Inbreeding depression of reproductive traits in Japanese Black cattle using genomic information.

BackgroundPedigree-based inbreeding coefficients have been generally included in statistical models for genetic evaluation of Japanese Black cattle. The use of genomic data is expected to provide precise assessment of inbreeding level and depression. Recently, many measures have been used for genome-based inbreeding coefficients; however, with no consensus on which is the most appropriate. Therefore, we compared the pedigree- ({F}_{PED}) and multiple genome-based inbreeding coefficients, which were calculated from the genomic relationship matrix with observed allele frequencies ({F}_{GRM}), correlation between uniting gametes ({F}_{UNI}), the observed vs expected number of homozygous genotypes ({F}_{HOM}), runs of homozygosity (ROH) segments ({F}_{ROH}) and heterozygosity by descent segments ({F}_{HBD}). We quantified inbreeding depression from estimating regression coefficients of inbreeding coefficients on three reproductive traits: age at first calving (AFC), calving difficulty (CD) and gestation length (GL) in Japanese Black cattle.ResultsThe highest correlations with {F}_{PED} were for {F}_{ROH} (0.86) and {F}_{HBD} (0.85) whereas {F}_{GRM} and {F}_{UNI} provided weak correlations with {F}_{PED}, with range 0.33–0.55. Except for {F}_{GRM} and {F}_{UNI}, there were strong correlations among genome-based inbreeding coefficients (ge 0.94). The estimates of regression coefficients of inbreeding depression for {F}_{PED} was 2.1 for AFC, 0.63 for CD and -1.21 for GL, respectively, but {F}_{PED} had no significant effects on all traits. Genome-based inbreeding coefficients provided larger effects on all reproductive traits than {F}_{PED}. In particular, for CD, all estimated regression coefficients for genome-based inbreeding coefficients were significant, and for GL, that for {F}_{UNI} had a significant.. Although there were no significant effects when using overall genome-level inbreeding coefficients for AFC and GL, {F}_{ROH} provided significant effects at chromosomal level in four chromosomes for AFC, three chromosomes for CD, and two chromosomes for GL. In addition, similar results were obtained for {F}_{HBD}.ConclusionsGenome-based inbreeding coefficients can capture more phenotypic variation than {F}_{PED}. In particular, {F}_{ROH} and {F}_{HBD} can be considered good estimators for quantifying inbreeding level and identifying inbreeding depression at the chromosome level. These findings might improve the quantification of inbreeding and breeding programs using genome-based inbreeding coefficients.

ObjectiveThe objective of this study was to identify environmental factors strongly associated with and to estimate genetic parameters of reproductive traits in Japanese Black heifers.MethodsData included reproduction records of Japanese Black heifers born between 2004 and 2014. First service non-return rate (NRR) to 56 days from first to successful insemination (FS), number of services per conception (IN), age at first calving (AFC) and gestation length were analyzed with the use of the general linear model. Genetic parameters were estimated with the use of the univariate animal model of the residual maximum likelihood.ResultsAverages of reproductive traits over eleven years were assessed, and the effects of farm, year, month, artificial insemination technician and interaction of farm×year on the traits were determined. Estimated heritability of FS was very low and that of AFC was higher than that of the other traits. A close genetic relation was observed among NRR, IN, and FS; however, their heritabilities were very low. AFC shows favorable genetic correlation with IN and FS.ConclusionLow heritabilities of most reproductive traits in Japanese Black heifers are strongly influenced by farm management practices, and that large residual variances make genetic evaluation difficult. Among the reproductive traits, AFC is potentially more useful for genetic improvement of heifer reproductive traits because it has high heritability and favorable genetic correlations with IN and FS.

Simple SummaryHanwoo cattle is considered one of the most economically important species and sources of nutrition for Koreans. Thus, both the reproductive performance and growth traits play an important role in the continuous development and productivity of Hanwoo farming. Therefore, to improve beef production and the profitability of Hanwoo farming, estimations of genetic parameters for birth weight (BW) and weaning weight (WW) and their relationship with age at first calving (AFC) and gestation length (GL) are necessary to understand and improve their responses to selection. Thus, this study estimated the variance components, heritability estimates of birth weight (BW) and weaning weight (WW) and their genetic and phenotypic relationship to age at first calving (AFC), and gestation length (GL). Results revealed a moderate and high heritability estimate for BW and WW, which suggests a sluggish and rapid response of these traits to selection, respectively. The moderate and high genetic correlation between BW and reproductive traits (AFC and GL) revealed that the selection of a heavier BW might result in a longer AFC and GL. Although the genetic correlation for BW and AFC was moderate and positive, the phenotypic correlation of close to zero may indicate that the phenotypic expression for these traits is likely to be influenced by the genotype-environment interaction (GxE). Moreover, the genetic and phenotypic correlation between WW and reproductive traits (AFC and GL) indicates that the selection of a heavier WW may not influence the AFC and GL of Hanwoo cow. These estimated genetic parameters and correlations for the studied traits can be utilized for genetic breeding programs of Hanwoo cattle.Hanwoo is one of the most economically important animal species in Korea due to its significant contribution to nutrition. However, the current selection index only focuses to improve carcass traits of Hanwoo. Thus, this study aimed to estimate the genetic parameters of birth weight (BW) and weaning weight (WW) and their genetic and phenotypic relationship to the age at first calving (AFC) and gestation length (GL) of Hanwoo. The genetic parameters for birth weight (BW) and weaning weight (WW) were estimated using the data obtained from 52,173 and 35,800 Hanwoo calves born from February 1998 to March 2017, respectively. Further, these data were used to determine their genetic and phenotypic correlation to age at first calving (AFC) and gestation length (GL). The heritability estimates of BW and WW and correlation coefficients were obtained using the average information restricted maximum likelihood (AIREML) procedure, fit in single and two-trait linear animal models. The estimated direct heritability for BW and WW was moderate (0.22 ± 0.02) and high (0.51 ± 0.03), respectively, while the maternal heritability for both traits was 0.12 ± 0.01 and 0.17 ± 0.01, respectively. The genetic correlation of BW and reproductive traits (AFC and GL) showed a moderate and high positive correlation coefficient of 0.33 ± 0.06 and 0.53 ± 0.02, respectively, while close to zero and low positive phenotypic correlations of 0.06 ± 0.01 and 0.21 ± 0.06 were also observed between the correlated traits, respectively. For the correlation analysis between WW and AFC, both the genetic and phenotypic correlation showed close to zero values of 0.04 ± 0.06 and −0.01 ± 0.01, respectively. Meanwhile, the genetic and phenotypic correlation between WW and GL showed low and negative correlations of −0.09 ± 0.06 and −0.09 ± 0.01, respectively. These obtained estimated variances for BW and WW and their corresponding genetic and phenotypic correlation to AFC and GL can be used as information for genetic improvement and subsequent economic improvement of Hanwoo farming.

Reproductive performance is receiving increased attention from beef cattle producers. There are concerns that intensive selection for carcass traits might reduce the reproductive performance of females. Genetic parameters among six carcass traits and, age at first calving (AFC), gestation length (GL), days open (DO) and calving interval (CI) under year-round artificial insemination were estimated. Reproductive traits were extracted from 174005 calving records of Japanese Black cows and were analysed with 31364 carcass records. The restricted maximum likelihood procedure under animal models was used to estimate the parameters. Heritabilities of AFC, GL, DO and CI were estimated to be 0.20, 0.40, 0.05 and 0.05, respectively, and those of carcass traits were higher, ranging from 0.38 to 0.56. Genetic correlations of CI with AFC and GL were 0.25 and 0.16, respectively, while no relationship was observed between AFC and GL. Correlations among carcass traits were generally favourable and a slightly negative estimate was obtained between subcutaneous fat thickness and marbling score. Genetic correlations for AFC were -0.27 with carcass weight and -0.24 with marbling score. In contrast, GL, DO and CI were genetically independent of carcass traits. Genetic relationships between reproductive and carcass traits were generally low, and therefore serious antagonism was not observed. The results suggested that selection for carcass traits would not compromise genetic progress in reproductive traits.

This study aimed at assessing inbreeding and its effect on growth and fertility traits using the longtime closed line 1 Hereford cattle population. Inbreeding was estimated based on pedigree (FPED) and genomic information. For the latter, three estimates were derived based on the diagonal elements of the genomic relationship matrix using estimated (FGRM) or fixed (FGRM0.5) minor allele frequencies or runs of homozygosity (ROH) (FROH). A pedigree containing 10,186 animals was used to calculate FPED. Genomic inbreeding was evaluated using 785 animals genotyped for 30,810 SNP. Traits analyzed were birth weight (BWT), weaning weight (WWT), yearling weight (YWT), ADG, and age at first calving (AFC). The number of ROH per animal ranged between 6 and 119 segments with an average of 83. The shortest and longest segments were 1.36 and 64.86 Mb long, respectively, reflecting both ancient and recent inbreeding occurring in the last 30 to 40 generations. The average inbreeding was 29.2%, 16.1%, 30.2%, and 22.9% for FPED, FGRM, FGRM0.5, and FROH, respectively. FROH provided the highest correlations with FPED (r = 0.66). Across paternal half-sib families, with minimal variation in FPED, there were substantial variations in their genomic inbreeding. Inbreeding depression analyses showed that a 1% increase in an animal's FPED resulted in a decrease of 1.20 kg, 2.03 kg, and 0.004 kg/d in WWT, YWT, and ADG, respectively. Maternal inbreeding showed significantly negative effects on progeny growth performance. AFC increased by 1.4 and 0.8 d for each 1% increase in FPED of the cow and her dam, respectively. Using genomic inbreeding, similar impact on growth traits was observed although the magnitude of the effect varied between methods. Across all genomic measures, WWT, YWT, and ADG decreased by 0.21 to 0.53 kg, 0.46 to 1.13 kg, and 0.002 to 0.006 kg/d for each 1% increase in genomic inbreeding, respectively. Four chromosomes (9, 12, 17, and 27) were identified to have a significant association between their homozygosity (FROH-CHR) and growth traits. Variability in genomic inbreeding could be useful when deciding between full and half-sib selection candidates. Despite the high level of inbreeding in this study, its negative impact on growth performance was not as severe as expected, which may be attributed to the purging of the deleterious alleles due to natural or artificial selection over time.

The data of 35 years from 1980 to 2014 were analyzed to study the effect of genetic and non-genetic factors viz. period of calving, season of calving as fixed effect and sire as random effect on the reproduction trait (age at first calving) of Kankrej cattle maintained at Livestock Research Station, S.D. Agricultural University, Sardarkrushinagar, Gujarat. The least square mean of age at first calving in Kankrej cows was found to be 1376.0 9 ± 14.55 days. Heritability estimates was 0.44 ± 0.18 for the age at First calving. Genetic correlation of age at first calving (AFC) with first lactation 300 milk yield (F300Y), total milk yield (FLY) and lactation length (FLL) were 0.358 ± 0.218, 0.341± 0.216 and 0.661 ± 0.361, respectively while the phenotypic correlation were 0.055, 0.048 and 0.044, respectively. The effect of period of calving and sire was significant (P<0.01) on age at first calving. Season of calving did not affect significantly to this trait under study. Effect of season of calving was not significant on age at first calving indicated breed characteristic for adoption in particular environment. Age at first calving showed a significant variation over the period that indicated some selection measures for age at first calving.

Evaluation of genetic factors such as heritability value and non genetic factors of reproductive traits has a vital role in improving breeding and management practices of beef cattle. The aim of the present study was to evaluate heritability value and non-genetic factors affecting reproductive traits in Ongole grade cattle. Five hundred and fifty-three (553) records of reproductive traits including age at first calving (AFC), calving interval (CI), days open (DO) of cows distributed over a period of 8 years (2012 to 2019) were used to predict genetic and non-genetic parameters. Parity, sex, mating system, season, and year of birth calf were included in the model to estimate their effect on reproductive traits. Heritability estimation was calculated using Mixed Model analysis by SAS 9.4. The General Linear Model (GLM) procedure of SAS program, version 9.4 was used to estimate non-genetic factors. Overall mean values for AFC, CI and DO were 39.62±0.39 months, 393.81±2.85 days, 84.29±0.34, respectively. The results revealed that AFC, CI and DO were significantly (P<0.01) affected by mating system but sex, parity, year of birth had no significant (P>0.05) influence. Concerning AFC, season affected AFC of Ongole grade. Prediction of heritability AFC, CI and DO were 0.28±0.026; 0.46±0.007 and 0.21±0.040, respectively. We might conclude that the improvement of reproductive traits in Ongole grade cattle was possible by improving genetic merit by selection criteria using genetic parameters and utilization of controlled breeding techniques.

The age at first calving (AFC) is a critical parameter in dairy herd management due to its impact on feeding costs, genetic progress, longevity, and thus, farm profitability. With the growing global demand for buffalo milk products, recent advancements in reproductive practices and feeding techniques have contributed to a reduction in AFC in Italy. This study investigates the impact of AFC on the productive and reproductive performance of primiparous Italian Mediterranean buffaloes. Data were collected from 50,661 animals across 115 herds, covering 362,703 first-lactation test-day records from 2013 to 2023. The study analyzed productive traits, including milk yield (kg/d), days to milk peak (DMP, d), ECM (kg/d), fat and protein contents (%), and SCS. Reproductive traits, such as calving interval (CIN, d) and days open (DO, d), were analyzed from 2013 to 2021. Repeated mixed linear models were used to assess the effects of AFC on the afore-mentioned traits, accounting for DIM, calving year and season, and, when applicable, their interactions. Results highlighted a significant reduction in AFC (from 36 to 35 mo), CIN (from 457 to 447 d), and DO (from 147 to 136 d) over the studied period. Buffaloes with AFC >42 mo produced 0.52 kg/d more milk and 0.90 kg/d more ECM, with slightly higher fat content (+0.04%) compared with those with AFC ≤32 mo. This trend was consistent throughout DIM categories. Somatic cell score was significantly lower in buffaloes with AFC between 32 and 35 mo (2.78), whereas higher SCS was observed in those with AFC ≤32 mo (2.81) or >35 mo (2.80). Buffaloes with AFC comprised between 34 and 37 mo had significantly lower CIN and DO (449-450 and 137-139 d, respectively) compared with those with both lower or greater AFC (454 and 143 d, respectively), whereas DMP was not significantly affected by AFC. As expected, likely due to the out-of-breeding technique, the highest values for both CIN and DO were observed in buffaloes calving the first time in winter and spring (on average 455 and 145 d, respectively), and lower values were recorded for those calving in autumn and summer (on average 449 and 138 d, respectively). Buffaloes with AFC ≤30 mo that calved during winter exhibited significantly greater DO (>150 d) compared with those calving with AFC >42 mo during the same period (140 d). This is likely due to the lower capacity to restore ovarian activity that may reduce fertility in younger buffaloes compared with older ones. Conversely, buffaloes with AFC >42 mo that calved in summer tended to have extended DO (139 d) in respect to those with lower AFC (≤30 mo) in the same period (135 d). This may be due to the interaction between the increased photoperiod and the reduced feed intake caused by summer heat stress, which may have an effect on older buffaloes' fertility. Therefore, AFC between 34 and 37 mo represents the optimal window for Italian Mediterranean buffaloes, combining shorter CIN and DO with sustained milk production. The reduction of AFC could significantly enhance farm profitability and may be achievable through the integration of breeding programs, better reproductive technologies across seasons, and targeted nutritional strategies during the preweaning and prepartum phases.

Inbreeding depression is a genetic phenomenon associated with the loss of fitness and mean phenotypic performance due to mating between relatives. Historically, inbreeding coefficients have been estimated from pedigree information. However, the onset of genomic selection programs provides large datasets of individuals genotyped using SNP arrays, enabling more precise assessment of an individual's genomic-level inbreeding using genomic data. One of the traits most sensitive to issues stemming from increased inbreeding is reproduction. This is particularly important in equine, in which fertility is only moderate compared to other livestock species. To explore this further, we evaluated the effect of inbreeding on five reproductive traits (age at first foaling (AFF), average interval between foalings (AIF), total number of foalings (NF), productive life (PL) and reproductive efficiency (RE)) in Pura Raza Español mares using genomic data. Residual predicted phenotypes were obtained by purging these traits through the REML (wgResidual ) and ssGREML (gResidual ) approaches in reproductive data of 29,847 PRE mares using the BLUPF90+ program. Next, we used pedigree-based (Fped ) and ROH-based genomic (FROH ) inbreeding coefficients derived from 1018 animals genotyped with 61,271 SNPs to estimate the inbreeding depression (linear regression). Our results indicated significant levels of inbreeding depression for all reproductive traits, with the exception of the AIF trait when Fped was used. However, all traits were negatively affected by the increase in genomic inbreeding, and FROH was found to capture more inbreeding depression than Fped . Likewise, REML models (ssGREML) using genomic data for estimated predicted residual phenotypes resulted in higher variance explained by the model compared with the models not using genomics (REML). Finally, a segmented regression analysis was conducted to evaluate the effect of inbreeding depression, revealing that the levels of genealogical and genomic homozygosity do not manifest uniformly in reproductive traits. In contrast, the levels of inbreeding depression ranged from low to high as homozygosity increased. This analysis also showed that reproductive traits are very sensitive to inbreeding depression, even with relatively low levels of homozygosity.

Age at first calving (AFC) is an important trait for achieving earlier reproductive performance in cattle. To identify quantitative trait loci for AFC in Japanese Black cattle, we conducted a genome-wide association study using 866 animals with extreme AFC values selected from a larger group of 52, 009 animals. We identified single nucleotide polymorphisms (SNPs) on bovine chromosome 2 that were associated with AFC. These SNPs were located within 112.8-kbp intronic region of delta/notch-like EGF repeat containing (DNER) and proved to be in a state of high linkage disequilibrium. The association was replicated in an independent sample of 2963 animals. In the replicated population, the frequency of the reduced AFC allele (Q) was 0.463, and the allele accounts for 8% of the total genetic variance. The effect of allele substitution on AFC was a decrease of 11.54 days. The results suggest that the Q allele could serve as a useful marker in Japanese Black cattle to select animals with superior AFC performance.

This study aimed was to identify non-genetic factors strongly associated with reproductive traits on Japanese Black heifer. Artificial insemination and calving records were analyzed to investigate non-genetic effect on reproductive performances. A total of 2220 records of heifer raised between 2005 and 2016 were utilized in this study. Studied traits were first service non return rate to 56 days (NRR), first service pregnancy rate (FPR), days from first to successful insemination (FSI), number of services per conception (NSC), age at first calving (AFC), and gestation length (GL). Test of significance for effects in the statistical model was performed using GLM procedure of SAS 9.3. The yearling trend was plotted on the adjusted mean of parameters, by the least square mean procedure. Means of NRR, FPR, FSI, NSC, AFC and GL were 72%, 53%, 52.71 days, 1.76, 760.71 days and 288.26 days, respectively. The effect of farm was significant (P<0.001) for FSI, AFC, and GL. The effects of age of heifer at first insemination was significant (P<0.001) for AFC. Month of insemination and sex of calf were significant (P<0.001) for GL. Compared with average value of reproductive traits, NSC and GL were generally within standard values for Japanese Black cattle, while AFC was slightly earlier. The result indicated that different management of farms strongly influenced reproductive traits of Japanese Black heifer.

Conhecer as características reprodutivas da raça bovina Mirandesa é fundamental para o melhoramento e conservação desta raça de carne, sobretudo pela sua baixa diversidade genética. A depressão por consanguinidade acompanha-se frequentemente de desempenhos individuais e maternais mais fracos, que podem agravar os efeitos ambientais. Neste trabalho utilizaram-se 7386 registos do Livro Genealógico para caracterizar alguns indicadores reprodutivos: a idade ao primeiro parto (AFC), a duração da gestação (PL), o intervalo entre partos (CI), a distribuição partos no ano (CD) e a longevidade produtiva (PLf). Testaram-se ainda efeitos não genéticos na sua expressão, através de métodos não-paramétricos, por não estarem cumpridos os pressupostos de normalidade. A mediana para a AFC aproximou-se dos 32 meses, variando com o sistema de produção, a exploração, e o ano e estação de nascimento. A média de PL (287±8.9 dias) foi afetada pela paridade e sexo da cria. A mediana do CI foi de 378 dias, e variou apenas com o programa de reprodução, paridade, ano e estação. Os partos, irregularmente distribuídos ao longo do ano, mostraram padrões distintos segundo o sistema de produção. A longevidade produtiva desta raça foi de 6,45 anos, e 20% da população apresentou uma PLf superior a dez anos. Este trabalho sugere serem a estratégia do agricultor e a nutrição os principais efeitos não genéticos limitando o desempenho reprodutivo nesta raça, a considerar para aumentar o número de vitelos produzidos anualmente em paralelo com uma cuidada seleção de reprodutores para reduzir o inbreeding da raça.

Context The selection of animals for sexual precocity and reproductive efficiency is a trend to reduce the production cycle, promote higher economic viability to the system, increase selection intensity and higher genetic gain, as well to promote the profitability of production systems. To include these traits as selection criterion in cattle breeding programs, estimating genetic parameters and studying the possibility of obtaining genetic gains is required. The hypothesis tested was that the indicators of sexual precocity traits present genetic variance and moderate heritability that allows these to be used as a criterion of selection to obtain improvement for sexual precocity, without negative implications for the reproductive efficiency in Nellore cattle. Aims This study was carried out to estimate the genetic parameters for reproductive traits (scrotal circumference at 365 and 450 days of age, gestation length, days open, calving interval, real fertility, cumulative productivity, calf weight : cow weight ratio) and age at first conception and first calving in a Nellore cattle herd under selection for sexual precocity. Methods Data of reproductive traits and indicators of sexual precocity traits from 4081 Nellore cattle born between 2009 and 2015 were used. The covariance components, heritabilities and correlations were estimated using the restricted maximum likelihood method, available in the BLUPF90 package, in single- and multiple-trait animal mixed models. Key results Estimates of heritability and standard errors for scrotal circumference at 365 and 450 days of age, gestation length, days open, calving interval, real fertility, cumulative productivity, calf weight : cow weight ratio, age at first conception (AFCo) and age at first calving (AFCa) were 0.33 ± 0.03, 0.33 ± 0.01, 0.23 ± 0.03, 0.34 ± 0.11, 0.23 ± 0.12, 0.21 ± 0.16, 0.23 ± 0.08, 0.25 ± 0.10, 0.21 ± 0.08 and 0.24 ± 0.08 respectively. The genetic correlations estimated between AFCo and the other reproductive traits ranged from –0.61 to 0.14 (standard error 0.1–0.21), and between AFCa and the other reproductive traits ranged from –0.60 to 0.16 (standard error 0.1–0.19), all of them in a favourable direction. Conclusions Selection for sexual precocity based on AFCo and AFCa may promote improvement in reproductive efficiency and fertility, except for the calf weight : cow weight ratio, whose correlation was close to zero. Implications The estimates of heritabilities and genetic correlations suggest that selection programs for reproductive traits and indicators of sexual precocity traits for the Nellore breed may provide genetic gain. In addition, considering the genetic correlation obtained between AFCo and AFCa (0.96), when the selection objective is to increase the sexual precocity of heifers, we could use the age of the first conception as criterion, as the measurement of this trait occurs at a lower age at first calving, which implies reducing the time required for animal evaluation and decision-making.

Effects of age at first calving (AFC) on functional longevity of Czech Holstein cows and their reproduction traits in the first lactation were analyzed using the first lactation data of 605 538 Holstein cows first calved from 1993 to 2008. Three classes were formed for AFC: low age class (16&amp;ndash;24 months), average age class (25&amp;ndash;30 months), and high age class (33&amp;ndash;46 months). Effects of AFC on length of productive life (LPL), days open (DO), days between calving and first service (CTFS), and days between first service and conception in the first lactation (FSTC) were estimated by survival and linear model analyses. It was found that LPL was on average slightly shorter for cows with higher AFC who showed also a lower proportion of higher lactations and tended to longer DO and longer CTFS in the first parity. The results of survival analysis indicate that cows with higher AFC had a tendency to shorter LPL (risk of culling 1.118) and to longer DO (risk of conception 0.758), CTFS (risk of conception 0.757), and FSTC (risk of conception 0.754) in comparison with cows with lower AFC. When the effect of fertility traits on LPL was analyzed, it was found that longer DO, CTFS, and FSTC were connected with a lower risk of culling (0.132, 0.183, 0.206) regardless of the particular AFC group. In linear model analysis, the effects of AFC group were estimated from two datasets, where the second dataset included also the missing values of fertility traits. It was found that the cows group with the highest AFC showed worse values of fertility traits (16.75, 19.69, 20.46 days) than the cows groups with lower AFC. Results of all analyses showed that a high AFC is connected with worse cow&amp;rsquo;s fertility at the first lactation and with lower cow&amp;rsquo;s LPL. &amp;nbsp; &amp;nbsp;

An investigation was conducted on 729 Hariana cows maintained at Government Livestock Farm, Hisar, from 1973 to 1999, with an objective to compare the efficiency of various selection indices for attaining desired genetic gains in the index traits. The various traits included were age at first calving (AFC), service period (SP), calving interval (CI), days to first service (DFS), number of services per conception (NSPC), lactation milk yield (LY), peak yield (PY), dry period (DP). Except for LY, PY and AFC the heritabilities of all other traits were low. Desirable associations among reproductive traits are supportive of the fact that any one of these traits incorporated in simultaneous selection is expected to cause correlated response in other traits. Production traits (LY and PY) were positively correlated, while DP had low negative genetic correlation with LY, and high genetic correlation with PY. Thus, DP can be taken as additional criteria in selection index for better over all improvement. Almost all production traits except DP had low negative correlation with AFC, SP, DFS and CI meaning that reduction in reproduction traits up to certain level may increase production performance. While, the correlation of NSPC with LY and PY was moderate positive. Among four trait indices I23: incorporating PY, AFC, SP and NSPC and among three trait indices I1: incorporating LY, AFC and SP were the best as these required least number of generations (4.87 and 1.35, respectively) to attain desired goals. Next in order of preference were PY or LY along with DP and SP as the best indices (I20 and I16) of which, index with PY may be preferred instead of LY as it produced considerably high correlated response in LY and reduction in NSPC as well. (Asian-Aust. J. Anim. Sci. 2003. Vol 16, No. 6 : 789-793)