Linear Type Traits Research Articles

Correlations Among Linear Type Traits and Somatic Cell Counts

Genetic and phenotypic correlations between linear type traits and SCC were estimated from lactation average SCC from Pennsylvania DHIA and Holstein linear type evaluations from Sire Power, Inc. and Holstein Association using REML. Correlations were estimated between linear type traits and SCC measured in first lactation and between linear type traits measured in first lactation and SCC measured in second or third lactation. Data sets ranged in size from 4294 daughters of 216 sires to 58,235 daughters of 301 sires. Phenotypic and genetic correlations between the linear traits that reflect body and locomotive characteristics and SCC were generally small and unimportant. Phenotypic correlations between udder traits and SCC were variable, but cows with higher udder depth scores (higher udders) had lower SCC. Genetic correlations between udder traits and SCC were also variable. Genetic correlations between SCC and udder depth, SCC and fore udder attachment, and SCC and teat placement were negative (favorable). Genetic correlations between teat length and SCC tended to be positive. Genetic correlations were largest in magnitude between udder depth and SCC and ranged from –.21 to –.64 (weighted mean = –.35). Selection for higher udders and closer teat placement will likely improve resistance to mastitis in dairy cattle.

Adjustment of Linear Type Scores from Holstein Classification for Age and Stage of Lactation

Type scores from classification were obtained from the Holstein Association to compare methods of adjustment for age and stage of lactation at time of classification. Scores were for final score and 14 linear type traits and were analyzed separately for parity groups. Analysis was with ordinary least squares, and both age and stage of lactation were significant for most traits within parity groups. Multiplicative adjustment factors were calculated after addition or subtraction of least squares estimates to or from constants. Several methods of adjustment were compared by assessing uniformity of means and standard deviations for adjusted classes. The method that gave adjusted scores with least range of standard deviations for classes was deemed superior. Optimal method of adjustment differed for traits.

Relationships Among Survival and Linear Type Traits in Jerseys

Daughters of 330 Jersey sires were used to estimate genetic and phenotypic correlations between survival measures and type traits. Survival measures included survival through first lactation, survival to 20 mo after first calving, and length of productive life. Type traits included final score and 13 linear traits. Genetic correlations were estimated by REML from survival of registered cows with type appraisals, from survival of registered cows in herds that did not appraise for type (type data from registered paternal half sisters in appraised herds), and from survival of grade cows in herds that did not appraise for type (type data from registered paternal half sisters in appraised herds). First lactation milk yield (linear and quadratic) was included as covariate. Genetic correlations between survival traits and final score were positive (.21 to .78). Genetic correlations between the survival measures and body traits, rear legs, and foot angle were small or inconsistent across sources of survival data, except for rump angle (less slope tended to be associated with increased survival). Genetic correlations between udder traits and survival were positive (averaged .51) except for udder cleft. Continued selection for improved udder characteristics in Jerseys appears justified.

Estimation of genetic parameters for linear and miscellaneous type traits in Holstein-Friesian dairy cattle

Sixteen linear type traits (scored 1–9), total type score (10–99) and 33 miscellaneous characteristics (scored 0 or 1) were analysed on 73 940 first lactation Holstein-Friesian dairy cows, progeny of 748 sires. Heritabilities and correlations amongst the traits were estimated, and the heritabilities of the miscellaneous characteristics transformed from the binomial to the underlying normal distribution. In general, heritabilities for body and teat traits were higher than those obtained for leg, feet and udder traits. Phenotypic correlations between the 0/1 traits were mostly low, whereas the genetic correlations obtained were high between some traits, suggesting the feasibility of reducing the number of traits recorded. The incidence of a number of the miscellaneous characteristics was very low, and these traits could either be eliminated from the recording scheme or merged with other suitable traits. Incidences and heritabilities differed substantially among field officers (classifiers).

A Utility Function for Ranking Sires That Considers Production, Linear Type Traits, Semen Cost, and Risk

A procedure was developed to rank AI sires on utility. The utility function considered transmitting abilities for production, udder depth, teat placement; and foot angle, semen cost, timing of costs and revenues, gene flow, and risk. Weights for type traits relative to production and risk aversion were based on the literature. A three-generation planning horizon was used. Utility was expressed relative to an average first evaluation non-AI sire. Moderate change in the relative weights of production versus the type traits (3:1 versus 2:1) had little effect on sire rankings (rank correlations above .97). The effect of changing risk aversion on sire rankings was subtle except when risk aversion was increased to high levels (three times average levels reported in literature). Rank correlation between semen utility based on 7 units of semen required to produce a heifer at calving age and nine units of semen required to produce a heifer at calving age (and corresponding expected calving intervals) was .98. However, the correlation between semen utility based on 5 and 9 units was .91. Similar parameters could be used in ranking sires on utility for many producers. The procedure developed ranked sires differently than indices currently available.

Relationships Between Sire Evaluations for Linear Type Traits and Lifetime Relative Net Income from Grade or Registered Daughters

Relationships between sire evaluations for linear type traits and discounted relative net income were examined in Holsteins. Sire evaluations for income were determined separately for grade and registered cows, and resulting evaluations were merged with sire evaluations for linear type traits. Removal of sires with accuracies of evaluations for income, production, or type below .70 left 137 bulls with evaluations from grade and 79 with evaluations from registered daughters. Simple correlations between income and PD Dollars were .69 and .77 based on grade or registered daughters; those between income and angularity were .37 and .61, respectively. Partial correlations, adjusted for PD Dollars, were generally larger than simple correlations, positive for udder characteristics, but dissimilar for grades and registered for body traits. Prediction of income with PD Dollars and an additional type trait showed fore udder attachment, udder depth, and teat placement, each with positive regression, to be most useful in both grade and registered cows. Significant negative regressions for stature, strength, and body depth were found in grades only, and significant, positive regressions for PD Type and angularity were seen for registered cows only. Linear type traits contributed some useful information to prediction of lifetime profit after PD Dollars. However, with the exception of udder traits, traits of importance and signs of regression coefficients were not consistent between grade and registered cows.

Prediction of Transmitting Abilities for Holstein Type Traits

Heritabilities and genetic and phenotypic correlations among 14 linear type traits were estimated from Holstein Association data by multiple trait REML. Data used for parameter estimation were records of 779,391 daughters of 871 sires included in the January 1988 sire evaluation. Each daughter was represented by her appraisal closest to 30 mo of age. Highest heritability was .37 for stature, and lowest was .10 for foot angle. Gains in reliability from using correlated traits in multiple trait prediction were large for some traits (up to 60% for foot angle for cows). Final score variance parameters were estimated from 953,596 records, which were 43% of records included in the national sire evaluation. Sire models that adjusted or did not adjust for merit of mates were compared. Heritability of final score was .27 with adjustment for merit of mates by subtraction of predicted transmitting ability of dam from daughter's record compared with .29 if mate was ignored. Evaluations for type for several popular older sires were reduced moderately by adjustment for merit of mates, but estimated genetic trend increased slightly. An improved genetic grouping procedure that considers group effects as inherited was adapted for use in sire models. Parameter estimates and models presented were implemented by the Holstein Association for computing July 1988 genetic evaluations for linear traits and final score.

Genetic Correlations Between Survival and Linear Type Traits Measured in First Lactation

Sire evaluations for 173 sires by BLUP for survival to 48, 54, 84 mo, and age at last record from unregistered daughters were correlated with proofs for 14 primary linear type traits and PD type computed by the Holstein Association of America. Progeny tests for type traits were based on first available scores. Genetic correlations between survival or survival adjusted for milk yield and early culling and most type traits were low or antagonistic. Body characteristics especially had low or negative correlations. When the effects of milk yield were removed, foot angle and udder characteristics (except rear udder) had positive genetic correlations with survival. Udder depth and teats rear view had the highest genetic correlations with survival adjusted for yield (near .25). Correlations between udder traits and survival to 84 mo were only slightly reduced by removing the effects of early culling in addition to yield. This suggests that udder characteristics may be useful in selection to reduce involuntary culling even if culling in first lactation is known. In addition to milk yield, selection based on udder depth and perhaps teat placement and foot angle may be justified in commercial dairy cattle.

Genetic and Environmental Parameters Associated with Linearized Type Appraisal Scores

Linearized type records on 14,525 Holstein cows were analyzed to obtain genetic and environmental parameters. Each record consisted of scores on 15 linear type traits recorded on cows between March 1982 and October 1986. Genetic and environmental (co)variances were estimated by the algorithm of expectation-maximization of REML procedure. The model used included fixed herd-year effects, groups of unknown maternal grandsires, and linear and quadratic regressions for both age at calving and days in lactation as well as random sire and maternal grandsire effects. Heritabilities ranged from .07 for foot angle to .35 for stature. Environmental correlations were in general small: the highest was .55 between rear udder height and rear udder width. High genetic correlations were found among stature, body strength, and body depth and among the various udder traits measured. Genetic correlations among udder traits and the remaining traits were in general small. Genetic correlations among stature, body strength, and body traits with the remaining traits measured were small also, with the exception of correlations with rump width.

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).

Sire-Daughter and Dam-Daughter Paths: Research Geneticists’ View

The sire-daughter path of genetic improvement dominates the dam-daughter path. Within-herd management practices intended to enhance genetic progress should thus concentrate on the sire-daughter path. Studies of genetic progress via the sire-daughter path from historic and recent estimates show that rates for milk yield have increased in recent years; however, rates are still only half to two-thirds that theoretically possible from single-trait selection. Perceived importance of linear type traits, registry status, and reproductive management considerations influence genetic merit of service sires. Establishment of herd breeding goals and management of the breeding herd by fertility groups appear to be useful approaches to improve genetic merit of service sires. Impact of proposed changes in sire selection methods on demand for proven bulls and sample sires is discussed.

Influence of Reproductive Management Factors on Genetic Merit of Service Sires

Records were terminated (by sale or dry date) lactation records for cows on DHI test in Virginia for 1982 through 1984. July 1986 production evaluations, most recent type evaluations, and appropriate semen prices for date of service for AI bulls were merged with service sire identification from 384,990 DHI records. Repeat breedings and multiple lactations per cow were used. Least squares procedures revealed significant influences of season, mate's sire's PD for type and dollars, mate's milk yield deviation, registry status, and insemination number on production evaluations, PD type, and semen price of service sire. Significant effects of several of the same variables on linear type traits were observed. Season effects were possibly due to genetic trends. Genetic merit for production and type of service sire declined for daughters of sires with missing or low type and production evaluations, for mates with low or missing herdmate deviations, for grade cows, and for repeat services, especially fourth and later. Days between breedings were nonsignificant or of limited importance in predicting genetic merit of service sires. Proven bulls in AI accounted for 76.3% of all breedings, AI sample sires for 6.3%, and non-AI or unknown sires for 17.4% of breedings in these data.

Comparison between Factor Analysis from a Phenotypic and Genetic Correlation Matrix Using Linear Type Traits of Holstein Dairy Cows

Data on 18 linear type scores and production data for 43,428 records by 228 sires were used to compare two different factor-analyses procedures. Using a genetic correlation matrix to obtain a genetic factor matrix showed that the number of derived factors could be reduced to seven genetic factors vs. eight phenotypic factors. Genetic factors provided a good summary of the data and accounted for 79.3% of the total variation vs. 69.1% expressed by eight phenotypic factors. A comparison between the use of a genetic and phenotypic multiple regression analysis showed some difference for the basic rank of factor influence on production and herdlife.

Relationships Among Survival Rates, Predicted Differences for Yield, and Linear Type Traits

Sire proofs by BLUP for stayability to 54 and 84 mo were regressed on PD for yields alone and simultaneously with standardized transmitting abilities for 15 primary linear type traits and PD type computed by the Holstein Association of America. Estimates of progeny survival were based on either grade or registered daughters. Traits (after yield) significantly associated with survival to 54 mo in grade cattle were stature, body depth, udder depth, and teats rear view. Regression coefficients for udder depth and teats rear view were positive. In registered cattle most traits were associated with survival to both ages. Udder depth and teats rear view were significantly correlated with survival to 84 mo in grade cattle. Udder depth accounted for as much variation in stayability as yield. Udder depth and teats rear view were the traits most related to survival in both grade and registered cows. Body traits were favorably correlated with survival only in registered cows. Models were explored to determine best predictor models when more than one type trait was included. Highest R2 models were generally a combination of the best single traits. Multiple type traits were significant in some models.

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.

Inheritance of linear type traits in dairy cattle and correlations with milk production

ABSTRACTRecords on 18 939 Friesian-Holstein cows classified for 16 linear-type traits and total score in first lactation by the British Friesian Cattle Society and similarly on 13 192 cows in second lactation were analysed to estimate heritabilities and genetic correlations among the linear traits. These comprised progeny of 542 and 477 young sires, respectively, together with older sires included to increase connections. Correlations of type with milk production traits and correlations between type in first and second lactations were estimated from subsets (of about one-half) of the data. Effects due to proportion of Holstein in the sires were removed.Heritabilities of the linear traits were similar in first and second lactations, ranging from under 0·15 for one of the leg traits to about 0·5 for stature. Genetic correlations between traits in first and second lactation were generally over 0·75, whereas phenotypic correlations for most traits ranged from 0·3 to 0·6. Genetic and phenotypic correlations among the linear traits were generally low, except for those involving size.Phenotypic correlations between linear traits and milk yield and composition were all small, none exceeding 0·3. Genetic correlations were generally almost as small: taking first and second lactations together, the only consistent non-negligible correlations with yield were for angularity (+0·3), fore-udder attachment (–0·2) and udder depth (–0·4). The linear traits are not useful predictors of yield.

Evaluation of Corrective Mating for Type Traits in Jersey Cattle

First available appraisals of 14,721 Jersey cows having valid scores for 13 linear type traits, dams with cow indexes for linear traits, and sires and maternal grandsires with Predicted Differences for linear traits, were used to evaluate corrective mating for type traits. Predicted Differences of sires and four measures of merit of dams were used to predict offspring linear trait scores relative to herd average. Measures of dam's merit were phenotypic score relative to the overall mean, phenotypic score relative to herd mean, cow index, and half her sire's Predicted Difference.Regressions of offspring linear scores on a composite pedigree index (sire + dam measure) ranged near 1.0, whereas regressions on measures of sires and dams separately, yielded coefficients for sires that consistently were larger than those for dams. Mean squares and least squares means for measures of dam's merit suggested dam's cow index is superior to dam's phenotypic score for predicting mean score of offspring groups. Frequencies of predicted scores within ±4 points of actual scores ranged from 52% for stature to 80% for udder depth. Correlations between measures of sires and dams indicated little assortative mating has been practiced for linear type traits in Jersey cattle.

Impact of Trait Maximized on Sire Averages from Computerized Sire Selection

A computerized linear program, MAXBULL, selects groups of sires to attain or exceed goals of dairy producers and maximize one of four traits: Predicted Difference milk, Predicted Difference dollars, Predicted Difference milk minus its confidence interval, and Predicted Difference dollars minus its confidence interval. January 1985 Holstein herd breeding objectives in 315 MAXBULL goals were run for each maximization criterion holding herd breeding objectives constant. Realized Predicted Difference milk and dollars were predicted from 86 herds with goals and edits for all traits in the model. Predicted Difference fat percent was higher when Predicted Difference dollars and Predicted Difference dollars minus its confidence interval were maximized. Higher Repeatabilities resulted when confidence intervals were used. Little variation was found in sire averages for Predicted Difference fat, Predicted Difference type, and semen price when different traits were maximized. Goal for hind legs was the most limiting of the linear type traits in achieving higher sire averages for Predicted Difference milk or dollars. Higher goals or edits for price produced higher sire averages for Predicted Difference milk and dollars. Higher edits for Predicted Difference dollars and type reduced average sire merit for Predicted Difference milk and dollars.

Genetic and Phenotypic Relationships among Type Traits Scored Linearly in Holsteins

Phenotypic and genetic parameters were estimated for 12 type traits of Holstein cows scored linearly by personnel of an artificial insemination organization. Estimates were compared with those from programs offered by the breed association and by two other artificial insemination organizations. All programs were based on scoring guidelines of the National Association of Animal Breeders.Heritabilities of linear type traits ranged from .40 for stature to .14 for fore udder attachment with heritabilities for udder traits smaller than for nonudder traits. Largest genetic and phenotypic correlations were among udder traits with genetic correlations consistently exceeding phenotypic correlations.Similarities in relative magnitudes of phenotypic and genetic parameters suggest that linear type appraisal programs do not differ greatly among organizations using scoring guidelines of the National Association of Animal Breeders.

Components of Genetic Variance and Covariance for Linear Type Traits in Jersey Cattle

First available appraisals for 67,644 Jersey cows were used to estimate relative magnitudes of additive and selected sources of nonadditive genetic variance and covariance for 13 type traits scored linearly from 50 to 99 points.Covariances among four types of relatives were used to estimate components of genetic variance and covariance for each of the 13 traits. Direct additive, direct dominance, and additive maternal genetic variances and the direct-maternal additive genetic covariance were estimated using covariances among paternal half-sibs, full-sibs, daughters and dams, and maternal half-sibs.Estimates of additive genetic variance were 11 to 36% of variance within herd-appraiser subclasses with largest values for stature, strength, rump angle, rump width, and udder depth. Dominance components were two to four times the magnitude of additive components for dairy character, rump width, fore udder, rear udder height, rear udder width, and suspensory ligament but much smaller for other traits. Maternal effects and the direct-maternal additive genetic covariance appeared small for all linear type traits.