East Friesian germplasm: Effects on milk production, lamb growth, and lamb survival

Abstract

East Friesian (EF) crossbred rams (1/2 to 7/8 EF breeding) and Dorset rams were mated to crossbred ewes from 1993 through 1996. Growth, reproduction, and lactation performance of their progeny were compared. East Friesian-cross lambs had greater birth, weaning, and postweaning weights than Dorset-cross lambs. When lambing at 1 and 2 yr of age, EF-cross ewes gave birth to and reared more lambs per ewe mated, had more days in lactation, produced more milk and more weight of milk fat and milk protein, and had a lower percentage of milk fat and protein than Dorset-cross ewes. With the levels of EF breeding evaluated in this study (up to 50%), EF-cross sheep were superior to Dorset-cross sheep for lamb and milk production in the north-central United States. Early results from other U.S. studies show advantages of sheep of 50% EF breeding over domestic breeds and crosses for commercial lamb production. However, sheep producers should be aware that in many other countries where the EF has been imported to improve commercial milk production of local sheep populations, sheep containing more than 50% EF breeding have had lower survival, lower lamb production, and, in some cases, lower milk production than local breeds. Countries that have reported poor performance of high-percentage EF sheep are in the Mediterranean region, and the EF breed seems poorly adapted to the high environmental temperatures of that region. Although the environmental temperatures of much of the United States may not place a stress on EF sheep, they have also been shown to be more susceptible to some diseases than local breeds, most notably to pneumonia. Even though we have not designed a study to evaluate the effects of the proportion of EF breeding on performance, lambs of greater than 50% EF breeding in our 1999 lamb crop had significantly lower survival rates than lambs of lower percentages EF breeding. Therefore, there is a need for evaluation of pure EF or EF-cross sheep of greater than 50% EF breeding to determine the optimum amount of EF breeding for commercial sheep farms in the United States. Other dairy breeds also should be evaluated as they become available in the United States.