hps://doi.org/10.21897/rmvz.2733 Original Journal MVZ Córdoba 2022; 27(Supl):e2733 How to cite (Vancouver). Montes-Vergara D, Hernández-Herrera D, Carrillo-González D. Non-genetic effects on preweaning growth traits in Colombian Creole hair sheep. Rev MVZ Cordoba. 2022; 27(Supl):e2733. https://doi.org/10.21897/rmvz.2733 ISSNL: 0122-0268 ©The Author(s) 2022. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (https:// creativecommons.org/licenses/by-nc-sa/4.0/), lets others remix, tweak, and build upon your work non-commercially, as long as they credit you and license their new creations under the identical terms. ABSTRACT Objective. Determine the effect of some variation factors that affect the characteristics of birth weight (BW), adjusted weaning weight (AWW) at 90 days and pre-weaning weight gain (PWW) in Colombian hair sheep. Materials and methods. 525 data from Colombian hair sheep (OPC) offspring, reared in an extensive production system under conditions of the lower Colombian tropics were used. A linear fixed effects model (GLM) was used, which included the sex of the calf, the type of calving (single or multiple), the calving number of the ewe (primiparous or multiparous), the climatic season of birth (dry or rainy) and the year of birth (2017 to 2020) and their interactions. The analyzes were carried out with the statistical package SAS University ® 2021. Results. The BW, AWW and PWW values were 2.9±0.1 kg, 13.2±1.6 kg and 0.15±0.064 kg, respectively. The BW was significantly affected (p<0.05) by all the factors studied. So then, the males, the offspring of simple delivery, of first-time ewes, in the rainy weather season and in 2019 had better performance. The AWW only varied significantly due to the effects of calving number, the climatic season and the year. Finally, the PWW was only affected by the rainy weather season and by the year. Conclusions. The BW turned out to be the variable most sensitive to the factors analyzed. In maternal effects, the type of delivery did not affect the AWW and PWW, while the number of deliveries affected the AWW but not the PWW. Keywords: Pre-weaning growth; pre-weaning weight gain; birth weight; adjusted weight at weaning (Source: CAB). RESUMEN Objetivo. Determinar el efecto de algunos factores de variación sobre las características peso al nacimiento (PN), peso al destete ajustado (PDA) a los 90 días y la ganancia de peso predestete (GPP) en ovinos de pelo colombiano (OPC). Materiales y métodos. Se utilizaron 525 datos de crías de OPC, manejados en un sistema extensivo de producción, en condiciones del trópico bajo colombiano. Fue utilizado un modelo lineal de efectos fijos, que incluyó, el sexo de la cría, el tipo de parto (sencillo o múltiple), el número de parto de la oveja (primípara o multípara), la época climática de nacimiento (seca o lluviosa) y el año de nacimiento (2017 al 2020) y sus interacciones. Los análisis se realizaron con el paquete estadístico SAS University ® 2021. Resultados. Los valores de PN, PDA y GPP fueron 2.9±0.1 kg, 13.2±1.6 kg y 0.15±0.064 kg, respectivamente. El PN Non-genetic effects on preweaning growth traits in Colombian Creole hair sheep Donicer Montes-Vergara 1 * ; Darwin Hernández-Herrera 2 ; Diego Carrillo-González 1 . 1 Universidad de Sucre, Grupo de Investigación en Reproducción y Mejoramiento Genético Animal, Sincelejo, Colombia. 2 Universidad Nacional de Colombia, Facultad de Ciencias Agropecuarias, Departamento de Ciencia Animal. Palmira, Colombia. *Correspondence: donicer.montes@unisucre.edu.co Received: November 2021; Accepted: July 2022; Published: July 2022.