Estimates of genetic parameters of growth rate in sheep with reference to the method of estimation

1968 ◽  
Vol 10 (1) ◽  
pp. 109-112 ◽  
Author(s):  
E. Salah ◽  
E. Galal
Keyword(s):  
Growth Rate ◽  
Body Weight ◽  
Birth Weight ◽  
Genetic Parameters ◽  
Regression Coefficient ◽  
Research Station ◽  
Phenotypic Correlations ◽  
Genetic And Phenotypic Correlations ◽  
Heritability Estimates ◽  
Desert Research

There were 563 lambs in the study. They were single Barki lambs born during the period 1961–62 to 1965–66 in Ras El-Hekma Desert Research Station (U.A.R.). All lambs were weighed at birth and at weaning. From 1963–64 onward lambs were weighed nearly every 15 days.Two methods of estimating growth rate were compared:R1 = weaning weight — birth weight/age at weaningand R2 = the regression coefficient of weight on age. The effect of method of estimation on heritabilities and genetic and phenotypic correlations was examined.Heritability estimates of birth weight, R1 and genetic and phenotypic correlations between them were 0·18 ± 0·10, 0·24 ± 0·11, 0·50 and 0·12 respectively. From the data collected during the period 1963–64 to 1965–66 alone the heritability estimates of birth weight, R1 and R2 and the genetic and phenotypic correlations between birth weight and each of R1 and R2 were 0·15 ± 0·14, 0·39 ± 0·20 and 0·39 ± 0·20; 0·84 and 0·96; 0·28 and 0·27 respectively.For preweaning growth rate the method of dividing the gain in weight until weaning by age at weaning was virtually as good a method as using the regression of body weight on age. The correlation between the two methods was estimated as 0·91.

Genetic parameters of Barki sheep raised under semi-arid conditions

1969 ◽  
Vol 11 (3) ◽  
pp. 361-367 ◽  
Author(s):  
M. H. Fahmy ◽  
E. Salah E. Galal ◽  
Y. S. Ghanem ◽  
S. S. Khishin
Keyword(s):  
Genetic Parameters ◽  
Genetic Correlations ◽  
Research Station ◽  
Phenotypic Correlations ◽  
Arid Conditions ◽  
Body Weights ◽  
Genetic And Phenotypic Correlations ◽  
Fleece Weight ◽  
Semi Arid ◽  
Desert Research

SUMMARYRecords on 695 lambs were collected over a period of 5 years from 1961/62 to 1965/66, at Ras El-Hekma Desert Research Station, 230 km west of Alexandria. The characters studied were birth, weaning and yearling body weights, pre- and post-weaning daily gains and greasy fleece weight.Birth, 120-day and 365-day body weights were 3·4, 18·2 and 33·4 kg respectively. Greasy fleece weight at 16 months of age was 3·29 kg. Heritability estimates of birth, weaning, yearling weights, pre- and post-weaning daily gains and greasy fleece weight were 0·22, 0·45, 0·41,0·45 and 0·29 respectively. Genetic and phenotypic correlations between birth, weaning and yearling weights were all positive and significant. Genetic correlations between fleece weight and body characteristics were negative and low.

scholarly journals Realized Sampling Variances of Estimates of Genetic Parameters and the Difference Between Genetic and Phenotypic Correlations

Genetics ◽  
1996 ◽  
Vol 143 (3) ◽  
pp. 1409-1416 ◽  
Author(s):  
Kenneth R Koots ◽  
John P Gibson
Keyword(s):  
Genetic Correlation ◽  
Genetic Parameters ◽  
Genetic Parameter ◽  
Genetic Correlations ◽  
Phenotypic Correlation ◽  
Parameter Estimates ◽  
Sampling Variance ◽  
Phenotypic Correlations ◽  
Genetic And Phenotypic Correlations ◽  
Heritability Estimates

Abstract A data set of 1572 heritability estimates and 1015 pairs of genetic and phenotypic correlation estimates, constructed from a survey of published beef cattle genetic parameter estimates, provided a rare opportunity to study realized sampling variances of genetic parameter estimates. The distribution of both heritability estimates and genetic correlation estimates, when plotted against estimated accuracy, was consistent with random error variance being some three times the sampling variance predicted from standard formulae. This result was consistent with the observation that the variance of estimates of heritabilities and genetic correlations between populations were about four times the predicted sampling variance, suggesting few real differences in genetic parameters between populations. Except where there was a strong biological or statistical expectation of a difference, there was little evidence for differences between genetic and phenotypic correlations for most trait combinations or for differences in genetic correlations between populations. These results suggest that, even for controlled populations, estimating genetic parameters specific to a given population is less useful than commonly believed. A serendipitous discovery was that, in the standard formula for theoretical standard error of a genetic correlation estimate, the heritabilities refer to the estimated values and not, as seems generally assumed, the true population values.

Estimates of genetic parameters for pre-weaning and post-weaning growth traits of Chios lambs

1980 ◽  
Vol 30 (2) ◽  
pp. 271-276 ◽  
Author(s):  
A. P. Mavrogenis ◽  
A. Louca ◽  
O. W. Robison
Keyword(s):  
Body Weight ◽  
Birth Weight ◽  
Genetic Parameters ◽  
Growth Traits ◽  
Genetic Correlations ◽  
Heritability Estimate ◽  
Weaning Weight ◽  
Phenotypic Correlations ◽  
Selection For ◽  
Daily Gain

ABSTRACTData on 792 Chios lambs born during the 1972/73 and 1973/74 lambing seasons were used to estimate genetic and phenotypic parameters for birth weight, weaning weight, age at weaning, pre-weaning daily gain, body weight at 5, 10, 15 and 20 weeks of age, and postweaning daily gain. Body weight at 15 weeks of age had the highest heritability estimate (0·73 ± 0·17) and that of post-weaning daily gain was also high (0·56 ± 0·15). Selection for either weight at 15 weeks or post-weaning daily gain would be expected to yield a greater response than selection for pre-weaning daily gain or weaning weight. Genetic correlations among weights and/or gains were positive (approximately 0·20). Phenotypic correlations among weights and gains were generally higher than genetic correlations. However, the correlation between pre— and post-weaning daily gain was small (0·08). Likewise, post-weaning daily gain had low correlations with all weights before 10 weeks. Age at weaning had moderate negative associations with all weights but a very low positive correlation with post-weaning daily gain.

scholarly journals GENETIC ASPECTS OF PREWEANING PERFORMANCE OF NDAMA CATTLE

2021 ◽  
Vol 11 (2) ◽  
pp. 151-155
Author(s):  
A. O. Leigh ◽  
O. Akinokun ◽  
S. A. Adeyanju
Keyword(s):  
Birth Weight ◽  
Beef Cattle ◽  
Genetic Parameters ◽  
Weaning Weight ◽  
Livestock Farm ◽  
Phenotypic Correlations ◽  
Genetic And Phenotypic Correlations ◽  
Daily Gain

Records on birth weight (BW), preweaning daily gain (PWG) and weaning weight (WW) of Ndama beef cattle were obtained from the Fashola Livestock Farm in Oyo State of Nigeria between 1954 and 1964 and were analyzed to estimate the phenotypic and genetic parameters of preweaning performances of this breed of cattle. For birth weight, preweaning daily gain and weaning weight respectively heritability was estimated as 0.13 ± 0.08, 0.30 ± 0.14 and 0.25 ± 0.12 from paternal half-sib relationship. The estimates of genetic and phenotypic correlations obtained from these data among the three pre-weaning traits were found to be similar to those already in the general literature on beef cattle.

Phenotypic and genetic parameters of productivity in Galway ewes

1976 ◽  
Vol 23 (3) ◽  
pp. 295-304 ◽  
Author(s):  
G. J. More O'Ferrall
Keyword(s):  
Body Weight ◽  
Analysis Of Variance ◽  
Genetic Parameters ◽  
Genetic Correlations ◽  
Mean Values ◽  
Single Index ◽  
Phenotypic Correlations ◽  
Heritability Estimates ◽  
Fleece Weight ◽  
Index Value

SUMMARYRecords from a selection flock of Galway ewes collected over a 6-yr period (1966 to 1971) were used to obtain estimates of the phenotypic and genetic parameters of ewe productivity. The number of lambs born (NLB) and weaned (NLW), the weight of lamb weaned (WLW), ewe body weight (EBW) and greasy fleece weight (GFL) were used as measures of productivity, mean values being 1·25, 0·88, 25·6 kg, 52·8 kg and 2·8 kg, respectively. Each ewe's annual performance was adjusted to a 4-yr-old ewe equivalent and expressed as a deviation from the appropriate flock × year subgroup mean; these deviations were combined into a single index value for each ewe for NLB, NLW and WLW. Records for 975 individual ewes representing 84 sires which had three or more progeny were used in a half sib analysis of variance.Estimates of heritability were 0·18, 0·24 and 0·25 for NLB, NLW and WLW based on index record and 0·07, 0·16 and 0·30 respectively for 2-yr-old ewes. Heritability estimates of EBW and GFL were 0·73 and 0·52 respectively. The genetic correlations between EBW and NLB2, NLW2, WLW2 and GFL were 0·85, 0·42, 0·62 and 0·53 respectively; those between EBW and index records were slightly negative. Phenotypic correlations were generally lower than the corresponding genetic ones.Ewes born as multiples were more productive than singles. They were 1·8 kg lighter (P < 0·01) at 18 mo and weaned 2·5 kg more lamb (P < 0·05) at 2 yr of age. The repeatability of NLB ranged from 0 to 0·2.

GENETIC AND PHENOTYPIC PARAMETERS OF EARLY GROWTH TRAITS OF LAMBS REARED ARTIFICIALLY IN A CONTROLLED ENVIRONMENT

1985 ◽  
Vol 65 (1) ◽  
pp. 37-49 ◽  
Author(s):  
J. N. B. SHRESTHA ◽  
D. P. HEANEY
Keyword(s):  
Body Weight ◽  
Genetic Correlations ◽  
Research Centre ◽  
Breeding Cycle ◽  
Parameter Estimates ◽  
Controlled Environment ◽  
Phenotypic Correlations ◽  
Solid Diet ◽  
Genetic And Phenotypic Correlations ◽  
Heritability Estimates

This study involved body weights of 6078 lambs from 525 sires of two synthetic dam strains developed at the Animal Research Centre with 50% Finnish Landrace background. Breeding was practiced in flocks A and B for lambing at 4-mo intervals under an 8-mo breeding cycle. Lambs were housed indoors in a controlled environment on expanded metal floors in windowless barns, reared artificially with milk replacer and solid diet from birth to weaning at 21 days of age. Thereafter, all lambs were fed solid diet to 70 days of age. Paternal half-sib estimates of heritability for lamb weights at birth, weaning, 49 and 70 days of age were 0.25–0.26. Heritability estimates in the two synthetic dam strains were in close agreement (P > 0.05). Genetic and phenotypic parameter estimates did not demonstrate any significant linear trends across lambing periods. The moderate levels of heritability estimates for lambs reared artificially under a controlled environment suggest that genetic response to selection could be enhanced by selecting lambs independent of potential maternal effects and competition among litter mates for a fixed quantity of milk. Estimates of genetic and phenotypic correlations among various lamb weights ranged from 0.60 to 1.00, and from 0.51 to 0.93, respectively. Lamb weights having closer proximity in time showed higher correlations. Moderate to high genetic correlations between body weight of lambs at different ages indicated that selection for weight at one age should cause no adverse effects on body weight at other ages. Key words: Sheep, artificial rearing, lamb weights, heritability, genetic and phenotypic correlations

Genetic and phenotypic parameters of some measures of lifetime production and their relationship with milk yield in the first three lactations in Tharparkar cows

1982 ◽  
Vol 98 (2) ◽  
pp. 461-465
Author(s):  
V. K. Taneja ◽  
S. B. Basu ◽  
D. S. Bhatnagar
Keyword(s):  
Milk Production ◽  
Milk Yield ◽  
Genetic Parameters ◽  
Genetic Correlations ◽  
Production Traits ◽  
Correlated Responses ◽  
The Third ◽  
Phenotypic Correlations ◽  
Genetic And Phenotypic Correlations ◽  
Heritability Estimates

SUMMARYThe genetic parameters of lifetime production traits and their relationship with milk yield in first, second and third lactations were estimated from information on 753 Tharparkar cows. The heritability estimates for milk yield in first, second and third lactations were 0·22 ± 0·10, 0·33 ± 0·14 and 0·49 ± 0·17 and for number of lactations completed, lifetime milk production, number of days in milk and herd life 0·58 ± 0·23, 0·51 ± 0·22, 0·54 ± 0·22 and 0·34 ± 0·20 respectively. The genetic and phenotypic correlations among the four lifetime production traits were in the range of 0·83–1·0 and 0·84–0·85 respectively. The phenotypic correlations of milk yield in first, second and third lactations with lifetime production traits were significant and ranged between 0·15 and 0·56. The corresponding genetic correlations ranged between 0·26 and 0·83. For the first three lactations, the genetic correlations of lifetime traits with the third lactation were high and that between lifetime milk yield and yield in third lactation the highest (0·83 ± 0·17). The direct and correlated responses from single trait selection were also estimated.

Genetic evaluation of production traits between and within flocks of Merino sheep. I. Hogget fleece weights, body weight and wool quality

1989 ◽  
Vol 40 (2) ◽  
pp. 433 ◽  
Author(s):  
SI Mortimer ◽  
KD Atkins
Keyword(s):  
Body Weight ◽  
Environmental Effects ◽  
Genetic Variance ◽  
Research Centre ◽  
Production Traits ◽  
Merino Sheep ◽  
Wool Production ◽  
Phenotypic Correlations ◽  
Genetic And Phenotypic Correlations ◽  
Fleece Weight

Wool production traits were measured on Merino hogget ewes in an unselected multiple-bloodline flock over a 7-year period at Trangie Agricultural Research Centre, N.S.W. The traits measured were greasy fleece weight (GFW), skirted fleece weight (SKFW), yield (Y), clean fleece weight (CFW), fibre diameter (FD), body weight (BWT) and staple length (SL). These measurements were used to examine genetic differences between and within flocks of Merino sheep, and to estimate heritability of and genetic and phenotypic correlations among these traits. Significant strain, flock within strain and flock effects were present for all traits. Interactions between these effects and year were non-significant. Within-flock genetic variance was always larger than between-flock within strain genetic variance for each trait. The influence of environmental effects on these traits was also examined. The environmental effects of birth-rearing type, age at observation and age of dam together accounted for about 7-10% of the total within-flock variation in fleece weights and body weight.After adjusting for significant environmental effects, paternal half-sib heritability estimates were 0.29 �. 0.06 for GFW, 0.22 � 0.05 for SKFW, 0.35 � 0.05 for Y, 0.30 �0.06 for CFW, 0.48 �0.07 for FD, 0.34 �. 0.06 for BWT and 0.44 �0.07 for SL. Estimates for genetic and phenotypic correlations were in agreement with published estimates except for the genetic correlation between CFW and FD (0.40 �. 0.11), and the genetic correlations involving BWT, which were essentially zero. The implications of the results of this study for the genetic improvement of Merino sheep for wool production are discussed.

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.

Estimates Of Genetic Parameters For Economic Traits In West African Dwarf Goat

2021 ◽  
Vol 19 ◽  
pp. 114-119
Author(s):  
I. K. Odubote ◽  
J. O. Akinokun
Keyword(s):  
Body Weight ◽  
Litter Size ◽  
Genetic Parameters ◽  
West African ◽  
Economic Traits ◽  
West African Dwarf ◽  
West African Dwarf Goat ◽  
Heritability Estimates ◽  
Size At Birth ◽  
Birth Body Weight

Records of 848 West African Dwarf goat kids and 220 kiddings over a period of eight years (1982-1989) were analysed. The records were used to provide heritability and repeatability estimates for litter size at birth, kidding interval (repeatability estimate alone) and body weight at birth, weaning, 3 months, 6 months, 9 months and 1 year of age. Heritability estimates of 0.28±0.005, 0.18±0.003, 0.14±0.003, 0.29±0.005, 0.11±0.003 and 0.17±0.004 were obtained for litter size at birth, body weight at birth, and at weaning, 3 months, 6 months, and 9 months of age respectively. Corresponding repeatability estimates were slightly higher than the heritability estimates. However, repeatability estimates of 0.04±0.030 was obtained for kidding interval.

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