Crecimiento predestete de corderos en sistemas intensivos de pastoreo y manejo reproductivo en el altiplano central de México * Preweaning growth in lambs under intensive grazing and reproductive management systems in central Mexico

To study factors affecting birth weight (BW), weight at 30 days and 60 d, data from 917 Columbia lambs were analyzed. Lambs were born in april (N-B) from yearly breeding, or in april-may (A-M), december-january (D- J) and august-september (A-S) from an every eight months breeding program (I-B). Ewes and lambs were grazed on irrigated grass-legume temperate pastures; lambs had