Estimation of the growth curve in Colombian hair sheep using the Richards model

Objective. To describe growth in Colombian hair sheep (OPC) using the Richards model. Materials and methods. A total of 2086 records were obtained from weighing every 30 days in OPC sheep from birth to slaughter and weaning at 90 days. In addition, the sex (S), type of lambing (TP) and time of birth (Eponac) of the animals were considered. The data were analyzed with the Richards model using the NLIN procedure of SAS. Results. The asymptotic weight estimation indicated by parameter A for males was 7.8 kg higher than that of females; in the TP, this same parameter indicated a 22% superiority between single and multiple births; finally, in the Eponac variable, the best weight values corresponded to the rainy season with 5 kg more than the animals born in the dry season. For the K parameter, the reference values oscillate between 0.001 and 0.004 in the variables S, TP and Eponac; as well as the correlation between the A and K parameters, the values are between -0.98 and -0.99 in all the variables studied. Conclusions. The Richards model explained the development of the animals and allowed observing the effect of the variables S, TP and Eponac, evidencing in each of these a slow growth, but with high weights at maturity.