Genetic parameters and responses of linear type,yield traits,and somatic cell scores to divergent selection for predicted transmitting ability for type in Holsteins

The objective was to examine the direct and correlated responses of linear type, yield traits, and somatic cell scores (SCS) to divergent selection for predicted transmitting ability for type (PTAT) in Holsteins, while maintaining selection for yield traits across lines. For four generations, one-half of the University of Nebraska research Holstein herd was bred to Holstein sires with PTAT > 1.50 and the other half to sires with PTAT < 1.25, with nearly equal predicted transmitting abilities for yield traits for both groups. Estimates of genetic and residual correlations and heritabilities were obtained from REML estimates of (co)variance components. Model for type traits included fixed effect of date cows were classified, effects of age in days at freshening, and stage of lactation at classification. Year-season when cows freshened was fixed effect in model for yield and SCS. Animal genetic and residual effects were random. Final score, milk, fat, and protein yields, and SCS had heritability estimates of 0.38, 0.13,0.22, 0.09, and 0.38, respectively. Heritability estimates for type traits ranged from 0.04 to 0.52. Estimates of genetic correlations of final score with SCS and milk, fat, and protein yields were -0.64, 0.01, -0.18, and 0.06, respectively. Estimates of genetic correlations among linear type traits ranged from -0.77 to 1.00. Means of estimated breeding values for final score, stature, strength, body depth, fore udder attachment, rear udder height and width, udder cleft, udder depth, and front teat placement were significantly different between lines in the third generation. Milk, fat, and protein yields were not significantly different between lines in third generation, whereas SCS was significantly different. Estimate of genetic correlation between final score and SCS suggest that selection on PTAT would result in a change for SCS. In this study, divergent selection on PTAT of sires had a significant effect on udder and body traits, but little or no effect on feet and leg traits.     

Analysis of the relationship between type traits and functional survival in US Holstein cattle using a Weibull proportional hazards model

Survival analysis with a Weibull proportional hazards model was used to evaluate the effects of 15 linear type traits, 5 composite traits, and final score on the functional longevity of US Holstein cows. Culling data and type classification scores (measured in first lactation) from 891,524 cows with first calving from 1993 to 2000 were used. The data were divided into 9 geographical regions to determine whether the relationship between type traits and longevity differed according to climate or management system. Functional survival was defined as the number of days from first calving until culling or censoring, after correction for 305-d mature equivalent combined fat and protein yield. The Weibull model included time-dependent effects of herd-year-season, parity-stage of lactation, and within herd-year quintile ranking for combined fat and protein yield (nested within biennium), as well as time-independent effects of age at first calving and type classification score (type traits were analyzed one at a time). Type classification scores were rounded to the nearest 5 points, and the impact of each type trait on functional survival in each region was evaluated. Mean failure time ranged from 694 d in the South to 758 d in the North East. Risk of culling differed by region for several linear type traits, and differences were greatest for regions that were most dissimilar in climate and herd management (e.g., South East, East North Central, and West). Udder depth, fore udder attachment, udder cleft, and rear legs side view were consistently associated with functional longevity, regardless of region, but, the importance of some secondary traits, such as stature or dairy form, differed by region. The survival model applied in this study easily described both linear and nonlinear relationships between type traits and longevity while accounting for important time-dependent and time-independent explanatory variables.     

Phenotypic and genetic relationship between linear functional type traits and milk yield for five breeds

Lactation records of cows first calving between 18 and 35 mo were combined with linear type ratings assigned during the same lactation if before 43 mo. Phenotypic relationships were examined between final score and 13 type appraisal traits and first lactation milk yield from 2935 Ayrshire, 3154 Brown Swiss, 13,110 Guernsey, 50,422 Jersey, and 924 Milking Shorthorn records. Most phenotypic correlations between type and milk yield were low. Linear correlations of final score with first lactation milk yield were .18 to .38. Of the linear functional type traits, correlations with first lactation yield had greatest absolute values for dairy character (.19 to .53), udder depth (-.26 to -.30), and rear udder width (.20 to .31). Multiple correlations of all type appraisal traits with first lactation milk yield ranged from .41 to .59. Herd-year-season components of variance averaged 25% for type traits. Herd-year-season with sire interaction averaged 4%. Heritability estimates for final score from paternal half-sib analysis were from .11 to .21. Heritability estimates for linear traits ranged from .01 to .37. Genetic correlation between milk and final score was positive for Guernseys (.25) and Jerseys (.21). Genetic correlations between yield and most linear type traits were low to moderate except for dairy character (.53 to .77).     

Inheritance and relationships of linear type traits for age groups of Holsteins

Routine classifications from the linear type trait program of the Holstein Association were analyzed separately for age groups. Inheritance of linear type traits and their genetic and phenotypic relationships were evaluated. Estimates of genetic and phenotypic parameters were compared to other studies with experimental classifications from the Holstein Association and with data from artificial insemination organizations across age groups. Evaluation of sires for type traits across age groups may not properly rank sires if ages of daughters differ for sires. Future genetic evaluations of type by the Holstein Association will consider only classifications of cows closest to 30 mo, so heritabilities for linear type traits for only 2 yr olds from this study may have application. Some linear type traits are very similar genetically. Stature has substantial genetic association with final score as subjectively assigned by classifiers.     

Genetic parameters for female fertility, locomotion, body condition score, and linear type traits in Czech Holstein cattle

The aim of this study was to estimate genetic parameters for fertility traits and linear type traits in the Czech Holstein dairy cattle population. Phenotypic data regarding 12 linear type traits, measured in first lactation, and 3 fertility traits, measured in each of first and second lactation, were collected from 2005 to 2009 in the progeny testing program of the Czech-Moravian Breeders Corporation. The number of animals for each linear type trait was 59,467, except for locomotion, where 53,436 animals were recorded. The 3-generation pedigree file included 164,125 animals. (Co)variance components were estimated using AI-REML in a series of bivariate analyses, which were implemented via the DMU package. Fertility traits included days from calving to first service (CF1), days open (DO1), and days from first to last service (FL1) in first lactation, and days from calving to first service (CF2), days open (DO2), and days from first to last service (FL2) in second lactation. The number of animals with fertility data varied between traits and ranged from 18,915 to 58,686. All heritability estimates for reproduction traits were low, ranging from 0.02 to 0.04. Heritability estimates for linear type traits ranged from 0.03 for locomotion to 0.39 for stature. Estimated genetic correlations between fertility traits and linear type traits were generally neutral or positive, whereas genetic correlations between body condition score and CF1, DO1, FL1, CF2 and DO2 were mostly negative, with the greatest correlation between BCS and CF2 (−0.51). Genetic correlations with locomotion were greatest for CF1 and CF2 (−0.34 for both). Results of this study show that cows that are genetically extreme for angularity, stature, and body depth tend to perform poorly for fertility traits. At the same time, cows that are genetically predisposed for low body condition score or high locomotion score are generally inferior in fertility.     

Prediction of liveweight of cows from type traits and its relationship with production and fitness traits

Liveweight (LWT) data for Australian Holstein cows was predicted from different type traits based on actual LWT and type data of 932 cows collected from 20 different herds over a 3-yr period. In addition to LWT measured using scales, visual estimates of LWT were also available on 90% of the cows with LWT data. The future predictive ability of different models was assessed using 10-fold cross-validation. The relationships between LWT and selected type traits, including body condition score (BCS), were also calculated to assess the usefulness of various traits to predict LWT genetically. The relationships of predicted LWT measures with production and fitness traits were also estimated in an attempt to assess the consequence of continuous selection on an economic index that includes predicted LWT with a negative economic value. The heritability of LWT was 0.4. Among type traits, stature, chest width, bone quality, BCS, udder depth, central ligament, and muzzle width were correlated with LWT both genetically and phenotypically and were used to predict LWT of cows. Predicted LWT measures, using several sets of traits and visually estimated LWT were genetically highly correlated with each other (>0.73). Phenotypically, visually estimated LWT of cows was slightly more correlated with actual LWT than that predicted from type traits, but genetically both approaches gave the same accuracy. The predicted estimates of LWT were also positively genetically correlated with energy-corrected milk yield and had near zero correlation with survival. The correlations of different measures of LWT with fertility traits were unfavorable or near zero, suggesting that selection for reduced LWT may not cause deterioration in fertility traits. However, it may be useful to consider broadening the breeding objective to include traits that are associated with energy balance, particularly if traits such as BCS and bone quality are included in the set of traits used to predict LWT. Based on the results from this study, the inclusion of predicted LWT with negative economic values into the breeding objective would have no negative effect on fitness traits.     

Genetic selection for hoof health traits and cow mobility scores can accelerate the rate of genetic gain in producer-scored lameness in dairy cows

Cattle breeding programs that strive to reduce the animal-level incidence of lameness are often hindered by the availability of informative phenotypes. As a result, indicator traits of lameness (i.e., hoof health and morphological conformation scores) can be used to improve the accuracy of selection and subsequent genetic gain. Therefore, the objectives of the present study were to estimate the variance components for hoof health traits using various phenotypes collected from a representative sample of Irish dairy cows. Also of interest to the present study was the genetic relationship between both hoof health traits and conformation traits with producer-scored lameness. Producer-recorded lameness events and linear conformation scores from 307,657 and 117,859 Irish dairy cows, respectively, were used. Data on hoof health (i.e., overgrown sole, white line disease, and sole hemorrhage), mobility scores, and body condition scores were also available from a research study on up to 11,282 Irish commercial dairy cows. Linear mixed models were used to quantify variance components for each trait and to estimate genetic correlations among traits. The estimated genetic parameters for hoof health traits in the present study were greater (i.e., heritability range: 0.005 to 0.27) than previously reported in dairy cows. With the exception of analyses that considered hoof health traits in repeatability models, little difference in estimated variance components existed among the various hoof-health phenotypes. Results also suggest that producer-recorded lameness is correlated with both hoof health (i.e., genetic correlation up to 0.48) and cow mobility (i.e., genetic correlation = 0.64). Moreover, cows that genetically tend to have rear feet that appear more parallel when viewed from the rear are also genetically more predisposed to lameness (genetic correlation = 0.39); genetic correlations between lameness and other feet and leg type traits, as well as between lameness and frame type traits, were not different from zero. Results suggest that if the population breeding goal was to reduce lameness incidence, improve hoof health, or improve cow mobility, genetic selection for either of these traits should indirectly benefit the other traits. Results were used to quantify the genetic gains achievable for lameness when alternative phenotypes are available.     

Heritabilities and genetic correlations of body condition score and calving interval with yield, somatic cell score, and linear type traits in Brown Swiss cattle

This study aimed to estimate genetic parameters for body condition score (BCS), calving interval (CI), somatic cell score (SCS), yield, and linear type traits for the Italian Brown Swiss cattle population. A total of 32,359 records of first-parity lactating cows were collected from 2002 to 2004 in 4,885 dairy herds. The pedigree file included 96,661 animals. Multiple-trait animal models were analyzed using REML to estimate (co)variance components without repeated observations on traits. The estimated heritability was 0.15 for BCS, 0.05 for CI, and 0.06 for SCS, and ranged from 0.09 to 0.14 for test-day yield traits and from 0.07 to 0.32 for linear type traits. The genetic correlations of CI with yield and most linear type traits were positive, whereas the correlation between CI and BCS was negative (−0.35). For type traits, BCS showed, in general, a moderately negative genetic correlation except for strength, pastern, and heel height. The genetic correlation of CI or BCS with SCS was moderately low but favorable (0.19 and −0.26, respectively). The estimated correlations indicated that selection for greater yield and type traits can exert unfavorable effects on the reproductive ability of cows. To counterbalance these effects and to carry out early prediction of breeding values of bulls for fertility, inclusion of BCS in the breeding program is advisable.     

Genetic parameters for conformation traits in herds that differ in mean final score and completeness of pedigree and performance data

The objectives of this study were to assess differences in the heritability of type (conformation) traits between herds that differ in mean final score and completeness of pedigree and performance data and to estimate genetic correlations among these environments. Measurement of subjective characteristics, such as conformation traits, may be more difficult in herds with poor management conditions, and genetic evaluation of sires using data from such herds could lead to inaccurate selection decisions. Furthermore, missing pedigree data is a significant problem in many herds, and a lack of phenotypic data from maternal relatives may reduce the effectiveness of animal model evaluation systems. These hypotheses were examined using type classification scores of 1,728,836 first-parity Holstein cows (from 54,223 sires) that calved from 1993 to 2002 in 24,207 US dairy herds. These data included 480,927 records from progeny test daughters, but only 254,891 (47%) were from dams that had valid sire identification, and only 132,953 (28%) were from dams that had also been classified. Herds were grouped into quartiles by mean classification score, percentage of known maternal grandsires, and percentage of classified dams. Estimated heritability of final score was 0.20 in herds with mean score <74.5, 0.17 in herds with <25% known maternal grandsires, and 0.19 in herds with <18% classified dams. Conversely, estimates were 0.39 in herds with mean score >78.7, 0.35 in herds with 100% known maternal grandsires, and 0.37 in herds with >71% classified dams. Estimated genetic correlations between quartiles ranged from 0.86 to 0.95. Based on this study, it appears that improvements in animal identification and data collection in progeny test herds would lead to greater accuracy and stability of genetic evaluations for conformation traits in US Holstein cattle.     

Relationships Among Type Scores and Changes in Yield from First to Second Lactation

Changes between first and second lactation yields of days open adjusted milk and 3.7% FCM were correlated with classification traits. Yields within first and second lactation were corrected for herd-season, calving month within season, and age at calving. Classification scores during first lactation were available on 1341 cows appraised between 1971 and 1982 by Holstein Association of America classifiers in five North Carolina Department of Agriculture herds and a North Carolina State University research herd. All classification traits except final score were categorical. Final score, general appearance, dairy character, body capacity, mammary system, stature, rear udder, fore udder, and feet and legs were treated as continuous. Classification traits were adjusted for herd-year, age, and months in milk. First lactation milk was added as a covariate in selected analyses. Body capacity, dairy character, mammary system, back, rump, rear udder, and udder support each had significant effects on change in yield. Mammary system and final score showed a significant linear relationship with change in yield for at least one model. Dairy character and fore udder significantly predicted change in 3.7% FCM when first lactation milk was not in the model.     

Comparison among direct,indirect and index selections on agronomic traits and nutritional quality traits in common bean

BACKGROUND: Selection indices are linear combinations that allow the selection of several characters simultaneously. The objective of this study was to verify the efficiency of direct selection, indirect selection and selection indices in the identification of higher inbred common bean lines for grain yield, morphological, phenological and nutritional traits. RESULTS: There is genetic variability for grain yield, lodging, general adaptation note, cycle, insertion of the first pod, calcium and iron concentrations in the seeds. Moderate phenotypic correlation coefficients were observed between grain yield and general adaptation note (r = ? 0.57) and cycle (r = ? 0.57). When direct selection was performed for grain yield, the insertion of the first pod, calcium and iron concentrations showed negative indirect selection gains. The classic index showed that the distribution of gains has become more balanced: grain yield (39.05%), calcium (8.29%) and iron concentration (1.64%). CONCLUSION: Direct selection and indirect selection are not efficient in the simultaneous selection of agronomic traits and nutritional quality in common bean. The classical, base and multiplicative indexes provide responses of gain balanced among traits and superior genetic progress in the selection of inbred common bean lines, and have a high coincidence between the lines selected. © 2012 Society of Chemical Industry     

Type trait (co)variance components for five dairy breeds

(Co)variance components were estimated for final score and 14 or 15 linear type traits for the Ayrshire, Brown Swiss, Guernsey, Jersey, and Milking Shorthorn breeds. Appraisals from 1995 or later were used. New estimates were calculated to accommodate changes in scoring of traits and because of a change from multiplicative to additive adjustment for age and lactation stage. The adjustment method was changed for better support of the adjustment for heterogeneous variance within iteration, which was implemented in 2002. The largest changes in heritability were an increase of 0.10 for rump angle for Milking Shorthorns and a decrease of 0.11 for udder depth for Jerseys. The new estimates of (co)variance components should provide improved accuracy of type evaluations, particularly for traits that have had variance changes over time.     

Re-assessing the importance of linear type traits in predicting genetic merit for survival in an aging Holstein-Friesian dairy cow population

The cumulative improvement achieved in the genetic merit for reproductive performance in dairy populations will likely improve dairy cow longevity; therefore, it is time to reassess whether linear type traits are still suitable predictors of survival in an aging dairy cow population. The objective of the present study was therefore to estimate the genetic correlations between linear type traits and survival from one parity to the next and, in doing so, evaluate if those genetic correlations change with advancing parity. After edits, 152,894 lactation survival records (first to ninth parity) were available from 52,447 Holstein-Friesian cows, along with linear type trait records from 52,121 Holstein-Friesian cows. A series of bivariate random regression models were used to estimate the genetic covariances between survival in different parities and each linear type trait. Heritability estimates for survival per parity ranged from 0.02 (SE = 0.004; first parity) to 0.05 (SE = 0.01; ninth parity). Pairwise genetic correlations between survival among different parities varied from 0.42 (first and ninth parity) to 1.00 (eighth to ninth parity), with the strength of these genetic correlations being inversely related to the interval between the compared parities. The genetic correlations between survival and the individual linear type traits varied across parities for 9 of the 20 linear type traits examined, but the correlations with only 3 of these linear type traits strengthened as the cows aged; these 3 traits were rear udder height, teat length, and udder depth. Given that linear type traits are frequently scored in first parity and are genetically correlated with survival in older parities, they may be suitable early predictors of survival, especially for later parity cows. Additionally, the direction of the genetic correlations between survival and rear udder height, teat length, and udder depth did not change between parities; hence, selection for survival in older parities using these linear type traits should not hinder genetic improvement for survival in younger parities.