Heritability Of Reproductive Traits Research Articles

47 Genomic Studies of Reproductive Performance in American Mink

Abstract Improving reproductive efficiency is one of the main breeding goals in mink farming. Understanding the genetics of reproductive performance is essential for the development of effective breeding programs in mink. The objectives of this study are to 1) estimate the phenotypic and genetic parameters for litter sizes (LS), mortality rate at birth. (MB) and gestation-length (GL) traits; 2) perform genome-wide association studies (GWAS) for these reproductive traits; 3) implement GWAS results in the selection of mink for reproductive performance; 4) explore the potential for genomic selection in mink. The detailed reproductive performance on 3,500 female mink has been collected at the Canadian Center for Fur Animal Research at Dalhousie University (Truro, NS, Canada), in which, 1,000 of them will be genotyped with Affymetrix 50k SNP panel. A series of univariate and bivariate analyses were implemented in ASREML software to estimate the genetic and phenotypic parameters. Heritability estimates (±SE) were low-to-moderate, ranged from 0.06±0.02 for total number born to 0.23±0.03 for GL. High positive genetic correlations (±SE) were observed between LS traits, ranged from 0.59±0.18 to 0.85±0.11. There was a moderate genetic correlation (±SE) between MB and total number of kits born (0.46±0.15). However, MB had a favorable strong negative genetic correlation (±SE) with the number of weaned kits (–0.75±0.16). These estimated genetic parameters can be incorporated into Canadian mink breeding programs. Considering the low-to-moderate heritability of reproduction traits, the availability of the mink reference genome and genotyping panel will provide opportunities to accelerate mink breeding through genomics. The results of this project will contribute significantly to the current genetic knowledge of reproductive traits and identify the opportunities for genetic improvement through the application of genomics. The overall project aim is to develop a cost-effective, low-density panel of markers for the implementation of genomic selection for reproductive performance in mink.

Estimation of Heritability for Reproductive Traits and Newborn Mortality in Iraqi Buffaloes through the Relationship of Dams with Daughters

Estimation of Heritability for Reproductive Traits and Newborn Mortality in Iraqi Buffaloes through the Relationship of Dams with Daughters

Estimation of Genetic Parameters for Reproduction Traits in Munjal Sheep

Estimates of genetic parameters are important to determine the selection criterion and future breeding strategies. Munjal is one of the heaviest breed of sheep and is popular among farmers for faster growth rate and efficient reproduction. The data of reproduction traits of 287 Munjal sheep maintained at Lala Lajpat Rai University of Veterinary and Animal Sciences, Hisar for 16 years (2001-2016) were utilized to estimate the genetic parameters. The mixed linear model used for analysis included the sire as a random effect and period of birth and dam’s age at lambing as fixed effects. Heritability and genetic correlations for different traits were estimated by paternal half-sib correlation method using sire components of variance and covariance. All the reproduction traits under study viz., Age at first service (AFS), weight at first service (WFS), age at first lambing (AFL), weight at first lambing (WFL) and first lambing interval (FLI) were significantly affected by period of birth. However, effect of dam’s age at lambing was non-significant on all traits. The overall least squares mean for AFS, WFS, AFL, WFL and FLI were estimated as 563.08±14.43days, 29.06±0.16 kg, 713.48±14.02 days, 31.30±0.16 kg and 351.82±1.12 days, respectively. Heritability estimates for AFS, WFS, AFL, WFL and FLI were obtained 0.19±0.12, 0.24±0.15, 0.17±0.10, 0.27±0.15 and 0.05±0.01, respectively. The genetic correlation of AFS with AFL (0.96±0.01) and WFS with WFL (0.94±0.03) was high and positive indicating that ewes in good body condition at service maintaining it after lambing. Low estimates of heritability for reproduction traits indicated that these traits have low additive genetic variance and mostly influenced by environment. So, these traits can be improved by better managemental practices.

Genetic control of complex traits, with a focus on reproduction in pigs.

Reproductive traits are complex, and desirable reproductive phenotypes, such as litter size or semen quality, are true polygenetic traits determined by multiple gene regulatory pathways. Each individual gene contributes to the overall variation in these traits, so genetic improvements can be achieved using conventional selection methodology. In the past, a pedigree-based-relationship matrix was used; this is now replaced by a combination of pedigree-based- and genomic-relationship matrices. The heritability of reproductive traits is low to moderate, so large-scale data recording is required to identify specific, selectable attributes. Male reproductive traits-including ejaculate volume and sperm progressive motility-are moderately heritable, and could be used in selection programs. A few high-merit artificial-insemination boars can impact many sow populations, so additional knowledge about male reproduction-specifically pre-pubertal detection of infertility and the technologies of semen cryopreservation and sex sorting-should further improve global breeding efforts. Conversely, female pig reproduction is currently a limiting factor of genetic improvement. Litter size and farrowing interval are the main obstacles to increasing selection intensity and to reducing generation interval in a breeding program. Age at puberty and weaning-to-estrus interval can be selected for, thereby reducing the number of non-productive days. The number of piglets born alive and litter weights are also reliably influenced by genetic selection. Characterization of genotype-environment interactions will provide opportunities to match genetics to specific farm systems. Continued investment to understand physiological models for improved phenotyping and the development of technologies to facilitate pig embryo production for genetic selection are warranted to ensure optimal breeding in future generations.

Genetic associations between reproductive and linear-type traits of Holstein cows in Brazil

This study aimed to estimate heritability, genetic, and residual correlations between reproductive traits such as age at first calving, calving interval, dry period, and first service period and linear type traits measured in Holstein cows born between the years 1990 and 2008 in Brazil. The (co)variance components were estimated by restricted maximum likelihood, using the MTDFREML software. The heritability for reproductive traits and linear-type traits ranged from 0.02 to 0.03 and from 0.07 to 0.40, respectively. Estimates of genetic correlations between reproductive and linear-type traits ranged from -0.23 (top line) to 0.28 (angularity) to age at first calving, from -0.54 (final score) to 0.34 (foot angle) to calving interval, from -0.23 (angularity) to 0.56 (stature) to dry period, and from -0.52 (final score) to 0.36 (height udder) to first service period. Direct selection for any of the reproductive traits implies low genetic gains by virtue of their low heritabilities. Among the linear-type traits, the final score, chest width, top line, angularity, teat length, udder attachment, rear teat placement were highlighted as good auxiliary traits to improve reproductive efficiency of Holstein cows in Brazil. The simultaneous selection for reproductive and linear-type traits can lead a higher genetic progress in the reproductive traits.

Estimation of genetic parameters of various economic traits in a synthetic broiler dam line

A study to estimate heritability, genetic and phenotypic correlations for growth and egg production traits was carried out with the data pertaining to1624 broiler dam line maintained at Poultry Breeding Farm of Department of Animal Genetics and Breeding, LUVAS, Hisar. Traits recorded during the study were body weights at 6, 20 and 40 weeks, age at first egg, egg weight, egg number, egg mass, clutch, pause size up to 40 weeks of age, percent fertility of selected pullets, percent hatchability on total egg set basis and percent hatchability on fertile egg set basis. As per results, the pooled least squares means of BW6, BW20 BW40 AFE, EN40 EW40, EM40 CS, PS, PF, TES and FES 832.81±4.80 g, 2314.24±23.33 g, 2912.49±30.31 g, 147.89±0.77 days, 79.37±0.64, 53.18±0.21’g, 4220.67±35.74 g, 2.74±0.05 eggs, 1.97±0.08 days, 81.04±0.60 %, 59.65±0.76 % and 72.86±0.64 % respectively. Results pointed out that the effect of hatch within generation was significant (P<0.01) on the BW20, BW40, AFE, EW40, EN40, EM40, CS, PS, PF, TES and FES. The heritability of growth traits, production traits and reproduction traits ranged from 0.14±0.06 to 0.23±0.08, 0.22±0.08 to 0.32±0.11 and 0.15±0.29±0.07 respectively. Low to moderate estimates of heritability for growth and production traits and moderate estimates of heritability for reproduction traits indicated that these traits can be improved through family selection.

Reproductive Performance of Harnali Sheep

The 22 years (1992–2013) data pertaining to reproductive traits of 862 Harnali sheep developed by inter se mating of Corriedale and Russian Merino with Nali maintained at Lala Lajpat Rai University of Veterinary and Animal Sciences, Hisar, were analysed. The overall least squares means for age at first lambing (AFL), weight at lambing (WL) and average lambing interval (ALI) were 707.05±2.07 days, 26.91±0.10 kg and 402.85±2.40 days, respectively. The effects of year of birth and dam's weight at lambing were significant (P<0.01) for all the traits except the effect of year on ALI. No definite trend was observed over the years for the means of reproductive traits. Heritability estimates for AFI, WL and ALI traits were low and recorded as 0.02±0.05, 0.05±0.06 and 0.01±0.05 respectively. Genetic correlation of ALI with WL was negative. Phenotypic correlations of AFL with WL and ALI were positive and significant. Low estimates of heritability of reproduction traits indicate that phenotypic selection based on these traits cannot result in considerable genetic improvement.

Genetic parameters and correlated responses in female reproductive traits in the GIFT strain

The effect of selection for greater growth rate in the GIFT strain on traits related to female reproduction (weight at spawning, number of eggs, number of fry, total weight of fry and number of dead fry) was studied. Available records comprised 10 generations of data from a total of 935 breeding females with known pedigree. Female body weight at spawning was 255 g, whereas the averages for number of eggs, number of live fry at hatching, number of dead fry and total fry weight per spawning were 1444, 908, 64.90, and 7.24 g respectively. Heritabilities for reproductive traits were low to moderate (0.20 for number of eggs, 0.16 for number of hatched fry and 0.11 for fry weight per female at spawning). The genetic correlations between female body weight at spawning and reproductive traits were very low to low (0.01 to 0.31) and not significantly different from zero. The genetic correlations among reproductive traits (i.e. number of eggs, number of hatched fry and fry weight) were high (0.75 to 0.92). Phenotypic correlations were consistent with the genetic correlations, ranging from 0.56 to 0.85. Correlated responses in reproductive traits measured as differences in least squares means between Selection and Control lines were positive and significant (except for the number of dead fry) when age of females at spawning was fitted as a covariate. However, there were no significant differences in all studied traits when body weight of the female at spawning was fitted as a covariate within lines. This indicates that the greater reproductive rate was due to the greater size of females in the Selection line, but the efficiency of reproduction per unit weight of female did not change as a consequence of selection for growth.

Genetic Parameters and Genetic Gain for the Reproduction Traits in Latvian Landrace and Yorkshire Sows Populations

The aim of this study was to estimate genetic parameters for the reproduction traits of Landrace and Yorkshire sows and to analyze the genetic gain in these Latvian swine populations. Records of 14 577 first-parity and 27 359 later-parities Landrace sows and 6039 first-parity and 12 360 later-parities Yorkshire sows born between 2000 and 2012 were included in the analysis. The number of piglets born alive and 21-day litter weight at first and later parities, and weaning–conception interval between the first and second parity were included in the study. The genetic parameters were estimated using a single-trait animal model for the first parity and a single-trait repeatability animal model for later parities using REML procedure. Compared to heritability estimates for number born alive, heritabilities for litter weight were higher in both populations: in the first parity 0.10±0.015 vs. 0.31±0.021 for Landrace, and 0.05±0.016 vs. 0.23±0.028 for Yorkshire; in later parities 0.10±0.010 vs. 0.23±0.013 for Landrace, and 0.10±0.017 vs. 0.20±0.022 for Yorkshire. The heritability of reproduction traits was low; however, during the last ten years, reproduction traits in nucleus herds were improving. The results show that genetic progress in the last five years has been relatively low.

19 THE EFFECT OF FOLLICLE-STIMULATING HORMONE IN A MODIFIED CO-SYNCH SYNCHRONIZATION PROTOCOL ON SUBSEQUENT PREGNANCY RATES OF CROSSBRED LACTATING BEEF CATTLE

Heritability of reproductive traits is relatively low, leaving only management strategies as an alternative to affect reproductive efficiency in beef cattle. The use of assisted reproductive technologies such as fixed-timed AI (FTAI) offers the ability to increase reproductive efficiency through selection of superior genetics and manipulation of calving dates through estrous-synchronization protocols. Application of these technologies has not been fully embraced by cattlemen due to variation in success rate, primarily associated with the apparent lack of control of follicular waves. While it has been reported that an endogenous increase in FSH precedes the emergence of follicular waves in cattle, we could find no reports on the effects of exogenous FSH on FTAI pregnancy rates. Artificial insemination remains the most important reproductive technology that could positively affect cattlemen. Therefore, this experiment was conducted to test the hypothesis that incorporation of FSH into the CO-Synch synchronization protocol would increase FTAI pregnancy rates in beef cattle. Crossbred beef cows (n = 182) with a mean body weight (BW) of 596 ± 6.6 kg and mean body condition score (BCS) of 5.4 ± 0.07 from 3 different locations were stratified across treatment groups by BW, BCS, and days postpartum or cyclicity status based on plasma progesterone concentrations. Females were estrus synchronized using the 7-day CO-Synch+CIDR protocol. All females received a CIDR insert and 100 µg of gonadotropin-releasing hormone (GnRH; Factrel) on Day 0, followed by CIDR removal, 25 mg of prostaglandin (Lutalyse) IM and fitted with an estrus-detection patch (Estrotect) on Day 7. On Day 2, all females (n = 92) in the FSH treatment group were administered 20 mg of FSH (Folltropin) IM and the remaining females (n = 90) served as nontreated controls. Fixed-timed AI was performed at 72 h following CIDR removal when all females were administered 100 µg of GnRH and the estrus-detection patch was evaluated. The overall FTAI pregnancy rate was 55% (100/182) and there was no difference (P = 0.41) in pregnancy rates across locations so the data were pooled and reanalyzed. Pregnancy rates were not affected (P = 0.54) by treatment group and were 52% (48/92) for the FSH-treated females and 58% (52/90) for the nontreated control group. Similarly, based on evaluation of the estrus-detection patch, there was no difference (P = 0.68) in the percentage of females responding to the synchronization protocol [61% (55/92) v. 68% (61/90)] and no difference (P = 0.55) in the pregnancy rate of responding females [62% (34/55) v. 69% (42/61)] for the FSH-treated and nontreated control groups, respectively. In conclusion, administration of FSH 10 days prior to FTAI in CO-Synch+CIDR synchronized crossbred beef cows did not increase subsequent pregnancy rates. However, exogenous FSH administration should be evaluated further to determine its effects, if any, on follicular dynamics related to FTAI in the lactating beef cow.

Achieving Reproductive Efficiency in Beef Cow Herds

Excellent reproductive efficiency can be achieved in a beef herd by using a multifaceted approach focusing on herd production and management issues. Numbers that would define reproductive efficiency for most herds would include a 90-95% pregnancy rate, less than 2% abortion rate with 65, 88, and 100% of the calves born by days 21, 42, and 65 of the calving season, respectively. Heritability of reproductive traits tends to be low and disease causing reproductive failure in beef herds is uncommon in many parts of North America. Heifer selection and development, nutrition and utilizing heterosis are some of the keys to success. Efficiency is not synonymous with maximums, but rather is more closely aligned to ‘optimums’. Recent research with cost control as the core of heifer development shows that heifers can be developed more efficiently than previously thought.

GENETIC ANALYSIS OF REPRODUCTIVE TRAITS IN BALI CATTLE MAINTAINED ON RANGE UNDER ARTIFICIALLY AND NATURALLY BRED

The aim of this study was to evaluate genetic analysis including heritability and further phenotypicand genetic trends of reproductive traits in Bali cattle. Reproductive traits studied were age at firstcalving (AFC), calving interval (CI) and pregnancy rate (PR). Data of reproductive traits were collectedfrom Breeding Centre of Bali Cattle, Denpasar-Bali at the year period of 2000-2007. To evaluate thegenetic analysis, heritability were estimated using the Mixed Model Least Squares and MaximumLikelihood procedure. The phenotypic and genetic trends were calculated using regression equation.Estimation of heritability for AFC, CI and PR were 0.22, 0.41 and 0.40, respectively. The phenotypictrend of AFC, CI and PR decreased at an average rate of 1.70 month, 10.4 days and 0.75% per year,respectively. The same pattern was showed for genetic trends for AFC, CI and PR decreased at 0.38month, 4.25 days and 0.30% per year respectively in the same period. The heritability of reproductiontraits in Bali cattle were considered as moderate to high (0.22-0.41) which means that the selectionprogram will be more effective and efficient in improving the genetic merits in Bali cattle.

8 EFFECT OF CIRCULATING LEPTIN LEVELS AT SYNCHRONIZATION ON SUBSEQUENT FIXED-TIMED ARTIFICIAL INSEMINATION PREGNANCY RATES IN CROSSBRED BEEF HEIFERS

It is generally accepted that reproductive efficiency is the limiting factor in the profitability of most livestock operations. The heritabilities of reproductive traits are typically low, so most advances in reproductive efficiency must be achieved through changes in management practices. Recent research indicates that leptin may play a role in the reproductive processes for many domesticated livestock species. Leptin has been shown to affect nutrient intake, metabolic efficiency, and animal adiposity, and may be associated with age at puberty onset and the length of the postpartum interval in cattle. Therefore, the objective of this study was to determine whether circulating leptin concentrations during estrous synchronization would affect subsequent pregnancy rates after fixed-timed AI (FTAI) in crossbred beef heifers. Before the initiation of the spring breeding season, 54 crossbred (Red Angus × Simmental) long yearling heifers, averaging 326 ± 6.3 kg with a mean body condition score (BCS) of 5.2 ± 0.33, a mean reproductive tract score of 2.1 ± 0.57, and a mean ovary score of 2.7 ± 0.76, were synchronized with a controlled internal drug-release (CIDR) vaginal implant and 2 mg of estradiol benzoate (EB) on Day 0, a 25-mg injection of prostaglandin and CIDR removal on Day 7, and 2 mg of EB on Day 8, with FTAI occurring 52 hours post-CIDR removal. Blood samples were collected via jugular venipuncture 4 times: twice during the synchronization protocol starting 2 days post-CIDR insertion, once at insemination, and once 4 days after insemination. All females were inseminated with frozen–thawed semen from the same fertile bull. Pregnancy was determined 45 days postinsemination via transrectal ultrasonography. Twenty females (37%) were confirmed pregnant to FTAI. There was no difference in average weights (324 ± 6.6 v. 323 ± 3.7 kg), BCS (5.1 ± 0.1 v. 5.2 ± 0.07), reproductive tract scores (2.2 ± 0.5 v. 2.1 ± 0.5) or ovary scores (2.7 ± 0.2 v. 2.7 ± 0.1) for the pregnant and nonpregnant females, respectively. However, those females that were pregnant from FTAI had higher (P = 0.02) mean plasma leptin concentrations (3.33 ± 0.22 ng mL–1) compared with heifers that did not conceive to FTAI (2.66 ± 0.19 ng mL–1) across all sampling days. In addition, as early as 2 days post-CIDR insertion, females that became pregnant from FTAI tended to have higher (P = 0.13) plasma leptin concentrations (2.76 ± 0.18 ng mL–1) compared with those heifers that did not conceive to FTAI (2.19 ± 0.15 ng mL–1). These results indicate that circulating plasma leptin levels in beef cattle during synchronization may be associated with subsequent fertility and might be a useful tool to select females to increase the efficacy of FTAI protocols in beef cattle.

138 GENETIC PARAMETER ESTIMATION FOR EMBRYO TRANSFER TRAITS

Genetic selection has made tremendous progress on economically important traits in the beef industry. Most of the progress has been from quantitative genetics through use of expected progeny differences (EPD). These values allow prediction of differences in progeny of a sire compared to progeny of other sires. Development of EPD for male and female reproductive traits has largely been ignored because of low heritability of reproductive traits, even though reproduction plays a vital role in the economics of beef operations. Therefore, continued research in the area of genetic selection for fertility is becoming increasingly important. Critical limiting factors for animal breeding programs using MOET nucleus schemes include variability in superovulatory response of donor animals and resulting pregnancy of transferred embryos. Thus, the overall objective of this research was to develop genetic parameters associated with MOET to assist producers in identifying animals with greater genetic merit for these protocols. Records were examined from a large-scale MOET system in beef cattle that contained data only for cows in which at least one transferable embryo was obtained. Data on these animals were extracted and analyzed on 10 425 transferred embryos (2900 collections) from 611 donor animals (Angus, Brangus, and Charolais) utilizing semen from 215 bulls. Phenotypic traits examined included pregnancy status of the recipient following transfer (ET-preg; determined by rectal palpation at 60 days post-transfer and/or confirmed calving date of recipient), number of transferable embryos per collection (ET-trans), and number of unfertilized ova at collection (ET-UFO). Basic statistical analysis and pedigree/trait files were developed using procedures in SAS (SAS Institute, Cary, NC). Genetic parameters were estimated for a single-trait animal model using restricted maximum likelihood (REML) procedures in Wombat (Meyer K 2007 Zhejiang Uni. Science B 8, 815–821). Wombat also computed EPD and standard errors for each trait evaluated. The model included fixed effects of year as well as random animal and residual effects. The EPD for ET-preg ranged from –6.1 to 4.4% (SE = 2.2 to 4.2) for semen sires (sires of the transferred embryos) and –5.3 to 3.8% (SE = 3.2 to 4.2) for donor animals. Additionally, the heritability estimated for ET-preg was 0.03. Heritability estimated for ET-trans was 0.00, indicating minute genetic variation and thus, EPD were not presented. Heritability estimated for ET-UFO was 0.05 with EPD values (deviation of the number of UFO from the mean) ranging from –0.6 to 0.8 (SE = 0.3 to 0.6) for semen sires and –0.4 to 1.1 (SE = 0.5 to 0.6) for donor cows. As previously shown for reproductive traits, heritability of ET-preg, ET-trans, and ET-UFO was low. Genetic improvement in fertility by selection on embryo transfer traits is possible, but progress would be slow. Further studies are underway on a larger dataset to refine these estimates and to examine repeatability.

Heritability of reproductive traits and genetic correlations with growth in the black tiger prawn Penaeus monodon reared in tanks

Captive-reared broodstock of the black tiger prawn ( Penaeus monodon) have exhibited poor reproductive performance limiting attempts to domesticate this species. The potential for improved reproductive performance was assessed by determining heritabilities of four measures of reproductive performance, their genetic correlations with each other and with growth rate and weight at age. Heritability estimates ( h 2 ± S.E.) obtained from √ (days to spawn), √ (egg number), √ (nauplii number) and arcsin√ (proportion hatched) were 0.47 ± 0.15, 0.41 ± 0.18, 0.27 ± 0.16, and 0.18 ± 0.16, respectively. Estimates of genetic correlations between reproductive traits and weight at age, or growth rate were less than 0.5 except for √ (egg number) and weight at 54 weeks (0.93 ± 0.19) and √ (egg number) and 16–54-week growth (0.63 ± 0.29).

Repeatability and heritability of reproductive traits in free‐ranging snakes

The underlying genetic basis of life-history traits in free-ranging animals is critical to the effects of selection on such traits, but logistical constraints mean that such data are rarely available. Our long-term ecological studies on free-ranging oviparous snakes (keelbacks, Tropidonophis mairii (Gray, 1841), Colubridae) on an Australian floodplain provide the first such data for any tropical reptile. All size-corrected reproductive traits (egg mass, clutch size, clutch mass and post-partum maternal mass) were moderately repeatable between pairs of clutches produced by 69 female snakes after intervals of 49-1152 days, perhaps because maternal body condition was similar between clutches. Parent-offspring regression of reproductive traits of 59 pairs of mothers and daughters revealed high heritability for egg mass (h2= 0.73, SE=0.24), whereas heritability for the other three traits was low (< 0.37). The estimated heritability of egg mass may be inflated by maternal effects such as differential allocation of yolk steroids to different-sized eggs. High heritability of egg size may be maintained (rather than eroded by stabilizing selection) because selection acts on a trait (hatchling size) that is determined by the interaction between egg size and incubation substrate rather than by egg size alone. Variation in clutch size was mainly because of environmental factors (h2=0.04), indicating that one component of the trade-off between egg size and clutch size is under much tighter genetic control than the other. Thus, the phenotypic trade-off between egg size and egg number in keelback snakes occurs because each female snake must allocate a finite amount of energy into eggs of a genetically determined size.

Heritability for reproduction traits in Polish and Norwegian populations of dairy goat

Estimation and verification of the variance components of the reproduction traits in dairy goats was the purpose of the investigation. The study included Polish and Norwegian populations. Since the numbers of goats were generally lower and the pedigree information poorer, in the Polish population, the results obtained for the Norwegian one were treated as the reference. The Polish data included records on 9283 goats maintained in herds from 1983 till 2001. The information on the first parity litter size (LS1), number of kids born alive (NBA1), and total losses (TL1) regarded 8479 does while the data on the second parity traits (LS2, NBA2, TL2) included 5729 does. Age at first kidding (AK1) was known for 7370 does and age at second kidding (AK2) and kidding interval (KI)—for 4545 does. The pedigree included 13 618 animals with the eldest born in 1977. The Norwegian data set covered 68 240 does with 64 903 having recorded LS1 and K1, 51 266—LS2 and AK2, and 45 704—KI. The goats were maintained from 1991 till 2002. The pedigree data covered 150 677 animals with the eldest born in 1966. The variance components were estimated with the REML method using animal model. The heritability estimates of LS1, NBA1, TL1, and AK1 were 0.14, 0.11, 0.04, 0.13; of LS2, NBA2, TL2, and AK2—0.11, 0.09, 0.04, and 0.13, in the Polish population. The heritability of KI reached only 0.015. In the Norwegian population the heritabilities of LS1, LS2, and KI were 0.18, 0.13, and 0.03, respectively. The estimates of heritabilities in the second parity were lower or at most equal to those in the first one. The magnitude of the heritability estimates for LS1, LS2, NBA1, and NBA2 indicate possibility of an effective selection for those traits.

Predicting efficiency of selection on reproductive traits in the medicinal leech Hirudo medicinalis L

A set of selection measures for increasing reproduction efficiency in Hirudo medicinalis has been developed. The optimal values of reproductive traits corresponding to the highest progeny number were determined and recommended. The probability of correlated selection response in traits "number of threads in a cocoon" and "weight of threads" was estimated. Based on earlier results on phenotypic variation and heritability of reproductive traits in medicinal leech, efficiency of different selection modes was predicted.

Estimation of additive and non‐additive genetic parameters for reproduction, growth and survival traits in crosses between the Moroccan D’man and Timahdite sheep breeds

Genetic breed differences, heterosis, recombination loss, and heritability for reproduction traits, lamb survival and growth traits to 90 days of age were estimated from crossing D’man and Timahdite Moroccan breeds. The crossbreeding parameters were fitted as covariates in the model of analysis. The REML method was used to estimate (co)variance components using an animal model. The first estimation of crossbreeding effects for Timahdite and D’man breeds shows that breed differences in litter traits are mainly of maternal genetic origin: +1.04 lambs, +1.88 kg, +0.60 lambs, and +2.23 kg in favour of D’man breed for litter size at lambing, litter weight at lambing, litter size at weaning, and litter weight at 90 days, respectively. The breed differences in lamb growth and survival are also of maternal genetic origin for the majority of traits studied, but in favour of the Timahdite breed: +3.48 kg, +45 g day−1 and +0.19 lambs for weight at 90 days, for average daily gain between 30 and 90 days of age, and for lamb survival to 90 days, respectively. The D’man direct genetic effect was low and negative for survival and birth weight of lambs during the first month of life. All traits studied showed positive heterosis effects. Recombination loss effects were not significant. Therefore, crossbreeding of Timahdite with D’man breeds of sheep can result in an improved efficiency of production of saleable lambs. Heritability estimates were medium for litter size but low for the other reproduction traits. Direct heritabilities were low for body weights and lamb survival at 90 days and the corresponding maternal heritabilities showed, however, low to moderate estimates. For litter traits, the estimates of genetic and phenotypic correlations were positive and particularly high for genetic correlations.

Heritabilities of reproductive traits in a beef cattle herd using multitrait analysis

Extracted from text ... Heritabilities of reproductive traits in a beef cattle herd using multitrait analysisR.R. van der Westhuizen 1 , S.J.Schoeman 1 , G.F. Jordaan 1 and J.B. van Wyk 21 Dept of Animal Science, University of Stellenbosch, P Bag X1, Matieland, 76022 Dept of Animal Science, University of Orange Free State; P O Box 339,Bloemfontein, 9300IntroductionReproduction is a critically important aspect of overall efficiency in the livestock industry. However,reproduction is a complex process with many components. Several such components have been used as measuresof reproductive performance. Calving interval (CI), calving rate, services per conception, age at first calving(AFC), days to calving and ..