Search

Breeding soundness examination data from 1,282 registered Angus bulls in four herds were used to estimate genetic parameters of breeding soundness traits, presence of seminal white blood cells, and common penile defects. Average age of the bulls at the time of evaluation was 383 days. Data were analyzed using single- and two-trait animal models and a derivative-free REML algorithm. Estimates of heritability for scrotal circumference (SC), percent motility, percent primary abnormalities, percent secondary abnormalities and percent total abnormalities were .56, 07, .35, .26 and .29, respectively. Estimates of heritability for the presence of seminal white blood cells, persistent penile frenulum, and penile fibropapillomatosis (warts) on the underlying normal scale were .02, .00, and .004, respectively. Genetic correlations between SC and semen quality parameters were low to moderate and favorable. Phenotypic correlations between SC and semen quality estimates were low and favorable. These results indicate that SC is the most heritable of breeding soundness components and that no undesirable responses in semen quality traits can be expected as a result of selection for increased SC. Conditions such as seminal vesiculitis, persistent penile frenulum, and penile fibropapillomatosis are of low heritability, and if corrected through management or treatment, should not be selected against by producers. Key Words: genetic parameters, scrotum, semen characters

The objective of this study was to determine some of the factors that affect student success in a genetics course. Genetics for the Kansas State University College of Agriculture is taught in the Department of Animal Sciences and Industry and covers Mendelian inheritance, molecular genetics, and quantitative/population genetics. Data collected from 1,516 students over 7 yr included year and semester of the course; age; gender; state of residence; population of hometown; Kansas City metro resident or not; instructor of course; American College Testing Program (ACT) scores; number of transfer credits; major; college; preveterinary student or not; freshman, sophomore, junior, and senior grade point average (GPA); semester credits when taking genetics; class standing when enrolled in genetics; cumulative GPA before and after taking genetics; semester GPA in semester taking genetics, number of semesters between the biology prerequisite and genetics; grade in biology; location of biology course; and final percentage in genetics. Final percentage in genetics did not differ due to instructor, gender, state of residence, major, or college (P > 0.16). Transfer students tended to perform better than nontransfer students (P = 0.09), and students from the Kansas City metro outscored students from other areas (P = 0.03). Preveterinary option students scored higher in genetics than non-preveterinary students (P < 0.01). Seniors scored higher than juniors and sophomores, who scored higher than freshmen (P < 0.02). We observed a tendency for students with higher grades in biology to perform better in genetics (P = 0.06). Students who took biology at Kansas State University performed better in genetics than students who transferred the credit (P < 0.01). There was a negative regression of hometown population on score in genetics (P < 0.01), and positive regressions of ACT score, all measures of GPA, course load, and cumulative credits on final percentage in the course (P < 0.02). To maximize chances for success in genetics, students should take biology from Kansas State, perform well in biology, and wait until at least sophomore standing to enroll in genetics. [ABSTRACT FROM AUTHOR]

To enable breeders to select for correct foot and leg structure to increase productive life of beef cattle, the American Angus Association is developing genetic selection tools for these important traits. The Association accepts categorical 1 to 9 scores, with 5 being ideal, from its members for two traits, foot angle and claw set. Objectives were to explore alternative genetic evaluation approaches for these traits and estimate genetic parameters using 5,722 records collected on Angus bulls and heifers ranging from 320 to 460 days of age. Frequency of observations in the 1 to 9 categories, respectively, were 0, 1, 6, 197, 3,845, 1,468, 166, 34, and 5 for foot angle and 0, 0, 5, 263, 3,251, 1,883, 270, 45, and 5 for claw set. All traits were analyzed using a linear animal model with ASREML 3.0. In addition to a model fitting all phenotypes (1 to 9), each of the traits was also analyzed as two independent traits depending on the score to investigate if foot angles 1 to 5 (steep) were different from 5 to 9 (weak) and claw sets 1 to 5 (spread) were different from 5 to 9 (scissor), with 5 being ideal for each trait. A two-trait model for foot angle and claw set (1 to 9) was used to investigate the genetic correlation. All models included contemporary group (customer, scoring date, sex, and diet type) and weaning creep type as fixed effects, age at measurement as a covariate, animal, and error as random effects. Heritability estimates were 0.34, 0.21, 0.16, 0.25, 0.22, and 0.37, respectively, for foot angle, claw set, spread, scissors, steep, and weak, with a low genetic correlation between claw set and foot angle (0.22) determined with the bivariate model. The moderate heritability estimates for these foot score traits indicate that genetic evaluations are warranted. The traits of scissor and weak (5 to 9) appear to have a slightly higher heritability than the respective overall (1 to 9) traits, but it is not clear if splitting the traits is warranted for genetic evaluation. These genetic parameters will play an important role in the American Angus Associations development of genetic evaluations for foot structure. [ABSTRACT FROM AUTHOR]

The American Angus Association (AAA) is currently evaluating two methods to incorporate genomic information into their genetic evaluation program: (1) multi-trait incorporation of an externally produced molecular breeding value as an indicator trait (MT) and (2) single-step evaluation with an unweighted G matrix (SS). Our objective was to quantify bias and accuracy of genomic predictions using these two approaches. Because phenotypic data was limited for actual carcass measures from genotyped bulls in the AAA database, we tested bias and accuracy using data from the germplasm evaluation program (GPE) at the U.S. Meat Animal Research Center. Traits evaluated included birth, weaning, and yearling weight, maternal weaning weight, carcass weight, marbling score, ribeye area, and backfat thickness. The GPE has sampled 197 AAA bulls over 45 years and has typically characterized weight and carcass data on 8 to 15 progeny from each bull. Of these 197 bulls, 128 had been genotyped using high density arrays. From the AAA database, EPDs were derived using MT, SS, and non -genomic (NG) animal model methods. To detect differences in accuracy, these EPD were correlated to multi-breed EPD derived from GPE. These correlations were restricted to bulls that had high-density genotypes. In addition, to quantify bias, breed-specific EPD regression coefficients were derived from GPE. Independent variables for regression analysis were derived by dropping the EPD from sampled bulls proportionally through the pedigree (1/2 reduction in each generation). These EPD regression coefficients were expected to be one if GPE conditions were similar to conditions in breed association databases. Regression coefficients were obtained for GPE progeny born after 1998, as bulls that produced these progeny were generally genotyped. The NG EPD were used as a benchmark for regression comparison, as any bias observed without genomic data was expected to persist with the addition of genomic information. Resulting correlations were very similar for all three methods for weight traits as correlations among MT, SS, and NG EPD were greater than 0.99. For carcass traits, SS and NG EPD were correlated to each other at 0.97 or more while correlations of each with MT were less than 0.93. For all traits, SS correlations were highest with GPE EPD. In regard to bias, SS regressions were always similar to NG regression while MT regressions were always lower. Data from outside sources, such as GPE, can be useful for evaluating alternative genetic prediction models. [ABSTRACT FROM AUTHOR]

Ultrasound carcass measurements were obtained on 7,031 yearling Limousin bulls and heifers and merged with a pedigree file containing 24,684 animals traced back to the original foundation dam of record. Approximately 25% of the measured animals traced back to a Limousin founder dam, and were categorized as being from a Limousin cytoplasmic line (LCL). The remaining records traced back to non- Limousin founder dam, and were categorized as being from a non- Limousin cytoplasmic line (NCL). The LCL versus NCL effects were evaluated using an animal model with contemporary group as a fixed effect and cytoplasmic line and animal as random effects on scan weight, rib fat, percent intramuscular fat and ribeye area. Results from MTDFREML showed that cytoplasmic line had virtually no effect on scan weight. The proportion of phenotypic variance explained by cytoplasmic line for ribeye area and percent intramuscular fat were 0.51% and 0.77%, respectively. LCL calves had .8949 sq cm larger ribeyes and .0649 percent less IMF than did NCL calves. Cytoplasmic line explained 2.2% of phenotypic variance for rib fat, and LCL calves had .0351 cm less rib fat than did the NCL calves. The magnitude of cytoplasmic line effects is small enough as to not bias current BLUP EPD predictions when such effects are ignored. [ABSTRACT FROM AUTHOR]

The objectives of this study were to determine how well a bull's tenderness Expected Progeny Differences (EPD) actually predicted his progeny's carcass performance, and to evaluate the effect of selection for tenderness EPD on other carcass measurements. In 2002, eight Hereford bulls with divergent tenderness EPD were mated randomly to crossbred cows. These EPD were developed from the NCBA Carcass Merit Project, and the accuracies ranged from 0.20 to 0.43. Steers, bulls, and cull heifers that were weaned in two groups were fed out and harvested with complete carcass data collected. Measurements collected on all cattle (n = 91) included feedlot in-weight (IW), final weight (FW), dressing percent (DP), hot carcass weight (HCW), ribeye area (REA), 12-13th rib fat thickness (FT), marbling score (MS), kidney pelvic heart fat (KPH), and yield grade (YG). A sub-set of cattle (n = 39) were evaluated for tenderness and sensory traits, including Warner-Bratzler shear force (WBSF), myofibril tenderness (MT), overall tenderness (OT), color (CO), purge loss (PL), juiciness (JU), flavor (FL), and average pH (PH). Data were analyzed using the GLM procedure of SAS. The model for all carcass and sensory traits included fixed effects of weaning group, sex, kill group, and sire EPD level. Sire tenderness EPD level did not have an effect (P > 0.05) on WBSF, MT, OT, CO, PL, JU, FL, or PH. Low accuracies on the sire EPD and small progeny numbers probably contributed to the lack of difference in tenderness between EPD levels. The regression of actual sire tenderness EPD on progeny WBSF was 0.32 ± 0.44. In the larger data set, IW, FW, DP, HCW, REA, FT, MS, KPH, and YG were unaffected (P > 0.05) by sire tenderness EPD level. These results from a larger sample of progeny indicate that selection on tenderness EPD should not affect other carcass traits. [ABSTRACT FROM AUTHOR]