Genomic characterization of Pinzgau cattle: genetic conservation and breeding perspectives

A genome-wide scan of Slovak Pinzgau cattle was prepared for the first time in order to estimate their genetic diversity at a more detailed level compared to previously published studies. The aim of this study was to describe the genetic diversity based on the runs of homozygosity (ROH_s), linkage disequilibrium (LD) and effective population size (N_eLD) using genome-wide data. Moreover, Bayesian clustering algorithms and multivariate methods were used to detect the population structure, potential admixture level and relationship between Austrian and Slovak Pinzgau cattle with respect to a large meta-population consisting of 15 European cattle breeds. The proportion of ROH segments ranged from 0.43 to 1.91% in Slovak Pinzgau, depending on the minimum size of an ROH. The genomic inbreeding coefficients were higher than the pedigree ones possibly due to the limited number of available generations in pedigree data. The observed N_eLD was close to the limit value characterizing the endangerment status, based both on genomic and pedigree data. Population structure within analyzed breeds based on the Wright’s F_ST index, Nei’s genetic distances, and unsupervised as well as supervised analysis has been established. Overall, these analyses clearly distinguished populations based on their origin. A detailed analysis of the introgression of each breed into the Pinzgau breeds prepared using a Bayesian approach showed that the contribution of Holstein cattle in Austrian as well as Slovak Pinzgau was larger than contribution of beef breeds. A possible reason is the recent usage of Holstein sires to increase milk production. There are considerable differences between well-defined regions that clearly distinguish Austrian and Slovak Pinzgau, despite their close common history. Generally, the breeding program of Austrian Pinzgau is more focused on meat production than Slovak Pinzgau, which was clearly reflected in the obtained autozygosity islands. Considering the genetic establishment of Slovak Pinzgau population the genetic potential of the breed is insufficiently used. On a long term, more global breeding program including very close populations will be more efficient providing higher genetic progress and diversity. Established methodology how to distinguish genealogically close populations on high-throughput molecular information based of Slovak and Austrian Pinzgau can be proposed as general for analysis of differences in all highly related breeds.     

Genetic relationships of Austrian cattle breeds

Methods of phylogenetic analysis were used to study the relationships of ten Central European cattle breeds using gene frequencies at eleven blood group and protein polymorphism loci. The results show remarkable agreement with historical and geographical relationships, but are different from the relationships postulated earlier in the century from studies of skull shape. Lowland cattle of Northern Germany are distinct from the West Alpine breeds, but the Pustertaler and Pinzgauer breeds from the Eastern Alps are more closely related to those lowland breeds than to the other Alpine breeds, suggesting they were brought from the North by Germanic settlers in the early Middle Ages. Thus, a sharp distinction between lowland cattle and all Alpine breeds seems unwarranted. Moreover, we find no evidence to justify a unique taxonomic position for Pustertaler, nor do we find any evidence that Spanish cattle might have influenced the Pinzgau. We find a close genetic relationship of the Murbodner breed to the Fleckvieh (Simmenthal) breeds that is not supported by any known historical relationship; it may indicate a little-known human migration.     

Ultra-low-density genotype panels for breed assignment of Angus and Hereford cattle

Angus and Hereford beef is marketed internationally for apparent superior meat quality attributes; DNA-based breed authenticity could be a useful instrument to ensure consumer confidence on premium meat products. The objective of this study was to develop an ultra-low-density genotype panel to accurately quantify the Angus and Hereford breed proportion in biological samples. Medium-density genotypes (13 306 single nucleotide polymorphisms (SNPs)) were available on 54 703 commercial and 4042 purebred animals. The breed proportion of the commercial animals was generated from the medium-density genotypes and this estimate was regarded as the gold-standard breed composition. Ten genotype panels (100 to 1000 SNPs) were developed from the medium-density genotypes; five methods were used to identify the most informative SNPs and these included the Delta statistic, the fixation (F_st) statistic and an index of both. Breed assignment analyses were undertaken for each breed, panel density and SNP selection method separately with a programme to infer population structure using the entire 13 306 SNP panel (representing the gold-standard measure). Breed assignment was undertaken for all commercial animals (n=54 703), animals deemed to contain some proportion of Angus based on pedigree (n=5740) and animals deemed to contain some proportion of Hereford based on pedigree (n=5187). The predicted breed proportion of all animals from the lower density panels was then compared with the gold-standard breed prediction. Panel density, SNP selection method and breed all had a significant effect on the correlation of predicted and actual breed proportion. Regardless of breed, the Index method of SNP selection numerically (but not significantly) outperformed all other selection methods in accuracy (i.e. correlation and root mean square of prediction) when panel density was ⩾300 SNPs. The correlation between actual and predicted breed proportion increased as panel density increased. Using 300 SNPs (selected using the global index method), the correlation between predicted and actual breed proportion was 0.993 and 0.995 in the Angus and Hereford validation populations, respectively. When SNP panels optimised for breed prediction in one population were used to predict the breed proportion of a separate population, the correlation between predicted and actual breed proportion was 0.034 and 0.044 weaker in the Hereford and Angus populations, respectively (using the 300 SNP panel). It is necessary to include at least 300 to 400 SNPs (per breed) on genotype panels to accurately predict breed proportion from biological samples.     

Molecular phylogeny of Pakistani riverine buffalo based on genetic variability of mitochondrial cytochrome b gene

Mitochondrial cytochrome b gene is considered to be one of the best markers for breed characterization as well as studying the ancestry in the vertebrates due to its exclusive maternal inheritance. DNA fingerprinting by single nucleotide polymorphism is most reliable and widely used molecular technique in modern forensics and is being considered in this study. Partial sequencing of 1,061?bp of aforementioned gene from 14580 to 15643 was conducted in two famous Pakistani buffalo breeds named Nili-Ravi and Kundi. In which we explore seven haplotypes within earlier and none in the latter breed. Nili-Ravi is polymorphic at four codons of this gene, and the protein translation is also different from the reference sample while monomorphic at three codons with no amino acid replacement. Haplotypes frequency distribution of these four haplotypes named NR3, NR4, NR5, NR7 revealed that the prevalence of each haplotype is 0.04?% in the Pakistani buffalo population of this Nili-Ravi breed while complete homoplasmy was observed in the Kundi breed population. Nili-Ravi breed of buffalo is genetically more variable than the Kundi breed as far as the gene in subject is concerned. It means later breed has spent more time to propagate its wild type haplotype which make this breed more ancestral as compare to Nili-Ravi. Secondly both breeds share their common ancestors with regional water buffalo rather than the swamp one.     

Use of linked loci as individuals or haplotypes for marker-assisted breed assignment

The objective of this study was to use simulation to evaluate the benefits of considering haplotypes of loci when linked single nucleotide polymorphisms are used for breed assignment. Three breeds of 10 000 females each were simulated under eight scenarios that differed according to the number of generations separating the breeds, size of breed founder populations and recombination rate between linked loci. Molecular genotypes consisted of 20 groups of three linked loci each. Breed assignment was performed in the final generation and was based on the frequency method. Haplotypes were reconstructed using the expectation–maximization algorithm. Accuracy of breed assignment was based on the frequency of correct breed assignment. Assignment accuracy increased as more genotypes (loci or haplotypes) were considered and more animals were used to estimate genotypic frequencies within breed. For most scenarios, use of haplotypes yielded equal or greater accuracies than when loci were considered independent. The advantage of haplotypes tended to increase as linkage disequilibrium between adjacent loci increased. The greatest advantage for using haplotypes was observed when recombination rate was low (0.001), breeds were separated by few generations (100), and a relatively large number of founder animals (110) was used to form new breeds. In this situation, 90% accuracy of breed assignment was achieved using nine to 14 haplotypes (i.e. 27–42 loci) depending on breed, vs. 39–57 individual loci.     

Characterization of the Russian beef cattle breed gene pools using inter simple sequence repeat DNA analysis (ISSR analysis)

The gene pools of beef cattle breeds bred in Russia were characterized on the basis of inter simple sequence repeat DNA analysis (ISSR analysis). Samples of Aberdeen Angus, Kalmyk, and Kazakh Whitehead breeds from Russia, as well as of Hereford breed, hybrids of Kazakh Whitehead and Hereford breeds, and Kazakh Whitehead breed from the Republic of Kazakhstan, were examined. In the examined breeds, 27 AG-ISSR fragments were identified, 25 of which were polymorphic. The examined breeds were different both in the fragment profiles (the presence/absence of individual ISSR fragments) and in their frequencies. It was demonstrated that the hybrid animals lacked some ISSR fragments that were present with high frequencies in parental forms, suggesting considerable genome rearrangement in the hybrid animals (at the regions of microsatellite localization) in crossings of the individuals from different breeds. The level of genetic diversity in Russian beef breeds was consistent with the values typical of farmed populations (breeds). The genetic diversity parameters assessed by applying Nei’s gene diversity index and the Shannon index varied from 0.0218 to 0.0605 and from 0.0225 to 0.0819, respectively. The highest Shannon index value was detected in the Kalmyk breed (0.0837) and Kazakh Whitehead breed from Russia (0.0819), and the highest level of Nei’s gene diversity index was found in the Kalmyk breed (0.0562) and in both populations of the Kazakh Whitehead breed (0.0509 and 0.0605). The high level of genetic similarity (according to Nei) was revealed between Russian beef cattle breeds and Hereford cattle: 0.839 (for the Kazakh Whitehead breed from Russia) and 0.769 (for the Kalmyk breed).     

Role of genetic factors in the occurrence of umbilical hernias in cattle. II. Heredity and the incidence of umbilical hernia in various crossing variants

To determine ethyology of Hernia umbilicalis in black-spotted cattle stock, a check crossing was carried out. The incidence of anomalia in the bull progeny of Zakaznik 82 (black-spotted breed) was 44%, this value being 107 in the progeny of Block 107 (holsteinfrisish breed) and 0% in the progeny of Vyaz 338 (holmogorsky breed). The data obtained indicate that Hernia umbilicalis is a hereditary anomaly in cattle.     

Breed assignment of Italian cattle using biallelic AFLP markers

The verification of the breed origin of animal products is relevant for food safety and authenticity. We assessed the suitability of AFLP molecular markers in the assignment of cattle individuals to their breed of origin. Three hundred and ninety-six animals belonging to 16 cattle breeds genotyped with 141 AFLP markers were used as reference data set. Assignment was performed with likelihood (aflpop) and Bayesian (structure) methods. The Bayesian approach was superior to the likelihood algorithm with respect to (i) the correct assignment of simulated individuals to their breed of origin (93% vs. 81% respectively), (ii) the correct assignment of 44 sampled Romagnola animals (91% vs. 45% respectively) and (iii) the correct classification of animals belonging to a breed that was not included within the reference dataset. Thus, AFLP profiling in combination with the Bayesian approach seems a useful tool for breed assignment.     

Ancestral matrilineages and mitochondrial DNA diversity of the Lidia cattle breed

To clarify the genetic ancestry and the mitochondrial DNA (mtDNA) diversity of the Lidia cattle breed, a 521-bp D-loop fragment was sequenced in 527 animals belonging to 70 herds distributed across 29 lineages. The mtDNA diversity recorded was similar to that seen for Middle Eastern breeds and greater than that recorded for the majority of European breeds. Haplotype T3 was the most common (81%), followed by the African T1 haplotype (17%); very low frequencies were recorded for haplotypes T and T2. The results agree with there being two major ancestral lines for the Lidia breed, European and African, similar to that seen for other Mediterranean breeds. A wide range of variation in haplotype frequencies was seen between the examined lineages. Haplotype T3 was present in all those analysed; in five it was the only one present, and in only one lineage (Miura) was its frequency lower than that of T1. T1*, a haplotype reported in Criollo breeds and to date in only a single European breed (the Retinta breed from Spain), was found in a single animal belonging to the Concha y Sierra lineage. Network analysis of the Lidia breed revealed the presence of two major haplotypes: T3 and T1. The Lidia breed appears to be more closely related to prehistoric Iberian and Italian than to British aurochs.     

Litter size at birth in purebred dogs--a retrospective study of 224 breeds

Despite the long history of purebred dogs and the large number of existing breeds, few studies of canine litter size based upon a large number of breeds exist. Previous studies are either old or include only one or a few selected breeds. The aim of this large-scale retrospective study was to estimate the mean litter size in a large population of purebred dogs and to describe some factors that might influence the litter size. A total of 10,810 litters of 224 breeds registered in the Norwegian Kennel Club from 2006 to 2007 were included in the study. The overall mean litter size at birth was 5.4 (± 0.025). A generalized linear mixed model with a random intercept for breed revealed that the litter size was significantly influenced by the size of the breed, the method of mating and the age of the bitch. A significant interaction between breed size and age was detected, in that the expected number of puppies born decreased more for older bitches of large breeds. Mean litter size increased with breed size, from 3.5 (± 0.04) puppies in miniature breeds to 7.1 (± 0.13) puppies in giant breeds. No effect on litter size was found for the season of birth or the parity of the bitch. The large number of breeds and the detail of the registered information on the litters in this study are unique. In conclusion, the size of the breed, the age of the bitch and the method of mating were found to influence litter size in purebred dogs when controlling for breed, with the size of the breed as the strongest determinant.     

Population structure and breed composition prediction in a multi-breed sheep population using genome-wide single nucleotide polymorphism genotypes

Knowledge of population structure and breed composition of a population can be advantageous for a number of reasons; these include designing optimal (cross)breeding strategies in order to maximise non-additive genetic effects, maintaining flockbook integrity by authenticating animals being registered and as a quality control measure in the genotyping process. The objectives of the present study were to 1) describe the population structure of 24 sheep breeds, 2) quantify the breed composition of both flockbook-recorded and crossbred animals using single nucleotide polymorphism BLUP (SNP-BLUP), and 3) quantify the accuracy of breed composition prediction from low-density genotype panels containing between 2000 and 6000 SNPs. In total, 9334 autosomal SNPs on 11 144 flockbook-recorded animals and 1172 crossbred animals were used. The population structure of all breeds was characterised by principal component analysis (PCA) as well as the pairwise breed fixation index (F_st). The total number of animals, all of which were purebred, included in the calibration population for SNP-BLUP was 2579 with the number of animals per breed ranging from 9 to 500. The remaining 9559 flockbook-recorded animals, composite breeds and crossbred animals represented the test population; three breeds were excluded from breed composition prediction. The breed composition predicted using SNP-BLUP with 9334 SNPs was considered the gold standard prediction. The pairwise breed F_st ranged from 0.040 (between the Irish Blackface and Scottish Blackface) to 0.282 (between the Border Leicester and Suffolk). Principal component analysis revealed that the Suffolk from Ireland and the Suffolk from New Zealand formed distinct, non-overlapping clusters. In contrast, the Texel from Ireland and that from New Zealand formed integrated, overlapping clusters. Composite animals such as the Belclare clustered close to its founder breeds (i.e., Finn, Galway, Lleyn and Texel). When all 9334 SNPs were used to predict breed composition, an animal that had a majority breed proportion predicted to be ≥0.90 was defined as purebred for the present study. As the panel density decreased, the predicted breed proportion threshold, used to identify animals as purebred, also decreased (≥0.85 with 6000 SNPs to ≥0.60 with 2000 SNPs). In all, results from the study suggest that breed composition for purebred and crossbred animals can be determined with SNP-BLUP using ≥5000 SNPs.     

Metagenomic bacterial community profiles of chicken embryo gastrointestinal tract by using T-RFLP analysis

Thirty microbial phylotypes of microorganisms were found in the gastrointestinal tract of chicken belonging to the Hajseks White breed, and 38 phylotypes were found in the gastrointestinal tract of chicken belonging to the Hajseks Brown breed. The microbiome of the gastrointestinal tract of the chicken embryos of the Hajseks White breed was dominated by the typical representatives of avian intestinal microflora—bacteria of the family Enterobacteriaceae (47.3%), orders Actinomycetales (13.6%) and Bifidobacteriales (20.6%), and the family Lachnospiraceae (1.1%). The microbiome of the gastrointestinal tract of the chicken embryos of the Hajseks Brown breed was dominated by the pathogenic bacteria of the order Rickettsiales (94.8%). The metagenome of gastrointestinal tract of both breeds also contained a small number of genes of unidentified bacteria.     

Genetic variability between two breeds based on restriction fragment length polymorphisms (RFLPs) of major histocompatibility complex class I genes in the pig

Summary Restriction fragment length polymorphism analyses of SLA class I genes were performed on 55 Duroc and 24 Hampshire boars from the 1986–87 national performance tests of each breed. Few boars were inbred. Southern blotting and hybridization procedures were performed on genomic DNA isolated from white blood cells by using Pvu II, Bam HI, and Eco RI endonucleases and a swine MHC class I probe. Genetic variability within and between the two breeds was estimated in terms of nucleotide diversity, by using a mathematical analysis based on the different RFLP patterns. The nucleotide diversity calculated within each breed was less than that between the two breeds. The results from the nucleotide diversity analysis suggested that genetic variability was greater in the Duroc breed than in the Hampshire breed. A relatively high level of genetic variability was shown in the class I major histocompatibility complex genes in the pig.     

What’s in a Name? Effect of Breed Perceptions & Labeling on Attractiveness,Adoptions & Length of Stay for Pit-Bull-Type Dogs

Previous research has indicated that certain breeds of dogs stay longer in shelters than others. However, exactly how breed perception and identification influences potential adopters'' decisions remains unclear. Current dog breed identification practices in animal shelters are often based upon information supplied by the relinquishing owner, or staff determination based on the dog''s phenotype. However, discrepancies have been found between breed identification as typically assessed by welfare agencies and the outcome of DNA analysis. In Study 1, the perceived behavioral and adoptability characteristics of a pit-bull-type dog were compared with those of a Labrador Retriever and Border Collie. How the addition of a human handler influenced those perceptions was also assessed. In Study 2, lengths of stay and perceived attractiveness of dogs that were labeled as pit bull breeds were compared to dogs that were phenotypically similar but were labeled as another breed at an animal shelter. The latter dogs were called "lookalikes." In Study 3, we compared perceived attractiveness in video recordings of pit-bull-type dogs and lookalikes with and without breed labels. Lastly, data from an animal shelter that ceased applying breed labeling on kennels were analyzed, and lengths of stay and outcomes for all dog breeds, including pit bulls, before and after the change in labeling practice were compared. In total, these findings suggest that breed labeling influences potential adopters'' perceptions and decision-making. Given the inherent complexity of breed assignment based on morphology coupled with negative breed perceptions, removing breed labels is a relatively low-cost strategy that will likely improve outcomes for dogs in animal shelters.     

The effect of nocturnal sampling on semen quality and the efficiency of collection in bovine species

This study evaluated night and day semen collection regimes in Holstein and Brahman bulls (four bulls of each breed) that were collected weekly, each during a morning and a night collection. Ejaculates (n=64) were obtained via artificial vagina over 4 weeks. The first collection of each week alternated between night and day. Two collection teams were employed. Bull behavior parameters included reaction time to first mount, time to ejaculation, a refractory period test, and a thrust intensity test. The numbers of interruptions were counted as a managerial parameter. Pre-freeze semen parameters included total volume, initial motility and concentration. Post-freeze semen parameters measured were: 0- and 3-h post-thaw motility; percent intact acrosomes; and percent sperm abnormalities. Data were analyzed by least squares methods. The bull within breed effect differed (P<0.05) for behavior parameters. The bull within breed effect for total motile sperm harvested was not significant. The bull within breed response was mixed for post-freeze semen viability parameters. Bull within breed was not significant for sperm abnormalities. The night versus day treatment was significant for the managerial parameter (P=0.002). Although a different collection schedule for Bos indicus cattle was not warranted, the efficiency of the collection process was affected by extraneous environmental conditions.     

10个牛品种线粒体12S rRNA基因多态性分析

以鲁西牛、渤海黑牛、大别山牛、南阳牛、晋南牛、秦川牛、中国西门塔尔牛、日本和牛、海福特牛和安格斯牛10个牛品种共计353头牛为研究对象,利用单链构象多态性（SSCP）分子标记方法对其线粒体DNA 12S rRNA基因进行了多态性分析,结果发现该基因出现分布频率不同的3种单倍型（Ⅰ、Ⅱ、Ⅲ）,其中单倍型Ⅰ出现的频率最低,仅在晋南牛1个个体中发现;单倍型Ⅱ在中国本地黄牛中都存在,在中国西门塔尔牛中的分布频率很低,但在3个国外品种海福特牛、安格斯牛和日本和牛中不存在;单倍型Ⅲ在这10个牛品种中均有分布,但以国外品种最丰富。计算平均多态信息含量,发现我国地方品种在0.232～0.423之间,基本属于中度多态,说明我国地方黄牛品种在12S rRNA上多态性比较丰富,国外品种较为贫乏;但是单倍型Ⅰ频率很低有丢失的趋势,需要对其进行保护。     

Estrous activity in different breeds and breed crosses of sheep

Estrus was monitored in 715 straightbred and crossbred ewes during spring lactation, postweaning, summer and/or late summer breeding periods. Straightbred ewes were comprised of seven breeds, and crossbreds consisted of Rambouillet- and Finnsheep-sired ewes of the seven breeds. Estrus was detected in 5.4% of the Rambouillet and Finnsheep crossbred ewes during lactation. After weaning, the incidence of estrus was 1.1% in all crossbred and straightbred ewes. The incidence of estrus was 5.2% for all ewes during the summer period. During late summer (July 28 to August 17), 42% of all ewes showed estrus and both breed of sire and breed of dam influenced estrous activity (P<0.01). Straightbred Rambouillet, Targhee, Dorset and most Rambouillet-sired crossbred ewes showed the greatest estrous activity and could be the genetic stock of choice for early lamb production. Straightbred Hampshire, Suffolk and most Finnsheep crossbred ewes showed estrous activity later in the season. Results support the conclusion that certain sheep breeds and breed crosses show estrous activity during August, while other breeds and breed crosses begin estrous activity later and continue until March or April. Thus, lambs may be produced from January through September each year by maintaining several different breeds or breed crosses in the breeding flock.     

Evaluation of the genetic diversity of Laiwu pigs using twenty-seven microsatellite markers

The Laiwu pig, an indigenous pig breed known for extremely high intramuscular fat content, is a well-preserved ancient breed due to long-term natural and artificial selections. In this study, using 27 microsatellite markers jointly recommended by the International Society of Animal Genetics (ISAG) and the Food and Agriculture Organization (FAO), we investigated the genetic diversity of the Laiwu pig breed. The genetic diversity of Laiwu pigs is dramatically low, with the observed heterozygosity ranging from 0.067 to 0.767. Among the 27 microsatellite markers, 10 were high polymorphic loci, 10 were moderate polymorphic loci, six were low polymorphic loci, and no polymorphism was detected at one locus (IGFI). Further analyses with the 10 high polymorphic loci and five moderate polymorphic loci revealed that the Laiwu pig breed was inbred and heterozygous deficient to some extent, but not severely, and that the Laiwu pigs were relatively pure, with almost no hybridization with other breeds. Two subgroups of the current 13 Laiwu pig pedigrees were identified. These results suggest that the Laiwu pig breed has a low diversity and a conservation program must be developed to preserve the “Laiwu pig” gene pool.     

Proteome analysis on differentially expressed proteins of the fat body of two silkworm breeds, Bombyx mori, exposed to heat shock exposure

Proteomes of heat tolerant (multivoltine) and heat susceptible (bivoltine) silkworms (Bombyx mori) in response to heat shock were studied. Detected proteins from fat body were identified by using MALDI-TOF/TOF spectrometer, MS/MS, and MS analysis. Eight proteins, including small heat shock proteins (sHSPs) and HSP70, were expressed similarly in both breeds, while 4 protein spots were expressed specifically in the bivoltine breed and 12 protein spots were expressed specifically in the multivoltine breed. In the present proteomics approach, 5 separate spots of sHSP proteins (HSP19.9, HSP20.1, HSP20.4, HSP20.8, and HSP21.4) were identified. Protein spot intensity of sHSPs was lower in the multivoltine breed than in the bivoltine breed after the 45°C heat shock treatment, while the difference between two breeds was not significant after the 41°C heat shock treatment. These results indicated that some other mechanisms might be engaged in thermal tolerance of multivotine breed except for the expression of sHSP and HSP70. There were visible differences in the intensity of heat shock protein expression between male and female, however, differences were not statistically significant.     

Comparison of sperm quality of Belgian Blue and Holstein Friesian bulls

Few data are currently available on sperm quality of Belgian Blue (BB) bulls. The present study compared sperm quality of BB to Holstein Friesian (HF) bulls of several age categories, by means of a classical semen evaluation. Volume and concentration, and consequently total sperm output depended largely on age. Gross, total, and progressive motility, % live and % normal spermatozoa were significantly lower in the BB breed. Primary sperm abnormalities, such as nuclear vacuoles, midpiece defects and cytoplasmic droplets which were noticed most frequently, occurred far more in the BB breed. Hence, disturbances in spermiogenesis are deemed to be the cause of the poorer BB sperm quality. Since these sperm abnormalities occur significantly more in the BB breed than in the HF breed, it seems as if the BB breed is genetically predisposed to a higher susceptibility to environmental stresses which are known to interfere with normal spermiogenesis. The small scrota typical of the inbred BB breed might in part be responsible for this, and therefore selection for larger scrota in the BB breed is advisable.