growth related traits as it plays a central role in growth and development of mammals. A relationship between serum IGF1 concentration and different growth traits in cattle has been documented. Furthermore, the IGF1-SnaBI SNP in the gene promoter region influences gene expression and IGF1 blood level. The current research was conducted to perform a genetic analysis of longitudinal data for growth curves through the evaluation of the influence of IGF1-SnaBI genotypes on the growth curve of beef cattle during highly anabolic stages. Data were taken on 275 Angus bull calves on two consecutive years, in two commercial cow–calf operations. Calves were weighed at birth, at weaning, and at 3 to 4 times before the year of age. A random regression animal model was employed for the analysis. Fixed effects were age of dam, herd-year, and age of calf (linear and quadratic terms nested within IGF1-SnaBI genotype). Random effects were age at measure (linear and a quadratic terms nested within animal). The analysis showed significant differences (P<0.01) in the growth curves at ages in between 66 and 291 days for the IGF1-SnaBI genotypes. At 210 days of age, the effect of substituting a T by a C was estimated to be 5.21 kg. These results suggest that the effect of IGF1-SnaBI over growth in cattle take place mostly before puberty.