scholarly journals Genetic evaluation modeling of the Tunisian dairy cattle: assessment of the test-day model (TDM) and lactation model (L305) in accordance to the flock size

2019 ◽  
Author(s):  
Yosra Ressaissi ◽  
Mohamed Ben Hmouda
Keyword(s):  
Dairy Cattle ◽  
Genetic Parameters ◽  
Significant Contribution ◽  
Genetic Evaluation ◽  
Data Availability ◽  
Flock Size ◽  
Breeding Values ◽  
Genealogical Data ◽  
Evaluation Approaches ◽  
Daily Milk

SUMMARYGenetic evaluation in dairy cattle has been commonly carried following the lactation model (L305) and the test-day model (TDM), the purpose of this study was to test the adjustment and the accuracy of these main models in relation to the size of the Tunisian dairy flocks while assessing the effect of genealogical data availability on both approaches. Data were obtained from the Tunisian official milk recording system and cows were classified in accordance to the flock sizes into eight groups. Genetic parameters and breeding values were estimated per size group for 305-days (L305) and daily milk yields (TDM) through two animal models and by using 3 pedigrees of different quality. Contemporary groups were defined as herd*calving year for L305 and as herd*control year for TDM. Genetic evaluation approaches were compared by connecting the different obtained results. Fixed factors were observed to be differently significant per group of flock size explaining a specific variance of the average milk yield and that small flocks are mostly affected by environmental factors. Using TDM and an equilibrated pedigree file, genetic parameters were higher, breeding values were fairly compared leading to a more objective ranking of the cows and a better illustration of genetic variabilities between the flock groups. Low genetic variability and significant contribution of unfavorable environmental conditions were observed within the Tunisian dairy flocks.

Multivariate REML estimates of genetic parameters of monthly test day milk production traits in first parity Iranian Holstein cows with the use of a repeatability test day model

2003 ◽  
Vol 2003 ◽  
pp. 139-139
Author(s):  
H. Farhangfar ◽  
P. Rowlinson ◽  
M. B. Willis
Keyword(s):  
Dairy Cattle ◽  
Milk Production ◽  
Genetic Parameters ◽  
Large Population ◽  
Genetic Evaluation ◽  
Major Influence ◽  
Production Traits ◽  
Milk Production Traits ◽  
Breeding Values ◽  
Repeatability Test

In practical dairy cattle breeding programmes, usually a small number of animals (selected from a large population) have a major influence on the genetic gain of the concerned population over a period of time (Hofer, 1998). Candidate animals are usually selected based on their breeding values that are predicted by using animal models. In order to predict breeding values, genetic parameters (calculated from variance and covariance components) of the traits under consideration should be estimated to be used in genetic evaluation systems either based on lactation or test day models. The use of test day models has increasingly become of interest in genetic evaluation of dairy cattle due to the fact that they can take more accurate account of the effects of environmental factors influencing test day milk yield over the course of lactation. The main objective of this study was to use a repeatability test day animal model to estimate genetic parameters of monthly test day milk production traits in first parity Iranian Holsteins.

scholarly journals Estimation of genetic parameters and prediction of breeding values for some economic traits of Black Bengal Goat under farming condition

2020 ◽  
Vol 20 (1-2) ◽  
pp. 8-17
Author(s):  
MA Jalil ◽  
S Akther ◽  
MP Choudhury ◽  
MA Habib
Keyword(s):  
Birth Weight ◽  
Litter Size ◽  
Milk Yield ◽  
Genetic Parameters ◽  
Breeding Values ◽  
Lactation Length ◽  
Total Milk ◽  
Daily Milk Yield ◽  
Black Bengal Goat ◽  
Daily Milk

The study was undertaken to evaluate the genetic progress of Black Bengal Goat (BBG) by estimating genetic parameters viz. heritability and breeding values for economically important productive and reproductive traits (birth weight, weight at 3, 6, 9 & 12 months, daily milk yield, lactation length, total milk yield and litter size of BBG goat population). Variance and co-variance components were analyzed applying Residual Maximum Likelihood (REML) approach by VCE 4.2.5 computer package. The heritability (h2) of birth weight was estimated as 0.2, which was low. The heritability estimates for 3-month weight (0.40), 6-month weight (0.50), 9-month weight (0.37) and 12-month weight (0.36) were found medium. Estimated h2 of daily milk yield, total milk yield and lactation length in this study were from 0.55 to 0.82.  h2 of litter size was 0.09. The maximum estimated breeding value (EBV) was found for 6 month body weight (12.94 kg), however, for daily milk yield, the value was 1.513 kg. The results found in this study revealed that genetic improvement of BBG for most of the traits is possible by selection and breeding. Bangladesh J. of Livestock Res. 20(1-2): 8-17, Jan-Dec 2013

scholarly journals  Estimation of genetic parameters and evaluation of test-day milk production in sheep

2012 ◽  
Vol 57 (No. 11) ◽  
pp. 522-528 ◽  
Author(s):  
J. Bauer ◽  
M. Milerski ◽  
J. Přibyl ◽  
L. Vostrý
Keyword(s):  
Milk Production ◽  
Fixed Effects ◽  
Genetic Parameters ◽  
Least Squares Method ◽  
Coefficient Of Determination ◽  
Suitable Model ◽  
Breeding Values ◽  
Parity Number ◽  
Daily Milk Production ◽  
Daily Milk

 Genetic parameters and breeding values were estimated based on 11 708 daily milk yields from 2255 lactations (1351 sheep, 19 different flocks) between the years 2004 and 2010. The pedigree covered 2334 individuals, including both the recorded animals and their known ancestors. The fixed effects were estimated by the least-squares method, while the genetic parameters were estimated by the REML method. The data were tested by 49 models, but on the basis of the coefficient-of-determination value and the significance of the effects, only 10 models were used for REML analysis. The most suitable model was chosen on the basis of the breeding values distribution and the heritability of daily milk production, which was estimated at 0.28. The fixed effects of the flock parity number, the flock test day, and the linear and quadratic coefficients of flock’s days-in-milk in the chosen model were all highly significant (P < 0.0001) for the test-day milk yield. The breeding values had a normal distribution and a standard deviation of 0.46 kg.  

Genetic evaluation of productive life in Iranian Holstein using survival analysis

2005 ◽  
Vol 2005 ◽  
pp. 131-131 ◽  
Author(s):  
M. Dadpasand Taromsari ◽  
S. R. Miraei-Ashtiani ◽  
M. Moradi Shahrebabak ◽  
R. Vaez Torshizi
Keyword(s):  
Survival Analysis ◽  
Dairy Cattle ◽  
Genetic Parameters ◽  
Linear Models ◽  
Failure Time ◽  
Genetic Evaluation ◽  
Time Analysis ◽  
Productive Life ◽  
Analysis Methodology ◽  
Time Dependent Covariates

Improvement of herd life increases profitability due to lower replacement costs of heifers, higher proportion of mature cows that produce at their maximum potential and increased opportunity for voluntary culling. Functional productive life (PL) after adjustment for production is the ability of a cow to remain healthy and delay involuntary culling (Ducrocq et al 1988). Survival or failure time analysis has replaced linear model approaches for routine genetic evaluation of dairy cattle in several countries (Sewalem et. al. 2003). It allows proper treatment of censored data, inclusion of time-dependent covariates and skewed or non normal distribution of data. Approximate estimates of the heritability of longevity traits typically range from 0.05 to 0.10 and 0.15 to 0.20 using linear models and survival analysis, respectively (Vollema et al. 2000 and Caraviello et. al. 2004). The objective of this study was to apply survival analysis methodology for assessing the most important factor influencing PL, estimation of genetic parameters of productive life and genetic evaluation in Iranian Holstein dairy cattle.

Genetic analysis of feet and leg traits of Australian Angus cattle using linear and threshold models

2012 ◽  
Vol 52 (1) ◽  
pp. 1 ◽  
Author(s):  
Gilbert Jeyaruban ◽  
Bruce Tier ◽  
David Johnston ◽  
Hans Graser
Keyword(s):  
Animal Model ◽  
Genetic Correlation ◽  
Genetic Parameters ◽  
Genetic Evaluation ◽  
The Other ◽  
Breeding Value ◽  
Value Analysis ◽  
Breeding Values ◽  
Angus Cattle ◽  
Six Traits

The advantages of using a univariate threshold animal model (TAM) over the conventional linear animal model (AM) in the development of a genetic evaluation system for feet and leg traits of Angus cattle were explored. The traits were scored on a scale of 1–9 with scores 5 and 6 being the most desirable. The genetic parameters and estimated breeding values for front feet angle (FA), rear feet angle (RA), front feet claw set (FC), rear feet claw set (RC), rear leg hind view (RH) and rear leg side view (RS) were compared from AM and TAM. In order to predict breeding values to identify the animals with intermediate optimum, the scores were categorised to form three groups to differentiate the desirable group (5–6) from the other two groups with less desirable feet and leg appearances (1–4 and 7–9). The AM and TAM were used to estimate genetic parameters for the grouped data as well as the original score data. A TAM using the group data was used to predict the probability and breeding value for the desirable intermediate group. For the original score data, estimated heritabilities on the underlying scale, using TAM, were 0.50, 0.46, 0.35, 0.44, 0.32 and 0.22 for FA, FC, RA, RC, RH and RS, respectively, and were 0.01–0.18 higher than the heritabilities estimated using AM. Genetic correlation between the six traits using a bivariate TAM with all scores ranged from 0.02 to 0.50 with front and rear angles had the highest genetic correlation at 0.50. For all six traits, proportion in the intermediate desirable group was higher than the other two groups combined. The low annual genetic change observed for all six traits over the 10 years of data recording reflected the lack of directional selection to improve the traits in Angus cattle. For genetic evaluation of feet and leg traits with an intermediate optimum, TAM is a preferred method for estimating genetic parameters and predicting breeding values for the desirable category. The TAM has now been implemented for regular estimated breeding value analysis of feet and leg traits of Angus cattle.

scholarly journals Estimation of genetic parameters and breeding values for daily milk production of dairy Simmentals in terms of heat stress

Genetika ◽  
2020 ◽  
Vol 52 (2) ◽  
pp. 641-650
Author(s):  
Goran Vuckovic ◽  
Tina Bobic ◽  
Pero Mijic ◽  
Mirna Gavran ◽  
Maja Gregic ◽  
...  
Keyword(s):  
Heat Stress ◽  
Milk Production ◽  
Genetic Parameters ◽  
Breeding Values ◽  
Daily Milk Production ◽  
Estimation Of Genetic Parameters ◽  
Daily Milk

Contemporary group alternatives for genetic evaluation of milk yield in small populations of dairy cattle

2019 ◽  
Vol 59 (6) ◽  
pp. 1022 ◽  
Author(s):  
R. J. Pereira ◽  
F. S. Schenkel ◽  
R. V. Ventura ◽  
D. R. Ayres ◽  
L. El Faro ◽  
...  
Keyword(s):  
Dairy Cattle ◽  
Milk Yield ◽  
Random Effect ◽  
Genetic Evaluation ◽  
Fixed Effect ◽  
Random Regression ◽  
Period Effect ◽  
Production Traits ◽  
Breeding Values ◽  
Contemporary Group

In the present study, different random regression models, focussed on the nature of the effect of the contemporary group, fixed or random, were compared for genetic evaluation of test-day milk yield in dairy Gir breed, whose herds are characterised by relatively reduced numbers of cows. Cows were assigned to the same contemporary group if they were tested in the same herd, year and month. In one of the evaluated models, the contemporary group was investigated as a fixed effect and a clustering procedure was adopted to group herd-year subclasses in order to, at the end of the process, all contemporary groups contained at least three cows. The models were compared by the quality of fit, the accuracy of the predicted breeding values and their estimates of genetic parameters. The clustering procedure did not significantly improve the accuracy of predicted breeding values. Moreover, the fit to the data for this model was negatively affected. Therefore, this strategy should not be further implemented. The model including the herd-calving period effect and contemporary group treated as random effect showed similar characteristics to its equivalent, where the contemporary group was modelled as a fixed effect. However, the fit to the data for this model was slightly worse. Thus, the results suggest a random regression model including the herd-calving period effect and the fixed effect of contemporary group for the genetic evaluations of production traits in dairy Gir cattle. These findings could be extended to small dairy cattle populations whose herds are small-sized.

Dairy cattle industry and genetic improvement programs in Thailand

2017 ◽  
Vol 57 (7) ◽  
pp. 1242
Author(s):  
Santi Pangmao ◽  
Peter C. Thomson ◽  
Mehar S. Khatkar
Keyword(s):  
Dairy Cattle ◽  
Fixed Effects ◽  
Genetic Parameters ◽  
Fat Percentage ◽  
Breeding Values ◽  
North East ◽  
The North ◽  
Breed Group ◽  
Improvement Programs ◽  
Genetic Trends

The objective of the present study was to estimate genetic parameters and evaluate the genetic trends of 100-day milk yield (MY), fat percentage (FP) and protein percentage (PP) in three government dairy cattle farms in Thailand, located in the north and north-east of the country. The data consisted of records from 1745 first-lactation cows that calved between 1986 and 2015, which were the progeny of 287 sires and 1237 dams. Most of the animals were crossbred Holstein-Friesian with native or zebu animals. The total number of animals in the pedigree was 4753. Univariate and bivariate linear mixed models were used to estimate genetic parameters and breeding values by using ASReml-R. The fixed effects in the model were herd, year of calving, season of calving, breed group and the interaction between year and season of calving, and the random effects were animal and residual. All fixed effects had significant effects on the three traits, except breed group. The estimated heritabilities for MY, FP and PP were 0.242 ± 0.061, 0.066 ± 0.048 and 0.329 ± 0.072 respectively. The genetic correlation for MY and FP, MY and PP, and FP and PP were 0.219 ± 0.352, –0.271 ± 0.177 and 0.452 ± 0.255 respectively. The genetic trends based on estimated breeding values over year of birth did not show consistent improvement in all three traits, although there was a slight declining trend in MY in the later years.

Combining direct and correlated traits into an aggregate index for dairy cattle fertility

2007 ◽  
Vol 2007 ◽  
pp. 64-64
Author(s):  
Stefano Biffani ◽  
Fabiola Canavesi ◽  
Maurizio Marusi
Keyword(s):  
Animal Model ◽  
Dairy Cattle ◽  
Milk Yield ◽  
Genetic Evaluation ◽  
Conception Rate ◽  
Calving Interval ◽  
Multiple Trait ◽  
Breeding Values ◽  
Breeding Goal ◽  
Aggregate Index

In January 2006, ANAFI (Italian Holstein Breeders Association) introduced a genetic evaluation for fertility based on a multiple-trait animal model (Biffani et al., 2005), which included the following traits: days from calving to first insemination (DTFS), calving interval (CI), first-service non return rate to 56 d (NR56), angularity (ANG) and mature equivalent milk yield at 305 d (ME305). Breeding values have been subsequently combined in an aggregate index (T), with the breeding goal to increase conception rate (CR). This paper will show how the breeding values have been combined into an aggregate index. At the same time the efficiency of selecting on alternative aggregate indexes versus the official aggregate index is presented.

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