Submitted to: Western Section of Animal Science Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 4/21/2008
Publication Date: 4/30/2008
Citation: Leeds, T.D., Mousel, M.R., Notter, D.R., Leymaster, K.A., Lewis, G.S. 2008. Evaluation of Columbia, USMARC-Composite, Suffolk, and Texel rams as terminal sires: Effects of ram breed on ewe productivity and F1 lamb survival and growth. Western Section of Animal Science Proceedings. 59:65-68. Interpretive Summary: Adverse terminal sire breed effects on ewe productivity and crossbred lamb survival can negate superior performance for growth and carcass composition in terminal crossbreeding systems. This study found no differences among Columbia, USMARC-Composite, Suffolk, and Texel sire breeds for ewe productivity and crossbred lamb survival. Thus, performance of crossbred lamb growth and carcass composition can be emphasized as criteria for selecting the appropriate terminal sire breed.
Technical Abstract: Objectives were to estimate effects of ram breed on ewe fertility, prolificacy, and F1 lamb survival and growth. Columbia, USMARC-Composite, Suffolk, and Texel rams (n = 15, 15, 15, and 13, respectively) were sampled from US flocks. Data were from 665 exposures to Rambouillet ewes (3 to 7 yr of age) and 1,243 F1 lambs over 2 yr. Ewes lambed in March or April and were herded with litters on sagebrush steppe and subalpine ranges. Lambs were weaned at 130 d of age (SD = 5.8 d). Ewe fertility (lambed or did not lamb), ewe prolificacy (number born; number born alive), lamb birth and weaning weights, and lamb survival from birth to weaning (age at death or censoring) were recorded. Fertility data were analyzed using a categorical analysis with effects of sire breed, year, and dam age. Prolificacy data were described using a mixed linear model that included fixed sire breed, year, and dam age effects and sire within breed and year as a random effect. Litter size and gender were added to the model to describe lamb weight data, and weaning age was included as a covariate for weaning weight. Survival data were analyzed using a Weibull survival model that included effects of sire breed, year, dam age, litter size, gender, and linear and quadratic effects of birth weight. Sire breed did not influence ewe fertility, prolificacy, or lamb survival (P > 0.10), but was important for weight traits (P < 0.05). No sire breed effect was detected (P > 0.10) for lamb survival when birth weight effects were removed from the model. Suffolk-sired lambs (5.26 kg) were 0.24 kg heavier at birth than USMARC-Composite- or Texel-sired lambs (P < 0.05), but not different from Columbia-sired lambs (5.13 kg). Suffolk-sired lambs (39.4 kg) were heaviest at weaning (P < 0.05). Texel-sired lambs (36.7 kg) were lighter at weaning than Columbia-sired lambs (37.8 kg; P < 0.05), but not different from USMARC-Composite-sired lambs (37.4 kg). These data provide breed comparisons in an extensive range environment that can be used to develop breeding objectives for terminal sires.