Breeding and Production of Beef to Optimize Production Efficiency, Retail Product Percentage and Palatability Characteristics

Abstract

The demand trend for beef with a higher percentage of lean is expected to continue at an accelerated rate. The trend toward more complete centralized processing at or near the point of slaughter will accelerate in order to gain efficiencies in transportation and labor and to add attractiveness and convenience to the product. Differences in efficiency of production of weaned calf weight are generally independent of cow size provided the nutritive environment is adequate to support reproduction. Maintenance requirements are greater for protein than for fat tissue. Differences in maintenance requirement are small between animals of the same weight and body composition. There is no evidence to support the concept that large genetic differences exist in shape of the growth curve if growth is considered on a fat free basis. Rank of different biological types of growing-finishing cattle in regard to feed efficiency is dependent upon interval of evaluation (time constant, gain constant or fat constant). Reducing the percentage of nutrients contributed by concentrate feed resources by one-half will result in little or no loss in beef palatability or in weight of retail product produced. More than 80% of the increased weight gain resulting from dietary energy densities above 2.7 Mcal metabolizable energy/kg dry matter is fat in growing-finishing steers. Yearling steers slaughtered off pasture without any concentrate feeding had longissimus muscle with lower palatability than steers fed concentrate feeds. However, after a feeding period of 49 d after removal from pasture, palatability characteristics of longissimus muscle were equal to those from steers fed for much longer periods. Differences in marbling score account for less than 10% of the variation in palatability attributes of young cattle produced in economically viable systems. Simultaneous selection for percentage of retail product and marbling score will not be effective for either character. When wholesale cuts are trimmed to a uniform degree of fatness as retail product, genetic differences in retail product percentage contributed by each wholesale cut are too small to justify a selection objective of increasing the percentage of the more preferred cuts. Crossbreeding systems to use both heterosis and complementarity can increase calf weight weaned by 7.75 to 12.1% with no increase in feed resources and with a small reduction in number of females in the beef breeding herd. Intact males produce 38% more edible product than castrate males/unit of digestible energy consumed. Much of the potential improvement in biological efficiency of beef production from growth, composition and reproduction is obtainable through heterosis and complementarity in crossbreeding systems and through production of intact males.