Genetic parameter estimates for reproductive traits of male and female littermate swine

Reproductive traits of purebred and crossbred pigs produced in a four-breed diallel mating system using the Duroc, Landrace, Spotted and Yorkshire breeds were collected for five consecutive farrowing seasons (two farrowing seasons/year) beginning in fall 1976. Paternal half-sib heritabilities and genetic correlations for testicular traits (120 boars from 36 sires), serum testosterone (TE) and luteinizing hormone (LH) concentrations before and after treatment with gonadotropin releasing hormone (GnRH; 131 boars from 37 sires) and breeding performance traits (151 boars from 38 sires) were estimated. Heritability estimates were generally small to moderate except for sperm/gram testis (SGT), LH concentrations before (LHO) and at 3 h (LH3) after treatment with GnRH (.73 +/- .48, .61 +/- .46 and 1.19 +/- .45, respectively). A large positive genetic correlation was found for LHO with LH3 (.94 +/- .39), while a negative relationship existed for LH3 with TE concentrations at 3 h after GnRH injection. The genetic correlation between a boar's average first service conception rate and average conception rate also was significant (.82 +/- .54). Genetic correlations among littermate traits would suggest that selection for decreased age at puberty in gilts could cause an increase in LH concentrations in boar offspring, before and after GnRH injection, and may also have adverse effects on their ability to settle females. Selection for increased weight at puberty of gilts could cause TE concentrations of boar offspring to increase while having little effect on their breeding performance.     

Genetic parameter estimates for growth traits in Horro sheep

Variance components and genetic parameters were estimated for growth traits: birth weight (BWT), weaning weight (WWT), 6‐month weight (6MWT) and yearling weight (YWT) in indigenous Ethiopian Horro sheep using the average information REML (AIREML). Four different models: sire model (model 1), direct animal model (model 2), direct and maternal animal model (model 3) and direct–maternal animal model including the covariance between direct and maternal effects (model 4) were used. Bivariate analysis by model 2 was also used to estimate genetic correlation between traits. Estimates of direct heritability obtained from models 1–4, respectively, were for BWT 0.25, 0.27, 0.18 and 0.32; for WWT, 0.16, 0.26, 0.1 and 0.14; for 6MWT 0.18, 0.26, 0.16 and 0.16; and for YWT 0.30, 0.28, 0.23, and 0.31. Maternal heritability estimates of 0.12 and 0.23 for BWT; 0.19 and 0.24 for WWT; 0.09 and 0.09 for 6MWT and 0.08 and 0.14 for YWT were obtained from models 3 and 4, respectively. The correlations between direct and maternal additive genetic effects for BWT, WWT, 6MWT and YWT were –0.64, –0.42, 0.002 and –0.46, respectively. On the other hand, the genetic correlations between BWT and the rest of growth traits (WWT, 6MWT and YWT, respectively) were 0.45, 0.33 and 0.31, whereas correlations between WWT and 6MWT, WWT and YWT and 6MWT and YWT were 0.98, 0.84 and 0.87, respectively. The medium to high direct and maternal heritability estimates obtained for BWT and YWT indicate that in Horro sheep faster genetic improvement through selection is possible for these traits and it should consider both (direct and maternal) h² estimates. However, since the direct‐maternal genetic covariances were found to be negative, caution should be made in making selection decisions. The high genetic correlation among early growth traits imply that genetic improvement in any one of the traits could be made through indirect selection for correlated traits.     

Phenotypic and genetic parameter estimates for reproductive traits in Zandi sheep

This study reports on the phenotypic and genetic (co)variance components for reproductive traits in Zandi sheep, using between 1,859 and 2,588 records obtained from 577 ewes. The data were collected from the Khojir Breeding Station of Zandi sheep in Tehran, Iran from 1994 to 2008. The basic traits were litter size at birth (LSB), litter size at weaning (LSW), litter mean weight per lamb born (LMWLB), and litter mean weight per lamb weaned (LMWLW), and the composite traits were total litter weight at birth (TLWB) and total litter weight at weaning (TLWW). Genetic analyses were carried out using the restricted maximum likelihood method that was explored by fitting the additive direct genetic effects and permanent environmental effects of the ewes as random effects and the ewe age at lambing and lambing year as fixed effects for all of the investigated traits. Akaike’s information criterion was used to choose the most appropriate model. LSB, LSW, LMWLB, LMWLW, TLWB, and TLWW direct heritability estimates were 0.07, 0.05, 0.12, 0.10, 0.08, and 0.14, respectively. The estimated fractions of variance due to the permanent environmental effects of the ewe ranged from 0.03 for LMWLB to 0.08 for LMWLW and TLWW. Corresponding repeatability estimates ranged from 0.10 for LSW to 0.22 for TLWW. Direct genetic correlations varied from ?0.61 for LSB–LMWLB to 0.88 for LSB–LSW and LSB–TLWB. Results indicate that genetic change depends not only on the heritability of traits, but also on the observed phenotypic variation; therefore, improvement of non-genetic factors should be included in the breeding programs.     

Genetic parameter estimates among scale activity score and farrowing disposition with reproductive traits in swine

The primary objective of this study was to determine if certain behavior traits were genetically correlated with reproduction. If 1 or both of the behavior traits were found to be correlated, a secondary objective was to determine if the behavior traits could be useful in selecting for more productive females. A scale activity score taken at 5 mo of age and a farrowing disposition score taken at farrowing were selected as the behavioral traits. Scale activity score ranged from 1 to 5 and farrowing disposition ranged from 1 to 3. Reproductive traits included age at puberty, number born alive, number born dead, litter birth weight, average piglet birth weight, number weaned, litter weaning weight, average weaning weight, wean-to-estrus interval, ovulation rate including gilts, and postweaning ovulation rate. Genetic correlations between scale activity score and reproduction ranged from -0.79 to 0.61. Three of the correlations, number born alive (P < 0.01), average piglet birth weight (P < 0.001), and wean-to-estrus interval (P = 0.014), were statistically significant but included both favorable and antagonistic correlations. In contrast, all but 1 of the farrowing disposition correlations was favorable and ranged from -0.66 to 0.67. Although only the correlation with litter birth weight was significant (P = 0.018), the consistent favorable direction of all farrowing disposition correlations, except average weaning weight, shows a potential for inclusion of farrowing disposition into a selection program.     

Genetic and phenotypic parameter estimates for growth traits in Boer goat

An understanding of influencing factors and genetic principles affecting the growth traits is needed to implement optimal breeding and selection programs. In this study, heritabilities (direct additive and maternal) of body weights at birth (BW0), 90 days (BW90) and 300 days (BW300) of age and average daily gains from birth to 90 days (ADG0-90), birth to 300 days (ADG0-300) and 90 days to 300 days (ADG90–300) of age in Boer goats were estimated on the basis of 1520 Boer goats at Boer Goat Breeding Station in Yidu, China, during 2002–2007. The parameters were estimated using a DFREML procedure by excluding or including maternal genetic or permanent maternal environmental effects, four analysis models were fitted in order to optimize the model for each trait. Influencing factors such as parity, litter size, kidding year and season, as well as sex of kids and some significant interactions among these factors were investigated as the fixed effects for the models. The results showed that the birth year and maternal genetic effects such as parity and litter size of dam were important determinants of the genetic parameter estimates for pre-weaning growth traits, and environmental effects such as birth year, season and sex of kids had some significant effect on post-weaning growth traits. The mean values and standard errors (SE) of direct additive heritability estimates calculated with the optimum model were 0.17 ± 0.07, 0.22 ± 0.08, 0.07 ± 0.07, 0.10 ± 0.08, 0.30 ± 0.12 and 0.08 ± 0.10 for BW0, BW90, ADG0-90, BW300, ADG0-300 and ADG90–300, respectively. For pre-weaning weights, correlation estimates between direct additive and maternal genetic (r_a–m) effect were high and negative ranging from − 0.74 to − 0.86.     

Genetic parameter estimates for preweaning growth traits in Santa Gertrudis cattle

Genetic parameters were estimated for birth weight and weaning weight from records collected on 1,894 Santa Gertrudis calves (939 bulls, 955 heifers) during the 8-yr period, 1978 through 1985. Variance and covariance components were estimated separately by sex and combined across sexes utilizing mixed-model, least-squares procedures (Henderson's Method 3). The mathematical model assumed for estimating variance and covariance components by sex included effects of year, sire-within-year and age of dam. Also, calf weaning age was included as covariate for birth weight and weaning weight. Estimates were obtained across sexes utilizing the same model, with the addition of effects of sex of calf and the sex-of-calf X age-of-dam interaction. Heritabilities and genetic and phenotypic correlations were estimated using paternal half-sib techniques. The heritability estimate for birth weight for bulls was 1.6 times larger than that for heifers (.38 +/- .12 vs .24 +/- .10). Conversely, the heritability estimate for weaning weight for heifers was 1.5 times larger than that for bulls (.45 +/- .12 vs .30 +/- .11). However, based upon their approximate standard errors, neither of these differences was significant. Heritability estimates calculated across sexes were .32 +/- .07 and .42 +/- .08 for birth weight and weaning weight, respectively. Estimates of genetic and phenotypic correlations of birth weight and weaning weight by sex were .43 +/- .21 and .31, respectively, for bulls and .33 +/- .22 and .27, respectively, for heifers. Calculated across sexes, the genetic correlation was .40 +/- .14 and the phenotypic correlation was .29.     

Genetic and phenotypic parameter estimates for reproduction traits in indigenous Arsi-Bale goats

The study was conducted to evaluate reproductive performances and estimate genetic parameters for reproduction traits in Arsi-Bale goats. A total of 792 kidding records collected from 2001 to 2007 were used. Parity of dam, year, season and type of kidding were investigated as fixed effects by PROC GLM of SAS. Derivative-Free Restricted Maximum Likelihood (DFREML) method was used to estimate genetic parameters by fitting four animal models. Parity of dam and year of kidding influenced (P < 0.05) all the traits. The overall means for age at first kidding (AFK), kidding interval (KI), litter size at birth (LSB), litter size at weaning (LSW), litter weight at birth (LWB), litter weight at weaning (LWW), abortion and dystocia were 574.9 ± 8.3 days, 280.0 ± 13.7 days, 1.6 ± 0.03, 1.37 ± 0.03, 3.7 ± 0.08 kg, 9.11 ± 0.38 kg, 3.8% and 0.13%, respectively. The estimates of direct additive heritability for the traits, except for abortion and dystocia, under the best model (direct animal for AFK and repeatability model for other traits) were 0.245 ± 0.19, 0.060 ± 0.08, 0.074 ± 0.05, 0.006 ± 0.05, 0.125 ± 0.05, 0.053 ± 0.07, respectively, while the corresponding permanent environmental effects were 0.00 ± 0.00, 0.07 ± 0.07, 0.08 ± 0.05, 0.172 ± 0.06, 0.03 ± 0.04 and 0.07 ± 0.05, respectively. Repeatability estimates for KI, LSB, LSW, LWB and LWW were 0.13, 0.15, 0.18, 0.16 and 0.12, respectively. Genetic correlations between reproductive traits vary from medium to high. Arsi-Bale goats have good reproductive performance with low incidence of reproductive disorder. Except for AFK, other traits have low estimates of heritabilities with high genetic correlation among the traits. Repeated measures of the traits are needed before deciding to keep or cull the animal.     

Genetic parameter estimates for growth traits and prolificacy in Raeini Cashmere goats

The main objectives of this study were to estimate genetic and phenotypic parameters for growth traits and prolificacy in the Raeini Cashmere goat. Traits included, birth weight (BWT), weaning weight (WWT), 6-month weight (6WT), 9-month weight (9WT), 12-month weight (12WT), average daily gain from birth to weaning (ADG1), average daily gain from weaning to 6WT (ADG2), average daily gain from 6WT to 12WT (ADG3), survival rate (SR), litter size at birth (LSB) and litter size at weaning (LSW) and total litter weight at birth (LWB). Data were collected over a period of 28 years (1982-2009) at the experimental breeding station of Raeini goat, southeast of Iran. Genetic parameters were estimated with univariate models using restricted maximum likelihood (REML) procedures. In addition to an animal model, sire and threshold models, using a logit link function, were used for analyses of SR. Age of dam, birth of type, sex and of kidding had significant influence (p < 0.05 or 0.01) all the traits. Direct heritability estimates were low for prolificacy traits (0.04 ± 0.01 for LSB, 0.09 ± 0.02 for LSW, 0.16 ± 0.02 for LWB and 0.05 ± 0.02 for SR) and average daily gain (0.12 ± 0.03 for ADG1, 0.08 ± 0.02 for ADG2, and 0.07 ± 0.03 for ADG3) to moderate for production traits (0.22 ± 0.02 for BWT, 0.25 ± 0.02 for WWT, 0.29 ± 0.04 for 6WT, 0.30 ± 0.02 for 9WT, 0.32 ± 0.05 for 12WT). The estimates for the maternal additive genetic variance ratios were lower than direct heritability for BWT (0.17 ± 0.03) and WWT (0.07 ± 0.02).     

Genetic parameter estimates for postweaning traits of beef cattle in a stressful environment

Postweaning growth data, collected from a Hereford herd located in the Southwest, were used to estimate genetic parameters for weights and gains. The herd was maintained on unsupplemented range forage, and average weight losses from weaning to yearling age were 9% for bulls and 12% for heifers. Data were grouped into years with poor and good environments based on contemporary group means for gain from 8 to 12 mo. Postweaning growth data (12- and 20-mo weights, 8- to 12-mo gain and 12- to 20-mo gain) were analyzed by least squares methods with a model that included year of birth, sire within year of birth, age of dam and a covariate of age for 12- and 20-mo weights. Heritability estimates of 12- and 20-mo weights for bulls were .58 +/- .15 and .55 +/- .22 in good environments vs .32 +/- .11 and 1.09 +/- .15 in poor environments; for heifers these estimates were .19 +/- .08 and .35 +/- .12 in good environments vs .38 +/- .07 and .47 +/- .09 in poor environments. Heritability estimates of 8- to 12-mo and 12- to 20-mo gain for bulls were .32 +/- .14 and .51 +/- .24 in good environments vs .16 +/- .11 and .09 +/- .14 in poor environments; for heifers these estimates were .21 +/- .08 and .14 +/- .10 in good environments vs .10 +/- .06 and .44 +/- .10 in poor environments. Genetic correlations among the preweaning traits of birth and weaning weight and postweaning weight traits were positive and of a moderate to large magnitude, with the exception of birth and 12-mo weight in a poor environment (-.06 +/- .49). Genetic correlations between 8- to 12-mo gain and birth weight in poor environment and weaning weight in all environments were negative (range from -.06 +/- .33 to -.53 +/- .41). Genetic correlations among 12- and 20-mo weights were large and positive in all environments. Relationships among gains were more variable.     

Genetic parameter estimates for preweaning traits of beef cattle in a stressful environment

Data collected from 1957 through 1985 from a Hereford herd located in the Southwest were analyzed separately for each sex to evaluate the heritabilities of and genetic correlations among preweaning growth traits within groups of environmentally similar years. Data were grouped into years with poor, moderate and good environments based on contemporary group means for male calves' weaning weight. A total of 7,690 records were analyzed for birth weight, weaning weight and preweaning daily gain with a model that included year of birth, sire within year of birth, age of dam and a covariate of day of birth for birth weight or age at weaning for the weaning traits. Year of birth was a significant source of variation in all environments for all traits, accounting for more of the variation in the good and poor years than in moderate years. Heritability estimates for all traits were greater in good and moderate years than in poor years for bull calves. For heifers, however, estimates for weaning weight and preweaning daily gain were greater in the poor environment. Genetic correlations among birth weight and preweaning gain increased from the good environment to the poor environment (-.49 +/- .26 to .82 +/- .56 for male calves and -.09 +/- 2.6 to .46 +/- .25 for female calves) but phenotypic correlations were near zero in all environments.(ABSTRACT TRUNCATED AT 250 WORDS)     

Population parameter estimates for performance and reproductive traits in Polish Large White nucleus herds

Performance test records from on-farm tests of young Polish Large White boars and reproductive records of Polish Large White sows from 94 nucleus farms during 1978 to 1987 were used to estimate population parameters for the measured traits. The number of boar performance records after editing was 114,347 from 3,932 sires, 21,543 dams, 44,493 litters and 1,075 herd-year-seasons. Reproductive performance records of sows involved 41,080 litters from 2,348 sires, 18,683 dams and 1,520 herd-year-seasons. Both data sets were analyzed by using restricted maximum-likelihood programs. The model used for the performance records included fixed herd-year-seasons, random sires, dams and error effects, and covariances for the year of birth of sire and year of birth of dam. The model used for the reproduction data set was the same as the performance data with parity as an additional fixed effect. Estimated heritabilities were .27, .29, .26, .07, .06, .06 for average daily gain standardized to 180 d (ADG), backfat thickness standardized to 110 kg BW (BF), days to 110 kg (DAYS), litter size at birth born alive (NBA), litter size at 21 d (N21) and litter weight at 21 d (W21), respectively. Estimated common environmental effects for the same traits were .09, .10, .09, .06, .07 and .08, respectively. Genetic correlations were .25 (ADG and BF), -.99 (ADG and DAYS), -.21 (BF and DAYS), .91 (NBA and N21), .68 (NBA and W21) and .80 (N21 and W21). The respective phenotypic correlations were .23, -.99, -.20, .88, .75, .86. These population parameters for Polish Large White pigs are similar to those for breeds in other countries.     

Genetic parameter estimates and strain comparisons of egg compositional traits 1

1. Genetic parameters and responses to selection involving egg composition and allied traits were estimated, using two unselected control strains and three selected strains of White Leghorns.

2. Heritability estimate for yolk weight was 0.5 ± 0.1; for albumen percentage protein, 0.6 ± 0.1; and for yolk percentage solids, 0.5 ± 0.1.

3. Genetic correlation estimates indicated that there was no antagonistic relationship between the weight of any egg component and its composition but, because of the unreliability of the estimates of the genetic correlations involving the egg number traits, it is impossible to predict the correlated effects that selection for egg composition would have on egg number.

4. Eggs from selected strains weighed an average of 3‐. g more, contained more albumen, and greater amounts of albumen percentage solids and percentage protein than controls, whereas no differences were found for yolk weight; yolk percentage solids changed little in the selected strains.

5. Comparisons of one control strain with four commercial strains suggest that the findings may be applicable to commercial stocks.     

Genetic parameter estimates for semen production traits and growth rate of a paternal rabbit line

Variance components of sperm production traits (volume in ml, V; concentration in ×10⁶ sperm/ml, CN; sperm production in ×10⁶ sperm, PROD) were estimated in a paternal line of rabbit selected for 25 generations based on daily weight gain (DG, g/day) between 28 and 63 days of age. Features of the marginal posterior distributions for ratios of genetic variance, variance owing to non‐additive plus environmental permanent male effects and variance owing to common litter of birth effects with respect to phenotypic variance are reported. The correlations between sperm production traits and the selection criteria were also estimated. Three sets of two‐trait analyses were performed, involving 12908 records of DG, 2329 ejaculates corresponding to 412 bucks and 14700 animals in pedigree file. The heritabilities (h²) of the semen traits were 0.13 ± 0.05, 0.08 ± 0.04 and 0.07 ± 0.03 for V, CN and PROD, respectively. The permanent environmental effects were lower than the corresponding values of h² and varied between 0.06 and 0.11. A favourable and moderate genetic correlation was observed between V and DG (0.36 ± 0.34; p > 0: 0.83), together with a non‐favourable and moderate correlation between permanent environmental effects owing to common litter of birth for both traits (?0.35 ± 0.35; p < 0: 0.85). On the other hand, the correlation between male permanent environmental effects for semen traits and DG was moderate and non‐favourable (?0.51 ± 0.29 with p < 0: 0.95 for DG‐CN, and ?0.31 ± 0.37 with p < 0: 0.79 for DG‐PROD).     

Stability of genetic parameter estimates for production traits in pigs

Changes in variance component estimates in growing sets of performance data in two pig breeds were investigated. Data was used from the field and station test of Czech Landrace (LA: 75 099 observations) and the Slovakian breed, White Meaty swine (WM: 32 203 observations). In LA the traits analysed were estimated lean meat content (LM) and average daily gain (ADGF) on field test and average daily gain (ADGS) and weight of valuable cuts (VCW) on station test. In WM the traits analysed were backfat thickness on field and station test (BFF, BFS, respectively), proportion of valuable cuts (VCP) on station test, ADGF and ADGS. Covariance components were estimated from four- and five-trait animal models using the VCE software. Omitting data from factor levels with a low number of records led to 4.2% of LA records and 21.7% of WM records being deleted. Changes in genetic and residual variance estimates were less than 5% for all traits in LA and less than 12% for all traits except ADGS in WM. The changes in estimated genetic variances caused by 18 months (LA) or 24 months (WM) of new data were 2–25% and the changes in estimated residual variances were less than 5% in LA and less than 20% in WM. In both breeds, changes in heritability estimates did not exceed 0.06 in absolute value. In LA, it is reasonable to use genetic parameter estimates for 3 years before re-estimation. In WM the time interval should be shorter because of changes in the estimates caused by their lower accuracy arising from the smaller size of the data-set and smaller frequency of station testing.     

Genetic parameter estimates for serum insulin-like growth factor-I concentration and carcass traits in Angus beef cattle

Divergent selection for serum insulin-like growth factor-I (IGF-I) concentration began at the Eastern Ohio Resource Development Center (EORDC) in 1989 using 100 spring-calving (50 high line and 50 low line) and 100 fall-calving (50 high line and 50 low line) purebred Angus cows. Following weaning, bull and heifer calves were fed in drylot for a 140-d postweaning period. At the conclusion of the postweaning test, bulls not selected for breeding were slaughtered and carcass data were collected at a commercial abbatoir. At the time of this analysis, IGF-I measurements were available for 1,283 bull and heifer calves, and carcass data were available for 452 bulls. A set of multiple-trait, derivative-free, restricted maximum likelihood (MTDFREML) computer programs were used for data analysis. Estimates of direct heritability for IGF-I concentration at d 28, 42, and 56 of the postweaning period, and for mean IGF-I concentration were .32, .59, .31, and .42, respectively. Direct heritabilities for carcass traits ranged from .27 to 1.0, .26 to 1.0, and .23 to 1.0 when the age-, fat-, and weight-constant end points, respectively, were used, with marbling score having the smallest heritability and longissimus muscle area having the highest heritability in each case. Maternal heritability and the proportion of phenotypic variance due to permanent environmental effect of dam generally were < or = .21 for IGF-I concentrations and for carcass traits other than longissimus muscle area. Additive genetic correlations of IGF-I concentrations with backfat thickness, longissimus muscle area, hot carcass weight, marbling score, quality grade, and yield grade averaged -.26, .19, -.04, -.53, -.45, and -.27, respectively, when carcass data were adjusted to an age-constant end point. Bulls with lower IGF-I concentrations had higher marbling scores and quality grades, but also had higher backfat thickness and yield grades regardless of the slaughter end point. Serum IGF-I concentration may be a useful selection criterion when efforts are directed toward improvement of marbling scores and quality grades of beef cattle.     

Genetic parameter estimates for body weight in local Venda chickens

Genetic parameters were estimated for Venda chicken body weights at hatching, and at 4 weeks, 10 weeks and 21 weeks of age. A single-trait animal model with restricted maximum-likelihood procedures was used. Random effects were additive direct and maternal genetic, common environmental and error. The heritability estimates for direct effects were 0.36, 0.25, 0.41 and 0.22 for hatch, 4 weeks, 10 weeks and 21 weeks, respectively. The maternal effects were estimated at hatch and 4 weeks of age and were not present at later ages. Common environmental effects disappeared with increasing age. There was an antagonistic relationship between direct and maternal effects. The results show potential for genetic improvement of indigenous Venda chickens through selection. Maternal effects should be considered if selection is carried out at early ages.     

Genetic and phenotypic parameter estimates for feed intake and other traits in growing beef cattle, and opportunities for selection

Growth, feed intake, and temperament indicator data, collected over 5 yr on a total of 1,141 to 1,183 mixed-breed steers, were used to estimate genetic and phenotypic parameters. All steers had a portion of Hereford, Angus, or both as well as varying percentages of Simmental, Charolais, Limousin, Gelbvieh, Red Angus, and MARC III composite. Because the steers were slaughtered on various dates each year and the animals thus varied in days on feed, BW and feed data were adjusted to a 140-d feeding period basis. Adjustment of measures of feed efficiency [G:F or residual feed intake (RFI), intake adjusted for metabolic body size, and BW gain] for body fatness recorded at slaughter had little effect on the results of analyses. Average daily gain was less heritable (0.26) than was midtest BW (MBW; 0.35). Measures of feed intake had greater estimates of heritability, with 140-d DMI at 0.40 and RFI at 0.52; the heritability estimate for G:F was 0.27. Flight speed (FS), as an indicator of temperament, had an estimated heritability of 0.34 and a repeatability of 0.63. As expected, a strong genetic (0.86) correlation was estimated between ADG and MBW; genetic correlations were less strong between DMI and ADG or MBW (0.56 and 0.71). Residual feed intake and DMI had a genetic correlation of 0.66. Indexes for phenotypic RFI and genotypically restricted RFI (no correlation with BW gain) were compared with simple economic indexes incorporating feed intake and growth to elucidate expected selection responses under different criteria. In general, few breed differences were detected across the various measurements. Heterosis contributed to greater DMI, RFI, and MBW, but it did not significantly affect ADG, G:F, or FS. Balancing output (growth) with input costs (feed) is needed in practicing selection, and FS would not be recommended as an indicator trait for selection to change feed efficiency. An index including BW gain and RFI produced the best economic outcome.     

Genome-wide association study of swine farrowing traits. Part I: Genetic and genomic parameter estimates

The primary objective of this study was to determine genetic and genomic parameters among swine (Sus scrofa) farrowing traits. Genetic parameters were obtained using MTDFREML. Genomic parameters were obtained using GENSEL. Genetic and residual variances obtained from MTDFREML were used as priors for the Bayes C analysis of GENSEL. Farrowing traits included total number born (TNB), number born alive (NBA), number born dead (NBD), number stillborn (NSB), number of mummies (MUM), litter birth weight (LBW), and average piglet birth weight (ABW). Statistically significant heritabilities included TNB (0.09, P = 0.048), NBA (0.09, P = 0.041), LBW (0.20, P = 0.002), and ABW (0.26, P < 0.0001). Statistically significant genetic correlations included TNB-NBA (0.97, P < 0.0001), TNB-LBW (0.74, P < 0.0001), NBA-LBW (0.56, P < 0.0017), NSB-LBW (0.87, P < 0.0395), and LBW-ABW (0.63, P < 0.0002). Genetic parameters are similar to others found in the literature. The proportion of phenotypic variance explained by genomic markers (GP) generated by GENSEL was TNB (0.04), NBA (0.06), NBD (0.00), NSB (0.01), MUM (0.00), LBW (0.11), and ABW (0.31). Limited information is available in the literature about genomic parameters. Only the GP estimate for NSB is significantly lower than what has been published. The GP estimate for ABW is greater than the estimate for heritability found in this study. Other traits with significant heritability had GP estimates half the value of heritability. This research indicates that significant genetic markers will be found for TNB, NBA, LBW, and ABW that will have either immediate use in industry or provide a roadmap to further research with fine mapping or sequencing of areas of significance. Furthermore, these results indicate that genomic selection implemented at an early age would have similar annual progress as traditional selection, and could be incorporated along with traditional selection procedures to improve genetic progress of litter traits.     

Genetic parameter estimates for gastrointestinal nematode parasite resistance and maternal efficiency indicator traits in Santa Inês breed

Infection with Haemonchus contortus is the most economically important gastrointestinal nematode parasitosis and the most important cause of mortality in sheep production. The aim of this study was to estimate variance components of gastrointestinal parasite resistance traits, maternal efficiency (ME) and ewe adult weight (AW) in Santa Inês breed in tropical conditions. The phenotypic records were collected from 700 animals, belonging to four flocks located south‐east and north‐east in Brazil. The evaluated traits were as follows: degree of anaemia assessed using the FAMACHA chart (FMC), haematocrit (HCT), white blood cell (WBC), red blood cell (RBC), haemoglobin (HGB), platelets (PLT), faecal egg count (EPG_log), ME, metabolic maternal efficiency (MME), AW and metabolic ewe adult weight (MAW). From the 700 animals, 576 (82% of the evaluated population) were genotyped with the Ovine SNP12k BeadChip (Illumina, Inc.). Markers with unknown genomic position, located on sex chromosomes, monomorphic, with minor allele frequency <0.05, call rate <90% and with excess heterozygosity were excluded. The variance components were estimated using a single‐trait animal model with ssGBLUP procedure. The correlation between the parasite's resistance indicators and the ME suggested that selecting animals with both higher adult weight and ME will also favour the selection of animals with better resistance to gastrointestinal nematodes parasites, specially H. contortus. Therefore, since there are few or no studies with Santa Inês breed in this area, it is important to study those traits to better manage selection programs.