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Lamb Production of Navajo Ewes Bred to Columbia and Romney Rams, and Navajo Crossbred Ewes Bred to Lincoln and Cotswold Rams¹

United States Departments of Agriculture and the Interior

Abstract

This was a study to observe differences in lamb production between some of the crossbred breeding groups maintained at the Southwestern Range and Sheep Breeding Laboratory, Fort Wingate, New Mexico.

Breeding and lambing records were analyzed for 721 matings of Navajo ewes with Romney and Columbia rams, and 974 matings of Navajo crossbred ewes with Cotswold and Lincoln rams.

In crosses involving Columbia and Romney rams with Navajo ewes, the percentages of ewes lambing were 88.3 and 90.2, respectively. The percentage of Navajo crossbred ewes lambing that were bred to Cotswold and Lincoln rams were 64.8 and 68.7, respectively. However, only very limited conclusions can be made regarding the low percentages of ewes lambing when mated to the Cotswold and Lincoln rams used in this study, for the following reasons: (1) Rams of the four breeds used were not all mated to the same ewes, (2) the number of rams of each breed used was small, and (3) semen tests indicated that the semen quality of three of the Cotswold and Lincoln rams was too poor to warrant their use and in others the quality was not high. However, because of the limited number of rams available, some of the undesirable ones were used.

In fecundity no significant differences were found between the various breeding groups. The average for all ewes was 141.4 percent. For percentage of live lambs of lambs born, the Romney and Lincoln crosses proved superior. There was no significant difference among the various breeding groups for percentage of lambs weaned of live lambs born.

The Cotswold cross lambs were significantly heavier at weaning age than lambs of the remaining breeding groups. The average weaning weights of the Columbia and Lincoln groups were significantly greater than the average weaning weight of the Romney group. The mean difference between the Columbia and Romney groups for pounds of lamb weaned per ewe bred was small. The Lincoln group was significantly better than the Cotswold group for this measurement while both the Lincoln and Cotswold groups were considerably poorer than the Columbia and Romney groups.

¹ The data for this study were collected at the Southwestern Range and Sheep Breeding Laboratory, Fort Wingate, New Mexico, under authority of the Bankhead-Jones Act, by the Bureau of Animal Industry, U. S. Department of Agriculture, in cooperation with the Bureau of Indian Affairs, U. S. Department of Interior, and the New Mexico Agricultural Experiment Station.

² U. S. Department of the Interior and collaborating with the U. S. Department of Agriculture. The assistance of Dr. H. H. Stonaker, Colorado A & M College is gratefully acknowledged.