First Calving Interval Research Articles

Genetic and Phenotypic Trends for Production and Reproduction Traits in Murrah Buffaloes.

The objective of the study was to estimate genetic and phenotypic trends for first lactation production and reproduction traits in Murrah buffaloes. The information of pedigree and targeted traits of 640 Murrah buffaloes was collected for the period from 1997 to 2020. The first lactation production traits included first lactation milk yield (FLMY), 305 days first lactation milk yield (305FLMY), first lactation length (FLL), first lactation peak yield (FPY) whereas reproduction traits included first service period (FSP), first calving interval (FCI) and first dry period (FDP). Genetic and phenotypic trends were estimated. Phenotypic trends for FLMY, 305FLMY, FLL and FPY exhibited as 36.96 ± 8.58 kg/year, 31.93 ± 8.34 kg/year, 1.47 ± 0.55 days/year and 0.12 ± 0.02 kg/year, respectively and respective genetic trends exhibited as 3.73 ± 1.67 kg/year, 1.94 ± 0.76 kg/year, -0.15 ± 0.07 days/year and 0.01 ± 0.01 kg/year, respectively. It was revealed that there were significant (p < 0.05) and positive phenotypic trends for all production traits while genetic trends were significant (p < 0.05) for FLMY and 305FLMY traits. The phenotypic trends of studied reproductive traits indicated that only FDP trait significantly (p < 0.01) decreased (1.87 days/year) over time. For FSP and FCI traits, nonsignificant (p > 0.05) genetic and phenotypic trends indicated no change over time. This study highlighted potential challenges in maintaining reproductive efficiency alongside productivity improvements in Murrah buffaloes.

Influence of additive and maternal effects on production and reproduction traits in Murrah buffaloes: Insights from Bayesian analysis.

The aim of this research was to assess genetic parameters for first lactation production and reproduction traits in Murrah buffaloes by employing additive and maternal effects. Data on pedigree and specific traits of 640 Murrah buffaloes were gathered from 1997 to 2020. These traits encompassed first lactation milk yield (FLMY), 305-day first lactation milk yield (305FLMY), first lactation length (FLL), first lactation peak yield (FPY), first service period (FSP), first calving interval (FCI) and first dry period (FDP). Genetic evaluations employed six univariate animal models, accounting for both direct and maternal effects, facilitated by THRGIBBS1F90 and POSTGIBBSF90 programs. Fixed factors included in the analysis were period of calving, season of calving and age at first calving. The Bayesian estimates for direct heritability, derived from the most suitable model, were as follows: FLMY: 0.28 ± 0.01, 305FLMY: 0.30 ± 0.01, FLL: 0.19 ± 0.01, FPY: 0.18 ± 0.01, FSP: 0.12 ± 0.01, FCI: 0.14 ± 0.01 and FDP: 0.12 ± 0.01. Maternal effects were found significant, ranging from 5% to 10%, in first lactation traits under Model 2 and Model 5. Additionally, positive and significant genetic and phenotypic correlations were observed among the studied traits. In conclusion, selection based on 305-day first lactation milk yield suggests potential for genetic enhancement in Murrah buffaloes, advocating its inclusion in breeding programmes to bolster early performance. Also, consideration of maternal influences is necessary for genetic progress of animals.

Modeling and forecasting of lifetime milk production in Hariana cattle

The present study was conducted on performance records of 648 Hariana cattle with respect to first lactation and lifetime traits spread over a period of 57 years (1962-2018) from DUVASU farm, Mathura and 23 years (1995– 2017) from State livestock farm Babugarh, Hapur. Lifetime production traits, viz. Lifetime 2 Milk Yield (LT2MY), Lifetime 3 Milk Yield (LT3MY), Lifetime 4 Milk Yield (LT4MY) and Lifetime 5 Milk Yield (LT5MY) were predicted by multiple linear regression analysis. Step-wise regression procedure was used to predict the lifetime milk yield from first lactation traits, viz. age at first calving (AFC), first calving interval (FCI) and first lactation total milk yield (FLTMY). The optimum models were selected with the help of Akaike information criterion (AIC), Bayesian information criterion (BIC), Mallow’s conceptual predictive value and variance inflation factor. The models with lower AIC, BIC and RMSE values and with higher co-efficient of determination were selected as optimum. The optimal models for lifetime production traits, viz. LT2MY, LT3MY, LT4MY and LT5MY with co-efficient of determination were 75.46%, 66.63%, 59.4% and 55.03%, respectively.

Influence of non-genetic factors on first lactation and lifetime performance traits in Nili-Ravi buffaloes

The objective of this research was to evaluate the effects of various non-genetic factors on first lactation and lifetime productivity in Nili-Ravi buffaloes, including season of birth, period of birth, age at first calving, season of first calving, period of first calving, and number of lactations completed. The livestock data on first lactation and lifetime performance traits relevant to 501 Nili-Ravi buffaloes were collected from the history sheet of the animal for a period from 1983 to 2017 (i.e., 35 years) and maintained at the Indian Council of Agricultural Research—Central Institute for Research on Buffaloes (ICAR-CIRB) sub-campus, in Nabha, Punjab, India. To evaluate the least-squares means (LSMs) and the effect of non-genetic factors on performance traits, a least-squares analysis model was applied. The overall LSM for age at first calving (AFC) was 45.03 ± 0.40 months and ranged from 34 to 54 months. The results indicated that the effect of AFC was highly significant (p ≤ 0.01) on first lactation total milk yield (FLTMY), first lactation standard milk yield (305 days or less) (FLSMY), first peak milk yield (FPY), and first lactation length (FLL) in the Nili-Ravi breed of buffaloes. FLTMY, FLSMY, and FPY were highest (2,250.08 ± 48.16 kg, 1,944.68 ± 31.20 kg, and 9.32 ± 0.16 kg/day, respectively) for animals with an AFC of 42–48 months. Furthermore, FLTMY, FLSMY, and FLL were highest (2,411.02 ± 68.68 kg, 2,008.81 ± 44.49 kg, and 357.43 ± 8.13 days, respectively) in animals that first calved in the autumn season. However, the lowest first dry period (FDP), first service period (FSP), and first calving interval (FCI) (110.63 ± 7.42 days, 125.48 ± 9.04 days, and 443.63 ± 9.00 days, respectively) were found for animals that first calved in the rainy season. The overall LSM for herd life (HL), productive life (PL), productive days (PDs), unproductive days (UDs), total lifetime milk yield (total LTMY), standard lifetime milk yield (standard LTMY), milk yield per day of productive life (MY/PL), milk yield per day of productive days (MY/PDs), and milk yield per day of herd life (MY/HL) were estimated as 3,779.84 ± 31.86 days, 2,078.55 ± 24.32 days, 1,552.74 ± 20.06 days, 525.81 ± 12.44 days, 10,229.71 ± 195.31 kg, 9,203.64 ± 173.52 kg, 4.86 ± 0.08 kg/day, 6.46 ± 0.08 kg/day, and 2.66 ± 0.04 kg/day, respectively. The effect of AFC on HL, PDs, UDs, total LTMY, and standard LTMY was highly significant (p ≤ 0.01). Furthermore, the effect of season of first calving on HL, PL, and PDs was significant (p ≤ 0.05). In addition, the effect of the period of first calving on HL, PDs, standard LTMY, and total LTMY was significant (p ≤ 0.05). In these contexts, it can be concluded that the buffaloes of the Nili-Ravi breed with an AFC of 42–48 months performed better than animals with a later AFC in terms of production, reproduction, and lifetime traits.

Association between age at first calving, first lactation traits and lifetime productivity in Murrah buffaloes.

ObjectiveThis study was conducted to estimate the association of age at first calving (AFC) with first lactation traits as well as lifetime performance traits in Murrah buffaloes.MethodsData on first lactation and life time performance of Murrah buffaloes (n = 679), maintained at Indian Council of Agricultural Research-Central Institute for Research on Buffaloes, Hisar, India during the period 1983 through 2017, were deduced to calculate heritability estimates, genetic and phenotypic correlation of different first lactation and lifetime traits. The univariate animal model was fitted to estimate variance components and heritability separately for each trait, while bivariate animal models were set to estimate genetic and phenotypic correlations between traits under study.ResultsThe heritability was high for first peak milk yield (FPY, 0.64±0.08), moderate for AFC (0.48±0.07) and breeding efficiency (BE 0.39±0.09). High genetic correlations of first lactation total milk yield (FLTMY) with first lactation standard milk yield (FLSMY, 305 days or less), FPY, and first lactation length (FLL) was seen. Likewise, genetic correlation of AFC was positive with FLTMY, FLL, first dry period (FDP), first service period (FSP), first calving interval (FCI), herd life (HL) and productive days (PD). Significant phenotypic correlation of FLTMY was observed with HL, productive life (PL), PD, total lifetime milk yield (LTMY), standard lifetime milk yield (standard LTMY). Moreover, positive genetic and phenotypic correlation of FPY was observed with HL, PL, PD, total LTMY and standard LTMY.ConclusionThis study reports that AFC had positive genetic correlation with FDP, FSP, FCI, and unproductive days while, negative association of AFC was observed with FLSMY, PL, total LTMY, standard LTMY, and BE. This suggests that reduction of AFC would results in improvement of lifetime performance traits.

Comparison of heritability estimates of first lactation fertility traits in Mehsana buffaloes

First lactation records of 3068 Mehsana buffaloes sired by 118 sires, under field progeny testing programme distributed in different 149 villages of 14 talukas maintained at Dudhsagar Research and Development Association, Dudhsagar Dairy, Mehsana over a period of 24 years (1989-2012) were used to estimate least squares means and heritability of fertility traits like, first service period (FSP), first calving interval (FCI) and daughter pregnancy rate (DPR). The least squares means of these traits were found to be 189.05±3.34 days, 472.97±2.87 days and 31.08±0.59%, respectively. Non genetic factors such as age at first calving and period of calving were found to have highly significant effect on all the traits, whereas, cluster found to be non-significant for FSP and significant for FCI and DPR. Heritability were estimated for FSP, FCI and DPR as 0.02±0.02, 0.004±0.015 and 0.095±0.031; 0.04±0.03, 0.026±0.024 and 0.089±0.032; and 0.01±0.02, 0.032±0.026 and 0.095±0.034 by LSML, BLUP-SM and BLUP-AM, respectively. BLUP-AM was found to be the best model for heritability estimation based on error variance and BLUP-AM gave highly significant and more accurate results than BLUP-SM and LSML in Mehsana buffaloes.

Genetic evaluation of some first lactation traits in Murrah buffaloes

A study was conducted for studying the inheritance pattern of some first lactation traits in Murrah buffaloes. Data on 577 Murrah buffaloes maintained at the farms - Firozpur, Ambala, Jallandhar, Jhansi, Lucknow, Bareilly, Agra and Pantnagar spread over 34 years was used. The traits considered were age at first calving (AFC), first calving interval (FCI), first lactation milk yield (FLMY), first lactation period (FLP), weight at first calving (FCI) and first service period (FSP). The heritability estimates (h2±S.E) for AFC, FCI, FLMY, FLP, WFC and FSP traits were found to be 0.40±0.15, 0.14±0.10, 0.31±0.14, 0.23±0.12, 0.36±0.13 and 0.06±0.0, respectively. The genetic and phenotypic correlations revealed that selection for lower age at first calving and higher lactation milk yield can be used as a selection criterion for the genetic improvement in Murrah buffaloes.

Genetic Parameters for First Lactation and Lifetime Traits of Nili-Ravi Buffaloes

The data on first lactation and lifetime performance records of 501 Nili-Ravi were collected for a period from 1983 to 2017 (35 years) maintained at ICAR-Central Institute for Research on Buffaloes, Sub-Campus, Nabha, Punjab. The data were analyzed to calculate heritability, genetic and phenotypic correlation for first lactation traits, viz., Age at First Calving (AFC), First Lactation Total Milk Yield (FLTMY), First Lactation Standard (305 days or less) Milk Yield (FLSMY), First Peak Milk Yield (FPY), First Lactation Length (FLL), First Dry Period (FDP), First Service Period (FSP) and First Calving Interval (FCI), Herd Life (HL), Productive Life (PL), Productive Days (PD), Unproductive Days (UD), Breeding Efficiency (BE), Total Lifetime Milk Yield (Total LTMY), Standard Lifetime Milk Yield (Standard LTMY), Milk Yield Per Day of Productive Life (MY/PL), Milk Yield Per Day of Productive Days (MY/PD), and Milk Yield Per Day of Herd Life (MY/HL). For estimation of variance component and heritability separately for each trait, the uni-trait animal model was equipped, whereas to estimate genetic and phenotypic correlations between traits, bi-trait animal models were fitted. The estimates of heritability for production and reproduction traits of Nili-Ravi were medium, i.e., 0.365 ± 0.087, 0.353 ± 0.071, 0.318 ± 0.082, 0.354 ± 0.076, and 0.362 ± 0.086 for FLSMY, FDP, FSP, FCI, and AFC, respectively. The estimates of heritability were low, i.e., 0.062 ± 0.088, 0.123 ± 0.090, 0.158 ± 0.090, 0.155 ± 0.091, and 0.129 ± 0.091 for HL, PL, PD, Total LTMY, and Standard LTMY and high, i.e., 0.669 ± 0.096 for BE. Genetic correlation for FLTMY was high with FLL (0.710 ± 0.103), and genetic correlation of FLTMY was high and positive with HL, Total LTMY, MY/PL, and MY/PD while low and positive with PL. Genetic correlation of AFC was low and negative with PL, PD, UD, BE, Total LTMY, Standard LTMY, MY/PL, and MY/PD and negative with MY/HL. Significant positive phenotypic association of FPY was seen with FLTMY, FLSMY, FLL, AFC, HL, Total LTMY, and Standard LTMY. Higher heritability of first lactation traits especially FPY suggests sufficient additive genetic variability, which can be exploited under selection and breeding policy in order to improve overall performance of Nili-Ravi buffaloes.

Genetic Parameters for Age at First Calving and First Calving Interval of Beef Cattle.

The objective of this study was to estimate genetic parameters for age at first calving (AFC) and first calving interval (FCI) for the entire beef cattle population and separately for the Charolais (CH) and Aberdeen Angus (AA) breeds in the Czech Republic. The database of performance testing between the years 1991 and 2019 was used. The total number of cows was 83,788 from 11 breeds. After editing, the data set contained 33,533 cows, including 9321 and 4419 CH and AA cows, respectively. The relationship matrix included 85,842 animals for the entire beef population and 24,248 and 11,406 animals for the CH and AA breeds, respectively. A multibreed multitrait animal model was applied. The estimated heritability was low to moderate. Genetic correlations between AFC and FCI varied depending on the breeds from positive to negative. Differences between variance components suggest that differences between breeds should be considered before selection and breeding strategy should be developed within a breed.

Maternal Genetic Effect on Expected Genetic Response of Selection Indices for Milk Production of Friesian Cows in Egypt

The present study aimed to estimate the genetic parameters of first lactation milk yield (FLMY), first lactation period (FLP), first dry period (FDP) and first calving interval (FCI) and inclusion these studied traits in selection indices through different animal models. The data utilized in this study were obtained from 1821 normal first lactation of Friesian cows belong to Sakha and EI-Karada Experimental stations of Animal Production Research Institute (APRI), Ministry of Agriculture, Dokki, Cairo, Egypt. Data were collected during the period from 1990 to 2016 and analyzed using the MTDFREML program. Covariance components were used to construct the different selection indices for FLMY kg, FLP day, FDP day and FCI day with four multiple animal models. Means for FLMY FLP, FDP and FCI were 2425 kg, 304 d, 170 d and 474 d, respectively. Direct additive heritability (h2a) for the above-mentioned traits were 0.32, 0.29, 0.27 and 0.18, respectively. The corresponding estimates of the maternal heritability (h2m) for the same traits were 0.25, 0.22, 0.30 and 0.27, successively. Estimates of direct genetic correlations among studied traits ranged from -0.52 to 0.61. Phenotypic correlations among investigated traits were ranging from -0.20 to 0.23. Animal model number two that included the additive and permanent effects had the highest accuracy. On the contrary, model number three that included additive and maternal effects. The ranking correlations among four animal models were higher than 0.93. This indicates that using one of the studied models can be achieved the genetic improvement. We would however recommend that included the permanent environmental effects on analytical models when selection for these traits in Friesian cows under Egyptian condition.

Identification of genomic regions related to age at first calving and first calving interval in water buffalo using single-step GBLUP.

In Brazil, water buffaloes have been used to produce milk for mozzarella cheese production. Consequently, the main selection criterion applied for the buffalo genetic improvement is the estimated mozzarella yield as a function of milk, fat and protein production. However, given the importance of reproductive traits in production systems, this study aimed to use techniques for identifying genomic regions that affect the age at first calving (AFC) and first calving interval (FCI) in buffalo cows and to select candidate genes for the identification of QTL and gene expression studies. The single-step GBLUP method was used for the identification of genomic regions. Windows of 1Mb containing single-nucleotide polymorphisms were constructed and the 10 windows that explained the greatest proportion of genetic variance were considered candidate regions for each trait. Genes present into the selected windows were identified using the UOA_WB_1 assembly as the reference, and their ontology was defined with the Panther tool. Candidate regions for both traits were identified on BBU 3, 12, 21 and 22; for AFC, candidates were detected on BBU 6, 7, 8, 9 and 15 and for first calving interval on BBU 4, 14 and 19. This study identified regions with great contribution to the additive genetic variance of age at first calving and first calving interval in the population of buffalo cows studied. The ROCK2, PMVK, ADCY2, MAP2K6, BMP10 and GFPT1 genes are main candidates for reproductive traits in water dairy buffaloes, and these results may have future applications in animal breeding programs or in gene expression studies of the species.

Estimation of Phenotypic and Genetic Trends in Economic Traits of Murrah Buffaloes

Background: Notable advancements in the selection indices have led to the development of exceptional breeding strategies, which have eventually led to the selection of elite dairy animals. The comparison of trends is facilitated by their estimation which permit the assessment of progress in a particular trait. The purpose of this study was to investigate genetic trends in economic traits of Murrah buffaloes, which is predominantly present as a high milk producer using the regression method. The study was designed to estimate the phenotypic, genetic and environmental trends, which represent the changes accrued over time and hence, determines the efficiency of breeding programme. Methods: The present study was conducted on 659 Murrah buffaloes, sired by 188 bulls, over a period of 27 years (1991-2017). The economic traits studied were first lactation milk yield (FLMY), first lactation length (FLL), age at first calving (AFC), first calving interval (FCI), first service period (FSP) and first dry period (FDP). The phenotypic trends were obtained as regression of population performance on year and the genetic trends were obtained by Smith method I and II. Result: The results revealed that the phenotypic trends obtained were significant and desirable for all the traits except for first lactation length, which was non-significant. The standard errors obtained by Smith method-I were higher than those obtained from method-II. As the Smith method-II avoids year to year fluctuations in the environment and those of contemporaries, it gives more realistic estimate as compared to the first method with lower standard error.

Effect of Season and Age at First Calving on Early Performance Traits in Murrah Buffaloes

The present investigation was carried on 659 Murrah buffaloes, sired by 188 bulls, maintained at Directorate of Livestock Farms, Guru AngadDev Veterinary and Animal Sciences University, Ludhiana, for the duration of 27 years (1991-2017). The purpose of this study was to investigate the effect of non-genetic factors like season and age at first calving on early reproductive and productive traits like age at first calving (AFC), first service period (FSP), first calving interval (FCI) and age at puberty (AAP), 305 day milk yield (305MY), first lactation length (FLL), first peak yield (FPY), first days to attain peak yield (DPY) and first dry period (FDP). Season of calving had highly significant influence on FSP, FCI and FDP, significant effect on AFC, AAP, 305MY, FLL and FPY and non-significant effect on DPY. Age at first calving had non-significant effect on all the studied traits.

Multivariate analysis of body morphometric traits in conjunction with performance of reproduction and milk traits in crossbred progeny of Murrah × Jafarabadi buffalo (Bubalus bubalis) in North-Eastern Brazil.

We studied the relationship between body morphometric traits, and their underlying association with milk production (MP), lactation length (LL), first calving interval (FCI) and subsequent calving interval (CI) of crossbred progeny of Murrah × Jafarabadi buffalo aiming to assist in selection programs. We carried out principal component analysis (PCA) of the body morphometric traits, which include breast width (BW), thigh width (THW), hip width (HW), rump width (RW), rump length (RL), body depth (BD), body length (BL), height withers (HEW), rear height (RH), shoulder width (SW), thorax width (TW), loin width (LW), distance from the head to ischium (DHI), and thoracic perimeter (TP). We determined the association of morphometric traits with milk/reproduction traits using canonical correlation analysis (CCA). The analysis revealed that the first six PCA accounted for 82.14% of the total observed variation, and the traits THW, HW, TW, LW, RW, HEW, TP, RH, and BW, accounted for almost half (48.00%) of the total variance indicating a higher contribution in body structural conformation. The first canonical function was significant (p<0.05), accounted for 72.46% of the total variance, and the canonical correlation was 0.56, indicating the dependence between both groups of traits. Higher canonical loadings were obtained for LL (0.49), FCI (0.46), BW (-0.71), BL (-0.56), DHI (-0.34), HEW, (-0.38) and TP (-0.50). These traits were most important for the derivation of canonical statistical variables, and presented a higher canonical correlations (r) between the dependent (LL/FCI) and independent (BW, BL, DHI, HEW and TP) groups. The results could suggest that the body morphometric traits THW, HW, TW, LW, RW, HEW, BD, TP, RH, and BW could play important role in body structural composition, indicating a suitable functional type, and aid designing of selection programs for buffalo breeding.

Parámetros genéticos para crecimiento y reproducción en ganado Simmental mediante parentesco por pedigrí y genómico

Objetivo. Estimar parámetros genéticos para peso a los ocho meses de edad (W8M), edad al primer parto (AFC) y primer intervalo entre partos (FCI) usando parentesco genómico y por pedigrí. Materiales y métodos. Se utilizaron 481, 3063 y 1098 registros fenotípicos para W8M, AFC y FCI, respectivamente. La información genómica estuvo compuesta por una población de 718 animales genotipados con un chip que incluyó 30106 marcadores genéticos tipo polimorfismo de nucleótido simple (SNP). Modelos univariado y bivariado fueron construidos bajo la metodología del mejor predictor lineal insesgado convencional (BLUP) y genómico en una etapa (ssGBLUP). Resultados. Las heredabilidades para W8M, AFC y FCI variaron desde 0.25 a 0.26, 0.20 a 0.22 y 0.04 a 0.08, respectivamente. Los modelos de AFC y FCI con la metodología ssGBLUP disminuyeron ligeramente el error y aumentaron la varianza genética aditiva, respectivamente. Conclusiones. La inclusión de información genómica mejora levemente la precisión de las estimaciones genéticas en esta población. Sin embargo, una población de animales genotipados más grande y con mayor conectividad genética por parentesco permitiría aumentar para los criadores el potencial de la metodología ssGBLUP en ganado Simmental de Colombia.

Genetic analysis of trends in production and reproduction traits over years using regression methods in Sahiwal cows

The present study was conducted on first lactation performance records of 820 Sahiwal cows maintained at NDRI, Karnal spread over 54 years (1962–2015) to study the effect of genetic and non-genetic factors on production and reproduction traits, to estimate genetic parameters and the genetic trends by different methods. The traits considered were age at first calving (AFC), first lactation 305 days milk yield (FL305DMY), first lactation total milk yield (FLTMY), first lactation length (FLL) and first calving interval (FCI). The effect of genetic and non–genetic factors like sire, month of birth/calving, period of birth/calving, AFC group and first service period group on normalized production and reproduction traits was assessed by GLM function of Statistical Analysis System (SAS Institute Inc., version 9.2). Paternal half sib correlation method was used to estimate the heritability of different characters. Phenotypic trend per year was estimated as the linear regression of the phenotypic value (P) on time (year).The genetic trend were estimated by Smith I, Smith II, BLUP (Sire Model), BLUP Animal Model methods respectively. The effect of sire was significant for all traits except calving interval. Effect of month was significant for all the traits except for FLTMY. Effect of period was significant for all the traits except FCI. Effect of AFC group was not significant on FCI. The heritability estimates of AFC, FL305DMY, FLTMY, and FLL were 0.45±0.14, 0.18±0.11, 0.19±0.10, 0.16±0.09, respectively. The repeatability estimate for FL305DMY was 0.45±0.17. The phenotypic trend of FL305DMY, FLTMY, FLL, AFC and FCI was –19.85±2.17 kg, –26.06±2.4 kg, –3.22±0.26 days, –0.05±0.31days and 0.041±0.47 days respectively per year and were statistically significant. Genetic trends were positive, significant and in desirable direction in production traits. Regression methods used for the estimation of genetic trends BLUP (Sire Model), BLUP Animal Model are superior to traditional methods because of small standard error. Low magnitude of genetic trend and unfavorable environmental trends indicated the need to increase herd size and improvement in managemental practices. Thus, dairy genetic improvement programmes needed to be redesign appropriate strategies that would be more beneficial to the currently changing scenarios.

Factors influencing production and reproductive performance of Frieswal cattle maintained at organized farm conditions

The effect of certain genetic and non-genetic factors, viz. sire, month, year, age group, and service period on the first lactation production and reproduction traits of Frieswal cattle reared at organized farm under tropical condition was assessed. The records on first lactation production and reproduction performance of 1,225 Frieswal cattle spread over a period of 24 years (1988-2011) were used for the study. The first lactation traits were first lactation milk yield (FLMY), first lactation 305 day or less milk yield (FL305DMY), first lactation length (FLL), age at firstcalving (AFC), first service period (FSP), first dry period (FDP) and first calving interval (FCI). The genetic and non-genetic factors incorporated in the models for FLMY, FL305MY, FLL, AFC, FSP, FCI and FDP accounted for 31.34, 26.42, 70.60, 15.87, 21.82, 21.60 and 71.97% of total variations, respectively. The effect of sire, year of calving, first service period and age at first calving had highly significant effect on FLMY, FL305MY and FLL. Among the non-genetic factors, year and month had highly significant effect on all reproductive traits except the effect of month on FDP. The effect of farm was significant on FSP and FCI and not on AFC and FDP. The effect of FSP was significant on FDP. The overall least squares averages of AFC, FSP, FCI and FDP were 949.32±5.47, 153.26±3.79, 432.92±3.73, 127.17±1.43, respectively in Frieswal cattle. It was concluded that the first lactation reproduction traits were influenced by the year of birth/ calving. The overall least squares averages for FLMY, FL305 and FLL were 2920.86±47.07 kg, 2765.92±42.84 kg and 307.49±1.51 days, respectively.

Genetic analysis of first lactation production and fertility traits in Karan Fries cattle

The present investigation encompasses the genetic analysis of first lactation production and fertility performance of Karan Fries cattle. Data were collected on 1,988 cows maintained at National Dairy Research Institute (NDRI), Karnal, Haryana over a period of 34 years (1978 to 2012). Least squares analysis was carried out to study the effect of non-genetic factors, viz. season of first calving (SC), period of first calving (PC), genetic group (GG) and age at first calving group (AFCG) on first lactation fertility and production traits. Least squares means of age at first calving (AFC), first calving to first service (FCFS), first service period (FSP), first lactation length (FLL), first calving interval (FCI), first lactation 305 day or less milk yield (F305MY), first lactation total milk yield (FTMY), milk yield per day of first lactation length (MY/FLL), milk yield per day of first calving interval (MY/FCI) and first lactation daughter pregnancy rate (FDPR) were 957.48±6.54 days, 79.46±3.58 days, 130.03±4.43 days, 347.02±5.51 days, 415.47±5.21 days, 3,213.91±47.61 kg, 3,760.49±74.27 kg, 10.49±0.12 kg/day, 9.14±0.13 kg/ day and 0.33±1.42, respectively. Overview of least squares analysis regarding first lactation traits indicated that most of the non-genetic factors excepting AFC group, significantly affected the performance of the animal. Results revealed the superiority of F1 over other GG of Karan Fries cows indicating a significant effect of heterosis. Heritability estimated by both analysis of variance and average information restricted maximum likelihood methods indicated that the fertility traits were less affected by additive gene action; the estimates for production traits indicated higher role of additive gene action. Both phenotypic and genetic correlation estimates indicated antagonistic association between fertility and production traits.

Growth and reproduction genomic-polygenic and polygenic parameters and prediction trends as Brahman fraction increases in an Angus-Brahman multibreed population

The objectives of this research were to estimate genomic-polygenic and polygenic parameters and to evaluate prediction trends as Brahman fraction increased from 0% to 100% in a subtropical multibreed Angus-Brahman (MAB) population for four growth and reproduction traits using single-step genomic-polygenic (GPM) and polygenic models (PM). Traits were 365-d yearling weight (YW), yearling reproductive tract score (RTS), age at first calving (AFC), and first calving interval (FCI). Numbers of phenotypic records were 1758 for YW, 381 for RTS, 1385 for AFC, and 985 for FCI. The pedigree file had 6869 calves, sires, and dams, and genotype file contained 115,711 actual and imputed GGPHD150k SNP markers from 1547 animals. The 4-trait GPM and PM included contemporary group, age of dam (YW only), sex of calf (YW only), direct heterosis, maternal heterosis (YW only) as fixed effects, and animal and residual as random effects. Genetic parameters were estimated using REML procedures and computed using AIREMLF90. Heritabilities were slightly higher for GPM than PM (0.47 vs. 0.45 for YW, 0.31 vs. 0.30 for RTS, 0.14 vs. 0.12 for AFC, and 0.31 vs. 0.29 for FCI). Genetic correlations were positive between YW and RTS (GPM: 0.55; PM: 0.60), negative between RTS and AFC (GPM: −0.22; PM: −0.55) and between AFC and FCI (GPM: −0.68; PM: −0.67), and near zero for all other trait pairs. The similarity between GPM and PM heritabilities and genetic correlations indicated that the 115,711 GGPHD150k SNP markers added little additional information to that contained in the pedigree. Regression coefficients of breed group EBV means on Brahman fraction were negative (P=0.0005) for YW, RTS, and FCI, and positive (P<0.0001) for AFC as Brahman fraction increased. This indicated that heifers with higher Brahman percentages tended to be lighter and less mature as yearlings, older at first calving, and have shorter FCI than heifers with higher Angus percentages under the subtropical environmental conditions of the MAB population. Regression coefficients of individual animal EBV on Brahman fraction showed similar trends, although absolute values were smaller. However, there was a high degree of variation in EBV values within breed groups. Consequently, animals with high, medium, and low EBV existed across all Brahman percentages, thus allowing the selection of replacement animals of all Brahman percentages based on a common set of objectives.

Heritability estimates of first lactation 300-day milk yield under single versus multi-trait animal models in Phule Triveni cattle

First lactation records of 493 Phule Triveni cows sired by 55 bulls on production traits, viz. first lactation 300- day or less milk yield (FL300DMY), first lactation length (FLL), first dry period (FDP) and reproduction traits like age at first calving (AFC), first calving interval (FCI) and first service period (FSP) were used to compare the heritability estimates of FL300DMY under single-trait animal model (ST-AM) versus multi-trait animal models (MT-AM) in Phule Triveni cattle. Under two-trait models, the heritability estimate was found to be highest in FL300DMY-AFC combination as 0.34 ± 0.14. Under three-trait models, the heritability estimate was highest (0.33 ± 0.14) in FL300DMY- AFC- FDP combination. Under four-trait models, the highest estimate of heritability (0.53 ± 0.12) was in FL300DMY-FLL-AFC-FCI combination. Comparison of heritability estimates of FL300DMY from different models revealed that the estimates were varying from single to multiple traits in different combinations. The lowest residual variance (190566) and highest heritability (0.53 ± 0.12) of four-trait combination FL300DMY- FLL-AFC-FCI indicated that this four-trait combination should be used for selection of Phule Triveni cows.