Search

The main goal of breeding programmes is to maximise the genetic improvement of the economic traits of farm animals. Beside the economic traits, the birds' survival has directly influenced on the economic gain. Therefore, this study aimed to investigate the genetic relationship between survival and productive traits in Japanese quail. A total of 1854 records were collected during four generations from 2017 to 2019 in Khorasan Razavi Agricultural Research and Training Centre (KRARTC). Data were used to estimate the genetic correlations among quail survival (S) with egg weight (EW) and body weight gain (BWG) traits. Linear-threshold model was used to estimate (co)variance components, and genetic parameters of traits via the Gibbs sampling method. The heritability of EW was 0.04, and the heritability estimates for survival at different ages ranged from 0.138 to 0.399 in joint analysis with EW. The highest negative genetic correlation between EW and S0–14 (i.e. survival up to 14 d) was obtained as −0.704. The highest and lowest heritability of weight gain traits for BWG0–7 and BWG7–14 were 0.583 and 0.116, respectively. The analyses of BWG traits with survival at different ages revealed that the genetic correlations ranged from 0.015 (between BWG0–7 and S0–14) to 0.638 (between BWG0–7 and S0–7). This study showed that the genetic selection for survival at different ages could be effective. On the other hand, selection for BWG0–7 could also indirectly improve the survival in quails because of the positive and high genetic correlation between BWG0–7 with S0–7. Genetic improvement of production traits in quail may lead to reduced survival in quail. Studies regarding on the survival of quail were yet not carried out. Heritability of the survival at different ages showed that genetic selection for this trait could improve the survival. Survival at different ages had a negative genetic correlation with egg weight (EW), and body weight gain (BWG) traits after 21 d of old. [ABSTRACT FROM AUTHOR]

Early growth traits in quails are considered as the growth performances before the inflection point which are genetically different from body weights (BW) at later stages. Moreover, in addition to growth performance, humoral immunity is moderately heritable and is considered in some breeding programs. However, estimating the direct genetic, particularly the maternal genetic correlations between growth and immunity in quail, are not studied sufficiently, which were the aims of the present study. The quails' BW were recorded at hatch (BW0) to 25 d of age with a 5-d interval and body weight gains (BWG) were measured as average growth performance of the birds in a 5-d period. Antibody titer against Newcastle disease virus (IgN) was measured through the hemagglutination inhibition (HI) test. For titration of anti-SRBC antibodies (IgY and IgM), a hemagglutination microtiter assay was used. In general, growth records in 4,181 birds and humoral immune responses in 1,023 birds were assigned to the study. The genetic parameters were estimated by single-trait analysis via Gibb's sampling. After finding the best model for each trait, multi-trait analysis was done to estimate the direct and maternal genetic correlations. Direct heritabilities (h2) were estimated to be moderate for BW (0.481−0.551) and BWG (0.524−0.557), while h2 for immune responses were low (0.035−0.079). Maternal environmental effect (c2) was only significant for BW0, BW5, and BWG0-5. Maternal heritabilities (m2) for BW and BWG were all lower than corresponding h2, ranging from 0.072 (BW25) to 0.098 (BW0). The m2 for IgN (0.098) was more than 2.5 times greater than h2 (0.040) for this trait. Direct (r a) and maternal (r m) genetic correlations between IgN-BW, IgY-BW, and IgY-BWG were negative, while ra and rm for IgM-BW, IgN-BWG, and IgM-BWG were positive. The r a between humoral immune responses were low to moderate and rm was significant only for IgY-IgM (0.339). Given positive genetic correlations in BWG-IgN and BWG-IgM as well as positive genetic correlations between both IgN and IgM with IgY, it is suggested that including the BWG in the breeding programs would directly result in the improvement of the birds' growth performance. It would also contribute indirectly to the improvement of the birds' humoral immune responses. [ABSTRACT FROM AUTHOR]

Highlights • Humoral immune responses in Japanese quail are heritable. • After immunization of the birds with SRBC, genetic correlations between immunoglobulin M (IgM) and early growth traits are positive, but for AbT and IgY are negative. • Genetic correlations for AbNDV with BW traits are negative, but with BWG traits are positive. • Genetic selection for IgM responses could improve growth traits. Abstract The aim of this study was to estimate genetic parameters of early growth performances and humoral immune responses (antibody titers against sheep red blood cells (SRBC) and Newcastle Disease Virus (NDV)) in Japanese quail. For this purpose, a total of 10,923 records of early growth traits including body weights (BW) at 0, 5, 10, 15 and 20 d old and body weight gain (BWG) between 0–5, 5–10, 10–15 and 15–20 days, and 2,314 records of humoral immune responses were used to estimate genetic parameters through multiple-trait Bayesian analyses. The estimates of heritability of BW and BWG traits were 0.14 to 0.28 and 0.08 to 0.10, respectively. The range of genetic and phenotypic correlations for BW traits varied from 0.63 to 0.98 and 0.17 to 0.89, respectively. Furthermore, estimates of genetic and phenotypic correlations for BWG traits at different ages were in the range of 0.46 to 0.86 and 0.12 to 0.46, respectively. Heritability estimates of total antibody titer (AbT), titer of immunoglobulin Y (IgY) and titer of immunoglobulin M (IgM) against SRBC were 0.21, 0.24 and 0.20, respectively, but h2 of antibody titer against NDV (AbNDV) was lower than those of estimated for SRBC antigen (h2 = 0.17). Genetic correlations between antibody titers against SRBC and NDV were similar (0.42 − 0.46). Genetic correlations were positive only for IgM with BW traits, however, estimates of genetic correlation between BW traits at different ages with AbT and IgY were negative and moderate (−0.30 to −0.66), and with AbNDV were negative and low (−0.13 to −0.25). Like BW traits, genetic and phenotypic correlations between AbT and IgY titers and BWG traits were negative and varied from −0.21 to −0.72, while genetic correlations of BWG traits with IgM and AbNDV titers were both positive (0.11 to 0.27 and 0.23 to 0.31, respectively). It is suggests that selection to improved BW and BWG traits may lead to decline of humoral immune responses in Japanese quail. However, improvement of BW and BWG traits and humoral immune responses would be possible through selection for IgM titers against SRBC due to its high and positive genetic correlation with growth traits. [ABSTRACT FROM AUTHOR]