Genetic analysis of longevity in specialized lines of rabbits

Nagar, El; Fawzy, Ayman Gamal

doi:10.4995/thesis/10251/52390

Cited by 3 publications

(2 citation statements)

References 47 publications

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“…The reported responses for LPL in the studied maternal lines are most likely associated, as previously indicated, directly to an unintended selection for longevity and not to a correlated response associated to the selection for criteria considered in each line. We proposed this idea because EL Nagar (2015) reported that, in the maternal lines under study, the genetic correlation between longevity and prolificacy traits (the selection criteria) were nearly null. In that study, the genetic correlation estimates between LPL and NBA were 0.01 (0.01), 0.01 (0.01), 0.16 (0.20), 0.09 (0.02) and −0.12 (0.33) for A, V, H, LP and R lines, respectively.…”

Section: Resultsmentioning

confidence: 99%

Functional longevity in five rabbit lines founded on different criteria: Comparison at foundation and at fixed times after selection

Nagar

Baselga

Mínguez

et al. 2021

J Animal Breeding Genetics

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The enhancement of rabbit female functional longevity, that is the ability to avoid voluntary culling, is a paramount aspect for the sustainability of meat rabbit production; this trait represents a direct indicator of female robustness. The objective of our study was to compare the functional longevity of five rabbit lines at their foundation and at fixed times during their selection processes. Four of them are maternal lines (A, V, H and LP) selected for litter size at weaning. The fifth line is the paternal line R, founded and selected for post‐weaning daily gain from 28 to 63 days. The comparison at foundation involved the complete data set (from March 1980 to March 2013; records of 15,670 does) and pedigree (19,405 animals). Latter comparisons were made when all lines shared the same environmental and management conditions, from March 1997 to September 1998 and from March 2011 to September 2012. In these second comparisons, the same model as that used in the comparison at foundation was used, but now the additive effect was excluded, only data from the corresponding periods were considered. At their foundation, lines V, H and LP showed larger functional longevity than lines A and R, being LP line that with the longest productive life. In the latter comparisons, lines A and R still showing the lowest functional longevities. However, as the selection process evolves, the differences between these two lines and the others were reduced. It could be concluded that the average longevity of a population greatly depends on the criteria followed for its foundation. In addition, along the selection for litter size, the differences of longevity between lines tend to decrease, this is due to an unintended selection for functional longevity, since only offspring from females reaching three parturitions are selected as breeding animals for the next generation.

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Section: Resultsmentioning

confidence: 99%

Functional longevity in five rabbit lines founded on different criteria: Comparison at foundation and at fixed times after selection

Nagar

Baselga

Mínguez

et al. 2021

J Animal Breeding Genetics

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“…(2008) reported that the mean of the relative risk between L and V lines was 0.80 (exp (−0.22)), which indicated that it was 1.24 times more likely for a V doe to be culled or to die than for an L doe. Moreover, the relative risks between V and L lines at their foundation and in present generations were reported to be 1.55 and 1.56, respectively, always in favour of L line (EL Nagar, 2015).…”

Section: Discussionmentioning

confidence: 96%

Genetic analysis of functional longevity in a complete diallel crossing experiment involving four maternal rabbit lines

Ragab

Baselga

Nagar

et al. 2020

J Animal Breeding Genetics

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In a diallel cross between four maternal lines of rabbits, the four maternal lines and the corresponding crossbred females (does) were evaluated concerning functional longevity, estimating their crossbreeding components. Sixteen genetic groups were produced by using four maternal lines of rabbit (A, V, H and LP (L)). The groups were distributed over 4 Spanish farms. In all farms, the V line was present as the reference group. A total of 7,211 does’ longevity records were recorded. Using a Cox proportional hazard model of fixed effects, survival analysis was performed to study longevity analysing the hazard of death or culling. Does from lines A, H and V had similar risks of death or of being culled, and they were more susceptible compared with those from line L. The lowest hazard was associated with L line does. No significant differences were found between the average of all crosses and the V line except when comparing the V line to the cross between A and H lines, favouring the former (1.30 higher risk of replacement for AH animals). Significant differences between reciprocal crosses were observed between VH and HV, in favour of HV (0.72 of relative risk of replacement) and between LH and HL, in favour of HL (0.76 of relative risk). Line V had the highest risk due to the direct genetic effects, and these differences were significant with the lines H (1.40 of relative risk) and L (1.43 of relative risk). The differences in maternal genetic effects were small and not significant except between lines H and V in favour of V line (0.75 of relative risk). The estimated direct heterosis effects do not always follow the same trend but they showed the importance of the crossing between specialized lines to produce crossbred does for intensive meat rabbit production.

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The Genetic Improvement in Meat Rabbits

García¹,

Argente²

2021

Lagomorpha Characteristics

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Rabbits are raised for many different purposes, such as breeding stock for meat, wool and fur, as an educational and experimental animal model, and as pets and show animals. However, this species is main used for meat production. France, Italy and Spain have an important role in the increase of world rabbit meat production through the development of selection programs in this species. Genetic improvement programs have based on development of maternal lines to improve prolificacy and paternal lines to improve growth rate, but the alternative development of multipurpose lines for litter size and growth traits will be discussed. In this chapter, the variance components of these traits, the response to selection and the main commercial available lines will be reviewed. Universities and public research centers have played a leading role in the development of these lines and in the diffusion of this genetic material through a pyramid scheme from selection nuclei to farmers. Recently, others functional traits are emerging successfully as selection criteria in breeding programs such as ovulation rate, prenatal survival, longevity, feed efficiency, meat quality, uniformity in production, and resistance to digestive disorders.

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Genetic analysis of longevity in specialized lines of rabbits

Cited by 3 publications

References 47 publications

Functional longevity in five rabbit lines founded on different criteria: Comparison at foundation and at fixed times after selection

Functional longevity in five rabbit lines founded on different criteria: Comparison at foundation and at fixed times after selection

Genetic analysis of functional longevity in a complete diallel crossing experiment involving four maternal rabbit lines

The Genetic Improvement in Meat Rabbits

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