Selection practices in three synthetic lines of beef cattle were evaluated based on data collected over 12 to 13 years. Sires from the Jersey, Angus and Simmental breeds were mated to three lines of foundation crossbred dams to produce first generation progeny. Subsequent calves were produced mating crossbred parents of the same generation. Crossbred sires were selected based on an index that included hip height and weight at weaning. At Rhodes, a total of 2.84 to 3.07 generations of selection have been carried out. This provided a mean generation interval of 4.33, 4.23 and 4.58 years in small, medium and large lines, respectively. At McNay, the corresponding generation interval values were 4.15 years for small and medium lines and 5.29 years for the large. The mean weighted sire selection differential for the index in the small line was 1.28 s/generation. In the medium cattle these values were -.57 s/generation (Rhodes) and -.36 s/generation (McNay). For the large synthetic cattle the index differential ranged from .71 s/generation at McNay to .92 s/generation at Rhodes. Of the total mean parental selection differential, sire contribution ranged from 86% to 95%. Selection differential values for components of the index indicated that the index equations often favored weaning weight, and this was very pronounced in the medium line. Regardless of the line, selection criteria have been strictly followed. However, all the maximum potential sires have not been utilized.

In this study two separate sets of data were used to develop prediction equations for Marbling Scores (MS) from actual percentage intramuscular fat. All regression parameters were significantly (P<.01) different from zero. Model-I explained only 49% of the variation in MS as compared with 83% for model- II. When these equations were validated on an independent data set, the correlations between the predicted and actual marbling scores were similar at 0.69 and 0.66 for model-I and model-II, respectively. Model-I has correctly classified 45.45%, 67.62%, 63.83%, and 42.86% of the bservations in trace, slight, small and modest classes, respectively. Model- II performed better than model-I for the extreme MS classes (practically devoid and moderate).

Data from two cattle feeding trials were used to estimate accuracy and repeatability of ultrasound measurements of 12–13th rib fat thickness and longissimus muscle area. In each trial, images from the last scan prior to slaughter were interpreted by two certified technicians. Each technician interpreted the image of each steer twice on two different days. Overall technician biases for ultrasound measurements of fat thickness and longissimus muscle area were −0.17 cm and 0.63 cm2, respectively. Mean bias in measurement of fat thickness by the two technicians was similar in amount and direction (−0.14 cm vs. −0.20 cm); however, bias in the measurement of longissimus muscle area by the two technicians took an opposite direction (−1.28 cm2 vs. 2.54 cm2). Repeatability of ultrasound-measured fat thickness was the same for both technicians (0.96 to 0.97). However, measurements of technician A showed a better repeatability (0.92) than technician B (0.79) for ultrasound-measured longissimus muscle area. Generally, except for minor differences, degree of experience did not show a consistent difference in the accuracy of ultrasound estimation of fat thickness and longissimus muscle area. Hence, it was concluded that technicians could easily be trained to make accurate predictions of fat thickness and longissimus muscle area. Key words: Beef cattle, carcass, ultrasound, repeatability, accuracy

A new beef breeding project will be conducted at the Rhodes and McNay farms of ISU. The project will use the field data of the American Angus Association along with the research resources (cattle) of the farms to study questions that will enhance the genetic investigations using the field data. It will build on the expertise developed at ISU with ultrasound to measure body composition in the live animal and in the carcass. Two selection lines, using registered Angus obtained as heifers and through ET, of 200 females each will be selected for increased intramuscular fat (Q line) and for increased retail product (R line). The estimation of the genetic correlation between quality and amount of product can best be accomplished through the study of one generation of selection using measures of body composition derived from ultrasound. A progeny test herd will be maintained to evaluate all sires used through progeny carcass testing and to further research with ultrasound. The project will study efficiency of body maintenance. Results will be shared through the Beef Improvement Federation to benefit all producers in the development of sound programs to profitably produce specified beef products.

A total of 1,072 observations collected over a six-year period were used to develop prediction models for retail product (percentage and weight) and hot carcass weight from live cattle measures. Independent variables used were: ultrasound fat thickness (UFAT), ultrasound longissimus muscle Area (ULMA), age, hip height (HT), live weight (WT), ultrasound-predicted percent Intramuscular fat (UIMF) and breed composition. Pearson product moment correlations between the dependent and independent variables were often significant (P < .01, P < .05). In the prediction of percent retail product, UFAT accounted for 29 to 42% of the variation. A complete model including all the independent variables explained 20% more of the variation. In the prediction of retail product weight, WT remained a highly significant independent variable accounting for 32 to 78% of the variation. Similarly, WT accounted for 38 to 81% of the variation in hot carcass weight. When independent variables were adjusted to a constant age, models from data adjusted to earlier ages (M-414, M-382) explained more variation than models from data adjusted to a mean age at slaughter (M-448).

A prediction model from a previous study was utilized to evaluate the degree of fit when this model is applied to an independent data set. The degree of fit was evaluated using means, regression analysis, correlation coefficient, distribution of residuals, and mean square error of prediction (MSEP). The model provided a reasonably accurate prediction of intramuscular fat with a mean bias of 0.13%. For 47.1% of the steers, percent intramuscular fat was predicted within ± 0.5%, and for 77.6% of the steers, prediction of percent intramuscular fat was made within ± 1%. Pearson product moment correlation between predicted and actual percent intramuscular fat was 0.74 (p < .01), and the square root of MSEP indicated a prediction error of 0.9%.

Data from two feeding trials were used to estimate accuracy of ultrasound measurements of fat thickness and ribeye area. In each trial, steers were scanned three or four times by one technician. Two beef improvement federation (BIF)-certified technicians with different levels of experience interpreted images from the last scan taken just before slaughter. Each technician interpreted the image of an individual steer twice on two different days. Accuracy of interpretation was evaluated using simple statistical measures, including means, standard deviations, regression and correlation coefficients, RMSE, and ESD. The overall technician biases for ultrasound measurements of fat thickness and ribeye area were -0.17 cm and 0.63 cm2, respectively. Mean bias by technician indicated a similar direction and amount of bias (-0.14 vs -0.20 cm). However, bias in the measurement of ribeye area by the two technicians took an opposite direction ( -1.28 vs 2.54 cm2). In all cases, technician bias was within the acceptable range for BIF certification. Pearson product moment correlations between carcass and ultrasound measurements of fat thickness and ribeye area were 0.70 and 0.40, respectively. In general, fat thickness for 52% of the steers was measured within ±0.254 cm and for 85.2 % of the steers, fat thickness was measured within ±0.508 cm. For ribeye area, ±51.2 % and ±71.4 % of the steers had measurements within ±6.65 cm2 and ±12.99 cm2, respectively .

Data from two feeding trials were used to evaluate repeatability of ultrasound measurements of fat thickness and ribeye area. In each trial, steers were scanned three or four times by one technician. Two beef improvement federation (BIF)-certified technicians with different levels of experience interpreted images from the last scan. Each technician interpreted the image of an individual steer twice on two different days. Repeatability was evaluated as an intra-class correlation. Additional statistics used to evaluate repeatability were the slope and intercepts from a regression analysis, RMSE, and ESD. Ultrasound measurements of fat thickness and ribeye area were repeatable both within and across technicians. The only exception was the across-technician measurements of ribeye area, where an apparent difference in variances of measurements was observed.

Dominance and additive x additive genetic variances were estimated for birth and weaning traits of calves from three synthetic lines of beef cattle differing in mature size. Data consisted of 3,992 and 2,877 records from lines of small-, medium-, and large-framed calves in each of two research herds located at Rhodes and McNay, IA, respectively. Variance components were estimated separately by herd and line for birth weight (BWT), birth hip height (BH), 205-d weight (WW), and 205-d hip height (WH) by derivative-free REML with an animal model. Model 1 included fixed effects of year, sex, and age of dam. Random effects were additive direct (a) and additive maternal (m) genetic with covariance (a,m), maternal permanent environmental, and residual. Model 2 also included dominance (d) and model 3 included dominance plus additive x additive (a:a) effects. In general, only slight changes occurred in other variance components estimates when day was included in Model 2. However, large estimates of additive x additive genetic variances obtained with Model 3 for 4 out of 24 analyses were associated with reductions in estimates of direct additive variances. Direct (maternal) heritability estimates averaged across herd-line combinations with Model 2 were .53(.11), .42(.04), .27(.12), and .35(.04) for BWT, BH, WW, and WH, respectively. Corresponding covariance (a,m) estimates as fractions of phenotypic variance (sigma p2) were .00, .01, .01, and .06, respectively. For maternal permanent environmental effects in Model 2, average estimates of variances as fractions of sigma p2 across herd-line combinations were .03, .00, .05, and .02, for BW, BH, WW, and WH, respectively. Dominance effects explained, on average, 18, 26, 28, and 11% of total variance for BWT, BH, WW, and WH, respectively. Most of the estimates for additive x additive variances were negligible, except for one data set for BWT, two for BH, and one for WH, where the relative estimates of this component were high (.21 to .45). These results suggest that most of the non-additive genetic variance in the traits studied is accounted for by dominance genetic effects.

SummaryGenetic parameters were estimated for repeated racing times on Thoroughbred horses for several racing distances both on turf and dirt. An additive genetic and permanent environmental model of multiple‐trait derivative‐free restricted maximum likelihood (MTDFREML) was used. The data used were collected by the Japan Racing Association from 1986 to 1990 and the effects of individual race, sex, age, jockey and weight carried were used. The generation 2 pedigree information was preferable for variance estimates. Heritability decreases as the racing distance increases. These values were 0.25, 0.16, 0.10, 0.12, 0.09 and 0.08 at 1000, 1200, 1400, 1600, 1800, and 2000 m, respectively, on turf, and 0.19, 0.22, 0.12, 0.09 and 0.17 at 1000, 1200, 1400, 1600, and 1800 m, respectively, on dirt track. The values of repeatability were from 0.43 to 0.70 on turf, and from 0.51 to 0.67 on dirt track. These suggest that racing times at the different racing distances may be regarded as different traits when the horse is to be evaluated genetically.ZusammenfassungSchätzung genetischer Parameter für Rennzeit von japanischen Vollblütern durcb eingeschrïhte max‐imale WahrscheinlichkeitDie Schätzung der genetischen Parameter erfolgte für wiederholte Rennzeiten von Vollblütern über mehrere Renndistanzen sowohl auf Rasen als auch auf Sandbahn. Zusätzlich wurde ein Permanent‐Umweltmodell (multiple‐trait derivative‐free restricted maximum likelihood (MTDFREML)) angewendet. Die Daten wurden von 1986 bis 1990 von JRA erhoben und die Wirkungen von Rasse, Geschlecht, Alter, Jockey und Tragegewicht geschätzt. Stammbaumdaten der Generation 2 dienten bevorzugt zur Varianzschätzung. Der Einfluß des Erbguts nimmt mit zunehmender Renndistanz ab, die betraffender h2 Werte waren 0,25, 0,16, 0,10, 0,12, 0,09 und 0,08 bei 1000, 1200, 1400, 1600, 1800 und 2000 m auf Rasen sowie 0,19, 0,22, 0,12, 0,09 und 0,17 bei 1000, 1200, 1400, 1600 und 1800 m auf Sandbahn. Der Wiederholbarkeitskoeffizient lag zwischen 0,43 und 0,70 auf Rasen und 0,51 bis 0,67 auf Sandbahn. Dies legt die Vermutung nahe, daß bei Zuchtwertschätzung Rennzeiten über verschiedene Distanzen als unterschiedliche Merkmale betrachtet werden sollen.RésuméEstimation des paramètres génétiques sur le temps de course chez les Pur‐sang au Japon, selon la méthode de probabilité maximum restreinteOn a estimé les paramètres génétiques pour les temps de course répétés chez les chevaux Pur‐sang pour plusieurs distances de course sur gazon et sur terre battue. On a utilisé un modèle additif génétique et environnementiel permanent de vraisemblence maximum restreinte à traits multiples et sans dérivé (MTDFREML: ‘multiple‐trait derivative‐free restricted maximum likelihood’). Les données utilisées ont été rassemblées par la JRA de 1986 à 1990 et on a utilisé les effets de la race, du sexe, de l'âge, du jockey et de la charge portée. L'information de pédigrée de génération 2 s'est avérée préférable pour les estimations de variance. L'effet de l'hérédité diminue avec l'augmentation de la distance parcourue. Ces valeurs sont de 0,25, 0,16, 0,10, 0,12, 0,09 et 0,08 sur 1000, 1200, 1400, 1600, 1800 et 2000 m respectivement sur gazon, et de 0,19, 0,22, 0,12, 0,09 et 0,17 sur 1000, 1200, 1400, 1600 et 1800 m respectivement sur terre battue. Les valeurs de répétabilité vont de 0,43 a 0,70 sur gazon et de 0,51 a 0,67 sur terre battue. Ces valeurs suggèrent que les temps de course sur différents distances peuvent être interprétés comme autant de traits différents quand le cheval est évalué génétiquement.

SummaryThe effects of race, age, jockey, and weight carried on racing time in Japanese Thoroughbred horses were examined by hypothesis testing (H:K′b = 0) of the fixed effects in the mixed model. The data used were collected by the Japan Racing Association from 1988 to 1990. Only races having more than two ages and connectedness between jockeys and horses were used. The data were also analysed with and without the inverse of the numerator‐relationship matrix. The significance levels did not change regardless of whether the A−1 was incorporated into the mixed‐model equations. Race, jockey, and weight carried were found to have highly significant (p < 0.01) effects on racing time over six different racing distances on turf and dirt tracks. The skill of the jockey is an important source of variation in racing time across distances and track types, therefore, it should be considered in deriving adjustment factors, estimating genetic parameters, and predicting genetic values for racehorses.RésuméEffect du jockey sur le temps de course des Pur‐sangL'effet de la race, de l'âge, du jockey, et du poids sur le temps de course des Pur‐sang au Japon a été examiné selon le procédé du testage d'hypothèse (H:K'b = 0) des effets fixes dans un modèle mixe. Les données utilisées ont été rassemblées par la Japan Racing Association de 1988 à 1990. Seules les courses comprenant deux âges ou plus et un rapport entre les jockeys et les chevaux furent utilisées. Les données furent analysées avec et sans l'inverse de la matrice de relation du numérateur. Les niveaux significatifs ne varient pas, que A−1 soit incorporé ou non aux équations de modèle mixe. La race, le jockey, et la charge portée ont prouvé avoir des effets significatifs (p < 0.01) sur le temps de course pour six parcours de course différents sur gazon et sur terre battue. Il est important de noter que puisque le talent du jockey est une source importante de variation sur le temps de course pour différentes distances et différentes types de piste, on devrait en tenir compte dans la dérivation de facteurs d'ajustement, dans l'estimation de paramètres génétiques et dans la prédiction de valeurs génétiques pour les chevaux de course.ZusammenfassungEinflub Jockeys auf die Rennzeit von VollblüternDie Wirkungen von Rasse, Alter, Jockey und Tragegewicht auf die Rennzeit von japanischen Vollblütern wurden unter der Hypothese feste Effekte (H:K′b = 0) im Mischmodell untersucht. Die verwendeten Daten wurden im Zeitraum von 1988 bis 1990 von der ‘Japan Racing Association' erhoben. Nur Rennen mit mehr als zwei Altersgruppen und möglicher Zuordnung von Jockeys zu Pferden wurden berücksichtigt. Darüber hinaus wurden die Daten auch mit und ohne Anwendung der Inversen der Verwandtschaftsmatrix analysiert. Signifikanzwerte blieben von der Einbeziehung von A−1 in die Gleichungen des Mischmodells unberührt. Es wurde deutlich, daß sich Rasse, Jockey und Tragegewicht mit hoher Signifikanz (p < 0,01) auf die Rennzeit auswirken, und zwar bei sechs verschiedenen Rennstrecken auf Rasen und Sandbahn. Das Können des Jockeys ist von großer Wichtigkeit für verschiedene Rennzeiten über Strecken und Bahnarten und sollte daher bei der Ableitung von Korrektur faktoren, der Schätzung von genetischen Parametern und der Voraussage von Zuchtwerten von Rennpferden berücksichtigt werden.

Journal Article Lanoy N. Hazel, 1911-1992: a brief biography Get access D. L. Harris, D. L. Harris *Roman L. Hruska U.S. Meat Animal Research Center, ARS, USDA, Clay Center, NE 68933-0166 Search for other works by this author on: Oxford Academic PubMed Google Scholar R. L. Wilham, R. L. Wilham *Roman L. Hruska U.S. Meat Animal Research Center, ARS, USDA, Clay Center, NE 68933-0166 Search for other works by this author on: Oxford Academic PubMed Google Scholar G. E. Dickerson G. E. Dickerson *Roman L. Hruska U.S. Meat Animal Research Center, ARS, USDA, Clay Center, NE 68933-0166 Search for other works by this author on: Oxford Academic PubMed Google Scholar Journal of Animal Science, Volume 72, Issue 8, August 1994, Pages 1923–1926, https://doi.org/10.2527/1994.7281923x Published: 01 August 1994

The American Angus Association has sponsored a carcass evaluation since 1974. The carcass data collected as a part of this program are used by the association to conduct a biannual sire evaluation for carcass merit. This paper presents age-adjustment factors and genetic parameter estimates for carcass traits to be used in the Angus carcass genetic evaluation program. Because of the large range in slaughter ages, age classes were defined as all those animals slaughtered at an age of < or = 480 d and those with a slaughter age > 480 d. Linear and quadratic partial regressions on slaughter age for hot carcass weight (HCW), USDA marbling score (MS), 12th rib longissimus muscle area (LMA), and 12th-rib fat thickness (FT) were estimated within sex and age class. Quadratic age regressions were not significant, nor was the linear age regression coefficient for FT in steers in the > 480-d age class. Heritability estimates for age-constant HCW, MS, LMA, and FT were .31, .26, .32, and .26, respectively. The estimated genetic correlation (rg) between HCW and LMA was .47. The estimated rg between HCW and FT was .38 and between MS and FT was -.13. The linear genetic trends for CWT and LMA were significantly positive at .414 kg/yr and .075 cm2/yr, respectively. The genetic trends for FT and MS were very small but significantly negative at -.004 cm/yr and -.003 units/yr, respectively.

Weight, height, and body condition score data supplied by the American Angus Association were used to determine the effect of body condition score on cow weight and to compute condition score adjustment factors. Single records on 11,301 cows for weight and 7,769 cows for height were collected at or near weaning, at which time a subjective condition score (9-point scale) was taken. Limited information on extreme scores 1 and 9 allowed only scores 2 through 8 to be included in the analysis. Cows were grouped into age classes corresponding to 2, 3, 4, 5, 6, 7 to 10, and 11+ yr of age. The mathematical model for a weight record included effects of fixed herd, year-month the record was collected, cow age, body condition score, and a random residual error term. The model for height excluded the condition score effect. Effects of herd, year-month, and cow age were highly significant (P less than .0001) for weight and height. Body condition score was a significant source of variation in weight (P less than .0001) and accounted for 16% of the total variation. Adjustment factors for weight (kilograms) by condition score were +116 (score 2), +91 (score 3), +69 (score 4), +39 (score 5), 0 (score 6), -40 (score 7), and -86 (score 8).

Journal Article Charles F. Curtiss, 1863–1946: a brief biography Get access R. L. Willham R. L. Willham 2Iowa State University, Ames 50011 Search for other works by this author on: Oxford Academic PubMed Google Scholar Journal of Animal Science, Volume 70, Issue 3, March 1992, Pages 609–611, https://doi.org/10.2527/1992.703609x Published: 01 March 1992 Article history Received: 29 August 1991 Accepted: 16 September 1991 Published: 01 March 1992

Journal Article H. H. Kildee, 1884–1973: a brief biography Get access R. L. Willham R. L. Willham 2Iowa State University, Ames 50011 Search for other works by this author on: Oxford Academic PubMed Google Scholar Journal of Animal Science, Volume 70, Issue 3, March 1992, Pages 612–613, https://doi.org/10.2527/1992.703612x Published: 01 March 1992 Article history Received: 29 August 1991 Accepted: 16 September 1991 Published: 01 March 1992

Genetic parameters for nuclear and cytoplasmic genetic effects were estimated from preweaning growth data collected on three synthetic lines of beef cattle differing in mature size. Lines of small-, medium-, and large-framed calves were represented in each of two research herds (Rhodes and McNay). Variance components were estimated separately by herd and size line for birth weight and 205-d weight (WW) by REML with an animal mode using an average of 847 and 427 calf records from Rhodes and McNay, respectively. Model 1 included effects of fixed year, sex of calf, age of dam, and random additive direct (a), additive maternal genetic (m), covariance (a,m), permanent environment affecting the dam, and residual error. Model 2 differed from Model 1 by including random cytoplasmic lineage effects and by ignoring permanent environmental effects. Model 1 - direct (maternal) heritability estimates for birth weight at Rhodes were .62(.03) for small, .67(.06) for medium, and .30(.11) for large lines. Genetic correlations between direct and maternal effects for birth weight were .67, -.16, and .48 for the respective size groups. For WW at Rhodes, direct (maternal) heritability estimates were .30(.29), .30(.14), and .10(.16) for small, medium, and large lines, respectively, with genetic correlations of -.34 (small), -.12 (medium), and .17 (large). Heritability estimates at McNay were similar to those at Rhodes, except that maternal genetic heritabilities for WW were smaller (.10, small; .01, medium; .00, large). Model 2 - estimates for nuclear genetic effects were consistent with the estimates from Model 1. Cytoplasmic variance accounted for 0 to 5% of the total random variance in birth weight. For WW, cytoplasmic variance was negligible at Rhodes and accounted for 4% of the total random variance in the large line at McNay, averaging less than the permanent environment. Results failed to indicate that cytoplasmic variance was important for preweaning performance.

Research on the racing performance of quarter horses has been used to develop genetic prediction summaries on all horses with at least one start on record at the American Quarter Horse Association. In the 1987 summary, records from a total of 212,065 horses were used to give genetic predictions on stallions, mares, geldings, fillies, and colts. A reduced animal model was used that incorporated the repeated records of individuals. The individual race was the contemporary group after the data were adjusted for distance, sex, and age. Estimates of heritability of .24 and repeatability of .32 suggest that increased racing performance can be achieved if the predictions are used by breeders. Continued research in variance component estimation includes the genetic covariances among the several distances, maternal influence, and genetic parameters for racing longevity.

A 24 factorial arrangement was used to measure effects of creep feeding and of timing of weaning, vaccination, and dehorning and castration upon weight gains of beef calves before and after sale to a feedlot. Linear and interaction effects were measured. Calves that were dehorned and castrated (DC) and vaccinated (V) 4 wk before sale and weaned after sale to a feedlot gained 13 kg less at sale time (P < .01) than animals not DC and V until after sale. However, animals that were DC and V 10 wk before sale and weaned 6 wk before sale were able to recover the weight lost from these stresses (P < .01) before sale time. Creep-fed animals gained more weight before sale to a feedlot than did non-creep-fed animals (P<.01). Creep-fed calves weaned before sale to a feedlot gained less weight before the sale than did creep-fed calves weaned at sale time (P < .01). Calves weaned 6 wk before sale to a feedlot had a higher average daily gain in the feedlot than animals weaned at sale (P < .05). Calves that were DC and V simultaneously, 4 wk before weaning, had higher average daily gains in the feedlot than those that were DC and V at different times, this suggests that animals that were stressed less frequently performed better.