Artificial Insemination Station Research Articles

206 GENOME-WIDE ASSOCIATIONS FOR REPRODUCTIVE TRAITS IN RUSSIAN HOLSTEIN POPULATION

Reproductive health is an important trait in selection of dairy cattle. A genome-wide association study (GWAS) is a powerful tool for annotating phenotypic effects on the genome and to get knowledge of genes and chromosomal regions associated with reproductive performance (Cole et al. 2011). Combining GWAS and genetic profiling of embryos before implantation enables to develop new strategies to select elite breeding genotypes before transfer (Humblot et al. 2010; Ponsart et al. 2013). The aim of the current study was to evaluate the association between single nucleotide polymorphisms (SNP) and estimated breeding values (EBV) for reproductive traits [interval to insemination (EBVII) and interval between calving (EBVIC)] for Russian Holstein cattle and to evaluate the effect of the biopsy procedure on the viability of bovine embryos produced in vitro as a basis for pre-implantation genetic diagnosis (PGD). Ninty-six progeny-tested sires of artificial insemination station Moscowskoe were selected based on the reliability for EBVII and EBVIC. Estimations of breeding values of sires were performed by best linear unbiased prediction (BLUP) mixed model equations. DNA was extracted from sire semen samples. SNP genotyping was performed using the Illumina BovineSNP50 BeadChip (Illumina Inc., San Diego, CA, USA) containing 54609 SNPs. Quality control information was carried out in PLINK (v. 1.07; Purcell et al. 2007 Am. J. Hum. Genet. 81). Based on the quality control information, 41442 SNPs were selected for subsequent GWAS. We have identified 3270 SNPs having significant effect (P < 0.05) on studied traits. The most significant associations with EBVII were found for SNPs Hapmap38548-BTA-97184 and ARS-BFGL-BAC-11821 with coefficient of determination (R2) of 0.2189 and 0.1937, and P-values 2.27 × 10–6 and 1.01 × 10–6, respectively. The most significant effect on EBVIC was detected for SNPs ARS-BFGL-NGS-59769 and ARS-BFGL-NGS-38020 with coefficient of determination (R2) of 0.236 and 0.2421, and P-values 1.49 × 10–8 and 7.24 × 10–8, respectively. The highest number of significant associations was found on BTA5, BTA12, BTA19, and BTA14. Bovine embryos were produced in vitro using a standard procedure. Six to 8 cell biopsies were carried out at Day 6.5 after fertilization. The viability of biopsied embryos was evaluated comparing the hatching rates to non-manipulated embryos. The study of embryos viability after biopsy showed that the hatching rate of biopsied embryos (the number of hatched embryos from the number of embryos in stages of late morula and early blastocyte) was 48% comparing to 67% for non-manipulated embryos. Embryo biopsy is not dramatically decreasing embryo viability. Combining our results of association studies, performed on Russian Holstein population, and technique of embryo biopsy will provide us a powerful tool for selection progress.This research was supported by the Russian Ministry of Education and Science, project No. 2014-14-576-0057-175.

Relationships between the results of hypo-osmotic swelling tests, sperm motility, and fertility in Estonian Holstein dairy bulls

 As an attempt to find an inexpensive and simple laboratory method for artificial insemination (AI) bull semen quality assessment, the osmotic resistance of spermatozoa was measured using the hypo-osmotic swelling (HOS) test, developed by Jeyendran et al. (1984) (labelled HOS-1), and its modifications (HOS-2, HOS-3), with decreased osmotic pressure aimed at challenging sperm survival ability. The test results were benchmarked against sperm viability measurements performed using the Computerized Motility Analyzer (CMA), and field fertility was calculated as non-return rate (NRR). Two age groups of Estonian Holstein bull sires were included in this study to test possible age effect on semen quality parameters. The HOS-1 test in fresh bull semen correlated well with sperm general motility (GMot) (r = 0.63, P < 0.001 at batch level and r = 0.77, P < 0.001 at bull level) as well as with progressive motility (PMot) in frozen-thawed (FT) semen (r = 66, P < 0.001 at batch level and r = 0.81, P < 0.001 at bull level), which makes the test suitable for the prediction of post-thaw semen quality. However, the HOS-2 and HOS-3 values in FT semen had high correlations with NRR (r = 0.65, r = 0.66, P < 0.001 at batch level and r = 0.63, r = 0.71, P < 0.01 at bull level), which was comparable to those between GMot and NRR or PMot and NRR. A combination of motility parameters and the results of the HOS-1 and HOS-3 tests provided a good model for predicting the potential fertility of bull semen. Values of sperm membrane post-thaw intactness, assessed using HOS-2, as well as of sperm motility measurements were higher in mature bulls compared to those in young bulls. Short conclusion: different modifications of the hypo-osmotic swelling test are useful for routine bovine semen quality assessment at AI stations.  

THE INFLUENCE OF TECHNOLOGICAL OPERATIONS ON THE CONSERVATION OF SPERMS

The information resulted from the processing of the bull’s seminal material and the artificial inseminations, shows certain signs, like the one, that between different dozes of seminal material coming from the same ejaculator , would be, significant differences concerning the number of pro doze spermatozoon’s as well as their vitality and the percentage of mobile spermatozoon’s from a doze. The experiments took place at the artificial insemination station from Germany, BVN. In the experiments were included 6 oxen, between two and seven years, belonging to the breeds dual use Simmental and Gelbvieh. As a diluent’s medium, were comparatively used, a diluent with egg yolk, Triladyl (MinitubGermany) and a diluent without egg yolk, Bioxcell (IMVFrance). Concerning the Motility’s values the impact of the dilators was not as high (table 3). However, slightly better values were indicated here for the BIOXCELL-variant. All in all the differences between the both dilution variants and the impact of the dilutors corresponded to earlier researches.

Efeito da idade do touro e do período de colheita de sêmen sobre as características físicas e morfológicas do sêmen de bovinos de raças européias e zebuínas

Este trabalho foi realizado com o objetivo de avaliar o efeito da idade de touros europeus e zebuínos e do período de colheita do sêmen sobre as características físicas e morfológicas do sêmen desses animais produzido em uma central de inseminação no período de 1993 a 1999. Os dados de produção de sêmen dos touros foram agrupados em cinco classes de idade (12 a 36 meses, 37 a 60 meses, 61 a 84 meses, 85 a 108 meses e 109 a 142 meses) e quatro períodos de colheita (período 1: dezembro a fevereiro; período 2: março a maio; período 3: junho a agosto e período 4: setembro a novembro). As classes de idade determinaram diferenças significativas no volume, turbilhonamento espermático, nas anormalidades primárias, secundárias, terciárias e totais, na integridade de acrossoma e na quantidade média de doses por ejaculado, cujos valores foram maiores nos zebuínos no período 4 (setembro a outubro). As maiores porcentagens de anormalidades totais, nas duas subespécies, foram observadas nos animais mais jovens (12 a 36 meses) e nos mais velhos (109 e 142 meses). Os zebuínos mais velhos produziram sêmen mais concentrado e maiores quantidades médias de doses por ejaculado. Em touros europeus, o sêmen menos concentrado e as maiores porcentagens de anormalidades espermáticas foram observadas no período 1 (dezembro a fevereiro), consequentemente, menores quantidades de doses de sêmen por ejaculado foram produzidas por essa subespécie, o que pode ter sido um efeito do estresse calórico sofrido por estes animais antes da colheita de sêmen. A idade e o período de colheita influenciam na qualidade do sêmen de touros doadores mantidos em regime de colheita para comercialização.

INFLUENCE OF ACCLIMATIZATION AND AGE OF IMPORTED BOARS ON THE QUALITY OF THEIR SPERM

In the paper the process of acclimatization and adaptation of boars on climate and microclimate conditions are described. The process of growth and sexual maturity during the breeding and accustoming of boars in taking sperms in the centers of artificial insemination or breeding stations are analyzed. It is concluded that appropriate microclimate conditions may solve sterility provoked by climate conditions and even increase fertility of pigs. For purchased and imported young boars it is very important that animals are raised in a proper way and trained for mounting and semen collecting. Ejaculate in the native sperm of imported boars is better quality comparing to the ejaculate of home breeds, but they are sensitive to unspecific infections that can reduce spermatozoa vitality, damage acrosome, disturb spermatozoa maturation and thus influence fertilizing of diluted semen. Housing and nutrition of high-born breed boars has important role in maximal exploitation of producing ability especially on longevity and lifetime production of the imported boars.

Zn and Pb Concentration in Seminal Plasma in Reference to Selected Parameters of Semiological Assessment of Bull Semen

The Zn and Pb concentration was determined in 45 samples of bull semen from three Artificial Insemination Stations (A,B,C) differing in degree of environmental pollution. Bull semen was diluted with Biociphos-Plus to such an extent as to obtain 16 million sperm cells in an insemination dose. The research aimed at assessing the correlation between zinc, lead and other parameters influencing the semiological assessment of bull semen. The content of zinc and lead was determined with the use of the flame method and an absorption spectrophotometer (AAS). Positive, statistically significant correlations between zinc concentration and semen motility were observed in station A at r = 0.61 and station C at r = 0.614. In station B these correspondences were not statistically confirmed. Positive correlation at r = 0.583 was observed in case of zinc and the ejaculate volume only in station B. No statistically significant correlation was observed between lead concentration and the analyzed parameters.

A new case of reciprocal translocation t(10;13)(q16;q21) diagnosed in an AI boar

A new case of reciprocal translocation t(10;13)(q16;q21) was detected in a hybrid boar (Large White x Pietrain x Duroc x Hampshire) from an artificial insemination (AI) station. Altogether, 258 sires of 4 pure breeds as well as hybrid lines and crossbreeds were investigated. The diagnosis was based on classical cytogenetic examination following the standard protocols of lymphocyte cultures, Giemsa staining and G-, C- and Ag-I banding techniques. The population screening performed was an initial part of a long-term karyotype control system of boars kept at AI stations, which was started by the National Research Institute of Animal Production in Poland in 2007.

Low incidence of bovine leukocyte adhesion deficiency (BLAD) carriers in Indian cattle and buffalo breeds

BLAD is an autosomal recessive genetic disease that affects Holstein-Friesian (HF) cattle worldwide. It is a disease characterized by a reduced expression of the adhesion molecules on neutrophils. The disease is caused by a mutation that replaces adenine at 383 with guanine, which causes an amino acid change from aspartic acid to glycine. Blood samples and a few semen samples were collected from 1250 phenotypically normal individuals, including HF (N=377), HF crossbred (N=334), Jersey (105), other breeds of cattle (N=160) and water buffalo Bubalus bubalis (N=274) belonging to various artificial insemination stations, bull mother farms (BMFs) and embryo transfer (ET) centres across the country. PCR-RFLP was performed to detect a point mutation in CD18, surface molecules of neutrophils. The results indicate that out of 1250 cattle and buffaloes tested for BLAD, 13 HF purebreds out of 377 and 10 HF crossbreds out of 334 appear to be BLAD carriers. In the HF and HF crossbred population, the percentage of BLAD carriers was estimated as 3.23%. The condition is alarming as the mutant gene has already entered the HF crossbred cattle population and therefore, the population of HF and its crossbreds needs regular screening to avoid the risk of spreading BLAD in the breeding cattle population of India.

Estimation of Genetic Variation in Holstein Young Bulls of Iran AI Station Using Molecular Markers

Genetic profiles of Iranian Holstein young bulls at the national artificial insemination station were determined on the basis of individual genotypes at 13 ISAG's recommended microsatellites, the most useful markers of choice for parentage identification. In the present study a total of 119 individuals were genotyped at 13 microsatellite loci and for possible parent-offspring combinations. A high level of genetic variation was evident within the investigated individuals as assessed from various genetic diversity measures. The mean number of observed alleles per microsatellite marker was 9.15 and the number of effective alleles as usual was less than the observed values (4.03). The average observed and expected heterozygosity values were 0.612 and 0.898, respectively. The mean polymorphic information content (PIC) value (0.694) further reflected a high level of genetic variability. The average exclusion of probability (PE) of the 13 markers was 0.520, ranging from 0.389 to 0.788. The combined exclusion of probability was 0.999, when 13 microsatellite loci were used for analysis in the individual identification system. Inbreeding was calculated as the difference between observed and expected heterozygosity. Observed homozygosity was less than expected which reflects inbreeding of -3.7% indicating that there are genetic differences between bull-sires and bull-dams used to produce young bulls. The results obtained from this study demonstrate that the microsatellite DNA markers used in the present DNA typing are useful and sufficient for individual identification and parentage verification without accurate pedigree information. (Asian-Aust. J. Anim. Sci. 2006. Vol 19, No. 4 : 463-467)

Ethologische Untersuchungen zur Beschäftigung von Ebern in Besamungsstationen mit Stroh

Abstract. Title of the paper: Ethological investigations on occupation with the bedding of boars in Artificial Insemination stations Continuous video recordings with infrared video technique and computer supported analysis with OBSERVER program took place with 78 Piétrain boars in three A.I. stations during 3 x 24 hours. The mean percentage of occupation with the bedding during 24 hours was 7.4 ± 4.4 % (= 106.6 minutes) with a minimum of 1.5 % and a maximum of 18.6 %. The factors A.I. station, season and pen size had a significant influence on occupation with straw as bedding material. The percentage of occupation with bedding in winter was 1.8 % higher than in summer. The percentage of occupation with bedding increased with increasing pen size (from 5.5 % to 11.9 %). The differences between the A.I. stations (between 6.4 % and 10.1 % on average) were caused by management, especially by the frequency of the timers feeding, bedding and watering. The more frequent the boars were caused to stand up by feeding, bedding and watering the higher was the percentage of occupation with the bedding.

Selenium status and GSH-Px activity in semen and blood of boars at different ages used for artificial insemination.

This study was performed to determine the relationship between selenium (Se) content and Se-dependent glutathione peroxidase (GSH-Px) activity in blood and semen, and semen quality of boars at different age used in an artificial insemination (AI) station. Routine macroscopic and microscopic analyses of semen quality were accompanied by measurement of Se content and GSH-Px activity in blood and semen. The Se concentration in blood plasma, seminal fluid and spermatozoa was measured by fluorometric method, the GSH-Px activity by a method based on NADPH-coupled reaction. A total of 155 ejaculates and 58 blood samples were investigated. The results of this study showed that there was no direct relationship between the Se content and GSH-Px activity in blood plasma and semen, and semen quality of sexual matured boars. The mechanisms controlling Se content and GSH-Px activity in blood and semen seem to be independent. The age of boars as a differentiating factor for Se content and GSH-Px activity in blood and semen is possible. It is concluded that a determination of Se status and/or GSH-Px activity in organism before Se supplementation is indicated.

Effect of age and season on sperm morphology of Friesland bulls at an artificial insemination centre in South Africa

The primary objective of this study was to investigate the effect of age, season and the interaction between age and season on the sperm morphological characteristics of a selected population of Friesland bulls kept at an artificial insemination (AI) centre. The study was done at the Taurus AI station, South Africa with 271 Friesland AI bulls aged 12, 24, 36, 48, 60, 72, 84 and 96 months and older over a period of five years. Semen was collected by means of an artificial vagina in all four seasons of the year. Semen samples were screened for the percentage of normal sperm, percentage and total major defects (e.g. knobbed acrosomes, pyriforms, abnormal lose heads, dag defects, nuclear vacuoles, degenerative heads, mid-piece reflexes), the percentage and total minor defects (e.g. normal lose heads, distal droplets, curled end-piece and lose acrosomes). The results indicated that the percentage of normal sperm and major sperm defects were affected significantly by age of the bulls. Bulls at 36 to 48 months of age exhibited a better sperm morphology than bulls older than 72 months and bulls younger than 36 months of age. Major sperm defects that were affected by age included pyriform, knobbed acrosomes, mid-piece reflexes and dag defects. Season of the year also affected the percentage of normal sperm significantly. Percentage of normal sperm and major sperm defects were recorded as 72.8±1.6%, 79.4±2.2%, 82.5±2.4% and 84.4±2.4% and 20.3±1.3%, 15.3±1.9%, 12.5±2.0% and 11.5±2.0% for summer, autumn, winter and spring, respectively. Major sperm defects such as proximal droplets and pyriform differed significantly with season. By contrast, knobbed acrosomes and mid-piece reflexes did not differ between seasons. Even though there was a wide variation in sperm morphology, better morphology was observed in spring and winter than in summer and autumn. Major sperm defects, particularly the prevalence of knobbed acrosomes and dag defects, were affected significantly by the interaction between age and season. Young bulls recorded a higher prevalence of major sperm defects during winter and old bulls a higher prevalence during the summer. It is concluded that age and season contribute significantly to the proportion of variation in the sperm morphological characteristics of Friesland AI bulls in South Africa. For successful AI programmes, semen collection in Friesland bulls should be done at 36 to 48 months of age and preferably during spring or winter.

Validation of the FACSCount AF system for determination of sperm concentration in boar semen.

A flow cytometric method has been developed for rapid determination of sperm concentration in semen from various mammalian species.* All cells containing DNA are stained with SYBR-14 or propidium iodide (PI) and sperm concentration is determined in relation to an internal standard of fluorescent microspheres (beads). Satisfactory staining can be achieved within 2-3 min and the following flow cytometric analysis on the FACSCount AF System rapidly provides the user with a precise and accurate assessment of the sperm concentration. In this study, the FACSCount AF System and Sperm Counting Reagent (BD Biosciences) was compared with microscopic counting using a Bürker-Türk haemocytometer. In addition, sperm concentration was determined using the Corning 254 spectrophotometer which is used routinely by Danish artificial insemination stations for boars. The results show that the agreement between flow cytometry and microscopic counting is very high. The slope for the regression line was 1.12 (SE = 0.03) with an estimated intercept with the Y-axis of 22 x 10(6) sperm/ml (SE = 10 x 10(6) sperm/ml) and an estimated error of the model of 10 x 10(6) sperm/ml. For the spectrophotometer, the slope of the regression line was 1.09 (SE = 0.07) with an estimated intercept of 137 x 10(6) sperm/ml (SE = 25 x 10(6) sperm/ml). The average error made by the spectrophotometer was 55 x 10(6) sperm/ml. In addition, the results obtained using flow cytometry was highly repeatable (CV = 2.7%) in comparison with the spectrophotometric method (CV = 6.3%). These results indicate that the FACSCount AF System is a valuable tool for precise and accurate assessment of sperm concentration in boar semen and that use of this system may lead to production of more uniform insemination doses containing a specific number of sperm per dose.

Impaired semen quality of AI bulls fed with moldy hay: a case report

The daily quality control of semen at a Finnish artificial insemination (AI) bull station is based on subjective motility and sperm morphology of young bulls entering the semen collection program. Semen quality dropped suddenly in autumn 1998. During 5 consecutive months, the number of rejected ejaculates and discarded frozen semen batches due to poor motility increased, and the number of all forms of abnormal spermatozoa increased. However, for the accepted ejaculates, a 60 day nonreturn rate was normal.The summer of 1998 in Finland was rainy, and the hay used in the AI station was visibly moldy. Immunoassay and gas chromatography–mass spectrometry (GC–MS) detected Fusarium mycotoxins HT-2 and T-2, but no zearalenone in the hay. Occurrence of mycotoxins such as T-2 and HT-2 in the moldy hay coincided with, and may have been responsible for the impaired semen quality in AI bulls. This case report will draw the attention to the possible hazards when feeding moldy hay.

Conservation and utilisation of the Sahiwal cattle in Kenya

SummarySahiwal cattle are indigenous to Pakistan and India, and were imported to Kenya in 1930s and 1940s. The breed has been developed as a dual-purpose breed and is utilised in smallholder farming systems, beef and dairy ranching in marginal areas of Kenya which form 80% of the country. Conservation efforts include keeping of Sahiwal herds on state farms, individual ranches and the establishment of the Sahiwal semen bank at the Central Artificial Insemination Station at Kabete near Nairobi. Breeding of the Sahiwal has been promoted by the formation of the Sahiwal Breeders Society which has established breed standards for registration of Sahiwal cattle with the Kenya Stud Book.

Persistent bovine pestivirus infection localized in the testes of an immuno-competent, non-viraemic bull

A post-pubertal bull on an artificial insemination station was found to be persistently shedding bovine viral diarrhoea virus (BVDV) in semen over a period of eleven months, while demonstrating no viraemia. Circulating antibodies to BVDV were consistently high, suggesting that the immune system was challenged repeatedly. Post-mortem findings confirmed that the virus was sequestered in the testes of the bull. It is hypothesized that the BVDV in this immuno-competent bull was protected from the bull's immune response by the blood-testes barrier. The barrier becomes functional only at puberty when tight junctions form between adjacent Sertoli cells, suggesting that this bull became persistently infected with BVDV during puberty.

The use of a polymerase chain reaction assay for the detection of bovine herpesvirus 1 in semen during a natural outbreak of infectious bovine rhinotracheitis

Nasal swabs from two bulls at an artificial insemination (AI) station were submitted to our laboratory. The animals showed clinical signs of Infectious bovine rhinotracheitis (IBR), although the station was supposedly free of bovine herpesvirus 1 (BHV1). DNA of BHV1 was detected using a polymerase chain reaction (PCR). Subsequently nasal swabs from 100 animals that could have been in contact were submitted. BHV1 DNA was detected in swabs from 23 animals. Using the PCR, BHV1 could only be detected in a limited number of semen samples over a period of two months prior to the outbreak or two months after the outbreak. Also, not all animals that shed BHV1 from the nose harboured detectable BHV1 in the semen. Finally BHV1 was detected in the semen of one bull, approximately six weeks before seroconversion. Presently the PCR is being used as a means of quality control of fresh semen from bulls that are seropositive for BHV1. We are able to produce a result within 6 h after the semen samples have been submitted, allowing the AI-station manager to take measures before semen distribution in the event of a positive reaction. So far 11 out of 318 samples were shown to contain BHV1 DNA. In order to be able to interpret these results an interlaboratory comparative study is proposed. In countries endemically infected with BHV1 the PCR can be a cost-effective method to minimize the risk of transmitting virus by semen.

An improved DNA test for bovine leucocyte adhesion deficiency

A modified DNA test, based on the polymerase chain reaction, was developed for the monogenic recessive disease bovine leucocyte adhesion deficiency ( BLAD). The test was improved by the selection of new primers which facilitated the interpretation of the results. An easily scorable banding pattern makes the test useful in cattle breeding schemes and for clinical diagnosis. A total of 2381 samples was analysed over a period of three years. The carrier rate among young bulls at artificial insemination ( AI) stations decreased from 11·6 per cent in 1993 to 9·9 per cent in the first five months of 1995. Continuous screening of young bulls before entering AI is still recommended unless both parents are proven to be genetically free of BLAD. The carrier rate among clinically suspect animals was not increased, and carriers are therefore not expected to be immunodeficient. Despite all efforts to eradicate the disease, calves with BLAD were still observed in 1995.

Effect of Breed, Month of the Year and Age of Bulls on Semen Quality of Bos Taurus Bulls in a Tropical Environment

Ejaculates from 48 bulls comprising equal numbers of Aryshire, Fresian, Guernsey and Jersey breeds at an artificial insemination station in Kenya were analysed. The effect of age, breed and month of the year on semen volume, spermatozoa concentration and motility were studied. The second ejaculate volumes, concentrations and motility were significantly higher (p The Kenya Veterinarian Vol. 18 (1) 1994: pp. 8-11

Evaluation of overseas pig breeds using imported semen 1. Growth and carcass performance

SummaryAlthough a given foreign breed may offer worthwhile genetic improvement, the cost of importing purebred stock makes its evaluation difficult. An experiment was performed in which the breeds compared were represented instead by semen from boars standing at national artificial insemination stations in their native countries. Contemporary groups of Large White × Norwegian Landrace females were inseminated, some with British Large White (LW) semen, and some with semen from Canadian Yorkshire (CY), Danish Landrace (DL), Norwegian Landrace (NL), or United States (American) Duroc (AD) or Yorkshire (AY). One pair (male castrate and gilt) from each litter was performance tested from 27 to 82 kg live weight fed ad libitum (AL), another pairwas tested over the same weight range but fed to a time-based scale (TS). The number of LW, CY, DL, AD, AY and NL sires used was 51, 12, 21, 7, 6 and 23 respectively; a total of 401 litterswas evaluated. The differences between the progeny of LW sires and those of CY, DL, AD, AY and NL were, respectively: in daily live-weight gain (g), AL, –30, 40, –80, –50, –40 (maximum s.E. 16) with no significant differences for TS; in food conversion ratio, AL,0·02, – 0·13, 0·03, –0·05, 0·00 and TS, 000, – 0·14, 0·05, –0·03, –0·06 (maximum S.E. 0·049 for both feeding regimens); in percentage of lean by weight in the rumpback joint, AL, –2·1, –1·9, –1·8, 2·3, –0·7 and TS, – 0·1, –0·9, –1·9, 3·0, – 1·4 (maximum s.E. 1·28 for both); in overall economic worth (pence per pig sired), AL, – 150, 50, – 170, 110, – 40 and TS, – 10, 100, – 200, 190, 30 (maximum s.E. 83 for both). The U.S. Yorkshire and Danish Landrace seem unlikely to be of use commercially in the U.K., while the most promising breeds, U.S. Duroc and Canadian Yorkshire, have not yet been evaluated with sufficient precision to reduce the risk involved in their use to an acceptable level.