Abstract
Low birth weights have been observed as a common occurrence among fall-born lambs under Texas conditions. An analysis of birth weights of 1600 Iambs indicated that these weights were closely related to or significantly affected by date of lambing within a fall lambing program. The observed birth weights ranged from 6.9 Ib. in mid-October to 10.2 Ib. for the third week in December. It is suggested that a part of this variation in weight could possibly be attributed to high temperatures during gestation. Two experiments involving 103 ewes were conducted to determine the effect of high environmental temperature (100–105° F.) during gestation on birth weight and lamb mortality. High temperatures during gestation significantly reduced birth weight and increased lamb mortality. Body weight of the ewes was not significantly affected. Number of lambs born favored those maintained in cooled chambers, but the differences in ewes lambing or lambs born were not significant. Copyright © 1964. American Society of Animal Science . Copyright 1964 by American Society of Animal Science

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