Heritability For Age Research Articles

Genome-wide association study for age at puberty in young Nelore bulls.

Selection for bulls that would reach puberty early reduces the generation interval and increases fertility and herd productivity. Despite its economic importance, there are few QTL associated with age at puberty described in the literature. In this study, a weighted single-step genome-wide association study was performed to detect genomic regions and putative candidate genes related to age at puberty in young Nelore bulls. Several protein-coding genes related to spermatogenesis functions were identified within the genomic regions that explain more than 0.5% of the additive genetic variance for age at puberty in Nelore bulls, such as ADAM11, BRCA1, CSNK2A, CREBBP, MEIOC, NDRG2, NECTIN3, PARP2, PARP9, PRSS21, RAD51C, RNASE4, SLX4, SPA17, TEX14, TIMP2 and TRIP13 gene. Enrichment analysis by DAVID also revealed several GO terms related to spermatogenesis such as DNA replication (GO:0006260), male meiosis I (GO:0007141), double-strand break repair (GO:0006302), base excision repair (GO:0006284), apoptotic process (GO:0006915), cell-cell adhesion (GO: 0098609) and focal adhesion (GO:0005925). The heritability for age at puberty shows that this trait can be improved based on traditional EBV selection. Adding genomic information to the system helps to elucidate genes and molecular mechanisms controlling the sexual precocity and could help to predict sexual precocity in Nelore bulls with greater accuracy at younger age, which would speed up the breeding programme for this breed.

Estimation of genetic parameters for some performance traits in a selected Barred Rock line

This study was conducted to determine the genetic correlation and heritability for age at sexual maturity, body weight at sexual maturity, egg yield, egg weight, egg shape index and L*, a*, b* values of egg shell in a Barred Rock line was applied selection. For this aim, a total of 1622 pedigreed Barred Rocks were selected. The present estimated heritability values for investigated traits were found between moderate-to-high. However, the heritability of egg yield, eggshell color and body weight at sexual maturity were found lower than those of other traits. It was calculated positive correlations among monthly egg yields, especially between egg yield at the second month with total egg yield. As a conclusion, selection studies did not cause much decrease in genetic variation of studied traits, except for egg yield and body weight at sexual maturity. Monthly egg yield data can be used selection studies.

Influence of age at first calving in a continuous calving season on productive, functional, and economic performance in a Blonde d'Aquitaine beef population.

The lifetime production of 7,655 cows with known age at first calving and a total of 27,118 parity records from 301 purebred Blonde d'Aquitaine herds were used to demonstrate the economic benefits of 2 yr of age at first calving. Ages at first calving ranged from 20 to 48 mo, and cows were divided into 5 calving groups, starting with early calving from age 20 to 27 mo up to late calving from age 40 to 48 mo. The information was gathered into 2 data sets, one for only primiparous cows and the second for all cows. The traits analyzed in this study were grouped as functional, linear type, and production traits. Functional traits were calving interval, calving ease, and number of calvings. Skeletal, muscle, and functional appraisal were included as linear type traits. The production traits studied were BW and weaning weight, carcass growth, and conformation of the offspring. The only significant traits found in primiparous cows were late age at first calving, which resulted in heavier BW calves, and early age at first calving, which resulted in calves with greater carcass conformation scores. Age at first calving was found to be significant only in its effect on BW and the number of calvings over a cow's lifetime, with lighter calves for early age at first calving. Heritability for age at first calving was 0.17. Genetic correlation of age at first calving with direct calving ease was positive (0.27) and that with maternal calving ease was negative (-0.39). Age at first calving showed a negative genetic correlation with lifetime number of calvings (-0.29) and a positive correlation with calving interval (0.14). Correlations with production and type traits were low, except for skeletal development (-0.29). Based on phenotypic and genetic analysis, there is a tendency for early-calving cows to produce a greater lifetime number of calves with less muscle but good carcass growth. Age at first calving affected the number of heifers in the herd, replacement rate, and number of animals slaughtered each year. Shortening the age at first calving from 3 to 2 yr led to a reduction of heifer feeding cost of US$21.24 (17.7€), a reduction of production cost of $26.52 (22.1€), and a profit increase of $25.80 (21.50€) per slaughtered animal per year over lifetime cow production.

Genetics of reproductive performance in seasonal calving beef cows and its association with performance traits

Due primarily to a lack of phenotypic data, little research has been undertaken on the genetics of reproductive performance in beef cattle. The objective of this study was to quantify, using data from the Irish national cattle herd, the contribution of additive genetics to phenotypic differences in reproductive performance in beef cattle and to investigate whether routinely available early predictors of genetic merit for reproductive performance exist. Up to 218,718 parity records from 156,506 animals were used to estimate variance components for a range of reproductive traits using repeatability animal linear mixed models. Covariances with performance traits were estimated using bivariate sire linear mixed models. The reproductive traits were age at first calving, calving in the first 42 d of the calving seasons (defined separately in heifers and cows), calving interval between consecutive calving events, and survival to the next lactation. Performance traits included calving dystocia, linear type traits describing the skeletal, muscular, and functional characteristics of an animal, live weight and price, carcass traits, and producer subjectively scored traits of weanling quality and docility. Heritability for age at first calving was 0.31 while the heritability of the remaining reproductive traits ranged from 0.01 to 0.06; repeatability estimates varied from 0.02 to 0.06. Increased muscularity, measured either by trained assessors or producers on live animals, or by mechanical grading machines on slaughtered animals (i.e., carcass conformation), was genetically correlated with reduced reproductive performance for some of the reproductive variables assessed. This is one of the largest studies undertaken on the genetics of reproduction in beef herds and clearly shows that genetic selection for improved reproductive performance in beef herds is feasible. However, breeding goals that select for muscularity and live weight or growth rate should be cognizant of indirect response to selection that may cause any deterioration in reproductive performance.

Animal Model Estimation of Genetic Parameters for Most Important Economic Traits in Iranian Native Fowls

(Co)Variance components and genetic parameters for economic traits in Iranian native fowls were estimated using multivariate animal model analysis with DFREML procedure. The data of four stations of native fowls breeding (Mazandaran: 49536, Esfahan: 23108, West Azarbaijan: 24890 and Fars: 30279) was containing records of cocks and hens collected during period of 1988 to 2006. The recorded traits were Body weight (at 8 weeks or 12 weeks), Age at first egg, egg number at 12 first weeks of production and mean egg weight between 28 to 32 weeks. The most estimated heritabilites, except egg number, were more than 0.20. The highest heritabilites for all traits were related to Fars station, whereas most heritabilites in West Azarbaijan were less than other stations. The heritability for egg number was estimated 0.099+/-0.018 for Esfahan to 0.322+/-0.012 for Fars. The estimated heritabilities of body weight were medium to high and varied from 0.228+/-0.014 for Esfahan to 0.548+/-0.014 for Fars, While, the heritabilities of mean egg weight were high and ranged from 0.223+/-0.021 for West Azarbaijan to 0.638+/-0.013 for Fars. The heritability for age at first egg was estimated 0.270+/-0.021 for Esfahan to 0.520+/-0.014 for Fars. The most estimated genetic correlations, except between Body weight and Egg weight and between age at first egg and egg weight, were negative. The direct genetic correlations between maturity age and egg number were high and negative, ranging from -0.384+/-0.033 to -0.987+/-0.003 for Mazandaran and Fars, respectively.

Genetic improvement of farmed tilapias: estimation of genetic variation and heritability for age and size at first spawning in Nile tilapia ( Oreochromis niloticus)

Genetic improvement of farmed tilapias: estimation of genetic variation and heritability for age and size at first spawning in Nile tilapia ( Oreochromis niloticus)

Direct and maternal genetic parameters of fertility traits in Friesian cattle

Variance and covariance components for sire of cow and sire of insemination of fertility traits were estimated by parity using REML procedures. Subsequently direct genetic and maternal components were calculated. Heritabilities for 56-day non-return rate, conception rate (heifers, parity one to three) and days open (parity one to three) varied between 0.007 and 0.049. The heritability for age at conception in heifers was 0.192. The maternal component for days open was greater than the direct genetic component. The genetic correlations between sire of insemination and sire of cow for non-return rate changed from −0.29 in heifers to 0.59 in parity three, that for conception rate from −0.74 to 0.48. The relation between maternal and direct genetic components changed from −0.94 to 0.26 and −0.97 to 0.12 for non-return and conception rates, respectively. Changes in correlations for days open from parity one to three were smaller. The results indicated that the genetic correlation between the sire of cow components for non-return and conception rate in heifers, first parity and older cows may differ from unity.

Response to individual selection for age at sexual maturity in Atlantic salmon

Atlantic salmon ( Salmo salar) that mature sexually at 1 year of age (as parr or precocious males), at 4 years of age (after two winters in the sea) and at 5 years of age (after three winters in the sea) were used to study response to individual selection for age at sexual maturity. Six mating groups were made: between fish of the same age (4 × 4 and 5 × 5); reciprocal matings between 4- and 5-year-old fish (4 × 5 and 5 × 4); and matings between 1-year-old precocious males and 4- and 5-year-old females (1 × 4 and 1 × 5). Parental age at sexual maturity was found to influence markedly the offspring age at sexual maturity. The heritability for age at maturity in the sea was estimated at 0.48 ± 0.20 from the offspring—dam regression. It is concluded that there is considerable opportunity to alter the age at sexual maturity in Atlantic salmon through selection. Evidence was found that maturation of parr is a heritable trait and that it is independently inherited from maturation in the sea.

Age at first egg and egg production--their inheritance and expected response to different methods of selection.

Synopsis Data pertaining to a closed White Leghorn flock maintained at the Punjab Agricultural University were used for estimating genetic and phenotypic parameters for age at first egg and 70‐d egg production and also to evaluate the expected response to different methods of selection. Records of 2377 pullets, a progeny of 1001 dams and 155 sires over a period of two years, were used. The birds in this flock attained sexual maturity on an average at the age of 176.6 d and produced on an average 33.6 eggs in first 70 d of egg production. Heritability for age at first egg and 70‐d egg production was obtained from different observational components. Age at first egg was found to have a medium heritability, the estimates being 0.370 ±0.003, 0.080 ±0.016 and 0.224 + 0.040 from sire, dam and full sib components, respectively. The heritabilities for 70‐d egg production were low. The estimates were 0.132±0.004, 0.214±0.011 and 0.173±0.06 from sire, dam and full sib components, respectively. Phenotypic, genetic a...