Abstract
Two comparisons have been made of the reactions of Southdown sheep to environments at Beltsville, Maryland and Middlebury, Vermont. In one comparison a flock was transferred from Beltsville to Middlebury, and returned to Beltsville after it failed to thrive at Middlebury. In another case, weanling lambs were transferred from Middlebury to Beltsville, and their performance was compared with that of animals born five years earlier and retained at Middlebury. In the first set of comparisons, (1936-43), ewes of all ages were lighter in body weight at Middlebury than at Beltsville before leaving and after their return. Lambing percentages were also lower at Middlebury in all the age groups having sufficient numbers to give a good indication of average performance.There was no indication of a difference in birth weights at the two locations, but with one minor exception weaning weights were consistently lower at Middlebury, the average difference being about 10 pounds.Fleece lengths and fleece weights were also lower in all age groups at Middle-bury. Weaning weights were not available in the second set of comparisons (1910-24), but there were no consistent indications of differences in performance in animals at Middlebury and Beltsville. However, ewes at Middlebury had heavier body weights in all the five age groups for which data were available. The reasons for the apparently different reactions in the two comparisons are not entirely clear. Some improvements were made in management and feeding at Beltsville, between the times of the earlier and later comparisons.Five years elapsed between breeding dates of the two groups used in the early experiments so that they may have been less alike genetically than the animals in the flock entering into the later comparisons. Also, the animals used in the early work were of a larger, more rugged type than those used later, and therefore may have been better adapted to the utilization of pasture and hay under conditions at Middlebury. Even though the reasons for the differences observed in these studies must remain somewhat obscure, the results indicate the importance of variations in adaptability to the environment in livestock production, and point to the need for much greater attention to problems of this type in animal husbandry research. Copyright © . .