a1 Department of Animal and Range Sciences, Montana State University, Bozeman, Montana, USA
Twin-born Rambouillet, Targhee and Columbia lambs were used to study the effect of sex of lamb and its co-twin on birth weight, weight at 60 days of age and weaning weight. Mean birth weights of female lambs were lower than those of males, and lambs born co-twin to males had a lower mean birth weight than those born co-twin to females. Lambs born co-twins to females grew faster from birth to 60 days of age and had a greater chance of surviving from birth to weaning than did lambs that were co-twins to males.
(Received October 07 1971)