Genetic Parameters For Litter Size Research Articles

Direct–Maternal Genetic Parameters for Litter Size and Body Weight of Piglets of a New Black Breed for the Taiwan Black Hog Market

The objective of this study was to estimate the genetic parameters of litter size and piglet weight from farrowing to weaning in KHAPS Black sows. The genetic parameters investigated were the direct (h2d), maternal (h2m), realized (h2r), and total (h2T) heritability, as well as correlations (rd, rm, and rdm) within and between traits. The analyses were performed using single- and three-trait animal models with and without maternal genetic effects. In the three-trait model with maternal genetic effect, all estimates of h2d and h2m were significantly different from zero except the h2d of mean birth weight. Positive values of rd and rm between traits were observed as expected in the range of 0.322-1.000. Negative values of rdm were found within and between traits and were less associated with mean piglet weight traits than litter size traits. Estimates of h2T were consistently larger than those of h2r in both the single- and three-trait model analyses. In addition, the three-trait model can take into account the association between the traits, so the estimates are more accurate with smaller SEs. In conclusion, maternal genetic effects were not negligible in this study, and thus, a multiple-trait animal model with maternal genetic effects and full pedigree is recommended to assist future pig breeding decisions in this new breed.

Genetic analysis of litter size and number of kids born alive across parities in Spanish goat breeds using a random regression model

Genetic parameters of litter size (LS) and number of kids born alive (NBA) were estimated across parities in Florida and Payoya goat breeds using a threshold random regression model (RRM). We analysed the reproductive records for the Florida and Payoya breeds separately, and a total of 130.849 and 67.478 reproductive records from the first to the seventh parities from Florida and Payoya, respectively, were included in the analysis. Random regressions on Legendre polynomials of standardised parity were included for permanent environmental and additive genetic effects. We based our estimation of all the covariance components on Bayesian inference under categorical distribution and considered heterogeneous residual variances in the model. The estimates of heritabilities ranged from null to 0.37 for LS and from 0.02 to 0.20 for NBA, while the repeatability estimates were between 0.008–0.60 and 0.03–0.44 for LS and NBA, respectively. Phenotypic correlations within-trait along parities ranged widely from −0.31 to 0.97, while the genetic correlations within-trait through parities showed a wider range and magnitude of values, from −0.98 to 0.99 for LS and from −0.72 to 0.99 for NBA. The estimates of genetic correlations between LS and NBA in the different parities were positive in the first two parities and negative in the later ones. Due to the noticeable changes in variance and the incomplete genetic correlations, the use of a random regression model to analyse LS and NBA is recommended in goat breeds. HIGHLIGHTS A bivariate threshold random regression model has been used for the first time to estimate genetic parameters of litter size and number of kids born alive across parities in Spanish goat breeds. The evolution of genetic parameters along parities is different between Florida and Payoya that have different production systems, being more intensive in the case of the Florida breed. Estimates of variance were not constant across parities for both traits and breeds. Genetic correlations within-trait across parities were different from unity. Thus, LS and NBA should be treated as different traits in successive parities. Given that the estimates of variance and covariances are not constant across parities for both traits and breeds, the use of RRM is highly recommended.

Index selection as a key in the selection process for pigs

Submitted 2020-06-30 | Accepted 2020-08-09 | Available 2020-12-01 https://doi.org/10.15414/afz.2020.23.mi-fpap.74-78 Farrowing records of the Duroc, Hampshire and Pietrain breed were analysed by means of a three-trait repeatability animal model. The examined traits were number of piglets born alive (NBA), number of weaned piglets (NWE) and litter weight at weaning (LWWE). Heritability estimates were 0.10, 0.08 and 0.12 for NBA, NWE and LWWE, respectively. The ratios of the permanent environmental variance to the phenotypic variance were 0.08, 0.05 and 0.03 for NBA, NWE and LWWE, respectively. Using the estimated breeding values a desired index was constructed in order to improve each trait by one additive genetic standard deviation. NWE and NBA have a high correlation and range within breeds from 0.87 to 0.91, but LWWE had poor to moderate correlation with NBA and NWE (0.13 to 0.59). Animals ranking based on index showed better genetic merit for Duroc breed and the index scores ranged from 49.77 to 186.56. In the case of Hampshire and Pietrain breeds somewhat lower index scores (30.92 to 165.97) were observed. The estimated genetic trend for NBA was highest for the Pietrain breed (0.02), but for Duroc and Hampshire breeds the estimates were zero and negative (-0.01). For NWE the estimated genetic trends were practically zero for Duroc and Pietrain breeds and it was 0.02 for Pietrain. LWWE showed highest genetic trend for Duroc breed (0.17) but it was lower (0.09) for Pietrain and and negative (-0.24) for Hampshire. Keywords: pig, selection, breeding value, desired gain index, aggregate genotype References Brascamp E.W. (1984). Selection indices with constraints. Animal Breeding Abstracts 52, 645-654. Groeneveld E, Kovac M, Mielenz N. (2008). VCE User’s guide and reference manual. Version 6.0. Neustadt, Germany: Institute of Farm Genetics; p. 1–125. Groeneveld E. (1990). PEST Users’ manual. Institute of animal husbandry and animal behaviour Neustadt: Federal Research Centre. Hamann, H., Steinheuer, R., & Distl, O. (2004). Estimation of genetic parameters for litter size as a sow and boar trait in German herdbook Landrace and Pietrain swine. Livestock Production Science, 85(2-3), 201-207. https://doi.org/10.1016/s0301-6226(03)00135-0 Hungarian Pig Breeders Association (2017). Pig performance testing code. Budapest, 1-39. Chen, P., Baas, T. J., Mabry, J. W., Koehler, K. J., & Dekkers, J. C. M. (2003). Genetic parameters and trends for litter traits in US Yorkshire, Duroc, Hampshire, and Landrace pigs. Journal of animal science, 81(1), 46-53. https://doi.org/10.2527/2003.81146x Irgang, R., Favero, J. A., & Kennedy, B. W. (1994). Genetic parameters for litter size of different parities in Duroc, Landrace, and Large White sows. Journal of Animal Science, 72(9), 2237-2246. https://doi.org/10.2527/1994.7292237x Nagy, I. (2017). Quantitative genetic studies in multiparous species. DSc. Thesis. 1-150. Nath, M., Singh, B.P., Kataria, M.C. Singh, R.V. (2002). MIX: A software for construction of multi-trait selection index. In: Proc. of the 7th World’s Congress on Genetics Applied to Livestock Production. August 19–23, 2002, Montpellier, France. Skorupski, M. T., Garrick, D. J., & Blair, H. T. (1996). Estimates of genetic parameters for production and reproduction traits in three breeds of pigs. New Zealand Journal of Agricultural Research, 39(3), 387-395. https://doi.org/10.1080/00288233.1996.9513198 Â

211 Changes in genetic parameters of fitness and growth traits under genomic selection in pigs

Abstract Genomic selection increases intensity of selection and decreases generation interval. However, intensive selection reduces genetic variation and can strengthen undesirable genetic correlations. The purpose of this study was to investigate changes in genetic parameters of litter size (LS), number born alive (NBA), number born dead (NBD) and average daily gain (ADG) and weight at off-test (WT) in pigs over time. The data set contained 20,086 (LS), 21,230 (NBA), 21,230 (NBD), 144,717 (ADG) and 144,718 (WT) phenotypic records. Pedigree file included 369,776 animals born between 2001 and 2018, of which 39,038 were genotyped. Two trait models were evaluated (LS-ADG, LS-WT, NBA-ADG, NBA-WT, NBD-ADG and NBD-WT) using 3-year sliding subsets starting from 2010. Variance components and genetic parameters were estimated using GIBBS2F90 program. Computations were performed with (BLUP) or without (ssGBLUP) genotypes. For BLUP (ssGBLUP), the changes in heritability from 2010–2012 to 2015–2018 were 0.08 to 0.09 (0.08 to 0.06) for LS, 0.33 to 0.24 (0.37 to 0.16) for ADG, 0.11 to 0.07 (0.10 to 0.07) for NBD, and 0.32 to 0.24 (0.38 to 0.17) for WT. Differences were also observed for genetic correlations as they were -0.23 to -0.73 (-0.31 to -0.58) for LS-ADG, -0.24 to -0.74 (-0.31 to -0.50) for LS-WT, -0.33 to -0.65 (-0.41 to -0.53) for NBA-ADG, -0.35 to -0.66 (-0.42 to -0.45) for NBA-WT, 0.12 to 0.04 (0.12 to 0.16) for NBD-ADG, and 0.11 to 0.05 (0.11 to 0.22) for NBD-WT. Genomic selection in pigs reduced heritabilities and emphasized the antagonistic relationship that are under strong selection. Heritabilities estimated from ssGBLUP declined more than those by BLUP while changes in the genetic correlations were smaller and more gradual by ssGBLUP. Differences between ssGBLUP and BLUP could be caused by genomic pre-selection unaccounted for by BLUP.

Genetic parameters and trends for litter size in Markhoz goats

Background: Prolificacy has a high economic value and is one of the most important reproduction traits in small ruminants such as Markhoz goats, which is an endangered breed. Objective: To estimate genetic, environmental and phenotypic trends, and genetic parameters for litter size (LS), as a prolificacy trait of Markhoz goat does. Methods: The study was conducted using kidding records of 3,064 Markhoz does from 1992 to 2015. Genetic parameters were estimated with a logit link function using ASReml software, fitting a repeatability animal model, with birth year, kidding year, and kidding age as fixed effects, and direct additive genetic and permanent environmental effects as random effects. Genetic, phenotypic and environmental trends were estimated by using regression of breeding value, phenotypic value and environmental deviation averages on birth year, respectively. Results: Low and negligible heritability (0.002), repeatability (0.054) and coefficient of permanent environment (0.052) were estimated for LS, which indicates low possibility to achieve rapid genetic progress through phenotypic selection. A non-significant -actually, zero- genetic trend (0.00004 heads/kidding/year), and significant negative phenotypic and environmental trends (-0.01097 and -0.01100 heads/kidding/year, respectively) were estimated in this study. Conclusion: Optimizing environmental conditions and application of high-throughput technologies in selection programs could help reducing the extinction risk of Markhoz breed.Keywords: extinction risk, genetic trend, heritability, phenotypic selection, prolificacy. Resumen Antecedentes: La prolificidad tiene un alto valor económico y es uno de los rasgos reproductivos más importantes en pequeños rumiantes, tales como la raza caprina Markhoz. que es esta en peligro de extinción. Objetivo: Estimar lastendencias genéticas, ambientales y fenotípicas, y los parámetros genéticos para el tamaño de la camada (LS), como rasgo de prolificidad de las hembras de cabras Markhoz. Métodos: Se utilizaron registros de partos de 3.064 hembras Markhoz, de 1992 a 2015. Los parámetros genéticos se estimaron con una función de enlace logit utilizando el software ASReml, ajustando un modelo animal de repetibilidad, con el año de nacimiento, el año del parto y la edad al parto como efectos fijos, y genéticos aditivos directos y efectos ambientales permanentes como efectos aleatorios. Las tendencias genéticas, fenotípicas y ambientalesse estimaron mediante la regresión del valor de la cría, el valor fenotípico y los promedios de desviación ambiental en el año de nacimiento, respectivamente. Resultados: Se estimó la heredabilidad -baja e insignificante- (0,002), repetibilidad (0,054) y coeficiente de ambiente permanente (0,052) para LS, lo que indica una baja posibilidad de lograr un progreso genético rápido a través de selección fenotípica. Se estimó una tendencia genética no significativa -de hecho, cero- (0,00004 cabezas/parto/año) y se estimaron tendencias fenotípicas y ambientales negativas significativas (-0,01097 y -0,01100 cabezas/parto/año, respectivamente) en el período estudiado. Conclusión: La optimización de las condiciones ambientales y la aplicación de tecnologías de alto rendimiento en los programas de selección podrían reducir el riesgo de extinción de la raza Markhoz.Palabras clave: heredabilidad, prolificidad, riesgo de extinción, selección fenotípica, tendencia genética. Resumo Antecedentes: Aprolificidade tem um elevado valor económico e é uma das maisimportantes características de reprodução nos pequenos ruminantes, como a raça de caprinos Markhoz, que está em perigo de extinção. Objetivo: Estimar tendências genéticas, ambientais e fenotípicas, e parâmetros genéticos para o tamanho da serapilheira (LS), como um traço de proliferação de cabras Markhoz. Métodos: Este estudo foi realizado usando registros de parto de 3.064 Markhoz entre 1992 e 2015. Os parâmetros genéticos foram estimados com uma função logit link utilizando o software ASReml, ajustando um modelo animal de repetibilidade, com o ano de nascimento, o ano de parto ea idade de caçoar como efeitos fixos e efeitos ambientais diretos e genéticos diretos como efeitos aleatórios. As tendências genéticas, fenotípicas e ambientais foram estimadas pela regressão do valor de criação, valor fenotípico e médias de desvio ambiental no ano de nascimento, respectivamente. Resultados: Herdabilidade baixa e negligenciável (0,002), repetibilidade (0,054) e coeficiente de ambiente permanente (0,052) foram estimadas para LS, o que indica baixa possibilidade de alcançar um progresso genético rápido através da seleção fenotípica. Foi estimada uma tendência genética não-significativa e realmente zero (0,00004 cabeças/parto/ano) e tendências fenotípicas e ambientais negativas significativas (-0,01097 e -0,01100 cabeças/parto/ano, respectivamente) no período estudado. Conclusão: Parece que a otimização das condições ambientais ea aplicação de tecnologias de alto rendimento em programas de seleção poderiam reduzir o risco de extinção para a raça Markhoz.Palavras-chave: heritabilidade, prolificidade, risco de extinção, seleção fenotípica, tendência genética.

Genetic parameters for litter size, piglet growth and sow's early growth and body composition in the Chinese-European line Tai Zumu.

Genetics of piglet growth in association with sow's early growth and body composition were estimated in the Tai Zumu line. Piglet and sow's litter growth traits were calculated from individual weights collected at birth and at 3 weeks of age. Sow's litter traits included the number of piglets born alive (NBA), the mean piglet weight (MW) and the standard deviation of weights within the litter (SDW). Sow's early growth was measured by the age at 100 kg (A100), and body composition included backfat thickness (BF100). A main objective of this study was to estimate separately the direct genetic effect (d) and the maternal genetic effect (m) on piglet weight and daily weight gain during lactation. Variance components were estimated using the restricted maximum likelihood methodology based on animal models. The heritability estimates were 0.19 for NBA, 0.15 and 0.26 for SDW and MW at 3 weeks and 0.42 and 0.70 for A100 and BF100. The NBA was almost independent from SDW. Conversely, the A100 and BF100 were correlated unfavourably with SDW (rg <-0.24, SE<0.12). A stronger selection for litter size should have little effect on litter homogeneity in weights. Selection for lean growth rate tends to favour heterogeneity in weights. The direct effect on piglet weight at birth and daily weight gain accounted for 12% (h(²) (d) = 0.02) and 50% (h(²) (d) = 0.11) of the genetic variance, respectively. The association between d and m for piglet weight was not different from zero at birth (rg = 0.19, SE = 0.27), but a strong antagonism between d and m for daily weight gain from birth to 3 weeks was found (rg = -0.41, SE = 0.17). Substantial direct and maternal genetic effects influenced piglet growth until weaning in opposite way.

Estimation of genetic parameters for litter size in Charollais, Romney, Merinolandschaf, Romanov, Suffolk, Šumava and Texel breeds of sheep

The objective of this investigation was to estimate genetic parameters for litter size in Charollais, Romney, Merinolandschaf, Romanov, Suffolk, Šumava and Texel breeds of sheep. These breeds account for more than three quarters of the recorded sheep population in the Czech Republic. A total of 143,896 lambing records from 1990 to 2012 were analyzed. Variance components and genetic parameters for litter size were estimated separately for each breed using the animal model with repeatability. The model equation contained ewe age as a fixed effect and random effects of contemporary group, permanent environment and direct additive genetic effect of the animal. Estimates of phenotype variance (σP2) increased across breeds (0.236 for Šumava to 0.779 for Romanov) with increasing breed average for number of lambs per litter. Variance component estimates for permanent environmental effect of the ewe were low (0.0001–0.0262). The variance of common environment of contemporary group (σCG2=0.0223–0.1309) had bigger influence on the total variability of litter size in almost all breeds then additive genetic variance (σa2=0.0146–0.0587). The lowest heritability and repeatability estimates were for the Šumava (h2=0.0619; rrep2=0.0823) and Romney breeds (h2=0.0626; rrep2=0.0811); while the highest were for Merinolandschaf (h2=0.1091; rrep2=0.1129). We conclude that genetic parameters did differ among the investigated breeds, which should be taken into account in breeding value estimation.

Genetic parameters for litter size in Black Slavonian pigs

The objective of this study was to estimate genetic parameters for litter size of Black Slavonian pigs using the repeatability, multiple trait, and random regression models, and to consider the possibility to increase litter size in Black Slavonian pigs by selection. A total of 4733 litter records from the first to the sixth parity from sows that farrowed between January 1998 and December 2010 were included in the analysis. Individual record consisted of the following variables: breeding organisation (eight regions), parity (1-6), service boar, and farrowing season (month-year interaction). Estimation of all the covariance components with three different models was based on the residual maximum likelihood method. Estimate of additive genetic variance and heritability for number of piglets born alive with repeatability model was 0.23 and 0.10, respectively. Estimates of additive genetic variance with multiple trait and random regression model were in a wider range from 0.05 to 0.65 across parities, and heritabilities were estimated in the range between 0.03 and 0.26. Estimates of phenotypic and additive genetic correlations were much smoother with random regression model in comparison with multiple trait model. Due to unexpected changes of variances along trajectory obtained with multiple trait and random regression model, the best option for genetic evaluation of litter size for now could be the use of repeatability model. With increasing number of data with proper data structure alternative modelling of litter size of Black Slavonian pig using multiple trait and random regression model could be taken into consideration.

Genetic parameters for litter size in Black Slavonian pigs with each parity treated as a different trait

The objective of this study was to estimate genetic parameters for litter size in Black Slavonian pigs using a multiple trait model with each parity treated as a different trait. A total of 4733 litter records from the first to the sixth parity from sows that farrowed between January 1998 and December 2010 were included in the analysis. Estimates of additive genetic variance with a multiple trait model were in the range from 0.05 to 0.48 across parities, and heritabilites were estimated in the range between 0.03 and 0.21. Estimates of phenotypic correlations were much lower than those of genetic correlations. Due to the unexpected changes of variances with a parity, the best option for genetic evaluation of litter size could be the use of repeatability model. With increasing number of data and with proper data structure alternative, modelling of litter size of Black Slavonian pig using multiple trait model could be taken into consideration.

Can number and size of offspring increase simultaneously? - a central life-history trade-off reconsidered

BackgroundTo maximize their fitness, parents are assumed to allocate their resources optimally between number and size of offspring. Although this fundamental life-history trade-off has been subject to long standing interest, its genetic basis, especially in wild mammals, still remains unresolved. One important reason for this problem is that a large multigenerational pedigree is required to conduct a reliable analysis of this trade-off.ResultsWe used the REML-animal model to estimate genetic parameters for litter size and individual birth size for a common Palearctic small mammal, the bank vole (Myodes glareolus). Even though a phenotypic trade-off between offspring number and size was evident, it was not explained by a genetic trade-off, but rather by negative correlations in permanent and temporary environmental effects. In fact, even positive genetic correlations were estimated between direct genetic effects for offspring number and size indicating that genetic variation in these two traits is not necessarily antagonistic in mammals.ConclusionsOur results have notable implications for the study of the life-history trade-off between offspring number and size in mammals. The estimated genetic correlations suggest that evolution of offspring number and size in polytocous mammals is not constrained by the trade-off caused by antagonistic selection responses per se, but rather by the opposing correlative selection responses in direct and maternal genetic effects for birth size.

Genetic parameters of litter size in Creole goats and their implication for a breeding programme including adaptation traits

Genetic parameters of litter size in Creole goats and their implication for a breeding programme including adaptation traits

Genetic parameters for Finnish blue fox population: litter size, age at first insemination and pelt size

Pelt size has increased rapidly in the Finnish blue fox population during the last decade. However, average number of pups per mated female has slightly decreased after the mid-1990’s. In this study we estimated genetic parameters of litter size in the first two parturitions, age of female at first insemination, and pelt size with a linear multitrait animal model. Heritability of litter size in first and second parturition was 0.06 and 0.10, respectively. Heritability estimate for age at first insemination was 0.15 and for pelt size 0.29. Genetic correlation between pelt size and first litter size was –0.30, between first and second litter size 0.76, and between second litter size and age at first insemination 0.70. Thus, genetic correlation between fertility and pelt size was unfavorable.;

Estimação de parâmetros genéticos em tamanho de leitegada de suínos utilizando análises de características múltiplas

Registros de animais da raça Large White foram utilizados para estimar componentes de co-variâncias e parâmetros genéticos para a característica número de leitões nascidos como medida do tamanho de leitegada. Na obtenção dos componentes de co-variâncias e dos parâmetros genéticos, utilizou-se o método da Máxima Verossimilhança Restrita, com o algoritmo Livre de Derivadas, por meio do programa MTDFREML. O modelo misto continha o efeito fixo de grupo contemporâneo e os efeitos aleatórios genético aditivo direto e residual. Dados das primeiras quatro parições foram usados em duas análises: análises unicaracterísticas e análise multicaracterística separada em séries de análises bicaracterísticas, na qual cada parição foi tratada como característica diferente. As estimativas de herdabilidades aditivas diretas para as parições obtidas nas análises multicaracterísticas foram consistentes com as estimativas obtidas nas análises unicaracterísticas, que variaram de 0,14 a 0,20. Estimativas de correlação fenotípica foram menores que as correlações genéticas. As correlações genéticas foram menores que 0,75 em todas as parições, exceto entre a terceira e a quarta parição, cuja correlação foi alta (0,91). A menor correlação genética foi observada entre a primeira e a segunda ordem de parto (0,60).

Genetic parameters for litter size and weight at different parities in Iberian pigs

Genetic progress for reproductive performance in pigs is limited by mothering ability. It is a critical aspect for dam lines, in which litter weight at weaning could be included with litter size in the selection goal. Our objective was to investigate in Iberian pigs the genetic basis of the number of alive born piglets (NBA) and the litter weight at 21days (LW21) over the successive parities (t). Records for NBA were available from 6,775 litters born from 1,893 sows of the Torbiscal line, and LW21 records proceeded from 1,431 sows and 2,963 litters without crossfostering. Genetic parameters were estimated using an animal model with repeatability, a multi-trait animal model, and a random regression model. Estimated values of heritabilities for NBA and genetic correlations between parities confirm a partially different genetic control of prolificacy at parity 1 and at later parities. Results for LW21 indicate that this trait may be partially controlled by different genes at the first two parities and at the later ones. Estimated genetic parameters for NBA (t = 1), NBA (t &gt;/= 2), LW21 (t /= 3) were: heritability, hE2 = 0.15, 0.12, 0.22 and 0.15, respectively, and coefficient of permanent environmental effects, pE2 = 0.05, 0.02 and 0.24, respectively for the three last traits. The values of genetic correlations ranged from 0.44 to 0.84. A multitrait approach would be useful to estimate accurate genetic parameters, and to improve the low persistency of reproductive performance in the later parities of Iberian sows.

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

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

Phenotypic and Genetic Parameters for Litter Size in Some Regional Synthetic Sheep Genotypes: Evidence for a Major Gene Effect

Phenotypic and Genetic Parameters for Litter Size in Some Regional Synthetic Sheep Genotypes: Evidence for a Major Gene Effect

Estimation of genetic parameters for litter size after natural and hormone-induced oestrus in sheep

Genetic parameters for litter size after natural and hormone-induced oestrus were estimated for Ovin Ile de France, Blanc du Massif Central and Mouton Vendéen sheep, using REML methods in animal and sire model BLUP for observed litter size and normal scores of litter size. Litters born after hormone-induced oestrus and after natural oestrus were treated as different traits in order to estimate the genetic correlation between the traits and the genetic parameters of each trait. Explanatory variables were the year * flock * season of lambing effect, the physiological condition factor combining the type of rearing, age at the first lambing, interval between lambings and number of lambs suckled at the previous lambing, the month of birth nested within gestation number, a permanent environmental effect associated with the ewe and the additive genetic effect (sire or animal effect). For the three breeds, the heritability estimates for natural litter size, equal to 0.10, was higher than the heritability estimates for induced litter size, equal to 0.06. The estimate of genetic correlation between the two fertilization types was closed to 0.75. This result suggests that natural and induced litter size can be considered as two different traits, although controlled by a great number of common genes. This genetic correlation was higher than the previous estimate (0.40) reported by Bodin (1979) [Bodin, L., 1979. Estimation des paramètres génétiques de la taille de portée des agnelles Lacaune après fécondation sur oestrus naturel et induit. Ann. Génét. Sél. Anim. 11 (4), 413–424].

Estimation of genetic parameters for litter size as a sow and boar trait in German herdbook Landrace and Pietrain swine

Variance components for number of pigs born alive (NBA) were estimated by Gibbs Sampling using an animal model for the additive genetic maternal and paternal effect. The analysis was based on 48,577 litter records of German Landrace (DL) and 23,003 litter records of Pietrain (PI) herdbook sows. All data sets were provided by the official performance recording organization in Bavaria. The variance components for NBA were estimated in a bivariate animal model for first parity sows and sows with parities 2 to 10 taking into account the fixed effects of herd-year-season and parity number. Permanent environment of the sow and the paternal and maternal additive genetic effects were modelled as randomly distributed effects. The estimate for paternal heritability in both breeds was h 2 p=0.05 in parity number 1 and h 2 p=0.03 in parity numbers 2–10. The corresponding estimates for maternal heritability were h 2 m=0.15 in parity number 1 in both breeds and h 2 m=0.11 (DL) and h 2 m=0.09 (PI) in parity numbers 2–10. Genetic correlations between paternal and maternal additive genetic effects were positive and in the range from r pm=0.01 to r pm=0.25. Genetic correlations between paternal additive genetic effects in different parities were of medium size at r pp=0.47 for DL and r pp=0.34 for PI. This study confirms the additive genetic influence of a paternal component on NBA, in addition to the maternal component.

Multitrait and repeatability estimates of random effects on litter size in sheep

AbstractFive data sets with records of first, second and third lambings of the White Alpine sheep (WAS1, WAS2), the Brown-Headed Meat sheep (BFS), the Black-Brown Mountain sheep (SBS) and the Valais Black-Nose sheep (SNS) of Switzerland were used to estimate phenotypic and genetic parameters for litter size using a multitrait and a repeatability model by the REML method. The sets contained litter information from 26 274, 25 165, 18 913, 14 953 and 21 726 ewes, respectively. Average numbers of litters per ewe were between 2·09 and 2·31. Average litter sizes at birth were between 1·36 and 1·57 lambs in first, between 1·52 and 1·75 in second and, between 1·56 and 1·86 in third parities. Multitrait estimates of heritability for size of first litters were 0·164, 0·157, 0·117, 0·223 and 0·116 for the WAS1, WAS2, BFS, SBS and SNS data, respectively. The corresponding estimates were 0·176, 0·165, 0·140, 0·208 and 0·134 for second and, 0·141, 0·155, 0·121, 0·145 and 0·107 for third litters. The systematic increase in phenotypic variances from first to third litter within data sets favoured the multivariate over the repeatability approach. Genetic correlations between size of the first three litters were, with one exception, above 0·927. Random flock ✕ year and sire of litter effects contributed between 2·2% and 13·2% and between 0·7% and 4·7% to the phenotypic variance of the traits, respectively. Residuals contributed between 70·6% and 84·2% to this parameter, estimates for the third litter were always highest. Heritability estimates from the repeatability model were smaller than the smallest multivariate estimates. Expected genetic gain in litter size from selection on the multitrait model was equal to the achieved response from the repeatability approach.

Genetic analysis of litter size in Targhee, Suffolk, and Polypay sheep.

Data on litter size, weaning weights at 60, 90, and 120 d, postweaning gains from weaning to 120 or 365 d of age, fleece weight, and fiber diameter from Targhee, Suffolk, and Polypay flocks participating in the U.S. National Sheep Improvement Program were used to estimate genetic parameters for litter size and genetic relationships between early-life traits and future litter size. Records on 7,591 lambings by 3,131 Targhee ewes, 10,295 lambings by 5,038 Suffolk ewes, and 6,061 lambings by 2,709 Polypay ewes were used. Heritability estimates for litter size ranged from .09 to .11 across breeds; repeatability ranged from .09 to .13. Additive genetic effects on litter size were generally positively, and occasionally significantly, correlated with animal additive genetic effects on weaning weights and postweaning gains. Genetic correlations (r(a)) ranged from .08 to .48 in Targhee and from .17 to .43 in Suffolk but were close to 0 in Polypay (-.14 to .09). Additive maternal effects on weaning weight were positively associated with litter size in Suffolk and Polypay; this correlation was negative (-.23 to -.35), but not significant, in Targhee. Fleece weight was not strongly associated with litter size; (r(a) = -.09 to .21). However, fiber diameter had a significant undesirable correlation with litter size (.30) in Targhee. Estimates of phenotypic correlations of litter size with early-life traits were uniformly small (-.02 to .08). Thus, although occasional genetic antagonisms between litter size and early-life traits were observed in these data, none appeared large enough to prevent simultaneous genetic improvement in both traits.