COBISS: 1.01 Agris category code: L10, L53
reproductive and growth performances
of four rabbit genotypes
Ajda KERMAuNER Jurij pOHAR 2
Received July 29, 2008; accepted September 24, 2009. delo je prispelo 29. julija 2008, sprejeto 24. septembra 2009.
Reproductive and growth performances of four rabbit genotypes
The insemination rate, probability of culling of does after the insemination, weight of does and weight of young, litter size, as well as litter weight were measured in groups of rabbits with different genotype. Four groups were formed: 30 muciparous does of SIKA maternal line (line A) were inseminated with males from the same line (AxA group), 23 multiparous does of SIKA sire line (line C) were inseminated with the males from the same line (CxC group), 30 multiparous does of line A were inseminated with the males from line C (AxC group) and 30 multiparous does of line A were inseminated with the males from Californian breed (AxCal group). The young were individually weighed once a week from birth to weaning (at the age of 35 days). Considering insemination rate, probability of culling and litter size from birth to weaning there were no heterosis effect found. There were no differences between groups AxC and AxCal in the majority of studied traits as well, except for the number of stillborn which was in group AxC significantly higher than in AxA and AxCal group. Live weight of young in group AxC was significantly higher than of group AxA at each weighting from birth to weaning, and higher than of group CxC at each weighting from birth to 21st day of age. Live weight of young in AxC group was significantly higher than live weight of young in AxCal at each weighting.
Key words: rabbits / genotypes / reproduction / reproductive performances / growth / selection
Plodnostne in rastne lastnosti kuncev štirih različnih genotipov
Primerjali smo uspešnost osemenitve, verjetnost izločitve samice po osemenitvi, telesno maso samic in mladičev ter velikost in maso gnezda v skupinah kuncev različnih genotipov. Formirali smo 4 skupine: 30 samic SIKA materne linije (linija A) smo osemenili s samci iste linije (skupina A vx A), 23 samic SIKA očetovske linije (linija C) s samci iste linije (skupina C x C), 30 samic linije A s samci linije C (skupina A x C) in 30 samic linije A s samci kalifornijske pasme (skupina A x Cal). Mladiče smo individualno tehtali tedensko od rojstva do odstavitve (na 35. dan starosti). Pri uspešnosti osemenitve, verjetnosti izločitve samic in velikosti gnezda od kotitve do odstavitve se heterozis ni pojavil, prav tako ni bilo razlik med A x C in A x Cal skupino v večini proučevanih lastnosti. Izjema je bilo število mrtvorojenih mladičev v gnezdu, ki je bilo pri A x C skupini višje kot pri A x A in A x Cal skupini. Kunci v skupini A x C so bili statistično značilno težji od skupine A x A pri vseh tehtanjih od rojstva do odstavitve, od skupine C x C pa pri tehtanjih od rojstva do 21. dne starosti. Mladiči v skupini A x C so bili težji tudi od skupine A x Cal pri vseh tehtanjih.
Ključne besede: kunci / genotipi / reprodukcija / lastnosti plodnosti / rast / selekcija
1 introduction
In rabbits the traits directly or indirectly associated with reproduction, like insemination rate, number of litters per doe per year, number of liveborn and stillborn
offspring and weight gain of young/litter from birth to weaning are highly influenced by the genotype (mainly mother's), environmental circumstances like lighting duration, season and physiological conditions of the doe as well as nutrition (Lukefahr et al., 2000). The reproductive
1	Univ. of Ljubljana, Biotechnical Fac., Dept. of Animal Science, Groblje 3, SI-1230 Domžale, Slovenia, M.Sc., e-mail: ajda.kermauner@bfro.uni-lj.si
2	Same address, Prof., Ph.D.
A. KERMAUNER and J. POHAR
performance can be improved by crossing animals from adequate maternal and paternal lines. In Rabbit centre of Biotechnical Faculty the selection of Slovene selection line for meat production (SIKA) was established: the selection of maternal SIKA line (A line) started in 1988 and the sire SIKA line (C line) in 1995. In order to estimate the heterosis effect of cross between maternal line A and paternal line C, the reproductive performances of pure lines A and C were compared with the reproductive performances of does from maternal line A inseminated with sires from line C. The performance of this cross was compared with the reproductive performance of does from maternal line A inseminated with male from Cali-fornians breed which is one of the most used sire breeds for terminal crossing.
2 material and methods
four groups were formed by inseminating 30 mu-litparous does from line A with males from same line (AxA group), 23 mulitparous does from line C with males from the same line (CxC group), 30 mulitparous does from line A with the males from C line (AxC group) and 30 mulitparous does from line A with the males from Californian breed (AxCal group). At the start of the experiment all females were weighted. The does were weighted also on 28th day of pregnancy, at delivery and then once a week until the young were weaned. Young rabbits were weaned at the age of 35 days. The young were also weighted at birth and then each week until weaning. All animals were weighed individually. Animals were fed on standard feed mixture (17% CP, 14% CF) ad libitum. During the experiment the following traits were registered: the insemination rate, the probability of culling of
Table 1: The insemination rate and the probability of culling of does after the insemination
Preglednica 1: Uspešnost osemenitve in verjetnost izločitve samice po osemenitvi
Group Insemination rate (%) Probability of culling (%) Skupina Uspešnost osemenitve (%) Verjetnost izločitve (%)
AxA	87.66a	26.47a
CxC	91.30a	39.13a
AxC	86.66a	30.00a
AxCal	93.33a	23.33a
a,b Values marked with different letter differ significantly (P<0.05) a,b Vrednosti, označene z različnimi črkami, se statistično značilno razlikujejo (p < 0,05)
does after the insemination, the weight of does, the weight of young, the litter size (number of liveborn and stillborn young) and the litter weight. Data were analysed by using SAS GLM procedure (SAS, 2000). When analysing data we supposed that the following traits were distributed normally: the weight of does, number of liveborn, the weight of young and the litter weight. The number of stillborn was supposed to be distributed according to Poisson's distribution, and insemination rate and probability of culling according to Bernoulli distribution. For testing the significance of differences between groups we used Scheffe's multiply test of means for traits with normal distribution, and Wald's2 test for other traits.
3 results and discussion
Differences between groups in the insemination rate and in the probability of culling of does after insemination were not significant (Table 1).
Table 2: Litter size from birth to weaning Preglednica 2: Velikost gnezda od rojstva do odstavitve
At birth / Ob rojstvu	From birth to weaning / Od rojstva do odstavtive
Group Skupina		Stillborn Mrtvorojeni	Liveborn Živorojeni	7th day 7. dan	14th day 14. dan	21st day 21. dan	28th day 28. dan	35th day 35. dan
AxA	LSM	0.28 a	8.73 a	8.41 a	8.04 a	7.95 a	7.86 a	7.54 a
	±SE	0.14	0.34	0.35	0.36	0.38	0.37	0.35
CxC	LSM	0.71 ab	8.28 a	8.00 a	7.86 a	7.43 a	7.28 a	7.14 a
	±SE	0.27	0.43	0.44	0.45	0.47	0.46	0.44
AxC	LSM	0.90 b	7.38 a	7.19 a	7.00 a	6.47 a	6.46 a	6.45 a
	±SE	0.25	0.35	0.36	0.37	0.39	0.38	0.36
AxCal	LSM	0.26 a	8.69 a	8.35 a	8.26 a	8.04 a	7.96 a	7.87 a
	±SE	0.13	0.33	0.34	0.35	0.37	0.36	0.35
a,b Values marked with different letter differ significantly (P<0.05)
a,b Vrednosti, označene z različnimi črkami, se statistično značilno razlikujejo (p < 0,05)
Results presented in table 1 indicate that insemination rates in all groups were very high in comparison with data reported by other authors (Eiben et al., 2001; Lopez and Alvarino, 1998; Rebollar et al., 2001). The group AxC had the lowest insemination rate of all groups. The reason for this could be that the does in this group were a bit lighter and were inseminated a couple of hours later than does from other groups. There are data in literature indicating that the insemination rate is lower in does with lower live weight at insemination (Szendro and Biro-Nemeth, 1991) and that the rate of insemination is influenced by the time between semen collection and insemination (Lopez and Alvarino, 1998).
Groups did not differ significantly on number of liveborn and weaned rabbits (Table 2). Differences were observed only in the number of stillborn: the group AxC had significantly more stillborn rabbits than group AxA, while the difference between AxC and CxC group regarding this trait was not significant (Table 2).
Depres et al. (1996) found that genotype affected the litter size at birth but not the number of liveborn or stillborn rabbits: litters were larger in New Zealand White does inseminated with Californian bucks than in pure New Zealand White. Gomez et al. (1999) found larger number of liveborn and weaned rabbits in linecrossing between two Spanish lines selected for the litter size than in pure lines.
Heterosis effect can occur when different breeds or lines are used for crossing: larger is the difference between parent's genotypes larger heterosis effect can be expected (Borojević, 1986). The occurrence of heterosis effect in our experiment was not consistent: there was no heterosis effect observed in the litter size, while the heterosis effect appeared in the growth of young (Table 3). The young of group AxC were at birth significantly
heavier than young of groups and CxC. The results from Table 3 indicate that the Californian breed compared to line C is less appropriate as a sire line considering the group performance.
4 conclusions
Results obtained show no heterosis effect in litter size and a moderate heterosis effect in growth performance. For better expressed linecrossing effect the time from the beginning of the separate selection of maternal and sire lines is probably too short. Namely, the selection of sire SIKA line C started from one part of maternal SIKA line population as late as in the year 1995.
Comparison between line C and Californian breed as sire line indicate that SIKA line C is more appropriate than the Californian breed.
5 sklepi
Dobljeni rezultati kažejo, da do heterozisa ni prišlo pri velikosti gnezda, pri rasti mladičev v gnezdu pa se je pokazal zmeren učinek. Za bolj izrazit učinek križanja bi verjetno moralo preteči več časa, odkar selekcioniramo obe SIKA liniji ločeno. Selekcija moške SIKA linije C se je namreč začela iz dela populacije materne SIKA linije A šele leta 1995.
Primerjava med moško linijo C in kalifornijsko pasmo kot očetovsko linijo kaže, da je SIKA linija C primernejša od kalifornijcev.
Table 3: Live weight of young from birth to weaning Preglednica 3: Telesna masa mladičev od rojstva do odstavitve
Live weight of young (g) / Telesna masa mladiča (g)
Group Skupina		At birth Ob rojstvu	7th day 7. dan	14th day 14. dan	21st day 21. dan	28th day 28. dan	35th day 35. dan
AxA	LSM	65.14 a	143.07 a	253.42 a	366.04 a	532.94 a	836.61 a
	±SE	0.82	2.37	4.09	6.09	9.13	13.21
CxC	LSM	65.29 a	157.37 bc	252.20 a	349.21 a	632.33 c	1015.56 b
	±SE	1.03	3.03	5.19	7.87	11.86	17.01
AxC	LSM	69.69 b	168.33 c	300.33 c	424.18 c	665.89 c	1005.00 b
	±SE	0.91	2.61	4.49	6.79	10.19	14.48
AxCal	LSM	65.30 a	153.74 b	272.29 b	391.42 b	580.31 b	870.71 a
	±SE	0.80	2.36	4.02	6.00	9.03	12.89
a,b Values marked with different letter differ significantly (P<0.05)
a,b Vrednosti, označene z različnimi črkami, se statistično značilno razlikujejo (p < 0,05)
6 acknowledgement
The authors like to thank Mr. Božo Artnak for the possibility to work on his rabbit farm and Peter Lipovšek, Igor Urankar and Tatjana Markulič, B.Sc., for weighting enormous number of animals.
7 references
Borojević S. Geni i populacija. Novi Sad, Forum: 346 p.
Depres E., Theau-Clement M., Lorvelec O. Effect of the genotype, day length, season and physiological stage on reproductive performance of doe rabbits reared in Guadeloupe (F.W.I.). World Rabbit Sci., 4, 4: 181-185.
Eiben C., Kustos K., Sendro Z., Theau-Clement M., Godor-Surmann K. 2001. Effect of male presence before artificial
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Szendro Z., Biro-Nemeth E. 1991. Factors affecting results with artificial insemination of rabbits. J. Appl .Rabbit Res., 14: 72-76