scholarly journals Estimated variance components and breeding values for pre-weaning growth criteria in Romney sheep

2017 ◽  
Vol 21 (2) ◽  
pp. 73
Author(s):  
Eslam Faid-Allah ◽  
E. Ghoneim ◽  
A.H.M. Ibrahim
Keyword(s):  
New Zealand ◽  
Variance Components ◽  
Genetic Factors ◽  
Gene Marker ◽  
Breeding Values ◽  
Factors Affecting ◽  
Kleiber Ratio ◽  
Body Weights ◽  
Estimated Breeding Values ◽  
Positive Coefficients

<p class="abstrak2">This study was carried out to investigate variance components, direct heritability, maternal genetic parameters, estimated breeding values and factors affecting pre-weaning growth criteria of Romney sheep. Data were collected over the period from 2006 to 2012 with records of 4989 lambs descended from 76 rams and 2190 ewes of Romney sheep maintained at S. Island of New Zealand via Gene Marker Lab., Faculty of Agric. and Life Sci., Lincoln Univ., New Zealand. Results proved that genetic and non-genetic factors affecting studied criteria had significant effects (P&lt;0.05). Genetic and environmental estimates of live body weights at birth (LBW), weaning (LWW) and Kleiber ratio (KR) were 0.20±0.074, 0.15±0.042 and 0.14±0.052 for direct heritability (h<sup>2</sup>a±SE); 0.59±0.219, 0.41±0.023 and 0.08±0.002 for maternal heritability (h<sup>2</sup>m±SE); 0.11684, 2.6378 and 0.27565 for additive variances (σ<sup>2</sup>a), 0.34596, 7.1179 and 0.14532 for maternal variances (σ<sup>2</sup>m); and 0.002395, 10.1262 and 0.509339 for permanent environmental variances (σ<sup>2</sup>e), respectively. EBV’s of LBW, LWW and KR ranged from -0.555: 0.502, -1.554: 3.006 and -0.633: 0.242 direct, -0.863: 0.954, -4.942: 2.554 and -0.469: 0.179 maternal for rams, respectively; and -0.664: 0.830, -2.996: 4.586 and -1.651: 0.677 direct, 1.429: 1.142, -7.541: 4.920 and -1.223: 0.492 maternal for ewes, respectively. Results suggest the importance of considering the non-genetic factors in pre-weaning growth performance of lambs. Moderate heritability and positive coefficients of phenotypic and genetic correlation for studied criteria indicate to the possibility of improving them using traditional selection.</p>

scholarly journals A note on genetic parameters and accuracy of estimated breeding values in honey bees

2019 ◽  
Vol 51 (1) ◽  
Author(s):  
Evert W. Brascamp ◽  
Piter Bijma
Keyword(s):  
Honey Bees ◽  
Variance Components ◽  
Genetic Parameters ◽  
Additive Genetic Variance ◽  
Breeding Value ◽  
Phenotypic Variance ◽  
Breeding Values ◽  
Estimated Breeding Values ◽  
Additive Genetic Relationship ◽  
The Relationship

Abstract Background In honey bees, observations are usually made on colonies. The phenotype of a colony is affected by the average breeding value for the worker effect of the thousands of workers in the colony (the worker group) and by the breeding value for the queen effect of the queen of the colony. Because the worker group consists of multiple individuals, interpretation of the variance components and heritabilities of phenotypes observed on the colony and of the accuracy of selection is not straightforward. The additive genetic variance among worker groups depends on the additive genetic relationship between the drone-producing queens (DPQ) that produce the drones that mate with the queen. Results Here, we clarify how the relatedness between DPQ affects phenotypic variance, heritability and accuracy of the estimated breeding values of replacement queens. Second, we use simulation to investigate the effect of assumptions about the relatedness between DPQ in the base population on estimates of genetic parameters. Relatedness between DPQ in the base generation may differ considerably between populations because of their history. Conclusions Our results show that estimates of (co)variance components and derived genetic parameters were seriously biased (25% too high or too low) when assumptions on the relationship between DPQ in the statistical analysis did not agree with reality.

scholarly journals Estimates of (co)variance components and genetic parameters for body weights and growth efficiency traits in the New Zealand white rabbit

2017 ◽  
Vol 25 (4) ◽  
pp. 329 ◽  
Author(s):  
M. Sakthivel ◽  
D. Balasubramanyam ◽  
P. Kumarasamy ◽  
H. Gopi ◽  
A. Raja ◽  
...  
Keyword(s):  
Body Weight ◽  
New Zealand ◽  
Variance Components ◽  
Environmental Effect ◽  
Genetic Parameters ◽  
Growth Traits ◽  
Genetic Effect ◽  
Growth Efficiency ◽  
Body Weights ◽  
Heritability Estimates

The genetic parameters of growth traits in the New Zealand White rabbits kept at Sheep Breeding and Research Station, Sandynallah, The Nilgiris, India were estimated by partitioning the variance and covariance components. The (co)variance components of body weights at weaning (W42), post-weaning (W70) and marketing (W135) age and growth efficiency traits viz., average daily gain (ADG), relative growth rate (RGR) and Kleiber ratio (KR) estimated on a daily basis at different age intervals (42 to 70 d; 70 to 135 d and 42 to 135 d) from weaning to marketing were estimated by restricted maximum likelihood, fitting 6 animal models with various combinations of direct and maternal effects. Data were collected over a period of 15 yr (1998 to 2012). A log-likelihood ratio test was used to select the most appropriate univariate model for each trait, which was subsequently used in bivariate analysis. Heritability estimates for W42, W70 and W135 were 0.42±0.07, 0.40±0.08 and 0.27±0.07, respectively. Heritability estimates of growth efficiency traits were moderate to high (0.18 to 0.42). Of the total phenotypic variation, maternal genetic effect contributed 14 to 32% for early body weight traits (W42 and W70) and ADG1. The contribution of maternal permanent environmental effect varied from 6 to 18% for W42 and for all the growth efficiency traits except for KR2. Maternal permanent environmental effect on most of the growth efficiency traits was a carryover effect of maternal care during weaning. Direct maternal genetic correlations, for the traits in which maternal genetic effect was significant, were moderate to high in magnitude and negative in direction. Maternal effect declined as the age of the animal increased. The estimates of total heritability and maternal across year repeatability for growth traits were moderate and an optimum rate of genetic progress seems possible in the herd by mass selection. The genetic and phenotypic correlations among body weights and between growth efficiency traits were also estimated. Moderate to high heritability and higher genetic correlation in body weight traits promise good scope for genetic improvement provided measures are taken to keep the inbreeding at the lowest level.

Genetic and non-genetic factors affecting body weights in Marwari sheep

2015 ◽  
Vol 21 (1) ◽  
pp. 106 ◽  
Author(s):  
L.K. Nirban ◽  
R.K. Joshi ◽  
H.K. Narula ◽  
H. Singh ◽  
S. Bhakar
Keyword(s):  
Genetic Factors ◽  
Factors Affecting ◽  
Body Weights

A note on non-genetic factors affecting body weights of Bikaneri sheep (Magra strain)

1971 ◽  
Vol 13 (2) ◽  
pp. 349-351 ◽  
Author(s):  
S. C. Chopra ◽  
R. M. Acharya
Keyword(s):  
Least Squares ◽  
Genetic Factors ◽  
The Body ◽  
Factors Affecting ◽  
Body Weights

SUMMARYThe least squares analysis on birth, weaning, 6-month and yearling weights in Magra lambs showed that years of lambing, age and weight of dam at lambing and sex of lamb significantly affected all the body weights except the age of dam which did not significantly affect 6-month and yearling weights. Adjustment of these weights for significant effect will be necessary in obtaining estimates of genetic and phenotypic parameters.

scholarly journals Comparison of different traits to evaluate the growth of bulls

2008 ◽  
Vol 53 (No. 7) ◽  
pp. 273-283 ◽  
Author(s):  
J. Přibyl ◽  
J. Přibylová ◽  
H. Krejčová ◽  
N. Mielenz
Keyword(s):  
Variance Components ◽  
Performance Test ◽  
Live Weight ◽  
Random Regression ◽  
Breeding Values ◽  
Final Weight ◽  
Estimated Breeding Values ◽  
Simple Evaluation ◽  
Growth Of Animals ◽  
Daily Gain

The live weights of 8 243 performance-tested bulls from 100 to 400 days of age were analysed using random regression (RR) and single-trait animal models. Evaluations were done for live weight at 400 days of age and gains from 100 to 400 days of age at various monthly intervals. Estimates of variance components differed depending on the trait definition and model of analysis. Systematic environmental effects explained a higher proportion of variability in the RR for gains than for other definitions of growth. The expected average reliability of estimated breeding values was similar for all methods from 0.42 to 46, but the rankings of animals differed. Determinations (<I>r</I><sup>2</sup>) of breeding values between methods ranged from 0.64 to 0.94. Correlations of the breeding values of progeny at performance-test stations with parents were highest for the evaluation of gains in consecutive intervals evaluated by RR. Correlations of the breeding values of sires from their growth at performance-test stations with the breeding values of groups of progeny at progeny-test stations were from 0.26 to 0.38. Correlations were the highest for RR evaluations of gain using consecutive short intervals. Evaluation of the growth of animals according to daily gains in short consecutive intervals was preferred because more animals and more observations per animal were included in the evaluations, and the growth curve was separated into genetic and non-genetic parts. Simple evaluation of growth according to the final weight or daily gain in a long interval is not entirely correct, since environmental compensatory growth can occur.

Environment and genetic factors affecting wool production from sub-tropical coarse wool sheep

1977 ◽  
Vol 88 (2) ◽  
pp. 443-447 ◽  
Author(s):  
A. M. Aboul-Naga ◽  
E. A. Afifi
Keyword(s):  
Genetic Correlation ◽  
Reproductive Performance ◽  
Genetic Parameters ◽  
Genetic Factors ◽  
Factors Affecting ◽  
Wool Production ◽  
Body Weights ◽  
Performance Traits ◽  
Heritability Estimates ◽  
Fleece Weight

SUMMARYWool production from different flocks of Ossimi, Rahmani and Barki Egyptian local sheep, raised at six different locations in the country was studied. Different genetic parameters for greasy fleece weight of the three breeds were estimated.Location was of significant effect on annual greasy fleece weight of Rahmani sheep only. With the adjustment for differences in yield percentages, differences in clean wool production from one location to another were slight for the three breeds. Age of ewe was of highly significant effect on annual greasy fleece weight.Heritability estimates of annual greasy fleece weight of the ewes were found to be generally low in the three breeds (range 0·00–0·34). The estimates differed markedly with age; those of the yearling fleece weight of Rahmani and Barki ewes were the highest, being 0–19 and 0–34, respectively.Repeatability estimates of annual greasy fleece weight were also low, being 0·11–0·04 and 0·29 for Ossimi, Rahmani and Barki ewes, respectively.Estimates of genetic correlation between yearling greasy fleece weight of the Ossimi and Rahmani ewes and their weaning and yearling body weights were high and positive. Those between annual greasy fleece weight of the ewes and their reproductive performance traits differed greatly in the two breeds.

scholarly journals Estimation of (co)variance components across breeds by a test-day model adapted to New Zealand dairy cattle

2005 ◽  
Vol 2005 ◽  
pp. 114-114
Author(s):  
S. Vanderick ◽  
B. Harris ◽  
P. Mayeres ◽  
A. Gillon ◽  
C. Croquet ◽  
...  
Keyword(s):  
New Zealand ◽  
Dairy Cattle ◽  
Variance Components ◽  
Dairy Farmers ◽  
Breeding Values ◽  
Dairy Heifers ◽  
Breed Differences ◽  
Genetic Contributions

In New Zealand, crossbreeding is largely used by dairy farmers. Currently an important proportion of cows are crossbreds, mostly Holstein-Friesians (HF) x Jersey (JE). Crossbred bulls are currently being progeny tested in New Zealand. Actually, more than one third of the replacement dairy heifers are crossbred animals (Montgomerie, 2002). However currently available methods to model genetic contributions of purebreds to crossbreds take breed differences only partly into account and therefore do not permit an optimal use of crossbred data. The first objective of our study was to allow the modelling of different additive breeding values according to parental breeds to define overall additive breeding values as a function of breed composition.

Genetic and non-genetic factors affecting body weights in Sahiwal × Friesian crosses

1972 ◽  
Vol 14 (3) ◽  
pp. 295-298 ◽  
Author(s):  
V. K. Taneja ◽  
P. N. Bhat
Keyword(s):  
Birth Weight ◽  
Analysis Of Variance ◽  
Genetic Factors ◽  
Dairy Farms ◽  
Least Square ◽  
Factors Affecting ◽  
Genetic Groups ◽  
Body Weights

SUMMARYThe data were collected from seven dairy farms in India on Sahiwal × Friesian crosses over a period of 30 years (1937–1966). There were nine distinct genetic groups (grades); Sahiwal, 1/8, 1/4, 3/8, 1/2, 5/8, 3/4 and 7/8 Friesian and Indian Friesians (animals having 15/16 or more Friesian blood).Least-square analysis of variance was run to examine the effects of grades, farms, periods, seasons, and breed of sire on body weights at birth, 19 weeks, 12 months and 3 years. The effects due to grades, farms and periods were significant for all the traits. The effects due to season and breed of sire were significant for all traits except for weight at 3 years.The least-square constants showed that, with increase in Friesian inheritance, birth weight increased considerably, while the increase in body weights at 19 weeks, 12 months and 3 years was only marked up to the 1/2-Friesian group.

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