Abstract #717

# 717
Breeding strategies in sheep for low-input management systems.
Ronald M. Lewis*1, NapoleĆ³n Vargas Jurado1, Kreg A. Leymaster2, 1Department of Animal Science, University of Nebraska, Lincoln, NE, 2Roman L. Hruska US Meat Animal Research Center, USDA-ARS, Clay Center, NE.

Profitability of sheep enterprises increasingly depends on using low-input, pasture-based management systems where costs can be curtailed without sacrificing productivity. Their success rests on using maternal genetics well adapted to such systems yet with attributes to produce a quality product. In historically medium-wool industries, fleece has become a cost rather than a source of revenue. Therefore, hair sheep germplasm has been incorporated into maternal lines to facilitate wool shedding (WS), and to enhance health (e.g., internal parasite resistance) and fitness (e.g., vigor, aseasonality, longevity). Yet, there are caveats. Hair sheep are smaller in mature size and typically lighter muscled. Within the US, carcass weights are traditionally at least 30 kg, a challenge to achieve with smaller breeds. The Katahdin breed reflects that concern, where Caribbean hair sheep were combined with wool breeds and Wiltshire Horn, a larger mature size breed that sheds. Markets for hair sheep lambs of lighter weight have evolved, allowing greater flexibility. Crossing with terminal sires offers another option, although its impact on overall productivity needs attention. The definition of a maternal breed-type ideal for low-input systems is equivocal. At the US Meat Animal Research Center, a 1/4 Katahdin, 1/4 White Dorper and 1/2 Romanov composite has been established to attain an intermediate optimum. The inclusion of Romanov increased prolificacy, allowing identification of ewes able to produce, nurture and rear twin and triplet lambs in a low-input system. The composite retains 62.5% of heterosis benefiting health and fitness. Data on WS, color, horns, major genes affecting disease, and rearing status have been collected, and used independently in selection. Genetic analyses of WS data have been conducted. Among 3345 autumn WS records on ewes, 64% had less than 25% wool coverage; WS was moderately heritable (0.26) and repeatable (0.40). This composite is early in development, and further generations of inter se mating would benefit its evaluation. A breeding program for low-input systems necessitates combining breeds. A strategy capturing key attributes of a maternal breed-type, as defined through a selection index, is needed to sustain its role in the sheep industry.

Key Words: sheep, low-input, maternal composite

Speaker Bio
Ron Lewis is a Professor of Animal Breeding and Genomics at the University of Nebraska-Lincoln.  His research interests are in quantitative genetics and genomics with two main themes: (i) defining pragmatic strategies to improve the reliability of genetic evaluation, and thereby enhancing selection response, in livestock species; and, (ii) understanding how animals, changed through artificial selection, are influenced by and interact with their environment. His work involves a mix of theory, simulation and field studies, with species emphases in sheep, beef and poultry, with close collaborations in North America, Great Britain and Norway.