Genetic and phenotypic parameters for sow productivity

Data from 609 purebred Yorkshire, Hampshire and Duroc litters were utilized to obtain genetic and environmental parameter estimates for litter number and weight traits at birth, 21 d (first creep) and 42 d (weaning) considered as traits of the sow. Differences among paternal half-sib sets of sows were analyzed. Heritability estimates from this study were .26 +/- .12, .28 +/- .12 and .30 +/- .12 for litter size at birth, 21 and 42 d and .54 +/- .13, .17 +/- .11 and .15 +/- .11 for litter weights at those times, respectively. These estimates indicated that the dam's genetic contribution to litter weight was higher for prenatal growth than during nursing. The heritabilities for litter size were encouraging for within breed selection. Genetic correlations among litter sizes and genetic correlations among litter weights at birth, 21 and 42 d were large and positive. Large, positive genetic correlations also were found between litter size and weight at each of the three times. Negative correlations between litter size and average pig weight at both birth and 21 d and between litter size at birth and average pig weight at 21 d indicated that larger litters were associated genetically with smaller pigs. Phenotypic and environmental correlations generally indicated the same associations.     

Genetic correlations of pig performance and sow productivity traits

Records for a total of 732 daughter-dam pairs were analyzed to estimate the genetic correlations of pig performance traits with sow productivity traits, with implications to the development of specialized sire and dam lines for use in crossing. Major pig performance traits analyzed included average daily gain from 56 d of age to a final weight of 90.7 kg (ADG), average backfat thickness at 90.7 kg (BF) and a performance index (PI) consisting of ADG and BF. Major sow productivity traits included number of pigs born alive in a litter (NA), litter size (N21) and litter weight (W21) at 21 d of age and two sow productivity indexes, one with NA, N21 and W21 (SPI-3) and one with NA and W21 (SPI-2). All records were expressed as deviations from breed-line-year-season means of this population. Genetic correlations were computed from daughter-dam covariances. The mean genetic correlation of PI with SPI consisted of two correlations, that of daughters' PI with dams' SPI and that of dams' PI with daughters' SPI. The mean genetic correlation of PI with SPI-3 and SPI-2 was .07 +/- .12, suggesting that concurrent improvement in both PI and SPI would not be restricted by selection within a single composite line. The genetic correlation of daughters' PI with dams' SPI (-.18 +/- .13) was appraised as more critical than the reciprocal correlation of dams' PI with daughters' SPI (+.28 +/- .13). This appraisal is based on the fact that only one generation separates a daughter's PI from her dam's SPI, as compared with two generations in the reciprocal covariance. However, the -.18 correlation was not significantly different from zero, indicating that formation of specialized sire and dam lines for use in crossing would be only marginally more effective at best for improving the overall efficiency in pork production than use of a single composite line, aside from the heterosis effects from crossing the lines. Indexes were proposed for combining PI and SPI for use either in specialized sire and dam lines or in a single composite line.     

Genetic determination of individual birth weight and its association with sow productivity traits using Bayesian analyses

Genetic association between individual birth weight (IBW) and litter birth weight (LBW) was analyzed on records of 14,950 individual pigs born alive between 1988 and 1994 at the pig breeding farm of the University of Kiel. Dams were from three purebred lines (German Landrace, German Edelschwein, and Large White) and their crosses. Phenotypically, preweaning mortality of pigs decreased substantially from 40% for pigs with < or = 1 kg weight to less than 7% for pigs with > 1.6 kg. For these low to high birth weight categories, preweaning growth (d 21 of age) and early postweaning growth (weaning to 25 kg) increased by more than 28 and 8% per day, respectively. Bayesian analysis was performed based on direct-maternal effects models for IBW and multiple-trait direct effects models for number of pigs born in total (NOBT) and alive (NOBA) and LBW. Bayesian posterior means for direct and maternal heritability and litter proportion of variance in IBW were .09, .26, and .18, respectively. After adjustment for NOBT, these changed to .08, .22, and .09, respectively. Adjustment for NOBT reduced the direct and maternal genetic correlation from -.41 to -.22. For these direct-maternal correlations, the 95% highest posterior density intervals were -.75 to -.07, and -.58 to .17 before and after adjustment for NOBT. Adjustment for NOBT was found to be necessary to obtain unbiased estimates of genetic effects for IBW. The relationship between IBW and NOBT, and thus the adjustment, was linear with a decrease in IBW of 44 g per additionally born pig. For litter traits, direct heritabilities were .10, .08, and .08 for NOBT, NOBA, and LBW, respectively. After adjustment of LBW for NOBA the heritability changed to .43. Expected variance components for LBW derived from estimates of IBW revealed that genetic and environmental covariances between full-sibs and variation in litter size resulted in the large deviation of maternal heritability for IBW and its equivalent estimate for LBW. These covariances among full-sibs could not be estimated if only LBW were recorded. Therefore, selection for increased IBW is recommended, with the opportunity to improve both direct and maternal genetic effects of birth weight of pigs and, thus, their vitality and pre- and postnatal growth.     

Genetic relationships between sex-specific traits in beef cattle: mature weight, weight adjusted for body condition score, height and body condition score of cows, and carcass traits of their steer relatives

Data from the first four cycles of the Germplasm Evaluation Program at the U.S. Meat Animal Research Center (USMARC) were used to investigate genetic relationships between mature weight (MW, n = 37,710), mature weight adjusted for body condition score (AMW, n = 37,676), mature height (HT, n = 37,123), and BCS (n = 37,676) from 4- to 8-yr old cows (n = 1,800) and carcass traits (n = 4,027) measured on their crossbred paternal half-sib steers. Covariance components among traits were estimated using REML. Carcass traits were adjusted for age at slaughter. Estimates of heritability for hot carcass weight (HCWT); percentage of retail product; percentage of fat; percentage of bone; longissimus muscle area; fat thickness adjusted visually; estimated kidney, pelvic, and heart fat percentage; marbling score; Warner-Bratzler shear force; and taste panel tenderness measured on steers were moderate to high (0.26 to 0.65), suggesting that selection for carcass and meat traits could be effective. Estimates of heritability for taste panel flavor and taste panel juiciness were low and negligible (0.05 and 0.01, respectively). Estimates of heritability from cow data over all ages and seasons were high for MW, AMW, and HT (0.52, 0.57, 0.71; respectively) and relatively low for BCS (0.16). Pairwise analyses for each female mature trait with each carcass trait were done with bivariate animal models. Estimates of genetic correlations between cow mature size and carcass composition or meat quality traits, with the exception of HCWT, were relatively low. Selection for cow mature size (weight and/or height) could be effective and would not be expected to result in much, if any, correlated changes in carcass and meat composition traits. However, genetic correlations of cow traits, with the possible exception of BCS, with HCWT may be too large to ignore. Selection for steers with greater HCWT would lead to larger cows.     

A genetic analysis of sow productivity traits

Genetic and phenotypic parameters for sow productivity traits were derived from analyses of records for 999 purebred Duroc and Yorkshire litters at the Beltsville Agricultural Research Center. Included were 682 spring-farrowed litters and 317 fall-farrowed litters. Primary traits examined were number of pigs born alive in the litter (NA), litter size at 21 d of age (N21), litter weight at 21 d (W21) and an index (I21) combining the three traits. Also analyzed were total number of pigs farrowed alive or stillborn, litter weight of pigs born alive and litter size and litter weight at 42 d of age (weaning). Selection was based mainly on the sow productivity index among litters in the spring season and mainly on performance traits among fall-farrowed pigs. Select and control lines were maintained in both breeds in both seasons. Yorkshires started at higher levels of productivity than Durocs in spring 1975, showed more fluctuation and ended in spring 1982 at about their starting levels. Durocs started at lower productivity levels and recorded generally significant increases by 1982, with comparable selection differentials for the two breeds. Heritabilities, estimated from daughter-biparental (mid-dam, paternal granddam) regressions using records expressed as deviations from contemporary breed-line means, varied widely among the breed-line groups. Suggested composite heritability estimates were 5, 10 and 20% for NA, N21 and W21, respectively. Genetic correlations, computed from daughter-biparental covariances, were high and positive (.7 or above) among all traits. Based on estimated genetic gains, it was proposed that W21, alone or in combination with N21 and(or) NA in an index, be used as the primary selection criterion to bring about genetic improvement in sow productivity traits.     

Genetic relationships between scrotal circumference and female reproductive traits

Records for yearling scrotal circumference (SC; n = 7,580), age at puberty in heifers (AP; n = 5,292), age at first calving (AFC; n = 4,835), and pregnancy, calving, or weaning status following the first breeding season (PR1, CR1, or WR1, respectively; n = 7,003) from 12 Bos taurus breeds collected at the Meat Animal Research Center (USDA) between 1978 and 1991 were used to estimate genetic parameters. Age at puberty (AP) was defined as age in days at first detected ovulatory estrus. Pregnancy (calving or weaning) status was scored as one for females conceiving (calving or weaning) given exposure during the breeding season and as zero otherwise. The final model for SC included fixed effects of age of dam at breeding (AD), year of breeding (Y), and breed (B) and age in days at measurement as a covariate. Fixed effects in models for AP and AFC were AD, Y, B, and month of birth. Fixed effects in models for PR1, CR1, and WR1 included AD, Y, and B. For all traits, random effects in the model were direct genetic, maternal genetic, maternal permanent environmental, and residual. Analyses for a three-trait animal model were carried out with SC, AP, and a third trait (the third trait was AFC, PR1, CR1, or WR1). A derivative-free restricted maximum likelihood algorithm was used to estimate the (co)variance components. Direct and maternal heritability estimates were 0.41 and 0.05 for SC; 0.16 and 0.03 for AP; 0.08 and 0.00 for AFC; 0.14 and 0.02 for PR1; 0.14 and 0.03 for CR1; and 0.12 and 0.01 for WR1. Genetic correlations between direct and maternal genetic effects within trait were -0.26, -0.63, -0.91, -0.79, -0.66, and -0.85 for SC, AP, AFC, PR1, CR1, and WR1, respectively. Direct genetic correlations between SC and AP and between those traits and AFC, PR1, CR1, and WR1 ranged from -0.15 (between SC and AP) to 0.23 (between AP and WR1). Estimates of heritability indicate that yearling SC should respond to direct selection better than AP, AFC, PR1, CR1, and WR1. Variation due to maternal genetic effects was small for all traits. No strong genetic correlations were detected between SC and female reproductive traits or between AP and the other female traits. These results suggest that genetic response in female reproductive traits through sire selection on yearling SC is not expected to be effective.     

Genetic analysis of sow longevity and sow lifetime reproductive traits using censored data

Sow longevity is a key component for efficient and profitable pig farming; however, approximately 50% of sows are removed annually from a breeding herd. There is no consensus in the scientific literature regarding a definition for sow longevity; however, it has been suggested that it can be measured using several methods such as stayability and economic indicators such as lifetime piglets produced. Sow longevity can be improved by genetic selection; however, it is rarely included in genetic evaluations. One reason is elongated time intervals required to collect complete lifetime data. The effect of genetic parameter estimation software in handling incomplete data (censoring) and possible early indicator traits were evaluated analysing a 30% censored data set (12 725 pedigreed Landrace × Large White sows that included approximately 30% censored data) with DMU6, THRGIBBS1F90 and GIBBS2CEN. Heritability estimates were low for all the traits evaluated. The results show that the binary stayability traits benefited from being analysed with a threshold model compared to analysing with a linear model. Sires were ranked very similarly regardless if the program handled censoring when all available data were included. Accumulated born alive and stayability were good indicators for lifetime born alive traits. Number of piglets born alive within each parity could be used as an early indicator trait for sow longevity.     

Economic weights for sow productivity traits in nucleus pig populations

Economic values or weights measure the net economic gain per unit genetic increase of a given trait. These were derived for sow productivity traits for use as weighting factors in a dam line selection index used by purebred or nucleus dam line breeders. The profit function approach was used in order to provide flexibility to alternative production systems, market requirements or population trait levels. The approach accounted for constraints on perinatal survival rate imposed by larger birth litter sizes. The effect of accounting for these constraints was to reduce the economic value of birth litter size as the population average increased; without this, the economic weight for litter size was constant. Weights for the other traits were not affected. Economic weights were calculated for both the 100 kg finished pig and the 25 kg feeder pig market, and for a range of average birth litter sizes, with constant values for all other traits, using average market conditions, prices and costs in Canada as an example. The relative importance of litter size for the finished pig market decreased from 64% of the total breeding value when average litter size was 8 pigs to 29% when average litter size was 20 pigs, whereas that of perinatal survival increased from 17% to 42%, and that of survival to weaning increased from 7% to 18%. The relative importance of litter size for the feeder pig market also decreased from 45% to 15% as average litter size increased from 8 to 20 pigs, whereas that of piglet weaning weight increased from 22% to 41%, that of perinatal survival increased from 12% to 22% and that of survival to weaning increased from 5% to 9%. The relative importance of age at puberty and weaning to conception interval were both less than 8% of the total in both markets at all litter sizes. These results show that economic weights for litter size designed for populations with relatively small litter sizes should be reduced when the average litter size becomes large and more emphasis should be placed on other traits, particularly perinatal survival.     

Genetic associations between accumulated productivity, and reproductive and growth traits in Nelore cattle

The total meat yield in a beef cattle production cycle is economically very important and depends on the number of calves born per year or birth season, being directly related to reproductive potential. Accumulated Productivity (ACP) is an index that expresses a cow's capacity to give birth regularly at a young age and to wean animals of greater body weight. Using data from cattle participating in the “Program for Genetic Improvement of the Nelore Breed” (PMGRN — Nelore Brasil), bi-trait analyses were performed using the Restricted Maximum Likelihood method based on an ACP animal model and the following traits: age at first calving (AFC), female body weight adjusted for 365 (BW365) and 450 (BW450) days of age, and male scrotal circumference adjusted for 365 (SC365), 450 (SC450), 550 (SC550) and 730 (SC730) days of age. Median estimated ACP heritability was 0.19 and the genetic correlations with AFC, BW365, BW450, SC365, SC450, SC550 and SC730 were 0.33, 0.70, 0.65, 0.08, 0.07, 0.12 and 0.16, respectively. ACP increased and AFC decreased over time, revealing that the selection criteria genetically improved these traits. Selection based on ACP appears to favor the heaviest females at 365 and 450 days of age who showed better reproductive performance as regards AFC. Scrotal circumference was not genetically associated with ACP.     

Genetic parameters for feed efficiency and body weight traits in Japanese quail

1. The objectives of the present study were to estimate heritability and genetic correlations for feed efficiency and body weight (BW) in Japanese quail.

2. Recorded traits during different weeks of the growing period were BW from hatch to 35 d, feed intake (FI), feed conversion ratio (FCR) and residual feed intake (RFI) from hatch to 28 d of age.

3. Genetic parameters were estimated by restricted maximum likelihood method using ASREML software. The results showed that heritability estimates for BW ranged from 0.11 to 0.22, and maternal permanent environmental effect was the highest at hatch (0.45). FCR, RFI and FI showed moderate heritabilities ranging from 0.13 to 0.40.

4.Genetic correlations of BW₂₈ with FI_0–28 (0.88) and RFI_0–28 (0.1) and genetic correlation of FI_0–28 with FCR_0–28 (0.13) and RFI_0–28 (0.52) were positive. A negative genetic correlation was found between BW₂₈ and FCR_0–28 (?0.49). There was a high positive genetic correlation (0.67) between RFI_0–28 and FCR_0–28.

5. In conclusion, selection for increased BW and reduced FI in a selection index could be recommended to improve feed efficiency traits including FCR and RFI in Japanese quail.     

Genetic parameters for body weight, reproduction, and parasite resistance traits in the Creole goat

We estimated the genetic parameters for BW, reproduction, and parasite resistance traits to implement a breeding program for the Creole goat. The traits were preweaning BW at 70 d of age (BW70d), BW at 11 mo of age (BW11), fecal egg count at 11 mo of age (FEC11) for all animals, packed cell volumes of lactating does (PCV), and their fertility (FER) and litter size (LS). We analyzed about 30 yr of data, which included 18,450 records on 11,970 animals from the INRA experimental flock in Guadeloupe (French West Indies). Heritability estimates were low for reproduction traits (0.11 ± 0.02 for LS and FER) to moderate for production traits (0.32 ± 0.03 for BW11; 0.20 ± 0.03 and 0.08 ± 0.02 for the direct and maternal heritability estimates of BW70d, respectively). Heritability estimates for gastrointestinal nematode resistance traits were situated in an intermediate range (0.13 ± 0.05 for PCV and 0.18 ± 0.04 for FEC11). Genetic correlations between FER, PCV, BW11, and the maternal effect of BW70d were altogether positive, whereas LS and FEC11 were almost uncorrelated phenotypically and genetically. These correlations are very favorable for setting up a breeding program, making it possible to improve BW, reproduction, and parasite resistance traits simultaneously.     

Genetic and environmental parameters for traits derived from the Brody growth curve and their relationships with weaning weight in Angus cattle

Direct and maternal genetic and environmental variances and covariances were estimated for weaning weight and growth and maturing traits derived from the Brody growth curve. Data consisted of field records of weight measurements of 3,044 Angus cows and 29,943 weaning weight records of both sexes. Growth traits included weights and growth rates at 365 and 550 d, respectively. Maturing traits included the age of animals when they reached 65% of mature weight, relative growth rates, and degrees of maturity at 365 and 550 d. Variance and covariance components were estimated by REML from a set of two-trait animal models including weaning weight paired with a growth or maturing trait. Weaning and cow contemporary groups were defined as fixed effects. Random effects for weaning weight included direct genetic, maternal genetic, and permanent environmental effects. For growth and maturing traits, a random direct genetic effect was included in the model. Direct heritability estimates for growth traits ranged from .46 to .52 and for maturing traits from .31 to .34. Direct genetic correlations between weaning weight and weights and growth rates at 365 and 550 d ranged from .56 to .70. Correlations of maternal weaning genetic effects with direct genetic effects on weights at 365 and 550 d were positive, but those with growth rates were negative. Between weaning weight and degrees of maturity at both 365 and 550 d, direct genetic correlation estimates were .55 and maternal genetic correlations estimates were -.05, respectively. Direct genetic correlations of weaning weight with relative growth rates and age at 65% of mature weight ranged from .04 to .06, and maternal-direct genetic correlation estimates ranged from -.50 to -.56, respectively. These estimates indicate that higher genetic capacity for milk production was related to higher body mass and degrees of maturity between 365 and 550 d of age but was negatively related to absolute and relative growth rates in that life stage.     

Scrotal circumference in yearling Hereford bulls: adjustment factors, heritabilities and genetic, environmental and phenotypic relationships with growth traits

Field data on 4,233 yearling Hereford bulls were analyzed using fixed and mixed model least-squares procedures to examine factors affecting scrotal circumference; determine appropriate adjustment factors; and study genetic, environmental and phenotypic relationships among scrotal circumference and growth traits. Scrotal circumference was affected by postweaning feed level; contemporary group/feed level; age of dam; and covariates age, weight and height. Of the three covariates, weight had the greatest effect, and any factor which caused an increase in weight tended to increase scrotal circumference. Quadratic effects of age, weight, height and age X age of dam interaction effects were significant or approached significance, but were of minor importance. Large contemporary group effects suggested the need for expressing scrotal circumferences as trait ratios or as deviations from contemporary group means. Scrotal circumference adjustment factors recommended for yearling Hereford bulls were .026 cm X d-1 of age and .8, .2 and .1 for sons of 2-, 3- and 4-yr old dams, respectively. Heritability of weight-adjusted scrotal circumference was .46 +/- .06 compared with .49 +/- .06 for age-adjusted scrotal circumference, indicating considerable additive genetic variation for relative scrotal size. Correlations between scrotal circumference and growth traits were moderate to high. The genetic correlation between scrotal circumference and yearling weight was the highest of these at .44 +/- .16. Potential implications of this relationship are discussed.     

Evaluating breeding objectives for sow productivity and production traits in Large White Pigs

the objective of the study was to develop and evaluate different breeding objectives for sow productivity and for production traits, using economic selection indices. Genetic parameters were generated using a repeated records model for sow productivity traits and a maternal effects model for production traits, in ASREML. Stochastic simulation models based on a hypothetical 100-sow model were performed for each line, i.e., a dam line and a terminal sire line, respectively, to derive economic values. The traits included in the study were number born alive (NBA), 21-day litter size (D21LS), 21-day litter weight (D21LWT), average daily gain (ADG), feed conversion ratio (FCR), age at slaughter (AGES), dressing percentage (DRESS), lean content (LEAN) and backfat thickness (BFAT). The economic values for LEAN and BFAT were derived using the partial differentiation of the profit function, while those for the other traits were derived using the partial budget approach. An economic value of a trait was the change in profit per unit genetic change in that trait. Breeding objectives were developed with a corresponding selection index, for improvement of that objective. Three combinations of breeding objectives and selection indices were developed for sow productivity traits, while there were 15 combinations for production traits. Responses to selection and economic return were computed for each combination to determine the most appropriate combination for the improvement of the breeding objective traits. The most appropriate index to improve sow productivity consisted of NBA and D21LWT. For production traits, the combination that consisted of a selection index with AGES, DRESS and BFAT, and the breeding objective ADG, DRESS, FCR and LEAN, was considered the most appropriate. Age at slaughter and BFAT were, respectively, included as indicator traits for ADG and LEAN. The recommended breeding objectives were sensitive to changes in economic values, indicating that economic values for breeding goal traits should be updated periodically to ensure proper weighting of traits, hence maximization of economic return.     

Genetic relationships between calving performance and beef production traits in Piemontese cattle

The aim of the study was to obtain estimates of genetic correlations between direct and maternal calving performance of heifers and cows and beef production traits in Piemontese cattle. Beef production traits were daily gain, live fleshiness, and bone thinness measured on 1,602 young bulls tested at a central station. Live fleshiness (six traits) and bone thinness were subjectively scored by classifiers using a nine-point linear grid. Data on calving performance were calving difficulty scores (five classes from unassisted to embryotomy) routinely recorded in the farms. Calving performance of heifers and cows were considered different traits. A total of 30,763 and 80,474 calving scores in first and later parities, respectively, were used to estimate covariance components with beef traits. Data were analyzed using bivariate linear animal models, including direct genetic effects for calving performance and beef traits and maternal genetic effects only for calving performance. Due to the nature of the data structure, which involved traits measured in different environments and on different animals, covariances were estimated mostly through pedigree information. Genetic correlations of daily gain were positive with direct calving performance (0.43 in heifers and 0.50 in cows) and negative with maternal calving performance (-0.23 and -0.28 for heifers and cows, respectively). Live fleshiness traits were moderately correlated with maternal calving performance in both parities, ranging from 0.06 to 0.33. Correlations between live fleshiness traits and direct calving performance were low to moderate and positive in the first parity, but trivial in later parities. Bone thinness was negatively correlated with direct calving performance (-0.17 and -0.38 in heifers and cows, respectively), but it was positively correlated to maternal calving performance (0.31 and 0.40). Estimated residual correlations were close to zero. Results indicate that, due to the existence of antagonistic relationships between the investigated traits, specific selection strategies need to be studied.     

Variance components and heritabilities for sow productivity traits estimated from purebred versus crossbred sows

Genetic parameters were estimated for number of pigs born alive (NBA), adjusted litter weaning weight (ALWT), and the interval from weaning to first service (W2E) using 2002 purebred litter records and 14 583 crossbred litter records from a swine production unit with a defined great‐grandparent, grandparent, and parent stock genetic system structure. Estimation of (co)variance components was carried out by REML methods. Heritability estimates from this study for NBA were 0.155, 0.146, 0.145 for the purebred, crossbred, and pooled data, respectively. Heritability estimates for ALWT were 0.162, 0.195, and 0.183 for the purebred, crossbred and pooled data, respectively. Heritability estimates for W2E were 0.205, 0.239 and 0.202 for the purebred, crossbred and pooled data, respectively. Genetic correlations between NBA and ALWT were weak and positive for the three groups. The genetic correlation between W2E and ALWT were ?0.158 for the purebred Yorkshires, 0.031 for the crossbreds and 0.051 for the pooled data. The genetic correlation between W2E and NBA was ?0.027 for the purebred Yorkshires, 0.310 for the crossbreds and 0.236 for the pooled data. These similarities suggest that pooling of purebred and crossbred data may be considered, which may potentially increase the accuracy of breeding value estimates, which would result in increased genetic progress.     

Genetic parameters and relationships between hip height and weight in Brahman cattle

Genetic parameters for weaning hip height (WHH), weaning weight (WWT), postweaning hip height growth (PHG), and hip height at 18 mo of age (HH18) and their relationships were estimated for Brahman cattle born from 1984 to 1994 at the Subtropical Agricultural Research Station, Brooksville, FL. Records per trait were 889 WHH, 892 WWT, and 684 HH18. (Co)variances were estimated using REML with a derivative-free algorithm and fitting three two-trait animal models (i.e., WHH-WWT, WHH-PHG, and WWT-HH18). Heritability estimates of WHH direct effects were 0.73 and 0.65 for models WHH-WWT and WHH-PHG and were 0.29 and 0.33 for WWT direct for models WHH-WWT and WWT-HH18, respectively. Estimates of heritability for PHG and HH18 direct were 0.13 and 0.87, respectively. Heritability estimates for maternal effects were 0.10 and 0.09 for WHH for models WHH-WWT and WHH-PHG and 0.18 and 0.18 for WWT for models WHH-WWT and WWT-HH18, respectively. Heritability estimates for PHG and HH18 maternal were 0.00 and 0.03. Estimates of the genetic correlation between direct effects for the different traits were moderate and positive; they were also positive between WHH and WWT maternal and WWT and HH18 maternal but negative (-0.19) between WHH and PHG maternal, which may indicate the existence of compensatory growth. Negative genetic correlations existed between direct and maternal effects for WHH, WWT, PHG, and HH18. The correlation between direct and WWT maternal effects was low and negative, moderate and negative between WHH direct and PHG maternal, and high and negative (-0.80) between WWT direct and HH18 maternal. There is a strong genetic relationship between hip height and weight at weaning that also affects hip height at 18 mo of age. Both product-moment and rank correlations between estimated breeding values (EBV) for direct values indicate that almost all of the same animals would be selected for PHG EBV if the selection criterion used was WHH EBV, and that it is possible to accomplish a preliminary selection for HH18 EBV using WHH EBV. Correlations between breeding values for WHH, WWT, and HH18 indicate that it will be possible to identify animals that will reduce, maintain, or increase hip height while weaning weight is increased. Thus, if the breeding objective is to manipulate growth to 18 mo of age, implementation of multiple-trait breeding programs considering hip height and weight at weaning will help to predict hip height at 18 mo of age.     

Genetic relationship between purebred and crossbred sow longevity

Background: The overall breeding objective for a nucleus swine selection program is to improve crossbred commercial performance. Most genetic improvement programs are based on an assumed high degree of positive relationship between purebred performance in a nucleus herd and their relatives' crossbred performance in a commercial herd. The objective of this study was to examine the relationship between purebred and crossbred sow longevity performance. Sow longevity was defined as a binary trait with a success occurring if a sow remained in the herd for a certain number of parities and including the cumulative number born alive as a measure of reproductive success. Heritabilities, genetic correlations, and phenotypic correlations were estimated using THRGIBBS1F90.Results: Results indicated little to no genetic correlations between crossbred and purebred reproductive traits.This indicates that selection for longevity or lifetime performance at the nucleus level may not result in improved longevity and lifetime performance at the crossbred level. Early parity performance was highly correlated with lifetime performance indicating that an indicator trait at an early parity could be used to predict lifetime performance. This would allow a sow to have her own record for the selection trait before she has been removed from the herd.Conclusions: Results from this study aid in quantifying the relationship between purebred and crossbred performance and provide information for genetic companies to consider when developing a selection program where the objective is to improve crossbred sow performance. Utilizing crossbred records in a selection program would be the best way to improve crossbred sow productivity.