Genome-wide association study on abdomen depth, head width, hip width, and withers height in native cattle of Guilan (Bos indicus).

Native breeds in any country are a national capital, and their preservation is of great importance. Native Cattle of Guilan (NCG) is one of the few pure native breeds in Iran and the West Asia region. During the last decade, NCG population has decreased by more than 40%. This study aimed to identify significant single nucleotide polymorphisms (SNPs) and candidate genes associated with meat production traits in NCG using a genome-wide association study (GWAS). The blood and hair samples were collected from 72 NCG individuals and genotyped using the Illumina Bovine SNP50 chip. The results of the genomic scan showed that several SNPs were associated with abdominal depth, head width, hip width, and withers height in NCG. Several candidate genes were identified, including multiple epidermal growth factor-like domains 11 (MEGF11), Methionine Sulfoxide Reductase A (MSRA), chondroitin sulfate synthase 3 (CHSY3), Cyclin-Dependent Kinase 7 (CDK7), and Parkin (PRKN) genes, which are involved in muscle growth, meat tenderness, differentiation of fat cells, fat metabolism, and adipogenesis. These genes can contribute to meat quantity and quality in NCG. This study provided valuable insights into the genetics of NCG and the identification of effective genes associated with meat production traits. The results of this study could be used for the preservation and sustainable use of this breed of native cattle, as an important genetic resource in Iran.

Genetic Analysis of Persistency for Milk Fat Yield in Iranian Buffaloes (Bubalus bubalis).

This study aimed to estimate heritabilities and genetic trends for different persistency measures for milk fat yield and their genetic correlations with 270-day milk yield in Iranian buffaloes. The records of test-day milk fat yield belonging to the first three lactations of buffaloes within 523 herds consisting of 43,818 records were got from the Animal Breeding Center and Promotion of Animal Products of Iran from 1996 to 2012. To fit the lactation curves based on a random regression test-day model, different orders of Legendre polynomial (LP) functions were selected. Three persistency measures were altered according to the specific condition of the lactation curve in buffaloes: (1) The average of estimated breeding values (EBVs) for test day fat yield from day 226 to day 270 as a deviation from the average of EBVs from day 44 to day 62 (PM1), (2) A summation of contribution for each day from day 53 to day 247 as a deviation from day 248 (PM2), and (3) The difference between EBVs for day 257 and day 80 (PM3). The estimates of heritability for PM1, PM2, and PM3 ranged from 0.20 to 0.48, from 0.36 to 0.47, and from 0.19 to 0.35 over the first three lactations, respectively. The estimate of genetic trends for different persistency measures of milk fat yield was not significant over the lactations (P > 0.05). Genetic correlation estimates between various measures of persistency were generally high over the first three lactations. Also, genetic correlations estimates between persistency measures and 270-day milk yield were mostly low and varied from 0.00 to 0.24 (between PM1 and 270-day milk yield), from -0.19 to 0.13 (between PM2 and 270-day milk yield), and from -0.02 to 0.00 (between PM1 and 270-day milk yield) over the first three lactations, respectively. Persistency measures that showed low genetic correlations with milk fat yield were considered the most suitable measures in selection schemes. Besides, medium to high heritability estimates for different persistency measures for milk fat yield indicated that relevant genetic variations detected for these characters could be regarded in outlining later genetic improvement programs of Iranian buffaloes.

Marker genotyping error effects on genomic predictions under different genetic architectures.

This study aimed to determine the effect of different rates of marker genotyping error on the accuracy of genomic prediction that was examined under distinct marker and quantitative trait loci (QTL) densities and different heritability estimates using a stochastic simulation approach. For each scenario of simulation, a reference population with phenotypic and genotypic records and a validation population with only genotypic records were considered. Marker effects were estimated in the reference population, and then their genotypic records were used to predict genomic breeding values in the validation population. The prediction accuracy was calculated as the correlation between estimated and true breeding values. The prediction bias was examined by computing the regression of true genomic breeding value on estimated genomic breeding value. The accuracy of the genomic evaluation was the highest in a scenario with no marker genotyping error and varied from 0.731 to 0.934. The accuracy of the genomic evaluation was the lowest in a scenario with marker genotyping error equal to 20% and changed from 0.517 to 0.762. The unbiased regression coefficients of true genomic breeding value on estimated genomic breeding value were obtained in the reference and validation populations when the rate of marker genotyping error was equal to zero. The results showed that marker genotyping error can reduce the accuracy of genomic evaluations. Moreover, marker genotyping error can provide biased estimates of genomic breeding values. Therefore, for obtaining accurate results it is recommended to minimize the marker genotyping errors to zero in genomic evaluation programs.

Genetic and environmental relationships among milk yield, persistency of milk yield, somatic cell count and calving interval in Holstein cows / Relaciones genéticas y ambientales entre el rendimiento lechero, la persistencia del rendimiento lechero, el recuento de células somáticas y el intervalo de partos en vacas Holstein / Relações genéticas e ambientais entre produção de leite, persistância de produção de leite, contagem de células somáticas e intervalo de pertos em vacas Holstein

Abstract Background: Fertility and health traits, other than production traits, have a major role in the profitability of dairy cattle. Therefore, it seems necessary to include the afore mentioned traits in breeding programs. Hence, genetic parameters are needed to establish breeding plans. Objective: To estimate heritabilities as well as genetic and environmental relationships among total milk yield (TMY), persistency of milk yield (PMY), mean somatic cell count (SCC), mean loge somatic cell count (LnSCC), standard deviation of somatic cell count (stdSCC), and calving interval (CI) using two-trait and multi-trait analyses in Iranian Holstein. Methods: The dataset consisted of 25,883 first lactation records collected from 2002 to 2007 in 97 Holstein dairy herds in Iran. Four criteria of persistency of milk yield (PMY) were calculated using the Wood's gamma function. The WOMBAT1.0 software was used to estimate the (co)variance components using the Average Information Restricted Maximum Likelihood algorithm. Results: Total milk yield (TMY) resulted in the highest heritability estimate (0.29). Heritability estimates for different criteria of persistency of milk yield (PMY) ranged from 0.05 to 0.10. The unfavorable genetic correlation between TMY and calving interval (CI) was 0.71, while that of PMY with CI was 0.46. The estimated environmental correlations were lower than the genetic correlations for all traits, but the trends were generally similar. Conclusion: The results indicate that including PMY in the breeding goals could increase TMY and CI, and decrease somatic cell count (SCC).

Resumen Antecedentes: Las características de fertilidad y salud, además de las de producción, tienen un papel importante en la rentabilidad de los hatos lecheros. Por lo tanto, parece necesario incluir los rasgos mencionados en los sistemas de mejoramiento. Por ende, los parámetros genéticos son necesarios para establecer planes de cría. Objetivo: Estimar la heredabilidad, así como las relaciones genéticas y ambientales entre el rendimiento total de leche (TMY), la persistencia del rendimiento lechero (PMY), el recuento medio de células somáticas (SCC), el recuento de células somáticas de loge promedio (LnSCC), la desviación estándar del recuento de células somáticas (stdSCC) y el intervalo de partos (CI) en vacas Holstein mediante análisis de dos rasgos y análisis múltiples. Métodos: Se analizaron registros de primera lactancia de 25.883 vacas Holstein, recolectados entre 2002 y 2007 en 97 rebaños lecheros de Irán. Se calcularon cuatro criterios de persistencia del rendimiento lácteo utilizando la función gamma de Wood. El software Wombat1.0 se utilizó para estimar los componentes de (co)varianza que emplean el algoritmo de máxima verosimilitud restringida de información promedio. Resultados: El rendimiento de leche (TMY) obtuvo la mayor heredabilidad estimada (0,29). Las estimaciones de heredabilidad para diferentes criterios de persistencia del rendimiento de la leche variaron de 0,05 a 0,10. La correlación genética desfavorable entre TMY e intervalo entre partos fue 0,71, mientras que la de PMY con el CI fue de 0,46. Las correlaciones ambientales estimadas fueron inferiores a las correlaciones genéticas para todos los rasgos, pero las tendencias fueron, en general, similares. Conclusión: Incluir el PMY en la meta de cría podría aumentar el TMY y CI, además de disminuir el recuento de células somáticas (SCC).

Resumo Antecedentes: As características de fertilidade e saúde, além das características de produção, têmum papel importante narentabilidade das vacas leiteiras. Por isso, parece necessário incluir as características já mencionadas nos sistemas de melhoramento genético. Assim, são necessários parâmetros genéticos para estabelecer planos de melhoramento genético. Objetivo: Estimar herdabilidade, bem como as relações genéticas e ambientais entre a produção total de leite (TMY), persistância da produção de leite (PMY), contagem médiade células somáticas (SCC), contagem média de células somáticas loge (LnSCC), desviopadrao da contagem média de células somáticas (stdSCC) e intervalo de pertosem (CI) vacas Holstein por duas análises de características e traços multiplos. Métodos: O conjunto de dados consistiuem registros de 25.883 vacas Holstein de primeira lactação coletadas de 2002 a 2007 em 97 rebanhos leiteiros em Iran. Foram calculados quatrocritérios de persistência da produção de leite utilizando a função gama de Wood. O software Wombat1.0 foi usado para estimar os componentes de (co)variância que empregam o algoritmo de máxima verossimilhança com informações restritas. Resultados: A maior herdabilidade (0,29) foi estimada para produção de leite. As estimativas de herdabilidade para diferentes critérios de persisténcia da produção de leite variaram 0,05 a 0,10. A correlação genética desfavorável entre o intervalo TMY eo intervalo de parto foi de 0,71 enquanto que a de PMY com CI foi de 0,46. As correlações ambientais estimadas foram inferiores às correlações genéticas para todos os traços, mas as tendencias foram geralmente semelhantes. Conclusão: Os resultados indicaram que a inclusão de PMY na meta de reprodução poderia aumentar TMY e CI, no entanto, diminuir a contagem de células somáticas.

Estimation of genetic variation for macro- and micro-environmental sensitivities of milk yield and composition in Holstein cows using double hierarchical generalized linear models.

The aim of this study was to estimate genetic parameters for environmental sensitivities in milk yield and composition of Iranian Holstein cows using the double hierarchical generalized linear model (DHGLM) method. Data set included test-day productive records of cows which were provided by the Animal Breeding Center and Promotion of Animal Products of Iran during 1983 to 2014. In the DHGLM method, a random regression model was fitted which included two parts of mean and residual variance. A random regression model (mean model) and a residual variance model were used to study the genetic variation of micro-environmental sensitivities. In order to consider macro-environmental sensitivities, DHGLM was extended using a reaction norm model, and a sire model was applied. Based on the mean model, additive genetic variances for the mean were 38.25 for milk yield, 0.23 for fat yield and 0.03 for protein yield in the first lactation, respectively. Based on the residual variance model, additive genetic variances for residual variance were 0.039 for milk yield, 0.030 for fat yield and 0.020 for protein yield in the first lactation, respectively. Estimates of genetic correlation between milk yield and macro- and micro-environmental sensitivities were 0.660 and 0.597 in the first lactation, respectively. The results of this study indicated that macro- and micro-environmental sensitivities were present for milk production traits of Iranian Holsteins. High genetic coefficient of variation for micro-environmental sensitivities indicated the possibility of reducing environmental variation and increase in uniformity via selection.

Genetic aspects of some reproductive, udder health and energy status traits in Holstein cows.

The objective of this study was to estimate heritability as well as genetic and environmental relationships between days to first heat (DFH), days to first service (DFS), interval from calving to conception (ICC), calving interval (CI) and number of inseminations per conception (NIS) with mastitis (Mast), number of mastitis occurrence (NumMast), different measures of somatic cell count (SCC) and fat to protein ratio (F:P) in the first lactation of Holstein cows in Iran using linear and threshold animal and sire models. The 33851 first lactation records of Holstein cows from five large dairy herds with calving dates from March 2002 to September 2014 were analyzed with univariate and bivariate linear and threshold animal and sire models using Gibbs sampling methodology. Data from parity one to nine comprising 62483 records were used to conduct repeatability model analysis for reproductive traits. Heritabilities of the reproduction traits varied from 0.067 (for ICC) to 0.105 (for DFH) using linear animal models. Also, the heritabilities of udder health traits varied from 0.005 to 0.102 using different models. The repeatabilities of reproductive traits ranged from 0.110 to 0.307. In general, the genetic correlations (rg) between reproduction traits were positive and high (with the exception of rg between DFH-NIS). The rg between reproduction traits with udder health traits ranged from -0.029 to 0.359 and 0.151 to 0.584 using linear-linear and threshold-linear animal models, respectively. Generally, there was favorable rg between reproduction traits with udder health traits; therefore, selection for one set of these traits would improve the correlated traits. However, due to different (co)variance components and economic weights in each country/region, it can be recommended to investigate inclusion of both sets of these traits in breeding objectives.

Economic values and selection indices for production and reproduction traits of Iranian buffaloes (Bubalus bubalis).

Iranian buffalo plays a critical role in supplying a portion of the income and the necessities of the rural population. The first step to design a breeding program is difinition of breeding goal (BG), a linear combination of breeding values for various traits and their economic values (EV). The current study was aimed at determining EVs for important traits of Iranian buffaloes, namely milk yield (MY), milk fat (MF), age at the first calving (AFC), and calving interval (CI), as well as at estimating the genetic response of applying various types of selection indices. Economic and management data of 50 buffalo herds from various main regions of buffalo rearing in Iran were collected. The EVs were estimated using a simple profit function. Five selection indices were constructed by combining information on various traits. The EVs for BG traits of MY, MF, AFC, and CI were 0.18, 4.66, - 0.36, and - 1.87 US$, respectively. The highest predicted genetic gain in BG was 16.95 and came from applying the selection index that included all traits. The smallest genetic gain (4.93) was predicted for the index with only AFC included. Predicted genetic gain from an index that included production traits and AFC as a reproduction trait (16.9) was higher than that from the index with only production traits (16.15). Results showed that inclusion of reproductive traits in the selection index had a positive effect on genetic gain for breeding goal.

Appropriate selection indices for functional traits in dairy cattle breeding schemes.

The objective of this study was to establish different single or multiple trait selection indices to calculate genetic and economic gains by combining some production, reproduction and udder health traits in a population similar to the overall practical situation in Iran, with and without imposing restrictions on genetic change for some traits. The SelAction software was used to perform the analyses based on selection index theory through a deterministic model. Results indicated that among established indices, the index that showed the highest genetic gain for milk yield did not maximize the total genetic and economic gains. Rather, the index that included all production, reproduction and udder health traits yielded the highest genetic and economic gains. When we placed restriction on the selection indices, the economic gain decreased and the amount of reduction depended on the heritability and the correlation of restricted trait(s) with other traits. Generally, regarding the economic genetic gain per generation, the indices based on records of 200 offspring were 4.819% more efficient than those that used information of 100 offspring.

A review on breeding and genetic strategies in Iranian buffaloes (Bubalus bubalis).

The aim of current study was to review breeding progress and update information on genetic strategies in Iranian buffaloes. Iranian buffalo is one of the vital domestic animals throughout north, north-west, south and south-west of Iran with measurable characteristics both in milk and meat production. The species plays an important role in rural economy of the country due to its unique characteristics such as resistance to diseases and parasites, having long productive lifespan and showing higher capability of consuming low-quality forage. In Iran, total production of milk and meat devoted to buffaloes are 293,000 and 24,700 tons, respectively. Selection activities and milk yield recording are carrying out by the central government through the Animal Breeding Centre of Iran. The main breeding activities of Iranian buffaloes included the estimation of genetic parameters and genetic trends for performance traits using different models and methods, estimation of economic values and selection criteria and analysis of population structure. Incorporating different aspects of dairy buffalo management together with improved housing, nutrition, breeding and milking, is known to produce significant improvements in buffalo production. Therefore, identifying genetic potential of Iranian buffaloes, selection of superior breeds, improving nutritional management and reproduction and developing the education and increasing the skills of practical breeders can be useful in order to enhance the performance and profitability of Iranian buffaloes.

Genetic perspective of milk yield persistency in the first three lactations of Iranian buffaloes (Bubalus bubalis).

The objectives of this study were to estimate the genetic parameters and genetic trends for different measures of persistency (PM) for milk yield in Iranian buffaloes using a random regression test day model. Test day records of the first three lactations of buffaloes within 715 herds comprising 43 014, 38 941 and 33 937 records, respectively, were obtained from the Animal Breeding Center of Iran during 1992 to 2012. Legendre polynomial functions were chosen to fit the lactation curves in the framework of a random regression test day model for estimating (co)variance components. Three measures of persistency were modified based on the lactation curve conditions of buffaloes: (1) The average of estimated breeding values (EBVs) for test day milk yields from day 226 to day 270 as a deviation from the average of EBVs from day 44 to day 62 (PM1), (2) A summation of contribution for each day from day 53 to day 247 as a deviation from day 248 (PM2), (3) The difference between EBVs for day 257 and day 80 (PM3). The highest heritability estimates were observed for PM2 over the first three lactations (0·29, 0·80 and 0·42, respectively). Estimates of genetic correlations between persistency measures and milk yield varied from -0·48 to 0·29 (first lactation), from -0·12 to 0·48 (second lactation), and from -0·62 to 0·63 (third lactation). Estimate of genetic trend for first lactation PM2 was negative (-0·0088 ± 0·0043; P < 0·05). It is essential to include milk yield persistency in the breeding goal of Iranian buffaloes along with other important traits such as milk yield or reproductive traits.

Genetic evaluation of dystocia and its relationship with productive and reproductive traits in Holstein cows¤ / Evaluación genética de distocia y su relación con las características productivas y reproductivas en vacas Holstein / Avaliação genética de distocia e sua relação com características produtivas e reprodutivas em vacas da raça Holandesa

Abstract: Background: dystocia is one of the most economically significant secondary traits in dairy cows and has adverse effects on the subsequent survival, health, and performance of mothers and offspring. Objective: the aim of this study was to estimate direct and maternal genetic parameters for calving ease (CE) and its relationship with productive and reproductive traits in Iranian Holstein cows. Methods: data from 1991 through 2011 were collected from the Animal Breeding Center of Iran, and contained 132,831 records of CE, 183,203 records of productive traits including 305-d adjusted milk yield (MY305), 305-d adjusted fat yield (FY305) and 305-d adjusted protein yield (PY305), and 129,199 records of reproductive traits including days open (DO), days to first service (DFS) and calving interval (CI). Univariate and bivariate linear animal models were used for the analysis of traits in two different models on which direct genetic effect (model 1) and direct + maternal genetic effects (model 2) using AI-REML algorithm were included. Results: estimated heritabilities for CE in model 1 were 0.02 in univariate and 0.02-0.03 in bivariate analyses. Direct and maternal heritabilities in model 2 were 0.02 and 0.002 for univariate, and 0.03 and 0.0004-0.006 in bivariate analyses, respectively. Genetic correlations between direct effects of CE with MY305, FY305, and PY305 were -0.99, 0.02 and-0.07 in model 1, and -0.2, -0.02 and -0.13 in model 2, respectively. Conclusion: this study suggested that a selection index that includes both direct and maternal effects should be included in CE breeding programs.

Resumen Antecedentes: la distocia es uno de los rasgos secundarios económicamente más significativos en las vacas lecheras y tiene efectos adversos sobre la posterior supervivencia, salud y el rendimiento de las madres e hijos. Objetivo: estimar parámetros genéticos directos y maternos para facilidad de parto (CE) y su relación con las características productivas y reproductivas en vacas Holstein iraníes. Métodos: se recogieron datos desde 1991 hasta 2011 en el Centro de Reproducción Animal de Irán, que contenían 132.831 registros de la CE, 183.203 registros de características productivas, incluyendo 305-d ajustado la producción de leche (MY305), 305-d de rendimiento graso ajustado (FY305) y 305-d de producción de proteína ajustada (PY305), y 129.199 registros de características reproductivas, incluyendo días abiertos (DO), días al primer servicio (DFS) y el intervalo entre partos (CI). Se utilizaron modelos animales lineales univariantes y bivariantes para el análisis de rasgos en dos modelos diferentes en los que se incluyeron el efecto genético directo (modelo 1) y los efectos genéticos maternos directos + (modelo 2) usando el algoritmo AI-REML. Resultados: las heredabilidades estimadas para la CE en el modelo 1 fueron 0,02 en uni y 0,02-0,03 en los análisis bivariados. Las heredabilidades directas y maternas en el modelo 2 fueron 0,02 y 0,002 para univariado, y 0,03 y 0,0004 a 0,006 en el análisis bivariado, respectivamente. Las correlaciones genéticas entre los efectos directos de la CE con MY305, FY305 y PY305 fueron -0,99, 0,02 y -0,07 en el modelo 1 y -0,2, -0,02 y -0,13 en el modelo 2, respectivamente. Conclusión: este estudio sugiere que un índice de selección que incluye tanto los efectos directos y maternos se debe incluir en los programas de mejoramiento de la CE.

Resumo Antecedentes: distocia é uma das características secundárias economicamente mais significativas em vacas leiteiras e tem efeitos adversos sobre a subsequente sobrevivência, saúde e desempenho de mães e filhos. Objetivo: o objetivo deste estudo foi estimar parâmetros genéticos direto e maternos para facilidade de parto (CE) e sua relação com características produtivas e reprodutivas em vacas da raça Holandesa iranianos. Métodos: dados de 1991 a 2011 foram coletados a partir do Centro de Melhoramento Animal do Irã, estes continham 132.831 registros da CE, 183.203 registros de características produtivas, incluindo 305-d rendimento ajustado leite (P305), 305-d produção de gordura ajustada (FY305) e 305-d rendimento ajustado proteína (PY305), e 129.199 registros de características reprodutivas, incluindo jornadas de portas abertas (DO), dias para o primeiro serviço (DFS) e intervalo entre partos (CI). Modelos animais lineares univariados e bivariados foram utilizados para a análise de características em dois modelos diferentes em que foram incluídos efeito genético direto (modelo 1) e efeitos genéticos maternos diretos + (modelo 2) usando o algorítmo AI-REML. Resultados: a herdabilidade estimada para CE no modelo 1 foi 0,02 na análise univariada e 0,02-0,03 na análise bivariada. A herdabilidade direta e materna no modelo 2 foi 0,02 e 0,002 para univariada, e 0,03 e 0,0004-0,006 na bivariada, respectivamente. As correlações genéticas entre os efeitos diretos da CE com P305, FY305 e PY305 foram -0,99, 0,02 e -0,07 no modelo 1 e -0,2, -0,02 e -0,13 no modelo 2, respectivamente. Conclusão: este estudo sugere que um índice de seleção que inclua efeitos diretos e maternos deve ser incluído em programas de melhoramento para CE.

Inbreeding effects on reproductive traits in Iranian Guilan sheep.

The objective of the present study was to evaluate the effects of inbreeding on reproductive traits in Guilan sheep. Traits included were litter size at birth (LSB), litter size at weaning (LSW), litter mean weight per lamb born (LMWLB), litter mean weight per lamb weaned (LMWLW), total litter weight at birth (TLWB), and total litter weight at weaning (TLWW). Data and pedigree information used in this study were collected during 1994 to 2011 by the Agriculture Organization of Guilan Province in the north of Iran. Data were comprised of 14,534 records of lambs from 136 sires and 2021 dams. All the animals were grouped into three classes according to the inbreeding coefficients (F) obtained by their pedigree: the first class included non-inbred animals (F = 0%), and the second and third classes included inbred animals (0 < F ≤ 5% and F > 5%, respectively). The regression coefficients of LSB, LSW, LMWLB, LMWLW, TLWB, and TLWW on lamb inbreeding for a change of 1% in inbreeding were estimated to be 0.035 ± 0.0038 (P < 0.001), -0.029 ± 0.0077 (P < 0.05), -0.333 ± 0.009 (P < 0.001), -2.21 ± 0.071 (P < 0.001), -0.254 ± 0.013 (P < 0.001), and -1.95 ± 0.093 (P < 0.001), respectively. Effect of inbreeding on reproductive traits in Guilan sheep was very pronounced in the flock. The utilization of a program for planned mating system, in the present flock, suggested keeping the level of inbreeding under control and avoiding appearance of its detrimental effects.

Population genetic structure analysis and effect of inbreeding on body weights at different ages in Iranian Mehraban sheep.

The objective of this study was to describe the population structure and inbreeding, and to quantify their effects on weights at different ages of Mehraban sheep in Iran. The analysis was based on the pedigree information of 26990 animals and 10278 body weight records from birth to yearling age. Data and pedigree information were collected during 1994 to 2011 by the breeding station of Mehraban sheep. The population structure was analyzed using the CFC program. Inbreeding of all animals was calculated by INBUPGF90 program. All animals were grouped into three classes according to their inbreeding coefficients: the first class included non-inbred animals (F=0); and the second and third classes included inbred animals (0

Estimation of genetic parameters for reproductive traits in Shall sheep.

The objective of this study was to estimate genetic parameters for reproductive traits in Shall sheep. Data included 1,316 records on reproductive performances of 395 Shall ewes from 41 sires and 136 dams which were collected from 2001 to 2007 in Shall breeding station in Qazvin province at the Northwest of Iran. Studied traits were litter size at birth (LSB), litter size at weaning (LSW), litter mean weight per lamb born (LMWLB), litter mean weight per lamb weaned (LMWLW), total litter weight at birth (TLWB), and total litter weight at weaning (TLWW). Test of significance to include fixed effects in the statistical model was performed using the general linear model procedure of SAS. The effects of lambing year and ewe age at lambing were significant (P<0.05). Genetic parameters were estimated using restricted maximum likelihood procedure, under repeatability animal models. Direct heritability estimates were 0.02, 0.01, 0.47, 0.40, 0.15, and 0.03 for LSB, LSW, LMWLB, LMWLW, TLWB, and TLWW, respectively, and corresponding repeatabilities were 0.02, 0.01, 0.73, 0.41, 0.27, and 0.03. Genetic correlation estimates between traits ranged from -0.99 for LSW-LMWLW to 0.99 for LSB-TLWB, LSW-TLWB, and LSW-TLWW. Phenotypic correlations ranged from -0.71 for LSB-LMWLW to 0.98 for LSB-TLWW and environmental correlations ranged from -0.89 for LSB-LMWLW to 0.99 for LSB-TLWW. Results showed that the highest heritability estimates were for LMWLB and LMWLW suggesting that direct selection based on these traits could be effective. Also, strong positive genetic correlations of LMWLB and LMWLW with other traits may improve meat production efficiency in Shall sheep.

Derivation of economic values for productive and reproductive traits of Bombyx mori (Lepidoptera: Bombycidae) from profit equation.

Using a deterministic model of profit equation compatible to cocoon production system in Iran, equations for estimating economic values of cocoon weight, shell weight, shell percentage, fecundity, fertility, and hatchability of three commercial varieties of silkworm Bombyx mori (L.) were derived. Economic values of these traits as well as their relative economic importance (REI) compared with cocoon weight were estimated. Estimates of economic value of a given trait differed among the varieties. Cocoon weight, shell weight, and shell percentage had the highest economic value in variety 107. The highest economic value for fecundity, fertility, and hatchability was estimated in variety 110. Shell weight and shell percentage were the most important production traits, and fecundity was the most important reproduction trait. The REI values of shell weight and shell percentage were higher than that of cocoon weight. The sensitivity of estimated economic values to principal factors of production system was studied by altering cocoon weight, shell percentage, fecundity, variable costs, and cocoon price by +/- 10%. The traits varied in the rate of sensitivity of their economic values to changes in production factors. Economic values of cocoon weight, fecundity, fertility, and hatchability had the most sensitivity to the changes in shell percentage. The most important factor affecting economic values of shell weight and shell percentage was the grade 1 cocoon price. Economic value equations provided in this study can help silkworm breeders to concentrate on the most important factors in predicting the future. Furthermore, when these factors change, silkworm breeders will be able to determine to what extent breeding goals have to change.