Genetic and Environmental Effects on Milk Production, Milk Composition and Mastitis Incidence in Crossbred Ewes

Abstract

Fifty-six 3- and 4-year-old ewes were hand milked approximately every 2 weeks for a 15-week lactation period to examine differences among eight crossbred groups in milk production, milk composition and lactation curve and to study the influence of ewe age, number of lambs suckled, stage of lactation and mastitis infection on milk production and composition. Ewes 1/2 Dorset or 1/2 Cheviot produced more milk than ewes 1/2 Finnsheep or 1/2 Romney (P<.10). Lactation curves were of similar shape for each crossbred group. Milk production peaked approximately 3 weeks postpartum and then decreased to the 15th week. Ewes nursing twins produced 22% more milk than ewes nursing a single lamb. Percentages of both protein and fat increased significantly with stage of lactation. Ewes free of mastitis produced 12% and 58% more milk than ewes with one-half or both halves of the udder infected, respectively. Milk from ewes free of mastitis had a lower protein percentage than milk from ewes with mastitis infection (P<.01). Cheviot crossbreds were above average, Dorset crossbreds were slightly above average and Finnsheep and Romney crossbreds were below average in incidence of mastitis. Mastitis occurred at random with respect to stage of lactation and number of lambs suckled but not with respect to repeated observations on the same ewe. The correlation between subjective condition score and total milk production was −.25. Copyright © 1979. American Society of Animal Science. Copyright 1979 by American Society of Animal Science.