Factors affecting reproductive performance and estimates of genetic parameters of litter size in Horro sheep

2002 ◽  
Vol 139 (1) ◽  
pp. 79-85 ◽  
Author(s):  
S. ABEGAZ ◽  
G. DUGUMA ◽  
E. NEGUSSIE ◽  
U. GELMESA ◽  
F. TEREFE ◽  
...  
Keyword(s):  
Animal Model ◽  
Litter Size ◽  
Age Structure ◽  
Reproductive Performance ◽  
Genetic Improvement ◽  
Genetic Parameters ◽  
Factors Affecting ◽  
Optimal Weight ◽  
Annual Means ◽  
Lambing Rate

Conception and lambing rate, and litter size were studied on data from a flock of Horro sheep. The CATMOD and GLM procedures of SAS were used for the analysis of these traits. A sire, direct additive genetic and a repeatability animal model were employed to obtain estimates of heritability and repeatability for litter size. The results obtained showed that year of mating, age and weight of ewes at mating and number of previous parities had significantly (P<0.01) affected the rate of conception and lambing while weight of rams at mating has shown no significant effect (P>0.05). An increase in both conception and lambing rates was observed with the increase in weight of ewes up to about 36 kg and declined thereafter. Ewes which previously had no or one parity had lower conception and lambing rates compared with ewes in later parities. However, a decline in both conception and lambing rates was also observed in old ewes. Year of lambing, parity and weight of ewes at mating had a highly significant (P<0.01) effect on litter size. The overall mean litter size in the flock was 1.34 with annual means ranging from 1.18 to 1.55. Litter size increased with parity from 1.26 in primiparous ewes to 1.44 for ewes of parities five and above. With respect to weight of ewes at mating, litter size increased by 2.5% for each kg increase in weight at mating. The estimates of direct heritability (h2) for litter size were 0.17, 0.11 and 0.06 under the sire, direct animal and repeatability models. Repeatability was estimated to be 0.12. Since heritability and repeatability estimates of litter size are low, genetic improvement by selection may not bring sizeable impact in increasing litter size. Therefore flock management for optimal age structure and optimal weight of ewes at mating should receive due consideration to improve rates of conception, lambing and litter size in Horro sheep.

Genetic analyses of piglet survival and individual birth weight on first generation data of a selection experiment for piglet survival under outdoor conditions

2007 ◽  
Vol 2007 ◽  
pp. 65-65
Author(s):  
R. Roehe ◽  
N. P. Shrestha ◽  
W. Mekkawy ◽  
P. W. Knap ◽  
K. M. Smurthwaite ◽  
...  
Keyword(s):  
Birth Weight ◽  
Litter Size ◽  
Genetic Improvement ◽  
First Generation ◽  
Genetic Parameters ◽  
Selection Experiment ◽  
Postnatal Mortality ◽  
Breeding Programmes ◽  
Potential Benefits ◽  
Piglet Survival

Peri- and postnatal mortality of piglets is reported to be around 20% and genetic improvement in piglet survival has great potential benefits in terms of animal welfare, economics and the environment. The indication of an unfavourable genetic correlation between litter size and survival in particular points to the importance of including piglet survival in those pig breeding programmes that currently only aim to increase litter size. Phenotypically, individual birth weight is closely associated with piglet survival (Roehe and Kalm, 2000). Genetic parameters for piglet survival traits and individual birth weight therefore need to be estimated in order to genetically improve piglet survival efficiency

Factors affecting reproductive performance of white-tailed deer subjected to fixed-time artificial insemination or natural mating

2013 ◽  
Vol 25 (3) ◽  
pp. 581 ◽  
Author(s):  
Miguel Mellado ◽  
Claudia G. Orta ◽  
Eloy A. Lozano ◽  
Jose E. García ◽  
Francisco G. Veliz ◽  
...  
Keyword(s):  
Litter Size ◽  
Reproductive Performance ◽  
Artificial Insemination ◽  
Fixed Time ◽  
Arid Environment ◽  
Factors Affecting ◽  
Litter Weight ◽  
Subsequent Period ◽  
Natural Mating ◽  
Game Hunting

The objectives of this study were to examine the effects of several factors affecting fawning rate, litter size, litter weight and neonatal fawn mortality in white-tailed deer inseminated either transcervically or by means of laparoscopy. Oestrus synchronisation with a controlled internal drug release (CIDR)-based protocol and fixed-time artificial insemination (FTAI) was conducted in 130 white-tailed deer (Odocoileus virginianus texanus) during three reproductive seasons (2007–2009; 271 services) in a game-hunting ranch in a hot–arid environment (26°4′ N, 101°25′ W). Ninety additional non-treated does were exposed to bucks for natural mating. Fawning rate did not differ between AI methods (40.0 vs 45.0% for transcervical and laparoscopic AI, respectively). Overall fawning rate (proportion of all does fawning after FTAI and a subsequent period of buck exposure) did not differ between transcervical (89.5%), laparoscopic (80.3%) or natural (88.9%) insemination. Litter size per fawning doe was higher (P&lt;0.05) in naturally-served does (1.65±0.48) than in transcervically-inseminated does (1.40±0.51) or in laparoscopically-inseminated does (1.48±0.50). The main conclusion was that no enhancement of fawning rate or litter size occurred as a result of intrauterine deposition of semen by laparoscopy compared with the transcervical insemination technique.

Reproductive performance and genetic parameters for Australian Dorset Sheep

1994 ◽  
Vol 45 (2) ◽  
pp. 427 ◽  
Author(s):  
LD Brash ◽  
NM Fogarty ◽  
AR Gilmour
Keyword(s):  
Litter Size ◽  
Reproductive Performance ◽  
Genetic Improvement ◽  
Genetic Correlations ◽  
Reproductive Traits ◽  
Reproductive Rate ◽  
Parameter Estimates ◽  
Reproduction Traits ◽  
Component Traits ◽  
Lamb Survival

Reproductive performance of ewes in a large Dorset stud flock is reported. The data included 2488 ewes with 10016 joining records over 25 years. Average performance for reproductive traits were: fertility 92%, litter size 1.31, neonatal lamb survival 91%, lamb survival to weaning 85%, with overall lambs born 1.20 and lambs weaned 1.02 per ewe joined. Differences between breeds (Poll Dorset and Dorset Horn), season of birth (spring and autumn) and season of joining (spring and autumn) were significant for most reproduction traits. Linear and quadratic regressions for age of ewe at joining were highly significant for all traits (P < 0.001) with maximum performance between three and six years of age. Estimates of heritability for ewe reproductive traits were: 0.062 � 0-02 for number of lambs born and 0.04 � 0.01 for number of lambs weaned per ewe joined, and component traits, 0.02 �0 -01 for fertility, 0 08 � 0 -02 for litter size and 0.00 � 0.01 for lamb survival. Estimates of repeatability were less than 0.14 for all the reproduction traits, which resulted in substantially higher predicted heritabilities when repeated records were used. Heritability estimates for average ewe lifetime performance, with approximately four records, were 0.08 � 0 06 for lambs born, 0.12 � 0.05 for lambs weaned, 0.08 � 0.04 for fertility, 0.l9 � 0 -04 for litter size and zero for lamb survival. The genetic correlations between litter size and lambs born and weaned were close to unity, whereas those for fertility were lower and declined from lambs born (0.6l � 0.22) to lambs weaned (0-45 � 0.30). The estimated heritability for ewe longevity, defined as the number of years the ewe remained in the breeding flock, was 0.00 � 0.03. The potential for genetic improvement in reproductive rate is discussed in relation to other reports in the literature and in the context of the roles of the Dorset breed in the Australian lamb industry. Increased reproductive rate in Dorset flocks impacts on stud profitability and the rate of genetic improvement from selection for other traits such as liveweight. The parameter estimates derived will be used in compiling breed-specific parameter sets for genetic evaluation in LAMBPLAN.

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.

Bayesian estimation of genetic parameters of litter size at birth in crossbred Mule ewes using repeatability and multiple trait threshold models

2007 ◽  
Vol 2007 ◽  
pp. 66-66
Author(s):  
W. Mekkawy ◽  
R. Roehe ◽  
R. M. Lewis ◽  
M. H. Davies ◽  
A. M. Van Heelsum ◽  
...  
Keyword(s):  
Litter Size ◽  
Reproductive Performance ◽  
Genetic Parameters ◽  
Reproductive Traits ◽  
Threshold Models ◽  
Multiple Trait ◽  
Repeated Observations ◽  
Improvement Programs ◽  
Size At Birth ◽  
Estimation Of Genetic Parameters

The reproductive performance of ewes is a major factor influencing the economic success of lowland flocks. Even so reproductive traits have not often been included in sheep genetic improvement programs because of their low heritabilities compared with other performance traits like body weight and carcass merit. Litter size is one of the most important traits affecting reproductive performance. There are two important factors to be considered in the genetic analysis of litter size. First, several authors have suggested that litter size in different parities is controlled in part by different genes, and therefore should be treated as different traits. Second, ignoring the categorical nature of litter size and analysing it using a linear model does not account for its non-normal distribution. As a consequence, threshold models are likely to be more appropriate for the analysis of categorical traits (Gianola and Foulley, 1983). Therefore, the objective of the current study was to estimate the genetic parameters for litter size of Mule ewes using both repeatability and a multiple trait threshold models for repeated observations of litter size across four different parities.

Genetic parameters and non-genetic influences related to birth weight in farmed white-tailed deer

2013 ◽  
Vol 152 (3) ◽  
pp. 497-503 ◽  
Author(s):  
G. M. PARRA-BRACAMONTE ◽  
X. F. DE LA ROSA-REYNA ◽  
N. TREVIÑO-MARTÍNEZ ◽  
W. ARELLANO-VERA ◽  
V. MORENO-MEDINA
Keyword(s):  
Animal Model ◽  
Birth Weight ◽  
Genetic Parameters ◽  
Genetic Factors ◽  
Genetic Changes ◽  
Factors Affecting ◽  
Genetic Components ◽  
Life Traits ◽  
Best Fitting ◽  
Sources Of Variation

SUMMARYStudying and understanding the sources of variation in early life traits in farmed deer are fundamental for management and/or breeding purposes. Data from a captive white-tailed deer population were analysed to identify non-genetic and genetic factors affecting the birth weight (BW) of fawns. The year, type of birth and sex were included in a fixed linear model to examine their significance. All of the examined non-genetic factors had a highly significant effect on BW (P<0·001). The examined years showed variation attributed to food availability affecting the gestational conditions of does. Male fawns were 193 g heavier than female fawns at birth (P<0·001), and singleton births were associated with a higher BW (2·97±0·043 kg) compared with twin (−0·261 g) and triplet (−0·642 g) fawning (P<0·001). The best-fitting animal model was selected by comparing reduced and complete models. Based on the selected animal model, which included direct genetic and common maternal effects, genetic components and parameters were estimated. The direct heritability was found to be 0·28±0·126, and a small but important contribution of common maternal environmental effects was identified (c2=0·15±0·062). The results support the importance of certain environmental factors affecting BW and indicate the relevance of direct genetic and maternal environmental influences to sustained genetic changes in BW and positively correlated traits in farmed white-tailed deer populations.

scholarly journals Genetic parameters for test-day milk yield in tropical Holstein Friesian cattle fitting a multiple-lactation random regression animal model

1970 ◽  
Vol 47 (3) ◽  
pp. 352-361
Author(s):  
S. Meseret ◽  
E. Negussie
Keyword(s):  
Animal Model ◽  
Milk Yield ◽  
Genetic Improvement ◽  
Genetic Parameters ◽  
Genetic Correlations ◽  
Random Regression ◽  
Likelihood Method ◽  
Holstein Friesian ◽  
Heritability Estimates ◽  
Friesian Cattle

Accurate estimates of genetic parameters are essential for genetic improvement of milk yield in dairy cattle and for setting up breeding programmes. Estimates of genetic parameters from test-day models, particularly for Holstein Friesian cattle maintained in tropical environments, are scant in the literature. The objective of this study was therefore to estimate genetic parameters for milk yield by fitting a multiple-lactation random regression animal model (RRM) based on data from Ethiopian Holstein Friesian herds. Data were used from the first three lactations of cows that calved between 1997 and 2013. The data comprised 13 421 test-day milk yield records from 800 cows from two large dairy herds. Variance components were estimated using the average information restricted maximum likelihood method fitting an RRM. Heritability estimates for first, second, and third lactations ranged from 0.20 to 0.26, 0.15 to 0.27, and 0.17 to 0.28, respectively. Heritability estimates ranging from 0.15 to 0.28 indicate that effective genetic improvement should be accompanied by a corresponding improvement of the production environment. Across-lactation genetic correlations between first and second, second and third, and first and third lactations, expressed on a 305-day yield basis, were 0.88, 0.83, and 0.70, respectively. These genetic correlations, less than or equal to 0.88, indicate that different lactations are different traits. For an accurate evaluation of the genetic merit of animals for milk yield, lactations should be treated as different, but correlated traits in a multiple-lactation analysis.Keywords: Genetic correlation, heritability, Legendre polynomial, test-day model

A note on the fertility of hill ewes mated to Finnish Landrace and Border Leicester rams

1970 ◽  
Vol 12 (4) ◽  
pp. 673-675 ◽  
Author(s):  
J. D. Barker ◽  
R. B. Land
Keyword(s):  
Litter Size ◽  
Reproductive Performance ◽  
Lambing Rate

SUMMARYThe litter size and lambing rate of 1531 ewes of British hill breeds which had been mated to Finnish Landrace or Border Leicester rams was found to be independent of breed of ram. It was concluded that Finnish Landrace rams do not have a particular effect on the reproductive performance of ewes to which they are mated.

Estimation of genetic parameters for litter size in sheep: a comparison of a repeatability and a multivariate model

1998 ◽  
Vol 66 (3) ◽  
pp. 685-688 ◽  
Author(s):  
M. J. de Vries ◽  
E. H. van der Waaij ◽  
J. A. M. van Arendonk
Keyword(s):  
Animal Model ◽  
Genetic Correlation ◽  
Litter Size ◽  
Genetic Parameters ◽  
Genetic Correlations ◽  
Multivariate Model ◽  
Phenotypic Variance ◽  
Multiple Trait ◽  
Environmental Correlations ◽  
Estimation Of Genetic Parameters

AbstractGenetic parameters were estimated for litter size in two prolific sheep breeds, i.e. the Zwartbles and the synthetic breed Swifter. Genetic parameters and breeding values for litter size in different parities were estimated using both a repeatability and a multivariate animal model. The estimated heritability from the repeatability model was 0·10 for the Zwartbles and 0·12 for the Swifter. For the multivariate model, heritability of litter size in first, second and third parity was 0·05, 0·07 and 0·10 for the Zwartbles and 0·09, 0·12 and 0·09 for the Swifter. Genetic correlation for litter size in Swifter was 0·81 between parity 1 and 2 and 0·99 between parity 2 and 3. For the Zwartbles genetic correlations were all very close to unity. Environmental correlations between litter size in subsequent parities were not constant over parities. Phenotypic variance in litter size in both breeds was 0·309 in first parity and was almost 50% higher in later parities. Based on the results it is recommended to apply a multiple trait model.

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