Also, its effects are not transmitted to the progeny and therefore may mask the genetic component as well as the expression of genetic material of the individual (Falconer & Mackay 2006). Their effects can be predicted and sound management practices can be applied to avoid lower phenotypic expression of reproductive and productive traits. Environmental and management factors are very important because they can modify the expected value of the phenotype. However, this breed is not used to its fullest potential, because farmers do not consider the environmental and management factors that could improve the reproductive and productive performance of ewes. 2013), so the knowledge of its effects is important in order to identify and plan sound management to improve the ewe Pelibuey performance. These traits are influenced by genetic and environmental factors (Wildeus 1997 Magaña-Monforte et al. Reproductive and productive traits of the ewe have important contribution to the biological efficiency and profitability of the production system (Rubianes & Ungerfeld 2002). In the Mexican tropics Pelibuey sheep is the main breed, either as purebred or crossbred, playing a maternal role for lamb production (Góngora et al. To improve the performance of Pelibuey ewes adjustments to management schemes should be made as well as to base the selection on more than one productive and reproductive indicator. In conclusion, productive and reproductive performance traits of Pelibuey ewes were influenced by environmental factors, and repeatability were lows. However, the other traits were influenced ( p < .05) by farm, lambing year, lambing season, parity and LSB (for LI and LSW). AFL was not affected by any of the environmental factors. Repeatability were calculated using the between and within ewe components of variance. Mixed models were used to determine the effects of farm, lambing season or birth, year of lambing or birth and parity number on above traits. The assessed traits were age at first lambing (AFL), lambing interval (LI), litter size at birth (LSB), litter size at weaning (LSW), litter weight at birth (LWB) and litter weight at weaning adjusted to 60 days (LWWA). Information of 956 Pelibuey ewes lambing from 2007 to 2013 in three farms were used ( n = 2215 lambing). The objective of this study was to determine the effect of some environmental factors on reproductive and productive performance traits and to estimate their repeatability in Pelibuey ewes in Yucatan, Mexico.
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