Nucleus Herds Research Articles

Estrutura e distribuição geográfica do rebanho de ovinos Santa Inês no estado do Piauí

Objetivou-se descrever o quantitativo, distribuição e estrutura do rebanho de ovino da raça Santa Inês no estado do Piauí. Foram analisados dados de registros genealógicos da raça Santa Inês, mantidos pela Associação Brasileira de Criadores de Ovinos (ARCO), referentes ao período de 1992 a 2012. Foram realizadas análises estatísticas descritivas de modo a conhecer como o rebanho Santa Inês está estruturado. Foi realizada a classificação do rebanho quanto a sua estrutura organizacional, determinada com base na origem e uso dos reprodutores, utilizando-se o programa ENDOG. v.4.8. O registro dos animais da raça Santa Inês, no Piauí, teve inicio em 1990, e a maior representatividade foi verificada no período de 1993 a 2001. Quanto à estrutura dos rebanhos, 56,8% foram classificados como rebanhos multiplicadores (estrato intermediário da pirâmide) e 43,2% como rebanhos comerciais (base da pirâmide), sendo que não se observou nenhum rebanho núcleo e nem isolado. A falta de rebanhos núcleo da raça no Estado pode ser uma das causas da redução do número de animais registrados nos últimos anos no Piauí.

The genetic relationships between conformation assessment of gilts and sow production and longevity

The longevity of sows is important for both the production economy and animal welfare. This study suggests that a selection for several conformation traits scored on gilts by utilizing phenotypic records from nucleus herds can contribute to a better longevity in sows. The aim of our study was to investigate the heritabilities and genetic correlations between conformation traits measured on unselected gilts, piglet production and longevity of the sows in the Norwegian Landrace population in order to contribute new knowledge on the relationship between conformation and longevity traits. For this study, eight phenotypes from a total of 78,000 gilts and sows were utilized; the traits were hind and front leg quality, motorics, hind leg standing under, the sum of the individual piglet weighed at 21 days in the first two litters (LWT), the total number of piglets born in the first two litters, the ability to stay in production for two parities (STAY) and the maximum parity number before culling (MAXL). The data for STAY and MAXL was analysed with two different models, both with and without correcting for breeding value (EBV) at culling. The latter is correcting for the fact that in nucleus herds sows are culled due to low EBVs. Our study found low to moderate heritabilities (0.05≤h2≤0.24) for all traits and substantial genetic correlations between most of the conformation traits (0.28≤r2≤0.66). The heritability of STAY and MAXL became significantly greater when including a correction for EBV at culling, and the genetic correlation between STAY and front leg quality became significant (rg=−0.12). This indicates that if the data from nucleus herds are used, a correction for EBV will improve the estimates. The results from our study show that there is not a strong genetic relationship between the conformation traits of the gilts and longevity. The inclusion of front and hind leg quality as traits in the breeding goal can contribute to increased longevity, although the results of such an indirect selection to longevity would be slow. Selection for improved conformation can counteract an undesired development in longevity.

Total cost estimation for implementing genome-enabled selection in a multi-level swine production system.

BackgroundDetermining an animal’s genetic merit using genomic information can improve estimated breeding value (EBV) accuracy; however, the magnitude of the accuracy improvement must be large enough to recover the costs associated with implementing genome-enabled selection. One way to reduce costs is to genotype nucleus herd selection candidates using a low-density chip and to use high-density chip genotyping for animals that are used as parents in the nucleus breeding herd. The objective of this study was to develop a tool to estimate the cost structure associated with incorporating genome-enabled selection into multi-level commercial breeding programs.ResultsFor the purpose of this deterministic study, it was assumed that a commercial pig is created from a terminal line sire and a dam that is a cross between two maternal lines. It was also assumed that all male and female selection candidates from the 1000 sow maternal line nucleus herds were genotyped at low density and all animals used for breeding at high density. With the assumptions used in this analysis, it was estimated that genome-enabled selection costs for a maternal line would be approximately US$0.082 per weaned pig in the commercial production system. A total of US$0.164 per weaned pig is needed to incorporate genome-enabled selection into the two maternal lines. Similarly, for a 600 sow terminal line nucleus herd and genotyping only male selection candidates with the low-density panel, the cost per weaned pig in the commercial herd was estimated to be US$0.044. This means that US$0.21 per weaned pig produced at the commercial level and sired by boars obtained from the nucleus herd breeding program needs to be added to the genetic merit value in order to break even on the additional cost required when genome-enabled selection is used in both maternal lines and the terminal line.ConclusionsBy modifying the input values, such as herd size and genotyping strategy, a flexible spreadsheet tool developed from this work can be used to estimate the additional costs associated with genome-enabled selection. This tool will aid breeders in estimating the economic viability of incorporating genome-enabled selection into their specific breeding program.

International genetic evaluations for feed intake in dairy cattle through the collation of data from multiple sources

Feed represents a large proportion of the variable costs in dairy production systems. The omission of feed intake measures explicitly from national dairy cow breeding objectives is predominantly due to a lack of information from which to make selection decisions. However, individual cow feed intake data are available in different countries, mostly from research or nucleus herds. None of these data sets are sufficiently large enough on their own to generate accurate genetic evaluations. In the current study, we collate data from 10 populations in 9 countries and estimate genetic parameters for dry matter intake (DMI). A total of 224,174 test-day records from 10,068 parity 1 to 5 records of 6,957 cows were available, as well as records from 1,784 growing heifers. Random regression models were fit to the lactating cow test-day records and predicted feed intake at 70d postcalving was extracted from these fitted profiles. The random regression model included a fixed polynomial regression for each lactation separately, as well as herd-year-season of calving and experimental treatment as fixed effects; random effects fit in the model included individual animal deviation from the fixed regression for each parity as well as mean herd-specific deviations from the fixed regression. Predicted DMI at 70d postcalving was used as the phenotype for the subsequent genetic analyses undertaken using an animal repeatability model. Heritability estimates of predicted cow feed intake 70d postcalving was 0.34 across the entire data set and varied, within population, from 0.08 to 0.52. Repeatability of feed intake across lactations was 0.66. Heritability of feed intake in the growing heifers was 0.20 to 0.34 in the 2 populations with heifer data. The genetic correlation between feed intake in lactating cows and growing heifers was 0.67. A combined pedigree and genomic relationship matrix was used to improve linkages between populations for the estimation of genetic correlations of DMI in lactating cows; genotype information was available on 5,429 of the animals. Populations were categorized as North America, grazing, other low input, and high input European Union. Albeit associated with large standard errors, genetic correlation estimates for DMI between populations varied from 0.14 to 0.84 but were stronger (0.76 to 0.84) between the populations representative of high-input production systems. Genetic correlations with the grazing populations were weak to moderate, varying from 0.14 to 0.57. Genetic evaluations for DMI can be undertaken using data collated from international populations; however, genotype-by-environment interactions with grazing production systems need to be considered.

Genetic Parameters and Genetic Gain for the Reproduction Traits in Latvian Landrace and Yorkshire Sows Populations

The aim of this study was to estimate genetic parameters for the reproduction traits of Landrace and Yorkshire sows and to analyze the genetic gain in these Latvian swine populations. Records of 14 577 first-parity and 27 359 later-parities Landrace sows and 6039 first-parity and 12 360 later-parities Yorkshire sows born between 2000 and 2012 were included in the analysis. The number of piglets born alive and 21-day litter weight at first and later parities, and weaning–conception interval between the first and second parity were included in the study. The genetic parameters were estimated using a single-trait animal model for the first parity and a single-trait repeatability animal model for later parities using REML procedure. Compared to heritability estimates for number born alive, heritabilities for litter weight were higher in both populations: in the first parity 0.10±0.015 vs. 0.31±0.021 for Landrace, and 0.05±0.016 vs. 0.23±0.028 for Yorkshire; in later parities 0.10±0.010 vs. 0.23±0.013 for Landrace, and 0.10±0.017 vs. 0.20±0.022 for Yorkshire. The heritability of reproduction traits was low; however, during the last ten years, reproduction traits in nucleus herds were improving. The results show that genetic progress in the last five years has been relatively low.

The Bio-economic Impact of the MOET Program for the Development of Vulnerable Genetic Resources Through Eco-innovative Reproduction Biotechnologies

MOET Program (Multiple Ovulation Embryo Transfer) has more important bioeconomy significance by biodiversity profile metabolic and hormonal of the donor and recipient female of transferred embryos and allowed access to animal genetic biotechnologies, with low costs and minimal risk of introducing diseases towards imports with live animals. The authors present synthesis postdoctoral research in program POSTDRU ID 63258, included in the Research Plan of the National Institute of Economic Research “Costin C Kiriţescu” on 2013 with original contributions to the application of systems MOET (with open circuit, closed circuit and Nucleus herd) which allowed some elite farms (ex.: Pantelimon, Otopeni - Ilfov County, Ardud – Satu Mare County and Matca – Galati County) to obtain genetic progress accelerated, evaluation by different methods biostatistics trough BLUP (Best Linear Unbiased Prediction).MOET Program was apply in Romania by imported embryos of SUA from Dr. Edwin Robertson of Harrogate Genetic International achieved a pregnancy rate after E.T. between 42-47%. Following the application of MOET program in this research made banks to preserve genetic resources with major risk of breed Pinzgauer and breed Grey Steppe in Country Haţeg -Retezat, Dancu- Iasi and CSCBAS-Bucharest by risk management of the reduction extinction of these animal breeds. In this paper the authors develop the idea of the establishment of gene banks based on their own experience and especially mobile containers laboratories have been described in a scientific paper presented at the annual meeting of D.A.G.E.N.E. (Danubian Countries Alliance for Conservation of Genes in Animal Species) of Timisoara this year

Seasonal Index and Breeding Efficiency of Red Chittagong Cattle in Bangladesh

The study was aimed to observe reproductive pattern and efficiency of Red Chittagong Cattle (RCC) including reproductive history taken from two different herds; nucleus herd (on-station) and community herd (on-farm) in Mymensingh district of Bangladesh. A total of 184 calving parity records from 66 RCC cows that included 317 estrous, 164 conception and 178 calving history covering a period from 2005 to 2011 were considered for analyses. The highest frequencies of estrous, conception and calving occurred in May (13%, 15% and 14%, respectively), while the lowest in September for estrous (4%) and conception (4%) and April and June for calving (5%). The month of the year had significant (p<0.001 to p<0.05) effect on both estrous and calving but not for conception (p>0.05). There was no significant effect of season with estrous or conception or calving, but numerically highest incidence of estrous and conception in summer (36% and 38%, respectively) and calving in winter (36%) are noted. The seasonal indexes of calving in the on-station and on-farm herds were 0.73 and 0.78 respectively, with an overall mean of 0.68. The breeding or reproductive efficiency of the nucleus herd was estimated based on calving interval and age at first calving along with calving interval and the calculated results were 79 % and 82%, respectively for those two methods of estimation. The result obtained in this study indicates the reproductive behavior of RCC did not differ significantly by season, but varied with month of the year. In addition, reproductive efficiency of RCC in this study was slightly lower than that of expected.

Evaluation of Red Chittagong Cows Based on Test Day Milk Production

The merit of Red Chittagong cows-a promising indigenous cattle genetic resource of Bangladesh was evaluated by using test day milk yield records of total 41 individuals. The data were collected from the Nucleus Herd of Red Chittagong (RC) cattle maintained at Bangladesh Agricultural University, Mymensingh from June, 2007 to October, 2008 under supervised animal recording system along with the previously recorded data from 2005 was also taken into consideration. Data were then analyzed for evaluating the cows based on lactation yield and average daily milk yield. Average lactation yield and daily milk yield were 453.86 ± 59.61 and 1.99 ± 0.14 kg, respectively. The highest lactation yield (538.04 kg) and daily milk yield (2.3 kg) was found in 4th and 5th lactation, respectively. The most probable producing ability (MPPA) of RC cows was calculated by using the test day records and then the animals were ranked on the basis of their MPPA value. For MPPA calculation two methods were followed; cow’s repeated lactation performance (MPPA1) and within lactation repeated test day records and averaged (MPPA2). The highest MPPA for lactation yield was shown by the cow no. 36 (645.61 kg) and the highest MPPA1 and MPPA2 for daily milk yield were 2.83 and 3.46 kg, respectively for cow no. 03. The result of this study suggests that test-day yields may well be used for genetic evaluation of cows to make recurrent selection decision in cattle breeding programs.DOI: http://dx.doi.org/10.3329/pa.v19i2.16950 Progress. Agric. 19(2): 101 - 109, 2008

Evaluation of effects of multiple candidate genes (LEP, LEPR, MC4R, PIK3C3, and VRTN) on production traits in Duroc pigs

We evaluated multiple effects of genetic variations of five candidate loci (LEP, LEPR, MC4R, PIK3C3 and VRTN) on four production traits (average daily weight gain (ADG); backfat thickness (BFT); loin eye muscle area (EMA); and intramuscular fat content (IMF)) in a closed nucleus herd of pure Duroc pigs. Polymorphisms in LEPR, MC4R and PIK3C3 had significant single gene effects on ADG and BFT. The additive genetic variance in ADG and BFT (16.99% and 22.51%, respectively) was explained by genetic effects of these three loci. No correlations were observed between the LEP genotype and production traits in this study. Although we detected marginally epistatic interactions between LEPR and PIK3C3 on the eye muscle area, there were no significant epistatic effects on any traits among all loci pairs. These results suggest that LEPR, MC4R, PIK3C3 and VRTN may independently influence growth rate and fat deposition. Furthermore, the statistical models for predicting the breeding values of each trait had the lowest Akaike's information criterion values when considering the effect of the MC4R, LEPR, PIK3C3 and VRTN genotype simultaneously. These results suggest that LEPR, MC4R, PIK3C3 and VRTN are useful markers for accurately predicting breeding values in Duroc pigs.

Genetic analysis of teat number and litter traits in pigs

The aim of this study was to analyse, on data on purebred Yorkshire pigs in Swedish nucleus herds, the genetic correlation between teat number (both functional and non-functional) recorded at performance testing (at approx. 100 kg live weight), litter size at birth and litter weight at 3 weeks of age. Animal mixed-model analysis was applied on the data available (57,000 performance tested pigs, 10,000 1st-parity litters and 6500 2nd-parity litters). The estimated heritability for number of functional teats was 0.31, for number of non-functional teats 0.09 and for total number of teats 0.39. Number of non-functional teats was negatively genetically correlated with number of functional teats (rG = -0.34), and positively correlated with litter size (parity 1; +0.20) and number of stillborn piglets (parity 2; +0.34).

Selection for increased number of piglets at d 5 after farrowing has increased litter size and reduced piglet mortality1

Selection for litter size at d 5 after farrowing (LS5) was introduced in 2004 to increase the number of piglets weaned and to reduce piglet mortality in Danish Landrace and Yorkshire. The objective of this study was to investigate selection responses for LS5, total number born (TNB), and mortality [MORT, defined as (TNB - LS5)/TNB] when selection for increasing LS5 was a part of the breeding goal. Data were collected from nucleus herds recorded from 2004 to 2010, including first litters of 42,807 Landrace sows and 33,225 Yorkshire sows. The data were analyzed using a 3-trait animal model of TNB, MORT, and LS5. Significant (co) variances were estimated between the 3 traits in both populations. The heritabilities of TNB, MORT, and LS5 were 0.10, 0.09, and 0.09 in Landrace and 0.12, 0.10, and 0.10 in Yorkshire. The genetic correlations were 0.28 and 0.22 between TNB and MORT, 0.74 and 0.68 between TNB and LS5, and -0.43 and -0.57 between MORT and LS5 in Landrace and Yorkshire, respectively. The results show that the genetic improvement of LS5 was a combination of increased TNB and reduced MORT. During the observation period, the genetic improvement was 1.7 piglets per litter for LS5, 1.3 piglets per litter for TNB, and 4.7% for MORT in Landrace and 2.2 piglets per litter, 1.9 piglets per litter, and 5.9% in Yorkshire. Phenotypic improvement was 1.4 piglets per litter for LS5, 0.3 piglets per litter for TNB, and 7.9% for MORT in Landrace and 2.1 piglets per litter, 1.3 piglets per litter, and 7.6% in Yorkshire. In addition, genetic gain was evaluated in 3 phenotypic groups of TNB, representing the 25% smallest litters, the 50% medium litters, and the 25% largest litters. In all 3 groups, the genetic and phenotypic gains of TNB and LS5 increased, whereas MORT reduced in both populations.

Influenza A(H1N1)pdm09 virus infection in Norwegian swine herds 2009/10: The risk of human to swine transmission

Influenza A viruses cause respiratory infection in humans and pigs, and some serotypes can be transmitted between these species. The emergence of influenza A(H1N1)pdm09 virus infections in the spring of 2009 quickly led to a worldwide pandemic in humans, with subsequent introduction of the virus to pig populations. Following a widespread infection in the human population in Norway, influenza A(H1N1)pdm09 virus was introduced to the influenza A naïve Norwegian pig population, and within a few months pigs in more than one third of Norwegian swine herds had antibodies against the virus. A cross-sectional study was performed on all swine nucleus and multiplier herds in Norway to analyze risk factors for introduction of infection, and the preventive effects of recommended biosecurity practices. A surveillance program provided information on infection status of the study herds, and a questionnaire was administered to all 118 nucleus and multiplier herds to collect information on herd variables. The surveillance program revealed that pigs in 42% of the herds had antibodies against influenza A(H1N1)pdm09 virus. The incidence of serologically positive pigs was similar in both multiplier herds (41%) and closed nucleus herds (43%). Multivariable logistic regression showed that presence of farm staff with influenza-like illness (ILI) (OR=4.15, CI 1.5–11.4, p=0.005) and herd size (OR=1.01, CI 1–1.02, p=0.009) were risk factors for infection. The rapid and widespread seroconversion for antibodies against influenza A(H1N1)pdm09 virus in the Norwegian pig population can be explained by the emergence of a novel virus that is readily transmitted between people and swine in a largely susceptible population of humans, and an entirely naïve population of pigs.

INFLUENCE OF THE PROLACTIN GENE POLYMORPHISM ON SELECTED REPRODUCTION TRAITS IN SOWS OF POLISH LARGE WHITE BREED

The objective of our analyses was to identify prolactin gene polymorphism and determine its effect on reproduction traits in sows. The research included 138 Polish Large White sows from four nucleus herds supervised by the Polish Pig Breeders and Producers Association “POLSUS” based in the kujawsko-pomorskie province. Molecular analyses were conducted using the PCR-RFLP method. Three PRL/TaaI genotypes and two alleles were found in the examined sows. The allele frequency was as follows: PRLIns – 0.50; PRLDel – 0.50, and the genotype frequency was at the following level: Del/Del – 0.27, Ins/Del – 0.45, Ins/Ins – 0.28. We determined the mean age at the first farrowing, and the mean number of piglets born alive and reared until 21 of their lives in two subsequent farrows. No statistically significant differences were found between the genotype variants within the analysed reproduction traits in Polish Large White pigs. The results we obtained prove that there is a need to continue research in this area using a larger group of animals.

Assessment of confidence in freedom from Aujeszky's disease and classical swine fever in Danish pigs based on serological sampling—Effect of reducing the number of samples

Confirming freedom from disease is important for export of animals and animal products. In Denmark, an intensive surveillance program is in place for Aujeszky's disease (AD) and classical swine fever (CSF), including 34,974 blood samples tested for AD and 37,414 samples tested for CSF (2008 figures). In the current system, 3.5% of sows and boars for export or slaughter are tested for both diseases, as well as all boars before entering boar stations. Furthermore, nucleus herds are tested every third month for classical swine fever.We investigated, whether the sample size could be reduced without compromising the posterior probability of freedom (PostPFree) from AD and CSF by use of a scenario tree model. Conventional herds and sows or boars were defined as risk factors (compared to SPF11SPF – specific pathogen free. A system in which the herds are regularly checked for freedom from a number of diseases according to the health declaration of the programme. A herd can be free from all or some of the diseases. The owner of the herd is obliged to inform the SPF company and the buyer about the health status before selling pigs and to follow a certain set of rules regarding biosecurity (Anon., 2008). herds and finisher pigs), with a relative risk of 2 and 5, respectively. The probability of introduction was modeled as a distribution (0.0042:0.0083; 0.05), and the within-herd and between-herd design prevalence were set to 0.05 and 0.01, respectively.If 50 and 75% of the test results from exported or slaughtered sows and boars were simulated to be removed at random, while the blood samples from boar stations were kept constant (reflecting a total reduction of 28 or 43%) the PostPFree from AD was reduced from 0.989 after 1 year testing to 0.980 or 0.971, respectively. Similarly, the confidence of freedom from CSF was reduced from 0.989 to 0.982 or 0.969, when the number of serological samples from abattoirs and export sows and boars is reduced by 50 or 75%, respectively (reflecting a total reduction of 34 or 51%), and further to 0.978 or 0.963 if sampling in nucleus herds was stopped (reflecting a total reduction of 41 or 59%).The results show that a reduction in the sampling size of Danish sows will have limited effect on the PostPFree from AD and CSF, and that sampling in nucleus herds for CSF adds little to the PostPFree from CSF.

Genetic associations between behavioral traits and direct-social effects of growth rate in pigs.

This study examined the behavioral consequences of selecting pigs using a social genetic model for growth. Calculations enable each member of a group of pigs to be given a direct breeding value (DBV) and a social breeding value (SBV), which can be summarized into a total breeding value (TBV) for growth. Selection for growth TBV could affect animal behavior because social effects account for within-group interactions. Data were recorded from 96 groups of Yorkshire and Yorkshire × Landrace pigs in a nucleus herd. Each group contained 15 pigs fed ad libitum from 2 feeders; the space allowance was 0.85 m2/pig. Average daily gain was quantified from 35 to 100 kg of BW. Fighting and bullying activity at mixing (period 1), lying frequency 3 wk after mixing (period 2), and counts of skin lesions in periods 1 and 2 were recorded. The DBV for these traits were estimated with a classic animal model. We simulated different correlations between the direct genetic effect and the social genetic effect on growth rate (r(DS)), 2 components that respectively determine a pig's genetic capacity to grow and its genetic influence on growth of group mates: r(DS) was successively assumed to be 0 and ±0.12, ±0.20, ±0.29, and ±0.58. Finally, the correlations between DBV, SBV, and TBV for ADG, as well as the DBV for behavior and skin lesions, were calculated and tested for a level of significance at P < 0.05. The gradient from negative to positive values of r(DS) refers to a progressive path running from genetic antagonism to genetic mutualism for growth. If rDS in the population truly ranged between -0.58 and -0.20, correlations for TBV for ADG with DBV for fighting and bullying progressively increased with rDS. Consequently, if rDS was low (between -0.12 and +0.12) or positive (>+0.12), pigs with high TBV for ADG had higher DBV for bullying other pigs in the group and for fighting than pigs with lower TBV for ADG. Pigs with high TBV for ADG did not differ from other pigs in their DBV for lesions to the anterior part of the body, but they had a lower DBV for posterior lesions, whereas in period 2, they had higher DBV for posterior lesions and lower DBV for lying. Under genetic mutualism for growth and in housing conditions similar to those in the present study, selection for growth TBV would promote the rapid establishment of the dominance relationships, with more aggressive contests among group mates at mixing. Pigs would subsequently be more active but, judging by skin lesions, less willing to fight in a more stable social situation.

Comparison of production systems for efficient use of indigenous pig breeds in developing countries

Conserving pig genetic resources and improving their productivity is important to increase returns over investment in developing countries. The purebred, first-cross, rotational cross and backcross matings representing production systems based on pig breeds indigenous to the country and exotic pig breeds were investigated. The number of pigs in the nucleus and commercial herds necessary to produce a defined quantity of pork was considered. The amount of heterosis between the indigenous and exotic breeds, superiority in meat production, and degree of inferiority in reproductive performance of the exotic breed compared with that of the indigenous breed were investigated. The number of breeding pigs in the whole system was in the following order: pure breeding (PB) > first-cross (F1) > rotational cross (RC) > backcross (BC) systems. The number of breeding pigs in the nucleus herds of the RC and BC systems was smaller than that in the nucleus herds of the PB and F1 systems. The degree of inferiority in reproductive performance of the exotic breed compared with that of the indigenous breed affected the efficiency of the production system.

Estimation of adjustment factors for standardizing age and season corrected 305 day milk yield and estimation of heritability and repeatability of stadardized milk yield of Red Chittagong cattle

Adjustment factors for lactation milk yield to mature age and season corrected 305–day were calculated and heritability and repeatability of 305-day and test day (TD) milk yields were estimated from the nucleus herd of Red Chittagong Cattle (RCC) reared during 2005 to 2009. Lactation records (116) of 50 lactating cows were used for estimation. The factors for standardizing incomplete lactations to projected 305-day were estimated by taking 4 calving age groups (&lt;4, 4–5, 5–6, and 6+ years of age) and 3 seasons (mid Feb to mid June, summer; mid June to mid Oct, rainy and mid October to mid Feb, winter) with the ratio factors. The heritability estimates for TD and 305-day milk yield were found as 0.41±0.08 and 0.35±0.08, respectively. Heritability estimates of individual TDs ranged from 0.24±0.33 to 0.64±0.06. Heritability of individual TD milk yield was highest in the first three months (TD2 to TD6) whereas, lowest in first few days and later after 3 months. The repeatability of 305-day and TDs milk yield were estimated as 0.28±0.12 and 0.49±0.04, respectively using intra-class correlation.

Technical Note: Year, season, and parity effect on weaning performance of the Carmagnola Grey Rabbit breed

To evaluate the main environmental factors in the productivity of Carmagnola Grey rabbits, an endangered breed indigenous to northern Italy, data collected over 8 years were analysed. Production data on the pure closed nucleus herd of the University of Turin were used. Effects of parity, season and age of weaning on the number of rabbits born alive and weaned, litter weight and individual average weight at weaning were studied. The following average performance rates over the 8 years period were determined: 8.1 live born and 7.2 weaned kits per litter and a litter weight at weaning of 7287 g or 1024 g individual weaning weight. Year and season both had a significant effect (P £ 0.001) on all the traits studied as well as weaning age (P £ 0.001).

Effect of Sex Ratio in the Litter in Which Polish Large White and Polish Landrace Sows were Born on the Number of Piglets Born and Reared

Effect of Sex Ratio in the Litter in Which Polish Large White and Polish Landrace Sows were Born on the Number of Piglets Born and RearedThe aim of the study was to determine the effect of sex ratio in the litter in which Polish Large White (PLW) and Polish Landrace (PL) sows were born on the number of piglets born and reared to 21 days of age. Results obtained in nucleus herds from one breeding region were analysed. A total of 518 multiparous sows (179 PLW and 339 PL) were evaluated based on data from their litters (790 PLW and 1540 PL litters). The proportion of females in the litter in which the sow was born served as a basis for dividing the females into groups: group 1 &lt;40%, group 2 - 40-50%, group 3 - 50-60%, group 4 - 60-70%, group 5 &gt;70%. Significant differences in the average number of piglets born were found between the groups for PLW sows; compared to sows from groups 1, 2 and 3, females from group 5 gave birth to 8.0% (P≤0.05), 9.4% (P≤0.01) and 6.6% more piglets (P≤0.01), respectively, and compared to sows from group 2, those from group 4 gave birth to 5.1% more piglets (P≤0.05). The average number of piglets born and reared to 21 days by PL sows did not differ significantly between groups. The greater the proportion of females in the litter in which the PLW sow was born, the greater the preweaning mortality of piglets: 0.79, 0.87, 0.99, 1.02 and 1.24 piglets in groups 1 to 5, respectively. Preweaning mortality of PL piglets (0.93, 0.89, 0.81, 0.76 and 0.65 in groups 1 to 5, respectively) decreased with increasing proportion of females in the litter of origin and was lower than that of PLW piglets. It seems appropriate to account for the sex ratio of the litter in which the gilts were born when selecting them as mothers of the next generation as part of herd replacement; this parameter may improve fertility and production efficiency.

Phenotypic and genetic correlations of milk and type traits of Holstein-Friesian bull dams

The study of the production capacities of cattleaimed at increase of the capacity of cattle to produce milk, milk fat and calves, greatly depends on pehotypic and genetic variability, heritability and correlation between preferable traits, as well as level of production in the population. Objective of the study was to calculate the variability, phenotypic and genetic correlation of milk and type traits by applying the method of linear scoring of cows in the nucleus herd of Holstein-Friesian bull dams and also to determine their significance in cattle selection. For all studied traits, main variation-statistical parameters were calculated by applying method of least squares: arithmetic mean, standard deviation, variation coefficient, standard error and variation interval. Negative phenotypic correlations between production of milk and type traits ranged from -0.12 (rear leg set, side view) to -0.01 (rump height and body depth) and positive from 0.03 (rear teat placement) to 0.23 (suspensory ligament). Phenotypic correlations between milk fat percentage and type traits varied in the range from -0.08 (fore teat placement) to 0.14 (rump height). Negative genetic correlations between milk production and type traits ranged from -0.11 (rear udder height) to -0.01 (rump width and dairy form), and positive from 0.03 (rear legs set, rear view) to 0.23 (suspensory ligament). Genetic correlations between the percentage of milk fat and type traits ranged from -0.15 (pelvic position) to 0.18 (rump height). Information about phenotypic and genetic correlations between milk and type traits can be of multiple significance in cow selection since it offers possibility to select heads of cattle for multiple traits at the same time.