Pedigree Index Research Articles

Plasma Somatotropin and Prolactin Concentrations in Young Dairy Sires Before and After a 24-Hour Fast

To examine the efficacy of plasma concentrations of bST or prolactin as predictors of expected daughter performance, blood samples were collected from young Holstein sires. Blood samples were collected at 15-min intervals via jugular cannulas from 1000 until 1600h (d 1), beginning 4h after morning hay feeding. Bulls were not fed again until after collection of blood samples on d 2. Samples were collected at 15-min intervals from 1000 until 1300h on d 2. Peak values and frequency of hormonal secretory patterns of each bull were characterized by an iterative process in which values>2 SD from the mean were flagged as peaks and excluded from the subsequent calculation of SD and mean. The process continued until an iteration in which no new peaks were flagged. Imposition of a 24-h fast did not alter mean basal bST or prolactin concentrations, but reduced mean peak and overall concentrations of both hormones. The number of bST peaks on d 1 was inversely related to both USDA and Northeast Artificial Insemination Sire Comparison Pedigree Index for milk yield and both USDA and Northeast Artificial Insemination Sire Comparison sire PD for milk yield, but was positively correlated on d 2 with USDA Pedigree Index for milk yield. Mean peak bST on d 2 was correlated with Northeast Artificial Insemination Sire Comparison Estimated Breeding Value for fat yield and sire USDA PD for fat yield. Prolactin peak frequency on d 1 was negatively related to Northeast Artificial Insemination Sire Comparison Pedigree Index for milk yield and sire PD for fat yield. Difference between mean prolactin on d 1 and 2 was negatively related to Northeast Artificial Insemination Sire Comparison Pedigree Index for milk yield and Estimated Breeding Value for fat yield. Endocrine parameters in young sires may be related to genetic merit for production parameters.

Relationships between sires' transmitting ability for production and daughters' production, food intake and efficiency in a high-yielding dairy herd

ABSTRACTMilk production and food intake records were available on individual animals from a high-yielding Holstein-Friesian herd in which selection had been practised on fat plus protein yield using nationally available artificial insemination sires. The relationship between sires and maternal grandsires' transmitting ability (ICC), expressed as a pedigree index (sire ICC + 0·5 maternal grandsire ICC), and offspring performance for milk production traits, food intake, and gross efficiency (milk energy (MJ)/total energy intake (MJ)) was investigated. The data comprised 475 26-week (data set 1) and 293 38-week (data set 2, a subset of 1) records, and for each data set analyses were conducted on heifers, cows and pooled lactations. Regressions of fat plus protein yield, fat yield, protein yield, and milk yield on their corresponding pedigree index were not far from the theoretical expectation (for a full lactation) of 1, for heifers (0·71 (s.e. 0·20), 0·72 (s.e. 0·20), 0·74 (s.e. 0·21) and 0·75 (s.e. 0·19), respectively), but slightly lower for the pooled lactations (0·57 (s.e. 0·20), 0·55 (s.e. 0·20), 0·67 (s.e. 0·19) and 0·64 (s.e. 0·15)) in data set 1. Regressions of fat plus protein yield, food intake and gross efficiency on pedigree index for fat plus protein yield, each trait expressed as a ratio of herd mean, were 1·31 (s.e. 0·37), 0·38 (s.e. 0·19) and 1·04 (s.e. 0·35) for heifers and 0·89 (s.e. 0·31), 0·48 (s.e. 0·18) and 0·59 (s.e. 0·26) respectively, for pooled lactations, in data set 1. Regressions for cow lactations were lower. Similar results were obtained with data set 2. In this study, a genetic increase of proportionately 0·1 in fat plus protein yield of daughters of sires of high genetic merit for fat plus protein yield, was accompanied by a proportional genetic increase of 0·029 in food intake and a 0·079 proportional genetic increase in efficiency.

Relationship Between Dam's Age at Bull's Birth and Bull's Genetic Evaluation

After accounting for year of birth of bulls, younger dams produced superior sons. Bulls’ PD, parent average, and pedigree index milk decreased with increasing age of dams at bull's birth. This appears to be due to decrease in maternal grandsire's PD milk and dam's Cow Index milk with increase in age of dam. Younger dams have an advantage of potentially higher genetic merit due to genetic trend but have less information included in their evaluations. Bull's latest parent average and pedigree index overestimated latest PD milk. This overestimation was not different with age of dam at bull's birth, suggesting that the bias in predicting bulls’ PD from eventual evaluations of dams chosen at a younger age is not different than for dams chosen at a later age.Data were for 2826 bulls sampled by four AI organizations and born between 1965 and 1981. The increase in PD milk of bulls was about 27 kg/yr, but the trend was larger (45 kg/yr) during the last 5 yr.Inclusion of dam's age did not improve prediction of bull's PD milk. Maternal grandsire's PD milk was the primary variable associated with dam's age that accounted for lower bull's PD milk, mainly because older dams tended to have sires of lower genetic merit.

REGIONAL HETEROGENEITY OF VARIANCES AND ITS EFFECT ON CANADIAN HOLSTEIN SIRE EVALUATION

Heritabilities were estimated within each of four artificial insemination stud regions in Ontario and Quebec, based on a total of 880 329 records for milk and fat yield and 441 230 records for final class score. The pseudo-expectation (PE) and tilde-hat (TH) approaches were used. Estimates ranged from 0.32 to 0.46 for milk yield, from 0.31 to 0.53 for fat yield, and from 0.17 to 0.47 for final class score. Differences between methods (PE and TH) were as large as differences between regions for all traits. TH regional estimates were less variable than PE estimates. Changes in sire rankings were trivial when using regional estimates versus using a common variance ratio in each region during evaluation. Rank correlations were 0.98 and higher between evaluations based on heterogeneous regional variances and evaluations based on homogeneous variances. For all three traits, variance ratios that have previously been assumed for national evaluation were more appropriate than estimates obtained in this study. Use of the previously assumed values resulted in a greater consistency, measured by the correlation, between the regional proofs of a sire and between a sire's proof and pedigree index. Key words: Pseudo-expectation, tilde-hat, heterogeneous variances, Holstein, sire evaluation

Relationships Between Characteristics of Herd of Bull-Dams and Predicting Transmitting Ability of Young Bulls

Young bulls selected from Michigan herds for sampling by Select Sires Incorporated from 1975 to 1982 were identified. Data for herds from which young bulls were selected for year of young bull's birth were acquired from the Michigan DHIA. Herd average milk production, intraherd standard deviation for milk production, coefficient of variation for milk production, average sire transmitting ability of cows in the herd, and intraherd standard deviation of sire transmitting ability were computed for each herd. These herd characteristics were used in prediction of young bull transmitting ability. When considered along with a pedigree index predictor, intraherd standard deviation for milk production was significant in prediction of young bull transmitting ability, but other herd characteristics were not. Young bulls were grouped by the intraherd milk variance of the herd from which they were selected. Evaluations based on progeny tests showed young bulls selected from herds with low intraherd milk variance were genetically superior to those selected from herds with high intraherd milk variance. Predicted transmitting abilities for young bulls selected from low variance herds were less biased, but predicted transmitting abilities for those selected from high variance herds were inflated. However, the variance of biasedness was slightly lower in higher variance herds.

A comparison between the actual progeny test of Friesian/Holstein bulls and indexes calculated from pedigree information

ABSTRACTTwo pedigree indexes were calculated for 754 Friesian/Holstein bulls born between 1974 and 1980 and tested by the Milk Marketing Board. Correlations between the indexes and the average progeny performance were used to compare the indexes calculated using information from different ancestors. The first index, or estimated predicted difference (EPD) was calculated as one-half the sire progeny test, known as an Improved Contemporary Comparison (ICC), plus one-quarter the maternal grandsire ICC. The second index or estimated ICC (EICC) was calculated from one-half the sire ICC plus one-half the dam cow genetic index (CGI). The correlations between the deregressed bull evaluations (DICC) and EPD, calculated from 310 bulls, were 0·40 for milk yield, 0·40 for fat yield and 0·39 for protein yield. The corresponding correlations between the DICC and EICC, calculated from 314 bulls, were 0·43, 0·40 and 0·41. The regression coefficients for predicting average progeny performance from the EPD index were 1·00 (s.e. 0·13), 0·97 (s.e. 0·12), 0·96 (s.e. 0·13), 1·09 (s.e. 0·12) and 1·08 (s.e. 0·10) for milk, fat and protein yield, fat and protein percentage respectively. Those for predicting progeny performance from the EICC index were 0·95 (s.e. 0·11), 0·81 (s.e. 0·10) and 0·84 (s.e. 0·10) for milk, fat and protein yield respectively. Although the correlations were lower than the expected values of 0·50 (EPD) and 0·55 (EICC) the regressions were near the expected value of 1. The results indicate that the indexes are useful as a preliminary means of selecting bulls prior to progeny testing.

Predictability of Pedigree Indexes for Bulls from Two, Three, and Four Generations

Pedigree indexes were calculated from two, three, and four generations for subsets of 380 Holstein bulls that had been progeny tested. Traits indexed were milk, fat, and type. Only male ancestors were considered. Regression coefficients of Predicted Difference and contemporary deviation on pedigree index usually were highest for pedigree index from three generations for milk and fat. Rank correlations of pedigree indexes from two and three generations were .95 to .98 but from three and four generations were .99 to 1.00. Maternal great-grandsires had detectable influence on genetic merit of bulls even though contribution was small as expected. Maternal great-great-grandsires did not contribute to predictability of pedigree indexes.

Sire-Son and Dam-Son Paths: Research Geneticist's View

Implementation of selection procedures for dairy cattle requires identification of all effects and modifications of any selection scheme for the whole cow population over space and time. Research in the early 70's provided complete modeling of selection effects in any population structure. Conventional situations for dairy cattle selection are compared. Reasons for underestimation of expected annual genetic change are mainly related to differences in population structure and breeding policies. One promising new way of improving genetic gain is to reduce generation interval on the dam-son path by early selection of bull dams through a two-stage heifer selection process. First, heifers are selected on pedigree index and all sons raised. Second, selection is on the heifer's own performance or cow index and may occur when sons are 1 yr old. Such an idea, associated with multiple ovulation and egg transfer techniques is the essence of more advanced proposals for selection within small nucleus herds. Benefits and limits of these methods are compared with improved conventional schemes in large populations.

PEDIGREE INDEXING YOUNG HOLSTEIN DAIRY BULLS USING ANCESTRAL INFORMATION FROM DIFFERENT COUNTRIES

A model is described for utilizing ancestor estimated transmitting abilities from different countries to increase the accuracy of prediction of the performance of young dairy bulls in artificial insemination within a country. The model was applied to young Canadian Holstein bulls having pedigree information from Canada and the United States. Models with varying sources of pedigree information were compared. When sire, dam and maternal grandsire were in the model, the correlations between pedigree index and actual progeny test were 0.64, 0.70 and 0.55 for milk yield, fat yield and fat percentage, respectively. There was little difference in accuracy using a sire and dam model. Average pedigree indices were calculated for bulls in artificial insemination in Canada. The average pedigree index has increased 0.87 BCA (breed class average) per year for milk yield over the last ten years. Key words: Holstein sires, pedigree indexes, production traits

Revision of Ancestor Merit for Modified Contemporary Comparison Sire Evaluations

Procedures for computing ancestor merit for Modified Contemporary Comparison sire evaluations were extended for protein and modified to improve accuracy and account for genetic trend for bulls without evaluated ancestors. Sire Summaries of bulls evaluated in October 1974 or later were analyzed to determine difference between daughter Modified Contemporary Deviation and pedigree index. Bulls were identified by birth year, sampling program, and pedigree information available. Means of differences weighted by Repeatability were computed for breed, parity group, yield trait, and pedigree category. Means were smoothed by linear regression over 9 consecutive yr centered on year for which mean was being estimated. Means for recent years were calculated from regression coefficients from last complete set of 9 yr. Ancestor merit, which when weighted by 1 minus Repeatability is pedigree contribution to Predicted Difference, was calculated as appropriate difference plus bull's pedigree index. Changes made in calculation of ancestor merit accounted for genetic trend in bulls without pedigree information available. Ancestor merit procedures were made self-updating to eliminate the assumption that trend estimated in the past will continue unchanged.

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.

Relationships Between Sires and Sons for Evaluations from First, All, and Later Records

January 1984 Modified Contemporary Comparison sire evaluations for first, all, and later records were used to create sire-son pairs in five dairy breeds. Each evaluation for each bull included 10 or more daughters. Regressions of son on sire for evaluations for first, all, or later records exceeded the expectation of .5 and were most divergent for Jerseys and Brown Swiss. Regressions and coefficients of determination were generally highest when sire's evaluation based on all records predicted sons’ evaluations from first, all, or later records. Regression of son on sire for difference in evaluations (later minus first) was positive in all breeds, ranging from .08 to .10, and was significant for all breeds except Brown Swiss. Coefficients of determination were low (.01 to .02). Both regression of son on sire for difference and coefficient of determination increased with son's Repeatability, with a regression of .33 and a coefficient of determination of .09 for sons over 99% Repeatability, Regressions for 8,055 Holsteins with evaluations for sires and maternal grandsires on those ancestors were .46 to .54 for sires and .25 to .31 for maternal grandsires. Regressions of son's evaluation on pedigree index were .94 for first, 1.05 for all, and 1.12 for later lactations.

Increasing Pedigree Contribution to Dairy Sire Evaluation

Methods to improve contributions of ancestor information to sire evaluations computed by the Modified Contemporary Comparison were studied. Pedigree index (one-half evaluation of sire plus one-fourth evaluation of maternal grandsire) was used to indicate ancestor merit with adjustment for type of sampling program and birth date. For Holsteins, effect of sampling through artificial insemination was 35kg for milk yield; effect of birth date (trend of daughter merit not accounted for by pedigree index or type of sampling) was 7.3kg/yr for milk yield and .36kg/yr for fat yield. Trends were larger for milk and fat yields of Ayrshires, Brown Swiss, Guernseys, and Jerseys except for fat yield of Ayrshires, which had no significant trend. Correlations of daughter merit with pedigree index and with present group average (average daughter merit of bulls with similar pedigree indexes for milk yield) were computed. For milk yield, correlations of daughter merit with pedigree index and with group average were nearly the same; however, for fat yield, pedigree index had a higher correlation with daughter merit than did group average. Accounting for residual trend resulted in further increase of correlation. Replacing one-fourth evaluation of maternal grandsire with one-half Cow Index of dam also improved correlations slightly. Evaluations can be modified so that pedigree index adjusted by birth date replaces group average in representing ancestor merit. Such evaluations better predict performance of future daughters than do evaluations with grouping by pedigree index for milk yield, particularly for evaluations for fat yield. Dam's Cow Index provides little additional information.

Profitability of Dairy Cow Herd Life

A dynamic model of a dairy herd was utilized to determine profitability of extending cow herd life. The model incorporated estimates of relationships between cow age, milk production, labor requirements, health costs, reproductive diseases, mastitis, and fertility. The basal situation simulated was a herd of approximately 80 cows producing their own replacements selected by pedigree index, culling cows on cost per unit of production, and breeding cows by artificial insemination with a time trend for sire genetic merit. Increasing cow herd life was simulated by lowering the culling criteria of cow profitability. Extending herd life resulted in more days open, lower annual milk yield per cow, decreased replacement cost and cull cow income, and increased cow health cost. Criterion of herd profitability was discounted income of cow or annual net income over 25 yr with future returns discounted 5% per year. Extending average herd life from 2.8 to 3.3 lactations increased average annual income by $29.92 per cow and increased discounted income by $314.52 (1977 to 1978 dollars). The profitability of a limited increase of average herd life was insensitive to increased feed price, poor management, decreased salvage value, trend of improving management, but high salvage value and low feed price significantly decreased profitability of extended herd life.

Effectiveness of Model for Cow Evaluation Intraherd

Cow evaluations for production derived from an intraherd model for six dairy breeds were studied. Cow evaluations calculated within each of two herds were correlated and agreed closely with correlations expected from selection index. Another study compared genetic trends from sires, dams, and cows and found that trends from sire usage were more than twice as large as trends from dams. Comparison of sire evaluations with average evaluations of mates showed that nonrandom mating of sires with dams occurred infrequently and likely had no influence on sire evaluations. Other possible uses of cow evaluations were for differences between herds, genetic trends within herds, pedigree indexes for future offspring, and relation of pedigree indexes to Estimated Transmitting Abilities.

Progeny Tested Sires Compared with Pedigree Selected Young Sires

First lactation records of 109,589 cows in 1,978 Holstein herds cooperating with three artificial insemination studs in young sire sampling were studied to compare performance of progeny of approximately the upper 15, 2, and 25% of sires, dams, and maternal grandsires for milk yield with selection differentials of +350, +2735, and +268kg milk when the young sires entered sampling programs. The 315 young bulls were sired by 88 sires.Mean weighted Predicted Differences for sires proven through artificial insemination were 130kg milk and 4.0kg fat, whereas weighted averages for naturally proven sires were 13kg milk and .4kg fat. For young sires, pedigree index of sire, dam, and maternal grandsire averaged 347kg milk and 11.8kg fat, and for an index including sire and maternal grandsire averaged 242kg milk and 7.6kg fat. Annual trends for ancestors were +31.8kg milk and +.9kg fat for sires.Within herd-year-season, production of daughters of progeny tested sires exceeded that of daughters of young sires by 84kg milk and 2.4kg fat. Progeny of young sires produced 103kg more milk than daughters of naturally tested bulls.

Sire Evaluation for Conformation of Jersey Cows

A procedure for sire evaluation was developed for Jersey type data; the model contained fixed effects for herd-year and genetic group and random effects for sires, herds-by-sires, and cows.In initial calculations artificial insemination and natural service bulls were grouped separately by year of birth with little evidence of genetic trend for final score. These evaluations then were used for pedigree indexes based on sire and maternal grandsire. Bulls of similar pedigree index for each trait were grouped for new evaluations. The correlation between pedigree index and evaluation for final score on 726 bulls with type information on sire and maternal grandsire and 10 or more classified daughters was .64. The correlation for 533 bulls with evaluation on sires only was .58. The regressions of evaluations for final score on pedigree indexes were .73±.03 and .77±.05. Predicted Difference milk had correlations of .18, .13, .55, .13, and −.04 with evaluations for final score, general appearance, dairy character, body capacity, and mammary system. Other correlations ranged from −.09 for back, rump, and tail to .20 for breed character. Correlations between these evaluations and previous estimates of genetic merit, daughter averages of latest score, were .63, .61, .54, .48, and .69 for final score, general appearance, dairy character, body capacity, and mammary system. Similar correlations for other traits ranged from .47 for breed character to .76 for stature. An index combined estimated transmitting ability for milk, fat, and final score. Bulls were ranked by indexes; different weights were used for production and type. The progress that could be expected from selection with each index was shown.

Trends in Genetic Merit of Dairy Sires at Initial Proving

Initial Modified Contemporary Comparison sire summaries from 1974 through 1978 were studied for 16,791 dairy sires of six breeds. These sires were grouped into five classes. Sires sampled through artificial insemination units were in one group; natural service sires further classified by number of herds (1, 2 to 3, 4 to 6, and 7+) in the initial (first published) proof were in the other four groups. Initial Repeatabilities of the progeny test for sires in these five classes were about 40, 18, 23, 29, and 35%.Genetic merit (pedigree indexes and Predicted Differences) was increasing over the 5 yr. Regressions of either measure of merit on year sampled averaged 19kg of milk and .6kg of fat. Bulls sampled through artificial insemination organizations were superior to natural service bulls in pedigree index and initial Predicted Difference. Genetic merit of widely sampled natural service sires showed no consistent advantage over natural service sires sampled in single herds.The initial sire summaries were compared with the most recent summary through 1978. There was a slight tendency for later summaries to average higher for all classes of sires. Sires sampled by artificial insemination organizations were more likely to increase in Predicted Difference.

Relationships Between Bulls’ Pedigree Indexes and Daughter Performance in the Modified Contemporary Comparison

The United States Department of Agriculture Modified Contemporary Comparison method calculating bull Predicted Difference is influenced directly by the merit of the bull's male ancestors. In this study, the appropriateness of that influenced and the accuracy of pedigree indexes on bulls were investigated. The complete United States Department of Agriculture-Dairy Herd Improvement Association sires files were examined. Sire pedigree indexes calculated from Predicted Differences resulting from the Fall 1974 Modified Contemporary Comparisons were nearly as accurate as expected. Regressions of average daughter performance (Modified Contemporary Deviation) on pedigree index was near the expected 1.0. Correlations were reasonably close to the approximated expected values. Corresponding relationships between Predicted Difference and pedigree index gave similar results.

RELATIONSHIP BETWEEN PEDIGREE INDEX AND PROGENY PERFORMANCE FOR CANADIAN DAIRY BULLS

Progeny performance was related to pedigree indexes for 216 Holstein bulls which entered Canadian Artificial Insemination units from 1962 to 1970. Progeny performance for body conformation (average point score) was related to pedigree index for point score, the sire’s point score proof, and an approximate index based on sire and material grandsire proofs at the time the bull entered the stud. Regression coefficients were 0.34 (±.07), 0.17 (±.14), and 0.32 (±.07), respectively. Regressions of progeny performance for Breed Class Average (BCA) milk (Herdmate Comparison) on pedigree index for BCA milk (Herdmate Comparison), the sire’s HMC index, and the approximate HMC index yielded coefficients of.70 (±.11),.44 (±.08), and.94 (±.15), respectively. In both cases, the pedigree index was the best indicator of progeny performance, followed by the approximate index and the sire’s index, respectively. As no Best Linear Unbiased Prediction (BLUP) pedigree index for BCA milk was available, progeny performance for BLUP proofs was related to pedigree index for milk (HMC), the sire’s BLUP proof and an approximate index based on the sire’s and maternal grandsire’s BLUP milk proofs. Regression estimates were.70 (±.10),.56 (±.08), and 1.16 (±.13). The approximate index was a better predictor of progeny performance (BLUP) than the pedigree index based on HMC milk proofs.