Genetic parameters of body weight, egg production and shell quality traits in the Brown Tsaiya laying duck

Genome-wide association analysis of the primary feather growth traits of duck: identification of potential Loci for growth regulation

The feather is an important epidermal appendage, plays an important role in the life activities of avian specie, and has important economic value. Revealing the molecular regulation mechanism of feather growth has a significant meaning in studying adaptive evolution, physiology, and mating of avian species and also provides a theoretical reference for poultry breeding. In this study, the genome-wide association analysis (GWAS) of 358 ducks was based on primary feather length phenotypic data (28-60 d), length growth rates (LGRs), and maturity scores (60 d) to explore the genetic basis affecting feather growth and maturation. The results showed that, among the primary feather 1 to 5 in ducks, the mean LGR of primary feather 2 was the fastest, with the longest length. The primary feathers in males grew and matured slightly faster than in females. The mean maturity scores of primary feather 10∼7 were higher than primary feather 1 to 3 in ducks. GWAS further showed 116 SNPs associated with feather length traits. In addition, 2 candidate regions (Chr1: 127,407,230-127,524,879 bp and Chr21: 182,061,707-183,616,298 bp) were associated with LGR, which contain total 13 candidate genes (The extremely significant SNPs were mainly located in 2 genes: Chr1: REPS2 and Chr21: PTPRT). Four candidate regions (Chr1: 29,113,036-28,675,018 bp, Chr2: 18,253,612-149,111,290 bp, Chr15: 6,489,774 to 12,138,221 bp and Chr21: 6,578,021-8,472,904 bp) were associated with feather maturity, which contain total 24 candidate genes (The extremely significant SNPs were mainly located in 4 genes: Chr1: IMMP2L, DOCK4 and DDX10, Chr2: LDLRAD4). In conclusion, sex factors influence feather growth and maturity, and the genetic basis of the growth /maturity trait between different feathers is similar. REPS2, PTPRT genes, and IMMP2L, DOCK4, DDX10, and LDLRAD4 are important candidate genes that influence feather growth and maturity, respectively.

Polymorphisms of melatonin receptor genes and their associations with egg production traits in Shaoxing duck

OBJECTIVE

In birds, three types of melatonin receptors (MTNR1A, MTNR1B, and MTNR1C) have been cloned. Previous researches have showed that three melatonin receptors played an essential role in reproduction and ovarian physiology. However, the association of polymorphisms of the three receptors with duck reproduction traits and egg quality traits is still unknown. In this test, we chose MTNR1A, MTNR1B, and MTNR1C as candidate genes to detect novel sequence polymorphism and analyze their association with egg production traits in Shaoxing duck, and detected their mRNA expression level in ovaries.

METHODS

In this study, a total of 785 duck blood samples were collected to investigate the association of melatonin receptor genes with egg production traits and egg quality traits using a direct sequencing method. And 6 ducks representing two groups (3 of each) according to the age at first eggs (at 128 days of age or after 150 days of age) were carefully selected for quantitative real-time polymerase chain reaction.

RESULTS

Seven novel polymorphisms (MTNR1A: g. 268C>T, MTNR1B: g. 41C>T, and g. 161T>C, MTNR1C: g. 10C>T, g. 24A>G, g. 108C>T, g. 363 T>C) were detected. The single nucleotide polymorphism (SNP) of MTNR1A (g. 268C>T) was significantly linked with the age at first egg (p<0.05). And a statistically significant association (p<0.05) was found between MTNR1C g.108 C>T and egg production traits: total egg numbers at 34 weeks old of age and age at first egg. In addition, the mRNA expression level of MTNR1A in ovary was significantly higher in late-mature group than in early-mature group, while MTNR1C showed a contrary tendency (p<0.05).

CONCLUSION

These results suggest that identified SNPs in MTNR1A and MTNR1C may influence the age at first egg and could be considered as the candidate molecular marker for identify early maturely traits in duck selection and improvement.

Selection response and estimation of the genetic parameters for multidimensional measured breast meat yield related traits in a long-term breeding Pekin duck line

Objective

This study was conducted to estimate the genetic parameters and breeding values of breast meat related traits of Pekin ducks. Selection response was also determined by using ultrasound breast muscle thickness (BMT) measurements in combination with bosom breadth (BB) and keel length (KL) values.

Methods

The traits analyzed were breast meat weight (BMW), body weight (BW), breast meat percentage (BMP) and the three parameters of breast meat (BB, KL, and BMT). These measurements were derived from studying 15,781 Pekin ducks selected from 10 generations based on breast meat weight. Genetic parameters and breeding value were estimated for the analysis of the breeding process.

Results

Estimated heritability of BMW and BMP were moderate (0.23 and 0.16, respectively), and heritability of BW was high (0.48). Other traits such as BB, KL, and BMT indicated moderate heritability ranging between 0.11 and 0.28. Significant phenotypic correlations of BMW with BW and BMP were discovered (p<0.05), and genetic correlations of BMW with BW and BMP were positive and high (0.83 and 0.66, respectively). It was noted that BMW had positive correlations with all the other traits. Generational average estimated breeding values of all traits increased substantially over the course of selection, which demonstrated that the ducks responded efficiently to increased breast meat yield after 10 generations of breeding.

Conclusion

The results indicated that duck BMW had the potential to be increased through genetic selection with positive effects on BW and BMP. The ultrasound BMT, in combination with the measurement of BB and KL, is shown to be essential and effective in the process of high breast meat yield duck breeding.

Eleven generations of selection for the duration of fertility in the intergeneric crossbreeding of ducks

A 12-generation selection experiment involving a selected line (S) and a control line (C) has been conducted since 1992 with the aim of increasing the number of fertile eggs laid by the Brown Tsaiya duck after a single artificial insemination (AI) with pooled Muscovy semen. On average, 28.9% of the females and 17.05% of the males were selected. The selection responses and the predicted responses showed similar trends. The average predicted genetic responses per generation in genetic standard deviation units were 0.40 for the number of fertile eggs, 0.45 for the maximum duration of fertility, and 0.32 for the number of hatched mule ducklings' traits. The fertility rates for days 2-8 after AI were 89.14% in the S line and 61.46% in the C line. Embryo viability was not impaired by this selection. The largest increase in fertility rate per day after a single AI was observed from d5 to d11. In G12, the fertility rate in the selected line was 91% at d2, 94% at d3, 92% at days 3 and 4 then decreased to 81% at d8, 75% at d9, 58% at d10 and 42% at d11. In contrast, the fertility rate in the control line showed an abrupt decrease from d4 (74%). The same tendencies were observed for the evolution of hatchability according to the egg set rates. It was concluded that selection for the number of fertile eggs after a single AI with pooled Muscovy semen could effectively increase the duration of the fertile period in ducks and that research should now be focused on ways to improve the viability of the hybrid mule duck embryo.

Heritabilities and genetic correlations of laying performance in Muscovy ducks selected in Taiwan

1. Genetic parameters in the base population of a closed experimental strain of Muscovy ducks, selected for body weight at 10 weeks of age, were estimated from data in 8 successive generations, for the following traits: age at first egg (AGE1EGG), total number of eggs laid at 40 and 52 weeks of age (NEGG40 and NEGG52), number of eggs laid during 15 and 22 weeks in the first laying cycle (NEGG15W and NEGG22W), and their Box-Cox transformed data. 2. The method of multi-trait restricted maximum likelihood with an animal model was used to estimate genetic parameters. Only the results obtained with non-transformed data are shown. 3. Heritability estimates for laying performance showed moderate values, increasing little with age: 0.20+/-0.03 (AGE1EGG), 0.23+/-0.03 (NEGG40), 0.27+/-0.03 (NEGG52), 0.20+/-0.03 (NEGG15W), and 0.22+/-0.03 (NEGG22W). 4. Genetic correlations between laying traits were high. Genetic correlation between AGE1EGG and egg number was negative, it was positive between total numbers of eggs at 40 and 52 weeks and egg numbers in the first laying cycle. 5. Body weight at 10 weeks of age exhibited positive genetic correlations (0.46+/-0.06) with age at first egg and negative with egg production traits (-0.28+/-0.06 to -0.41+/-0.06). 6. The cumulated predicted genetic gains, after 7 generations of selection, expressed per genetic standard deviation unit (sigma(g)) were 0.06 sigma(g), 0.07 sigma(g), 0.17 sigma(g), 0.23 sigma(g), and 0.25 sigma(g) for AGE1EGG, NEGG40, NEGG52, NEGG15W, and NEGG22W, respectively. 7. Selecting Muscovy ducks to improve laying in Taiwanese climatic conditions would be possible using the number of eggs laid up to 52 weeks of age as the selection criterion. Because unintended selection effects for laying traits were present, the selection experiment for body weight at 10 weeks of age was not antagonistic with laying traits.

Genetic parameters of reproductive traits in Brown Tsaiya ducks artificially inseminated with semen from Muscovy drakes

A selection experiment on maximum duration of fertility of Brown Tsaiya ducks after artificial insemination (AI) with pooled Muscovy semen has been conducted since 1992. The Brown Tsaiya ducks were divided into two lines: a control line (T) with no selection and a selected line (S). The traits measured were the number of eggs set that were laid from Days 2 to 15 after one AI (NES), the number of fertile eggs at candling (NEF), the total number of dead embryos (NED), the maximum duration of fertility (MD), and the number of hatched mule ducklings (NEH). The selected trait was NEF. Six generations with a total of 2,127 females were measured. The variance components were estimated for each line in a multiple-trait animal model, using the restricted maximum likelihood (REML) methodology, which yields estimates free of bias caused by selection and inbreeding. Estimates of the heritability and genetic correlation from the two lines were very similar. Heritabilities in the S and T lines, respectively, were 0.14 and 0.10 for NES, 0.30 and 0.26 for NEF, 0.06 and 0.09 for NED, 0.28 and 0.21 for MD, and 0.18 and 0.19 for NEH. High and favorable genetic correlations existed between NEF and MD (0.96 and 0.92), between NEF and NEH (0.86 and 0.91), and between MD and NEH (0.90 and 0.82). The results suggested that selection for NEF could improve the maximum duration of fertility, but it could be useful to check the estimates of genetic parameters in a meat-type female duck.

Heritabilities and genetic correlations of body weights and feather length in growing Muscovy selected in Taiwan

1. Heritabilities and genetic correlations in the base population of a closed strain of Muscovy duck, moderately selected for body weight at 10 weeks of age, have been estimated from the data of 9 successive generations for the following traits: male and female body weight at 10 and 18 weeks of age (BW10m, BW18m, BW10f, BW18f) and length of the 8th primary feather at 10 weeks of age (F110m, F110f). 2. Multivariate REML with an animal model was used, pooling data from the 9 generations (3283 and 3289 male and female offspring respectively). The same trait expressed in male and female was considered as 2 different traits. 3. The 8th primary feather was longer in females than in males by 6% to 22% at 10 weeks of age. Body weight was heavier in males than in females by 42% to 58% at 10 weeks of age and by 57% to 75% at 18 weeks of age. 3. The heritability estimates for body weight traits showed moderate values, being a little higher for females than for males at the same age, increasing with age from h2=0.24 at BW10m to h2=0.43 at BW18f. 4. The heritability estimates for feather length showed that a greater response would be obtained in selection for male feather length (h2=0.37) than for female length (h2=0.14). Both have high genetic correlations with body weight so they could be indirectly improved. 5. Heritabilities of the difference in body weights between males and females at 10 weeks (h2=0.07) and 18 weeks of age (h2=0.10) were small, as well as for feather length (h2=0.10). It would probably be difficult to modify sexual dimorphism in body weight through selection. 6. Genetic correlations between BW10m, BW18m and BW10f, BW18f were respectively r(g)=0.77 and r(g)=0.80. They were larger for body weight at the same ages between males and females, r(g)=0.90 (r(g)=0.88 between F110m and F110f). Body weight in males and females at the same age should be better considered as 2 different traits in a selection programme. 7. The cumulated predicted genetic gains expressed per unity of the genetic standard deviation (sigma(g)) over the 8 generations of selection were 1.3 sigma(g) and 1.4 sigma(g) respectively for the BW10m and BW10f. The predicted correlated responses were 1.2 sigma(g) for body weights at 18 weeks of age, 0.9 sigma(g) and 0.7 sigma(g) for F110f and F110m respectively.