Electronic Journal of Polish Agricultural Universities (EJPAU) founded by all Polish Agriculture Universities presents original papers and review articles relevant to all aspects of agricultural sciences. It is target for persons working both in science and industry,regulatory agencies or teaching in agricultural sector. Covered by IFIS Publishing (Food Science and Technology Abstracts), ELSEVIER Science - Food Science and Technology Program, CAS USA (Chemical Abstracts), CABI Publishing UK and ALPSP (Association of Learned and Professional Society Publisher - full membership). Presented in the Master List of Thomson ISI.
2004
Volume 7
Issue 2
Topic:
Animal Husbandry
ELECTRONIC
JOURNAL OF
POLISH
AGRICULTURAL
UNIVERSITIES
Rozempolska-Rucińska I. 2004. GENETIC BACKGROUND OF PERFORMANCE AND FUNCTIONAL TRAITS IN MINK, EJPAU 7(2), #03.
Available Online: http://www.ejpau.media.pl/volume7/issue2/animal/art-03.html

GENETIC BACKGROUND OF PERFORMANCE AND FUNCTIONAL TRAITS IN MINK

Iwona Rozempolska-Rucińska

 

ABSTRACT

The material comprised the data on 12 generations of animals collected from the breeding documentation of a standard mink reproduction farm. Reproduction and conformation traits covariance components were estimated by means of the REML method based on a multitrait animal model, using the DMU software package. Estimated heritability coefficients demonstrate a low additive effect of animal on the discussed traits. Particularly low values of this index were related to litter sizes at birth and at weaning. As to the conformation traits, the heritability coefficients remained between 0.116 and 0.218. Additive maternal effect on the level of reproduction and conformation traits was also estimated in the studies. The value of the parameter was about twice as high as the genetic variability resulting from the additive value of an individual and ranged from 0.037 to 0.202. A significant importance for breeding is attributed to genetic associations among individual traits taken into account in the br

Key words: mink, genetic variability, maternal effect.

INTRODUCTION

A goal for fur-gearing animal breeding and selection is to achieve large number of pelts of proper size and quality. Also, irrespective of the production goal, reproduction capabilities of the animals should be kept in mind as the properties affecting the performance [9]. The group of reproduction performance traits includes functional traits, related to animal's adaptation to its environment. The adaptation is of clear individual character, being dependent on both genetic background, age, sex, as well as acquired experience of the animal.

Constant improvement of both performance and functional traits, achieved due to phenotypic selection, is proportional to additive genetic variability. Thus, designing optimal breeding programme requires some knowledge on the variability of the traits included in the breeding objective. The variability are depicted by variance components, based on which genetic and environmental parameters are computed. Also, if we are to choose appropriate traits to be improved, we need to now any associations that might occur among them.

The aim of the studies was to determine the genetic background of economically-important performance and functional traits of standard mink.

MATERIALS AND METHODS

The material for the study comprised the data collected from the breeding documentation of a standard mink reproduction farm. The study covered 12 generations of animals. The information on mink reproduction referred to 7 376 breeding stock females, from which 12 455 litters were obtained.

Each year, during the period when the animals attained their full fur maturity, evaluation of youth conformation was carried out on the farm. During the studied period, a total of 10 163 animals (3 603 males and 6 560 females) were evaluated. During the analysed period, two different conformation standards were valid. Due to this fact, the evaluation results were standardised according to the present evaluation standard [18]. The scores were changed for each individual trait, converting a score from 30-point scale into the respective value on a 20-point scale. Length and density of hair, evaluated on a 30-point scale, was now a single trait according to the new standard and termed “pelage quality”.

The presented studies have not included one of the pelage traits, i.e. the colour type. In relation to standard mink, the animals achieve maximum score for this trait (no variability precluded any analyses).

Covariance components for performance and functional traits were estimated by means of the REML method based on a multitrait animal model, using the DMU software package [10]. Table 1 presents the factors included in genetic analyses of individual traits. These factor were selected based on previous statistical analyses. Whelping season represented the number of weeks from the beginning of a year until whelping. Sixteen classes of dam age x whelping season interactions were distinguished.

Table 1. Factors included in genetic analyses of individual traits

Trait

Typea

Number of born pups

Number of weaned pups

Functional traits

Body size
and
conformation

Colour
purity

Pelage
quality

Year of birth

F

     

x

x

x

Breeding year

F

x

x

x

     

Sex

F

     

x

x

x

Age of dam x whelping season

F

x

x

x

 

 

 

Size of weaned litter

C

     

x

x

x

Additive effect of individual

A

x

x

x

x

x

x

Additive effect of individual's dam

M

x

x

 

x

x

x

Specific environment of the animal

R

x

x

x

     
a Type of factor: F – constant factor, C – constant regression, A and M – random factor related to relationship matrix, R – random factor.

Due to a fact that the analysed traits were discrete variables, probit transformations of the obtained parameters were applied, according to the method by Żuk [19].

RESULTS AND DISCUSSION

Table 2 presents the values of the genetic parameters of the performance and conformation traits. Estimated heritability coefficients demonstrate that the additive effect of the animal on the studied traits was low. Particularly low values of the discussed index was those of litter sizes at birth (h2 = 0.017) and at weaning (h2 = 0.016). Phenotypic variability of the population was chiefly a result of the environmental impact. This is also confirmed by low values of the repeatability coefficients, which reached respectively, r2 = 0.084 and r2 = 0.075. In such a case, improved reproduction performance may be achieved through modulating the environmental factors. Low value of genetic parameters suggests that the methods of selecting parents for the next generation that have been applied so far (selection based on original litter size) are of low effectiveness.

Table 2. Heritability (h2), maternal effect (m2), and repeatability (r2) of the studied reproduction and conformation traits

Trait

h2

m2

r2

Number of born pups

0.0176

0.0378

0.0842

Number of weaned pups

0.0164

0.0591

0.0756

Body size and conformation

0.1167

0.2162

 

Colour purity

0.2185

0.1776

Pelage quality

0.1679

0.2028

The estimates obtained do not deviate to a large extent from analogical values estimated for the mink population by means of an animal model [7, 8]. However, the values of the estimated coefficients often differ in depending on animal species and, primarily, on the method of their estimation. In this case, the results achieved in this study were on the whole lower than those reported by other authors [5, 13, 14].

Additive effect of the dam (granddam of the litter) on the level of reproduction was also estimated in this study (Table 2). Despite low values of the discussed parameter, maternal effect proved a factor that at a higher degree shaped reproduction performance than the additive value of the individual. This effect proved stronger for the litter size at weaning [0.059].

Similar results were recorded by Jeżewska et al. [3], who studied a population of chinchillas. Comparable values were reported by Rastoga et al. [12] on a rabbit population. Additive maternal effect on the litter sizes at birth remained at the level of 0.09.

The heritability coefficients estimated in this study for conformation traits of mink ranged within 0.116 and 0.218 (Table 2). The highest values were those of the pelage colour purity; it is a trait that seems to a high degree susceptible to selection, which is not only the case in mink. Heritability coefficient for pelage colour purity, as estimated for Arctic foxes, was 0.603 [17]. Studies by other authors show that conformation-related traits belong to those of medium or high heritability [2, 8, 11, 13]. Compared to the mentioned authors, lower values of the discussed parameters were found in this study. Similar results on body size were reported only by Berg [1], who applied similar methods of estimating genetic variability, i.e. animal model/REML; the author also distinguished the additive maternal effect on the value of a given trait.

The analyses (Table 2) have demonstrated that maternal effect was particularly strong, stronger than the genetic variability resulting from the additive individual value, in the case of mink body size and conformation (m2 = 0.216) and pelage quality (m2 = 0.202). In the studies cited earlier [1], maternal effects represented 10-40% of the total variability of body weights and pelt sizes.

Table 3 presents phenotypic and genetic correlations between reproduction- and conformation-related traits. A high value of phenotypic correlations was recorded for the number of born and raised pups (0.887). These results did not differ from investigations on other fur-bearing animals, in which also high similarity was recorded between these traits [5, 15]. Correlations between individual traits of pelage as well as body size and conformation were negative (from -0.111 to -0.291). Similar results on Arctic fixes were reported by Socha [13].

Table 3. Genetic correlations (below diagonal) and phenotypic correlations (above diagonal) of reproduction and conformation traits

Trait

Number of born pups

Number of weaned pups

Body size and conformation

Colour purity

Pelage quality

Number of born pups

 

0.887

-0.023

0.047

-0.014

Number of weaned pups

0.974

 

-0.024

0.053

-0.016

Body size and conformation

-0.181

-0.272

 

-0.111

-0.115

Colour purity

0.324

0.358

-0.243

 

-0.291

Pelage quality

-0.123

-0.209

-0.223

-0.102

 

No significant phenotypic correlations between reproduction parameters and conformation-related traits were found in this study. The values ranged between -0.014 and 0.053. Similar results were reported by Korhonen and Hary [6], who found no significant correlations between litter sizes and adult body weights in raccoon dogs. Analogical results were found by Jeżewska et al. [4].

Genetic associations between individual traits included in the breeding objective are of significant importance for the breeding. The genetic correlations estimated in this study proved the highest for the number of born and raised pups (0.974). The results have been confirmed in the studies by other authors, in which analogical values – referring not only to studied species, i.e. mink – were also high, 0.810 and 0.894 [5, 15].

Negative correlations, on the other hand, were found between body size and conformation of the animals versus their pelage quality (-0.243 and -0.223). The character of these interrelations may, in some way, hamper parallel improvement of the analysed traits. In this case, it seems necessary to pay particular attention to proper distribution of selection pressure in relation to the traits under improvement, so as they would reflect their economic importance. Studies by other authors seem to confirm the recorded results [8, 13].

Associations that occur between reproduction parameters and pelage quality, or body size and conformation, are of high importance in fur animal breeding. The correlations estimated in this study for these traits ranged between -0.123 and 0.358 (Table 3). Positive correlations were found only for fecundity and fur colour purity of mink. In each of the analysed traits, stronger character of the relationships was related to the number of raised pups. The results show a possibility for reproduction performance to deteriorate should one-sided selection be applied in order to improve conformation traits of the animal. This has been also confirmed by the studies carried out also by Lagerkvist [7] and Lagerkvist et al. [8]. It has been found that selection for increasing body size had a negative effect on reproduction performance of mink, while in the reversed situation (selection for better fecundity) has led to deterioration of other, economically desired traits. Socha [13], on the other hand, has demonstrated a lack of relationships between reproduction parameters and conformation traits for Polar foxes. However, the author also suggests that selection for confor-mation improvement that lasts for many generations may lead to reduced fecundity of females.

In the case of fur animals, their functional traits are very important for the financial performance of the farm. Most often, the animals which have not produced offspring during the selection are culled from the breeding stock. An analysis of the results presented in Table 4 allows concluding that such actions are particularly recommended in the case of infertility. Heritability coefficient for this trait was relatively high (0.593). Additive individual value had a significant effect on the level of the remaining functional traits. The high value of heritability coefficient shows the necessity to eliminate from selection the animals originating from families in which abortions or destroying the young by females has been observed. Genetic background also had a significant effect on the ability of a female to produce offspring (h2 = 0.309). However, despite the fact that the additive value of an individual was a significant source of variability, al so environmental factor were of importance in this situation. Producing offspring in one reproductive season do not guarantee that the same animal will show positive reproduction performance in the following years of its management.

Table 4. Heritability (h2) of functional traits

Functional traits

h2

Probability of birth

0.309

Probability of destroying the litter

0.241

Probability of abortion

0.465

Probability of infertility

0.593

Genetic background of functional traits of another fur animal species, i.e. raccoon dogs, was the subject of studies by ¦laska et al. [16]. Heritability coefficients estimated by this author were slightly lower than those estimated in own studies (h2 ranged from 0.140 to 0.411). The values confirm, however, that the level of functional traits may largely be a result of the additive individual value.

CONCLUSIONS

  1. Additive individual value was a low-significance source of variability of reproductive traits. In this case, pre- and postnatal maternal effects were of much more importance.

  2. Low level of heritability for conformation traits was found, which – except for colour purity – were determined more by maternal effects rather then by the additive individual value.

  3. Probability of producing a litter and the way a female treats the litter was to a large extent determined by additive value of the animal, and the relatively high heritability coefficients show the necessity to cull from the breeding stock the animals originating from families in which abortions, infertility, or destroying the young by females has been observed.

  4. Genetic relationships between the studied traits were very strong for the number of born and weaned pups. Litter size, however, had only a slight negative effect on the offspring body size and conformation as well as on their pelage quality.

ACKNOWLEDGEMENT

The study was carried out within a research project financed by the Ministry of Scientific Research and Information Technology, grant no. 3P06D 003 23.

REFERENCES

  1. Berg P., 1993. Variation between and within Populations of Mink. I. Weight and Skin Lenght. Progeny testing in mink. genetic variation within and between populations. PhD theis Den Kongelige Veterinaer- og Landbohojskole Institut for Husdyrbrug og Husdyrsundhed Sektion fof Husdyrgenetik, 1-7.

  2. Filistowicz A., Żuk B., 1995. Zastosowanie programów hodowlanych w doskonaleniu zwierz±t futerkowych w Polsce [Application of breeding programmes to fur-bearing animals improvement in Poland]. Zesz. Nauk. Prz. Hod. 21, 55-67 [in Polish].

  3. Jeżewska G., Rozempolska-Rucińska I., Zięba G., Nowak M., 2003. Genetyczne uwarunkowania wybranych cech rozrodu szynszyli [Genetic conditions of the selected reproduction traits of chinchilla]. Zesz. Nauk. Prz. Hod. 68, 6, 35-41 [in Polish].

  4. Jeżewska G., ¦laska B. Tarkowski J., 1999. Influence of litter size on growth and pelt quality in raccon-dogs. Posibility and perspectives of production incresing in poltry and small animal husbandry. Zbornik z medzianarodnej vedeckiej konferencie. Nitra, Slovakia 14 September 1999. 236-240.

  5. Jeżewska G., Tarkowski J. Niezgoda G. Jakubczak A., 1996. Phenotypic and genetic variability of some reproductive features in blue fox (Alopex lagopus). Anim. Prod. Rev. Appli. Sci. Rep. 27, 199-204.

  6. Korhonen H., Harri M., 1985. Growth and fur parameter variations of raccon dogs. Arch.Tier. 35 (10), 761-772.

  7. Lagerkvist G., 1992. Selection for fertility, body size and pelt quality in mink and effects of crossing. Norw. Agric. Sci. 9, 39-48.

  8. Lagerkvist G., Johansson K., Lundeheim N., 1994. Selection for Litter Size, Body Weight, and Pelt Quality in Mink (Mustela vison}, Correlated Responses. J. Anim. Sci. 72, 1126-1137.

  9. Maciejowski J., Jeżewska G., 1993. Genetyczne uwarunkowanie cech rozrodu zwierz±t futerkowych [Genetic factors of fur animal reproduction traits]. Zesz. Nauk. Prz. Hod. 12, 5-12 [in Polish].

  10. Madsen P., Jensen J., 2000. A user's guide to DMU - a package for analysing multivariate mixed models. Version 6, release 4. Danish Institute of Agricultural Sciences.

  11. Pingel H., Schumacher J. Zunft P., 1986. Genetic analysis of body weight and fur quality in mink. Scientifur 3, 187.

  12. Rastogi R.K., Lukefahr S. D. Lauckner F. B., 2000. Maternal heritability and repeatability for litter traits in rabbits in a humid tropical environment. Livest. Prod. Sci. 67, 123-128.

  13. Socha S., 1995. Wyniki pracy hodowlanej nad lisami polarnymi na przykładzie fermy reprodukcyjnej [Results of breeding activities on polar foxes exemplified with reproduction farm]. Zesz. Nauk. Prz. Hod. 21, 27–53 [in Polish].

  14. Socha S., Adamska M., 2001. Analiza wyników rozrodu lisów polarnych i czynników wpływaj±cych na nie w wybranej fermie [Analysis of the results of reproduction of Polar foxes and factors, affecting them in the selected farm]. Zesz. Nauk. Prz. Hod. 58, 47-55 [in Polish].

  15. Socha S., Markiewicz D., 2001. Analiza czynników wpływaj±cych na płodno¶ć norki (Mustela vison Sch.) [Analysis of factors influencing mink fertility (Mustela vison Sch.)]. Med. Weter. 57, 840-843 [in Polish].

  16. ¦laska B, Jeżewska G, Łukaszewicz M, Zięba G., 2003. Genetic determination of chosen reproduction traits in raccoon dog (Nyctereutes procyonoides). Scientifur (w druku).

  17. Wierzbicki H., Filistowicz A., 1999. Genetyczne uwarunkowanie typu barwnego i okrywy włosowej lisa polarnego [Genetic determination of colur type, conformation and furcoat characteristic in Arctic fox]. Zesz. Nauk. Prz. Hod. 42, 11-19 [in Polish].

  18. Wzorzec oceny pokroju norek. CSHZ, 1997. [Standard for mink performance evaluation] Central Animal Breeding Office, Warszawa [in Polish].

  19. Żuk B., 1989. Biometria stosowana [Applied Biometrics]. PWN, Warszawa [in Polish].


Iwona Rozempolska-Rucińska
Department of Biological Bases of Animal Production
Agricultural University of Lublin, Poland
Akademicka 13, 20-950 Lublin, Poland
phone: +4881 445 66 28
e-mail: irr@sigma.ar.lublin.pl

Responses to this article, comments are invited and should be submitted within three months of the publication of the article. If accepted for publication, they will be published in the chapter headed ‘Discussions’ in each series and hyperlinked to the article.


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