The aim of study was to estimate dispersion parameters for litter size and teat number in Krškopolje pig, the only Slovenian indigenous breed. Analysis included 1950 records for litter size and 7431 for teat number. The model for teat number included season as fixed effects, while common herd environment, common litter environment and direct additive genetic effect were treated as random. Fixed part of the model for litter size also included parity class and age at farrowing within parity class using quadratic regression. Random part also included service sire and permanent environment effect. Phenotypic standard deviation was 3.06 for liveborn piglets and 1.22 for teat number. Heritability for liveborn piglets was 8%. Service sire explained 3% of phenotypic variance. The largest variance component was permanent environment effect (10%), common herd environment ratio was 2%. Obtained heritability for teat number was 13%. Common litter environment explained 14% and common herd environment 19% of variability for teat number

KOVAČ, Milena

MALOVRH, Špela

URANKAR, Janja

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8th International Symposium on the Mediterranean Pig, Slovenia, Ljubljana, October 10th−12th, 2013.Acta argiculturae Slovenica, Supplement 4, 57–60, Ljubljana 2013COBISS: 1.08Agris category code: L10 DISPERSION PARAMETERS FOR LITTER SIZE AND TEAT NUMBER IN KRŠKOPOLJE PIGJanja URANKAR 1, Špela MALOVRH 2, Milena KOVAČ 2 1 Univ. of Ljubljana, Biotechnical Fac., Dept. of Animal Science, Groblje 3, SI-1230 Domžale, Slovenia, e-mail: janja.urankar@bf.uni-lj.si2 Same addressABSTRACTThe aim of study was to estimate dispersion parameters for litter size and teat number in Krškopolje pig, the only Slovenian indigenous breed. Analysis included 1950 records for litter size and 7431 for teat number. The model for teat number included season as fixed effects, while common herd environment, common litter environment and direct additive genetic effect were treated as random. Fixed part of the model for litter size also included parity class and age at farrowing within parity class using quadratic regression. Random part also included service sire and permanent environment effect. Phenotypic standard deviation was 3.06 for liveborn piglets and 1.22 for teat number. Heritability for liveborn piglets was 8%. Service sire explained 3% of phenotypic variance. The largest variance component was per-manent environment effect (10%), common herd environment ratio was 2%. Obtained heritability for teat number was 13%. Common litter environment explained 14% and common herd environment 19% of variability for teat number. Key words: dispersion parameters / litter size / teat number / Krškopolje pig1 INTRODUCTIONKrškopolje pig (KP) is the only Slovenian indigenous pig breed (ULRS, 2004). Under extensive management is adapted to poor rearing and feeding conditions (Šalehar, 1994). KP has a good meat quality (Čandek-Potokar et al., 2003), good technological and nutritional fat quality (Žemva et al., 2010), good maternal ability, and moder-ate fertility (Malovrh et al., 2012). First breed descrip-tion was published at the end of 19th century. Rohrman (1899) among other traits mentioned also number of teats (10–12) and litter size (10–12 piglets per litter). The breed was neglected from 1971 onwards (Šalehar, 1991) and was almost extinct in 1990 when breed reconstruc-tion began. After the year 2003, the interest on rearing the KP has increased due to subsidies for indigenous breeds. Litter size is an important reproduction trait in pigs and is often included in breeding programme of maternal breeds (MB). In modern breeds, heritabilities for litter size have been estimated around 10%, while proportion of permanent environmental effect has been 8% as sum-marized by Peškovičová et al. (2002). Fernandez et al. (2008) compared dispersion parameters in repeatability, multivariate and random regression models in Iberian pig. Estimated heritability and permanent environment effect with repeatability model were 7%. Based on ge-netic correlations between parities, multivariate analysis was recommended when large set of reproductive data over a wide range of parities was available. Heritability with repeatability model in Black Slavonian pig were 8% (Luković et al., 2012), while contribution of permanent environment effect was close to zero. With an increased litter size, the teat number (NT) becomes more important to achieve uniform piglet growth and weight at weaning. Heritability for NT varied from 7% to 59% as summarized by McKay and Rahnefeld (1990) and Malovrh and Kovač (2010). Generally, studies indicate NT to be moderately heritable (approximately 30%). In Iberian pig, estimated ratios were reported be-Acta agriculturae Slovenica, Supplement 4 – 201358J. URANKAR et al.tween 30% and 75% depending on population consid-ered (Toro et al., 1986). The aim of study was to estimate dispersion parameters for litter size and NT in KP. 2 MATERIAL AND METHODSThe data of KP was provided by the central data-base of Slovenian Pig breeding organization. Litter size data was collected between June 1992 and May 2013. The average size of 1950 litters was 9.62 liveborn piglets per litter (NBA, Table 1) born to 507 dams and 123 sires in 88 herds. The extensive rearing caused gilts to be older at fist farrowing. Thus, a gilt gives the first litter at the average age of 14 months, while gilts on some farms were younger (close to 10 months) or older (20 months). On the average, there were 22 litter records per herd with half of the farms collecting less than 10 records and the largest farm contributing almost one third of the dataset. Due to small herds and natural mating, number of litters per sire was also small (10). There were 3.8 litters per sow in the dataset.Teat number (TN) was recorded on 3704 male and 3727 female piglets at tagging since September 2007 (Ta-ble 1). The number of piglets tagged was 7.8 per litter. TN was assessed in 950 litters on 76 farms. Nearly 100 piglets were recorded for TN within a herd. One herd collected almost 20% of the data. On the other hand, most herds were small and 45% of them contributed less than 30 TN records during the whole period. TN in the data varied from 6 to 19 with a mean of 14.3 TN. Pedigree contained 645 animals for NBA and 7944 piglets for TN. Only 7.75% of animals for NBA and 0.48% for TN were assigned to the base population. Dispersion parameters for NBA and TN were es-timated in two single trait analyses. The model for TN (yijkl, eq. 1) included season at birth (Si), common herd environment (hj), common litter environment (cijk), and direct additive genetic effect (aijkl). Sex of a piglet was ex-cluded based on preliminary results. Common litter en-vironment describes environment shared by piglets born in the same litter from birth to weaning or even later, if pigs from the same litter are kept together for a longer period. yijkl = μ + Si + hj + cijk + aijkl + eijkl [eq. 1]Fixed part of the model for NBA (yijklmno, eq 2) in-cluded season at farrowing (Si), parity class (Pj), and age at farrowing (xijklmno) as independent variable nested within parity class. Parity class had three levels: 1 for gilts, 2 for primiparous and 3 for multiparous sows. Common herd environment (hk), service sire (sl), common litter envi-ronment (cm), permanent environment (pkmn), and direct additive genetic effect (akmn) were treated as random. Permanent environment is mainly caused by gilt rearing conditions and their influence on lifetime fertility. Dur-ing preliminary analyses more models were tested, but other effects like previous lactation length and weaning to conception interval were not significant most probably due to extensive management.yijklmno = μ + Si + Pj + bIj(xijklmno − x–) + [eq. 2]  + bIIj(xijklmno − x–)2 + hk + sl +  + cm + pkmn + akmn + eijklmnoFixed part of model was developed by SAS/STAT statistical package (SAS Institute Inc., 2008). Covariance Litter size data Teat number dataN Mean Min Max N Mean Min MaxTeat number 7431 14.3 6 19Litter size 1950 9.62  0 20Age at farrowing (d)1st parity 434 427.3 299 6002nd parity 365 652.3 491 1123later parities 1151 1266.0 649 3079No. records perherd 88 22.2  1 642 76 97.8 3 1477service sire 123 10.2  1 99sow 507 3.8  1 16common litter 307 6.4  1 39 950 7.8 1 23Table 1: Descriptive statistics and data structureActa agriculturae Slovenica, Supplement 4 – 2013 59DISPERSION PARAMETERS FOR LITTER SIZE AND TEAT NUMBER IN KRŠKOPOLJE PIGcomponents were estimated by the residual likelihood method (REML) as implemented in the package VCE-6 (Groeneveld et al., 2010). 3 RESULTS AND DISCUSIONPhenotypic standard deviation was 3.06 NBA (Ta-ble 2), which is slightly higher than in Slovenian popula-tion of MB (2.62 NBA; Malovrh and Kovač, 2012). The higher variability was expected already from distribu-tion of NBA. Luković et al. (2012) reported smaller litter size (6 to 8 NBA) as well as smaller standard deviation (1.58 NBA) in Black Slavonian pigs. Moreover, genetic standard deviation was 0.87 NBA. Heritability was thus estimated to 8% and was very close to the estimate in MB (Malovrh and Kovač, 2012) as well as results in Ibe-rian (Fernandez et al., 2008) and Black Slavonian pigs (Luković et al., 2012). This means that NBA can be im-proved by selection. Nevertheless, because of small pop-ulation size, intensity of selection is rather low. Variance for permanent environment effect was slightly higher than genetic components (Table 2). Stand-ard deviation for permanent environment (0.95 NBA) is larger than in MB (0.66 NBA, Malovrh and Kovač, 2012) and explaining 10% of total variability. Estimates in other indigenous breeds reported by Fernandez et al. (2008) and Luković et al. (2012) were lower. The results are not surprising because KP gilts are sold to a new loca-tion early in life when they weigh only 20 to 40 kg. Herds are small and rearing conditions are more variable than in modern breeds including various indoor and out-door systems under enriched as well as barren environ-ment. Variance for common litter environment was close to zero, while its variance in MB was substantial (0.12 NBA, Malovrh and Kovač, 2012). A smaller proportion of variability is explained by common herd environment (2 %, Table 2). In MB (Malovrh and Kovač, 2012), herds were larger and were considered as interaction with year clarifying 4.8 %. Standard deviation was 0.46 NBA in KP to 0.57 NBA in MB. This means that variations in herd practice alone can bring a substantial difference among herds, up to 3 NBA per litter.Variation caused by service sire is even slightly higher (3%, Table  2). The effect covers some genetic components bounded with semen quality and embrio survival, as well as some environmental effect because the same boar was used for oestrus stimulation. Addi-tionally, there can be some confounding effects common to all litters within the period when only one boar was used. Maximum number of records per service sire was high (99, Table 1), although 10% of boars were used for one mating only.Phenotypic standard deviation was 1.22 teats in KP (Table 2), which is more than 0.97 teats in MB (Malovrh and Kovač, 2010). Heritability estimate for TN was unexpectedly low (0.13) which is much lower as in MB (Malovrh and Kovač, 2010) where genetic compo-nent explained 33% of total variation. It was higher also in Iberian pigs (Toro et al., 1986). The highest variance proportion (0.27, Table 2) for TN was caused by common herd environment. That was almost one fifth of pheno-typic variance. Common litter environment explained 14% of phenotypic variance. Litter variance as well as its ratio was twice higher than in MB (Malovrh and Kovač, 2010). 4 CONCLUSIONHeritability estimates were 8% for NBA and 13% for TB. Permanent environment explained 10% of phe-notypic variance for NBA, while ratio for common herd environment was 2% and for service sire 3%. For TN contribution to the total variance was 14% for common litter environment and 19% for common herd environ-ment. Further studies are needed to analyse non-additive genetic effect. Additional attention must be also given to Variance RatioNBA TN NBA TNPhenotype 9.34 1.50Additive genetic effect 0.76 ± 0.43 0.18 ± 0.04 0.08 ± 0.04 0.13 ± 0.02Service sire 0.28 ± 0.13 0.03 ± 0.01Permanent environment 0.91 ± 0.34 0.10 ± 0.04Common litter environment (0.00) 0.19 ± 0.02 0.14 ± 0.01Common herd environment 0.21 ± 0.20 0.27 ± 0.06 0.02 ± 0.02 0.19 ± 0.04Residual 7.14 ± 0.26 0.75 ± 0.01 0.76 ± 0.03 0.54 ± 0.03Table 2: Dispersion parameters with standard errors for liveborn piglets (NBA) and teat number (TN)Acta agriculturae Slovenica, Supplement 4 – 201360J. URANKAR et al.data quality, especially to the verification of pedigree and reliability of reproduction data.5 REFERENCESČandek-Potokar M., Žlender B., Kramar Z., Šegula B., Fazarin-ic G., Uršič M. 2003. Evaluation of Slovene local pig breed Krškopolje for carcass and meat quality. Czech Journal of Animal Science, 3: 120–128Fernandez A., Rodriganez J., Zuzuarregui J., Rodriguez M.C., Silio L. 2008. 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Dispersion parameters for litter size and teat number in Krškopolje pig

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Dispersion parameters for litter size and teat number in Krškopolje pig

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