Genetic Variation Among and Within Herds of Angus and Hereford Cattle

Historically, beef cattle record of performance programs have by necessity expressed variation as deviations or ratios from herd means because differences between herds are believed to be large primarily because of environment. To the extent differences between herds are genetic, this procedure underestimates or overestimates breeding values of individuals relative to breed average depending on whether they are produced in herds of above or below average genetic merit for a breed. We conducted this study in cooperation with the American Angus Association and the American Polled Hereford Association, and designed it to separate and evaluate the relative importance of between-herd and within-herd sources of genetic variation for birth, growth and carcass characteristics

Genetic Analysis of Some Growth and Carcass Characters in Beef Cattle

Animal Husbandr

Characterization of Breeds Representing Diverse Biological Types: Reproduction and Maternal Performance of F\u3csub\u3e1\u3c/sub\u3e Cows

It is estimated that today about 70 percent of the calves narketed from beef cattle herds in the U.S. are crossbred and hat between 50 and 60 percent of the cows are crossbred. This represents a major shift to crossbreeding from the straight-breeding programs which prevailed in the 1950\u27s and early 1960\u27s. This trend has been influenced by research demonstrating the favorable effects of heterosis and other advantages of crossbreeding. Also, increased use of feed grains in growing-finishing diets caused fatter carcasses contributing to increased consumer demand for leaner beef, which stimulated interest in breeds with greater potential for lean tissue growth and less fat. As a result, a large number of breeds, introduced from Europe via quarantine facilities in Canada, became available to North American beef producers. Interest in the newly Introduced breeds and in other breeds already available coincided with the establishment and development of the Roman L. Hruska U.S. Meat Animal Research Center (U.S. Meat Animal Research Center) in the late 1960\u27s. The Germ Plasm Evaluation (GPE) Program was initiated in 1969 at U.S. Meat Animal Research Center to characterize a broad range of biological types of cattle as represented by breeds that differed widely in genetic potential for milk production, growth rate, carcass composition, and mature size. The purpose of this paper will be to review results from the GPE Program for reproduction and maternal characteristics of first cross (F1) cows

Characterization of Breeds Representing Diverse Biological Types: Postweaning Growth and Feed Efficiency

On a life-cycle basis, about 30% of the energy requirements for beef production are consumed by steers and heifers during the period from weaning to slaughter. About 45 to 55% of the total feed costs are incurred in the postweaning period, depending on the cost of feed resources for the cow herd relative to those for the feedlot. We find it is important, therefore, to characterize breeds of cattle for rate and efficiency of postweaning gain

Characterization of Breeds Representing Diverse Biological Types: Reproduction and Maternal Performance of F\u3csub\u3e1\u3c/sub\u3e Cows

It is estimated that today about 70 percent of the calves narketed from beef cattle herds in the U.S. are crossbred and hat between 50 and 60 percent of the cows are crossbred. This represents a major shift to crossbreeding from the straight-breeding programs which prevailed in the 1950\u27s and early 1960\u27s. This trend has been influenced by research demonstrating the favorable effects of heterosis and other advantages of crossbreeding. Also, increased use of feed grains in growing-finishing diets caused fatter carcasses contributing to increased consumer demand for leaner beef, which stimulated interest in breeds with greater potential for lean tissue growth and less fat. As a result, a large number of breeds, introduced from Europe via quarantine facilities in Canada, became available to North American beef producers. Interest in the newly Introduced breeds and in other breeds already available coincided with the establishment and development of the Roman L. Hruska U.S. Meat Animal Research Center (U.S. Meat Animal Research Center) in the late 1960\u27s. The Germ Plasm Evaluation (GPE) Program was initiated in 1969 at U.S. Meat Animal Research Center to characterize a broad range of biological types of cattle as represented by breeds that differed widely in genetic potential for milk production, growth rate, carcass composition, and mature size. The purpose of this paper will be to review results from the GPE Program for reproduction and maternal characteristics of first cross (F1) cows

Predicting Beef Carcass Retail Product Using Real-time Ultrasound and Live Animal Measures: Progress Report

Two-hundred-eighty-two crossbred steers were scanned with real-time ultrasound (RTU), slaughtered, and fabricated into retail cuts to determine the potential for a combination of live animal and ultrasound measures to predict carcass retail yield. Ultrasound measures of fat thickness, ribeye area, rump fat thickness, and body wall thickness, as well as live weight and visual muscle score were recorded three to five days prior to slaughter. Carcass measurements were taken, and one side of each carcass was fabricated into retail cuts with .3 inches fat. Stepwise regression analysis was used to compare possible models for prediction of either pounds or percent retail product from carcass measurements or a combination of live animal traits and ultrasound measures. Results indicate that possible prediction models for percent or pounds of retail product using live animal and RTU measures were similar in their predictive power and accuracy when compared to models derived from carcass measurements

Genetic Correlations of Reproductive and Maternal Traits with Growth and Carcass Traits in Beef Cattle

Some genes may affect more than one trait. Therefore, the traits can be genetically correlated. Knowledge of genetic correlations among traits is useful for efficient selection of replacement bulls and heifers if the breeder considers more than one trait. In designed selection programs, emphasis to be placed on the various traits can depend, in part, on the genetic correlations among them. In addition, genetic correlations can be used to predict what is expected to happen to traits other than those used in selection as a result of that selection. This effect on traits other than those used in selection is referred to as correlated response. The objective of this study was to estimate from experimental data the genetic correlations between reproductive and maternal traits of beef females and growth and carcass traits of paternal half-sib steers. A more detailed account of the methodology and results can be found in the Journal of Animal Science, volume 58, pages 1171 to 1180

Biological Efficiency Differences Among \u3ci\u3eBos taurus\u3c/i\u3e x \u3ci\u3eBos taurus\u3c/i\u3e and \u3ci\u3eBos indicus\u3c/i\u3e x \u3ci\u3eBos taurus\u3c/i\u3e F\u3csub\u3e1\u3c/sub\u3e-Cross Cows

Matching germplasm to resources through designed crossbreeding programs can contribute to optimum beef production efficiency. This is particularly true in light of the wide diversity of environmental conditions encountered by beef producers in the U.S. This approach requires considerable knowledge about genetic diversity among breeds in components of performance and furthermore how those components interact to influence life-cycle efficiency in the production setting. It was largely this identified need, coupled with the importation of a number of new breeds from continental Europe, that gave impetus for the establishment of the Germplasm Evaluation (GPE) Program. In Cycles I and II of the GPE program, increases in cow output associated with higher breed potential for growth rate and milk production were largely offset by equivalent or greater increases in feed requirements for maintenance and lactation. Additionally, in Cycle III, output of calf weaned per cow in the breeding herd was high for Bos indicus x Bos taurus crosses relative to Bos taurus crosses. More information is needed to evaluate F1 cross of Bos taurus versus Bos indicus x Bos taurus sources of germplasm. Therefore, this study was conducted to: 1) estimate input/output components, and 2) estimate life-cycle efficiency of Cycle III breeds representing these types of F1 cross females

Germplasm Utilization in Beef Cattle

Heterosis achieved through continuous crossbreeding can be used to increase weight of calf weaned per cow exposed to breeding by 20%. Comprehensive programs of breed characterization have revealed large differences among breeds for most bioeconomic traits. About 55% of the U.S. beef breeding population involving 93% of the farmers and ranchers who produce beef cattle are in production units of 100 or fewer cows. Optimum crossbreeding systems are difficult to adapt in herds that use fewer than four bulls. Further, fluctuation in breed composition between generations in rotational crossbreeding systems can result in considerable variation among both cows and calves in level of performance for major bioeconomic traits unless breeds used in the rotation are similar in performance characteristics. Use of breeds with similar performance characteristics restricts the use that can be made of breed differences in average genetic merit to meet requirements for specific production - marketing situations. The potential of composite breeds as an alternative to continuous crossbreeding for using heterosis and for using genetic differences among breeds to achieve and maintain a more optimum additive genetic (breed) composition needed to be investigated in a comprehensive experiment. The primary objective of this experiment was to estimate the retention of combined individual and maternal heterosis in advanced generations of inter sè mated composite populations established with contributions from either four or five breeds. Retention of initial (F1) heterozygosity after crossing and subsequent random (inter sè) mating within crosses is proportional to (n-1)/n when n breeds contribute equally to the foundation. When breeds used in the foundation of a composite breed do not contribute equally, percentage of mean F1 heterozygosity retained is proportional to (Equation) where Pi is the fraction of each of n contributing breeds to the foundation of a composite breed. This loss of heterozygosity occurs between the F1 and F2 generations, and if inbreeding is avoided, further loss of heterozygosity in inter sè mated populations does not occur. A primary question in this experiment was the extent to which retention of heterosis in composite populations is proportional to retention of heterozygosity