Skip to main content
ARS Home » Pacific West Area » Dubois, Idaho » Range Sheep Production Efficiency Research » Research » Publications at this Location » Publication #107583
Title: THE GENETIC RELATIONSHIP OF OVINE MILK SCORE WITH RANGE LAMB WEANING WEIGHT

Author
item Snowder, Gary
item KNIGHT, A. - FORMER ARS, RETIRED
item BROMLEY, C. - UNIV OF NEBRASKA
item VAN VLECK, L. - UNIV OF NEBRASKA

Submitted to: Journal of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: 2/1/1999
Publication Date: N/A
Citation: Snowder, G.D., Knight, A.D., Bromley, C.M., Van Vleck, L.D. 1999. The genetic relationship of ovine milk score with range lamb weaning weight [abstract]. Journal of Animal Science 77(Suppl. 1):134.

Interpretive Summary: Range ewes are commonly evaluated for milking ability by producers as to the ewe's ability to rear lamb(s) under range conditions. The U.S. Sheep Experiment Station has been subjectively scoring (low, average, high) a ewe's milking ability within 24 hrs of lambing for many years. The objective of this study was to determine factors influencing milk score and ddetermine the genetic relationship between milk score and litter weight weaned. Only 1 to 10% of first time lambing ewes had a high milking ability. However, 29 to 40% of those ewes with two or more lambings were evaluated as high milking ability. Ewes with high milk scores did give birth to significantly heavier lambs in all breeds while ewes with low milk scores were associated with significantly higher lamb death losses at birth. Heritability estimates for milk score were moderate and similar among breeds (Columbia, .21; Polypay, .26; Rambouillet, .21; Targhee, .23). The genetic correlations between milk score and litter weight weane were also moderate and within a general range (Columbia, .51; Polypay, .44; Rambouillet, .46; Targhee, .38). The data suggests that milking performance at first lambing may not be a good indicator of future potential milking ability, milk score may be a good selection trait for improving maternal ability, and it appears useful under commercial range conditions weaning at older ages (120 d). Producers are encouraged to consider milk score in their selection schemes.

Technical Abstract: Range ewes are commonly evaluated for milking ability by producers as to the ewe's ability to rear lamb(s) under range conditions. The U.S. Sheep Experiment Station has been subjectively scoring (low, average, high) a ewe's milking ability within 24 hrs of lambing for many years. The objective of this study was to determine factors influencing milk score and destimate genetic parameters between milk score and litter weight weaned. Lambing records of Columbia (n=1731), Polypay (n=1129), Rambouillet (n=1704), and Targhee (n=1638) individual ewes were evaluated. Only 1 to 10% of first parity ewes were high subjectively scored as high milking ability. However, 29 to 40% of second or greater parity ewes were evaluated as high milking ability. Some positive association may exist between body size (kg) and milk score especially at third parity or later in all breeds. Ewe with high milk scores did give birth to significantly heavier lambs in all breeds while ewes with low milk scores were associate with significantly higher lamb death losses at birth. Heritability of milk score and the genetic correlation of milk score with litter weight weaned were determined by MTDFREML analyses within each breed. Heritability estimates were moderate and similar among breeds (Columbia, .21; Polypay, .26; Rambouillet, .21; Targhee, .23). The genetic correlations between milk score and litter weight weaned were also moderate and within a general range (Columbia, .51; Polypay, .44; Rambouillet, .46; Targhee, .38). Conclusions include first parity milking performance may not be a good indicator of future potential milking ability, milk score may be a good selection trait for improving maternal ability, and it appears useful under commercial range conditions weaning at older ages (120 d).