Effect of coat color on age at first lambing, prolificacy and lambing interval in a flock of hair ewes in Campeche, Mexico

The main objective of the study was to evaluate the effect of the ewe's coat color (brown, white, spotted, Blackbelly, and black) on age at first lambing (AFL, n = 578), prolificacy (PRO, n = 475), and lambing interval (LI, n = 438) in a flock of hair sheep in Campeche, Mexico. As a secondary objective, the effects of lambing year, lambing month, and the ewe's lambing number (prirniparous, multiparous) were also evaluated. Data collected on reproductive characteristics during 5 years (2006-2010) from 340 ewes and their lambs were analysed. The sheep were managed under semi-extensive conditions; ewes and their lambs were allowed to graze during the day and were penned overnight. The statistical analysis was performed with the GLM procedure of the SAS statistical package utilizing fixed effects models. Overall least-squares means for AFL, PRO, and LI were 463.9 13.0 days, 1.71 +/- 0.60 lambs born per ewe lambing, and 295,7 +/- 17,9 days, respectively. The ewe's coat color had a significant effect (P <= 0.05) on AFL and LI; the lowest averages for AFL were for white (435.8 +/- 1.4), brown (438.5 +/- 2,4) and spotted (439.7 +/- 3.6) ewes, while for LI the lowest averages were for spotted (284.9 +/- 6.9), white (288.8 +/- 1.6), and black (291.7 +/- 5.8) ewes. Significant effects ((P <= 0.05) of lambing year, lambing month, and lambing number were found on the three characteristics. Due to their lowest averages being obtained at first lambing and lambing interval, it is concluded that white and spotted ewes in this flock should be preferred for a selection program in an attempt to decrease the average of both characteristics.