1. Laboratory of Animal Production; Faculty of Agriculture and Forestry; Universidad de La Frontera; Av. Francisco Salazar 01145 Temuco Chile
2. Department of Mathematical Engineering; Universidad de La Frontera; Av. Francisco Salazar 01145 Temuco Chile
3. Faculty of Veterinary Medicine and Animal Husbandry; Universidad Nacional Autónoma de México; Distrito Federal 04510 México