Disease Resistance In Animals Research Articles

A specific GAGTT insertion/deletion variation in the IL-10 gene promoter alters the disease resistance of grass carp

IL-10, an anti-inflammatory cytokine, plays crucial roles in the context of infectious inflammatory diseases, whose gene variations and expression are tightly linked to disease resistance in animals. However, there is limited research on the genetic variations governing IL-10 expression and the underlying effects in fish. In this study, we identified a GAGTT insertion/deletion (Ins/Del) variation within the IL-10 gene promoter and analyzed the effects of this variation on IL-10 expression, inflammatory response and its association with disease resistance in grass carp. With dual luciferase reporter assays, we demonstrated that the GAGTT Ins/Del variation significantly altered the IL-10 promoter activity in grass carp. DNA pull-down combined with mass spectrometry revealed that the spectrum of transcription factors that bind to IL-10 promoter variants caused by GAGTT Ins/Del variation was quite different. Moreover, three representative transcription factors, JunD/AP-1, p50/NF-κB, and HMGB1, differentially transactivated grass carp IL-10 promoter variants, as confirmed by western blotting and dual luciferase reporter assays. Using the GAGTT/− genotype of the heterozygous grass carp parents, we obtained full-sib family offspring of the GAGTT/GAGTT, GAGTT/−, and −/− genotypes. During grass carp reovirus (GCRV) infection, these three IL-10 genotypes of grass carp offspring displayed different survival rates. Importantly, grass carp with the GAGTT/− genotype had greater survival than those with the other two genotypes after GCRV infection. Furthermore, the results indicated that the improved intestinal inflammation at 1 d post-GCRV infection and enhanced immunocompetence in the spleen at 5 d post-GCRV infection may contribute to the disease resistance of grass carp with the GAGTT/− genotype. Overall, this study offers new insight into the inflammatory and immune regulatory mechanisms specific to IL-10 from a genetic perspective in fish and may provide a valuable molecular marker for breeding disease-resistant grass carp.

Multiplexed CRISPR-Cas system targeting ASFV genes in vivo: solution lies within.

The emergence and spread of the African swine fever virus (ASFV) posed a significant threat to the global swine breeding industry, calling for innovative approaches benefiting viral containment and control. A recent study (Z. Zheng, L. Xu, H. Dou, Y. Zhou, X., et al., Microbiol Spectr 12: e02164-23, 2024, https://doi.org/10.1128/spectrum.02164-23) established a multiplexed CRISPR-Cas system targeting the genome of ASFV and tested the consequent antiviral activity both in vitro and in vivo. Application of this system showed a significant reduction of viral replication in vitro, while the germline-edited pigs expressing this system exhibited normal growth with continuous guide RNA expression. Although no survival advantage was observed upon ASFV challenge compared with nonengineered pigs, this marks the first attempt of germline editing to pursue ASFV resistance and paves the way for future disease-resistant animal breeding approaches utilizing CRISPR-Cas technology.

Study on the Evolution of Genetic Resources of Domestic Animals in Romania

Abstract The paper proposes the identification of animal breeds at risk of abandonment and the analysis of animal genetic resources from the perspective of the evolution of total herds and genetic quality determination programs. Data from the National Institute of Statistics show that in the period 2015–2022, Romania recorded a decline in the total livestock of cattle (−12.34%) and pigs (−32.44%) and slight increases in the total sheep and goats. On the other hand, the National Agency for Animal Husbandry indicates significant decreases in the number of breeding females, both in cattle (−14.7%) and pigs (−32.5%). Within the 4 species of animals analysed (cattle, sheep, goats and pigs), 14 breeds in danger of abandonment were identified, generally native breeds with lower production potential than that of improved breeds. For the identified animal breeds, genetic quality determination programs have been approved, which are implemented by animal breeders’ associations accredited for the establishment and management of Genealogical Registries. Maintaining the genetic diversity of local breeds in danger of abandonment can contribute to the diversification of existing populations, to restoring the vitality of selected lines, to increasing the productivity and disease resistance of animals.

Advances in Animal Disease Resistance Research: Discoveries of Genetic Markers for Disease Resistance in Cattle through GWAS

Advances in Animal Disease Resistance Research: Discoveries of Genetic Markers for Disease Resistance in Cattle through GWAS

Molecular Cloning and Functional Characterization of the 5′ Regulatory Region of the SLC11A1 Gene from Yaks

The solute transport protein family 11 A1 (SLC11A1), also recognized as natural resistance-associated macrophage protein 1 (NRAMP1), represents a transmembrane protein encoded by the SLC11A1 gene. A variety of prior investigations have illuminated its involvement in conferring resistance or susceptibility to bacterial agents, positioning it as a promising candidate gene for breeding disease-resistant animals. Yaks (Bos grunniens), renowned inhabitants of the Qinghai-Tibet Plateau in China, stand as robust ruminants distinguished by their adaptability and formidable disease resistance. Notwithstanding these unique traits, there is scant literature on the SLC11A1 gene in the yak population. Our inquiry commences with the cloning of the 5′ regulatory region sequence of the Zhongdian yak SLC11A1 gene. We employ bioinformatics tools to identify transcription factor binding sites, delineating pivotal elements like enhancers and cis-acting elements. To ascertain the promoter activity of this region, we amplify four distinct promoter fragments within the 5′ regulatory region of the yak SLC11A1 gene. Subsequently, we design a luciferase reporter gene vector containing four site-specific deletion mutations and perform transient transfection experiments. Through these experiments, we measure and compare the activity of disparate gene fragments located within the 5′ regulatory region, revealing regions bearing promoter functionality and discerning key regulatory elements. Our findings validate the promoter functionality of the 5′ regulatory region, offering preliminary insights into the core and principal regulatory segments of this promoter. Notably, we identified single nucleotide polymorphisms (SNPs) that may be associated with important regulatory elements such as NF-1 and NF-1/L. This study provides a theoretical framework for in-depth research on the function and expression regulation mechanism of the yak SLC11A1 gene.

Molecular breeding of livestock for disease resistance

Animal infectious diseases pose a significant threat to the global agriculture and biomedicine industries, leading to significant economic losses and public health risks. The emergence and spread of viral infections such as African swine fever virus (ASFV), porcine reproductive and respiratory syndrome virus (PRRSV), porcine epidemic diarrhea virus (PEDV), and avian influenza virus (AIV) have highlighted the need for innovative approaches to develop resilient and disease-resistant animal populations. Gene editing technologies, such as CRISPR/Cas9, offer a promising avenue for generating animals with enhanced disease resistance. This review summarizes recent advances in molecular breeding strategies for generating disease-resistant animals, focusing on the development of disease-resistant livestock. We also highlight the potential applications of genome-wide CRISPR/Cas9 library screening and base editors in producing precise gene modified livestock for disease resistance in the future. Overall, gene editing technologies have the potential to revolutionize animal breeding and improve animal health and welfare.

Individual Genomic Loci and mRNA Levels of Immune Biomarkers Associated with Pneumonia Susceptibility in Baladi Goats

The effectiveness of breeding for inherent disease resistance in animals could be considerably increased by identifying the genes and mutations that cause diversity in disease resistance. One hundred and twenty adult female Baladi goats (sixty pneumonic and sixty apparently healthy) were used in this study. DNA and RNA were extracted from blood samples collected from the jugular vein of each goat. SLC11A1, CD-14, CCL2, TLR1, TLR7, TLR8, TLR9, β defensin, SP110, SPP1, BP1, A2M, ADORA3, CARD15, IRF3, and SCART1 SNPs that have been previously found to be associated with pneumonia resistance/susceptibility were identified via PCR-DNA sequencing. The pneumonic and healthy goats differed significantly, according to a Chi-square analysis of the discovered SNPs. The mRNA levels of the studied immune markers were noticeably greater in the pneumonic goats than in the healthy ones. The findings could support the significance of the use of immune gene expression profiles and nucleotide variations as biomarkers for the susceptibility/resistance to pneumonia and provide a practical management technique for Baladi goats. These results also suggest a potential strategy for lowering pneumonia in goats by employing genetic markers linked to an animal's ability to fend off infection in selective breeding.

First report of structural characteristics and polymorphisms of the prion protein gene in raccoon dogs: The possibility of prion disease-resistance.

Prion diseases are fatal degenerative encephalopathies caused by misfolded prion protein (PrPSc) converted from normal prion protein (PrPC). Previous studies have reported that genetic polymorphisms of the prion protein gene (PRNP) play a critical role in susceptibility to prion diseases. In addition, prion disease-resistant animals showed unique structural features of prion protein (PrP) related to species-specific amino acids. However, investigations of genetic polymorphisms of the PRNP gene and structural characteristics of PrP have not been performed in raccoon dogs thus far. We investigated genetic polymorphisms of PRNP in 87 raccoon dogs using amplicon sequencing and analyzed the genotype, allele, haplotype frequencies, and linkage disequilibrium (LD) using Haploview version 4.2. In addition, we performed phylogenetic analysis and multiple sequence alignment (MSA) using MEGA X version 10.1.8 and Clustal X version 2.1, respectively. We estimated the impact of raccoon dog and Canidae family-specific amino acids using PolyPhen-2, PROVEAN, and AMYCO. Furthermore, we analyzed the effect of raccoon dog and Canidae family-specific amino acids using the AlphaFold2 and Swiss-PdbViewer programs. We found 4 novel single nucleotide polymorphisms (SNPs) of the raccoon dog PRNP gene. In addition, the raccoon dog PrP showed 99.61% identity and the closest genetic distance to dog PrP. Among the substitutions of Canidae-specific amino acids with interspecific amino acids, D163N showed increased amyloidogenic propensity, and R181H showed alterations of hydrogen bonds. Furthermore, electrostatic potentials were changed according to the substitutions of D163N and R181H. By comparing PrP between raccoon dogs and raccoons, R168K and K224R were found to be related to changes in hydrogen bonds, and K224R altered the electrostatic potential of raccoon dog PrP. In the present study, we first reported 4 novel synonymous SNPs of the raccoon dog PRNP gene. We also identified that the PrP of raccoon dog has high homology (99.61%) with PrP of dog, which is a prion-resistant animal. In addition, raccoon dog PrP-specific amino acids are related to low amyloid propensity and inherent characteristics of 3D structure of raccoon dog PrP compared to the PrP of prion-susceptible species.

Enhancing Animal Disease Resistance, Production Efficiency, and Welfare through Precise Genome Editing.

The major goal of animal breeding is the genetic enhancement of economic traits. The CRISPR/Cas system, which includes nuclease-mediated and base editor mediated genome editing tools, provides an unprecedented approach to modify the mammalian genome. Thus, farm animal genetic engineering and genetic manipulation have been fundamentally revolutionized. Agricultural animals with traits of interest can be obtained in just one generation (and without long time selection). Here, we reviewed the advancements of the CRISPR (Clustered regularly interspaced short palindromic repeats)/Cas (CRISPR associated proteins) genome editing tools and their applications in animal breeding, especially in improving disease resistance, production performance, and animal welfare. Additionally, we covered the regulations on genome-edited animals (GEAs) and ways to accelerate their use. Recommendations for how to produce GEAs were also discussed. Despite the current challenges, we believe that genome editing breeding and GEAs will be available in the near future.

A Review on Important Zoonotic Bacterial Tick-Borne Diseases in the Eastern Mediterranean Region.

Zoonotic diseases as health concerns worldwide account for more than half of the emerging infectious diseases. Arachnids are powerful vectors to transmit several diseases to humans. Additionally, these emerging zoonotic diseases have been a considerable health threat in the Eastern Mediterranean Region of the WHO (EMRO) due to the large population living close to farms and international trade with nearby countries. This review study is based on the reported three tick-borne diseases, Lyme disease, Tularemia, and Q fever, from Iran and other EMRO countries. To this end, we searched PubMed central, ISI web of Science, and Google with the related keywords in English at any time. The reported data are then sorted by countries for each disease. According to the published data, 15 countries in the region have one/more emerging infectious diseases. Q fever has been the most frequent infection in EMRO countries, while Lyme was less recorded. Furthermore, Iran is among the countries with documented history of all three investigated diseases. Tick-borne disease is popular among EMRO countries, indicating that they have natural conditions for infections in animals and humans. It appears necessary to develop a disease management strategy and control programs against tick-borne diseases (TBDs). Moreover, the disease-resistant animal could be bred instead of susceptible livestock. Therefore, research studies to control TBDs should be regarded as a top priority plan.

The First Report of Polymorphisms and Genetic Characteristics of the Shadow of Prion Protein (SPRN) in Prion Disease-Resistant Animal, Chickens

Prion diseases are irreversible neurodegenerative disorders caused by the aggregated form of prion protein (PrPSc) derived from the normal form of prion protein (PrPC). Previous studies have reported that shadow of prion protein (Sho) interacts with prion protein (PrP) and accelerates the conversion of PrPC to PrPSc. In addition, genetic polymorphisms of the shadow of the prion protein gene (SPRN) are related to the vulnerability of prion diseases in various hosts. However, to date, polymorphisms and genetic features of the SPRN gene have not been investigated in chickens, which are prion disease-resistant animals. We investigated genetic polymorphisms of the SPRN gene in 2 breeds of chickens, i.e., Dekalb White and Ross, using amplicon sequencing. We analyzed genotype, allele and haplotype frequencies and linkage disequilibrium (LD) among the genetic polymorphisms. In addition, we compared the amino acid sequences of Sho among several prion-related species to identify the unique genetic features of chicken Sho using ClustalW. Furthermore, we evaluated the N-terminal signal peptide and glycosylphosphatidylinositol (GPI)-anchor using SignalP and PredGPI, respectively. Finally, we compared the number of SPRN polymorphisms between prion disease-resistant and prion disease-susceptible animals. We identified 7 novel single nucleotide polymorphisms (SNPs), including 1 synonymous SNP in the open reading frame (ORF) of the chicken SPRN gene. We also found significantly different genotypes, allele frequencies and haplotypes between the 2 chicken breeds. In addition, we found that the interaction regions between Sho and PrP and the NXT glycosylation motif were conserved among all species. Notably, sequence similarity was extremely low in the N-terminal and C-terminal regions between mammals and chickens. Furthermore, we found that chicken Sho was the longest N-terminal signal peptide, and the amino acids of the cutting site of chicken are different from those of mammals. Last, unlike other species investigated, omega-site and signal sequences of the GPI-anchor were not found in chickens. To the best of our knowledge, this is the first report of genetic polymorphisms of the SPRN gene in chickens.

Dietary quercetin and vitamin E supplementation modulates the reproductive performance and antioxidant capacity of aged male breeder chickens

Aged male chickens experience rapid declines in spermatogenesis, antioxidant capacity, immunity, and hormone synthesis. Vitamin E plays a significant role in reproduction, nervous system function, and disease resistance in animals. Quercetin also exerts many biological effects, such as antioxidant ability, immunostimulation, and protection of spermatozoal plasma membranes. This study evaluated the effects of combining dietary quercetin (Q) and vitamin E (VE) on sperm quality, antioxidant capacity, immunity, and expression of genes related to spermatogenesis, immunity, apoptosis, and inflammation in aged male chickens. A total of 120 Tianfu breeder male chickens (65 wk old) were randomly allotted to 4 treatments with 3 replicates (10 birds each). The birds were fed diets containing Q (0.4g/kg), VE (0.2g/kg), Q+VE (0.4g/kg + 0.2g/kg), and a basal diet for 11 wk. At the end of the experimental period, blood, semen, liver, testes, and spleen samples were collected from 2 birds per replicate. Serum hormones, antioxidant parameters, cytokines, and immunoglobulins were evaluated; and the mRNA expression of genes related to spermatogenesis, apoptosis, and inflammation are determined in the testes and liver tissues.The results showed that the combination quercetin and vitamin E significantly promoted the sperm count and motility, as well as elevated the levels of testosterone, follicle-stimulating hormone, and luteinizing hormone, antioxidant enzymes (Superoxide dismutase, Glutathione, and Total antioxidant capacity), and serum immunoglobulins (IgA and IgM) in the aged male chickens; also Q+VE showed protective effects on the liver against injury. In addition, Q+VE significantly increased the expression of genes related to spermatogenesis (AR, pgk2, Cyclin A1, and Cyclin A2), immunity (IFN-γ and IL-2), and anti-inflammatory cytokines (IL-10) (P < 0.05), whereas the expression of proinflammatory cytokines (IL-1β and IL-6) was decreased (P < 0.05). Taken together, these data indicate that the combination of quercetin and vitamin E improved reproductive characteristics such as spermatogenesis, sperm quality, and hormone regulation, as well as promoted antioxidant defense, hepatoprotective capacity, and immune response in aged male chickens without any detrimental effects.

Understanding antimicrobial peptides and combatting antimicrobial resistance problems

Understanding antimicrobial peptides and combatting antimicrobial resistance problems

Yarrowia lipolytica, health benefits for animals.

The yeast Yarrowia lipolytica has been industrially adopted for docosahexaenoic acid and eicosapentaenoic acid production under good manufacturing practices over 2 decades. In recent years, it has claimed attention for novel biotechnological applications, such as a functional feed additive for animals. Studies have demonstrated that this yeast is safe and has probiotic and nutritional properties for mammals, birds, fish, crustaceans, and molluscs. Animals fed Y. lipolytica enhanced productive and immune parameters, as well as modulated microbiome, fatty acid composition, and biochemical profiles. Additionally, some Y. lipolytica-derived compounds have improved productive performance, immune status, and disease resistance in animals. Therefore, the aim of this review is to identify and discuss research advances on the potential use of this yeast for animals of economic interest. Challenges, opportunities, and trends were identified and envisioned in the near future for this industrially produced yeast. KEY POINTS: • Yarrowia lipolytica has probiotic and nutritional effects in animals. • Lipase2, EPA, and β-glucan from Y. lipolytica have health benefits for animals. • Y. lipolytica is envisioned in terrestrial and aquatic animal production systems.

A 192\xa0bp ERV fragment insertion in the first intron of porcine TLR6 may act as an enhancer associated with the increased expressions of TLR6 and TLR1

BackgroundToll-like receptors (TLRs) play important roles in building innate immune and inducing adaptive immune responses. Associations of the TLR genes polymorphisms with disease susceptibility, which are the basis of molecular breeding for disease resistant animals, have been reported extensively. Retrotransposon insertion polymorphisms (RIPs), as a new type of molecular markers developed recently, have great potential in population genetics and quantitative trait locus mapping. In this study, bioinformatic prediction combined with PCR-based amplification was employed to screen for RIPs in porcine TLR genes. Their population distribution was examined, and for one RIP the impact on gene activity and phenotype was further evaluated.ResultsFive RIPs, located at the 3' flank of TLR3, 5' flank of TLR5, intron 1 of TLR6, intron 1 of TLR7, and 3' flank of TLR8 respectively, were identified. These RIPs were detected in different breeds with an uneven distribution among them. By using the dual luciferase activity assay a 192 bp endogenous retrovirus (ERV) in the intron 1 of TLR6 was shown to act as an enhancer increasing the activities of TLR6 putative promoter and two mini-promoters. Furthermore, real-time quantitative polymerase chain reaction (qPCR) analysis revealed significant association (p < 0.05) of the ERV insertion with increased mRNA expression of TLR6, the neighboring gene TLR1, and genes downstream in the TLR signaling pathway such as MyD88 (Myeloid differentiation factor 88), Rac1 (Rac family small GTPase 1), TIRAP (TIR domain containing adaptor protein), Tollip (Toll interacting protein) as well as the inflammatory factors IL6 (Interleukin 6), IL8 (Interleukin 8), and TNFα (Tumor necrosis factor alpha) in tissues of 30 day-old piglet. In addition, serum IL6 and TNFα concentrations were also significantly upregulated by the ERV insertion (p < 0.05).ConclusionsA total of five RIPs were identified in five different TLR loci. The 192 bp ERV insertion in the first intron of TLR6 was associated with higher expression of TLR6, TLR1, and several genes downstream in the signaling cascade. Thus, the ERV insertion may act as an enhancer affecting regulation of the TLR signaling pathways, and can be potentially applied in breeding of disease resistant animals.

The Application of CRISPR/Cas9 Technology for Farm Animals: A Review

Livestock animal are important for agriculture economy and biomedical research. They are sources of Milk, meat, carcass, organic manure and other products. The development of genome editing technologies, especially CRISPR-Cas have revolutionized the generation of gene edited farm animals. In this review, we briefly introduce the CRISPR-Cas9 technology and highlight its application on livestock such as human disease modeling, disease resistant animal, and generation of hornless cattle, animal welfare and other agricultural and biomedical related traits which enhance the livestock production in order to meet the increasing demand of food worldwide. The ability to transfer sperm-producing stem cells or spermatogonial stem cells (SSCs) from a donor animal into the testes of a recipient male could have multiple applications. Production of BLG free milk in cattle provides a promising way to those who have allergy to cow milk. The knockdown of myostatin gene in different species like Sheep, Goat, Cattle and pig is very helpful in the economy of meat industry. Besides the several benefits of CRISPR-Cas9 technology, the risk factors and ethics issues related to this technology should be reconsidered before they enter into CRISPR era.

Progress on lncRNA regulated disease resistance traits in domesticated animals.

Long non-coding RNA (lncRNA) is a class of non-coding RNAs with a length greater than 200 nucleotides. Although lncRNAs do not have any protein coding capability, they can affect the phenotypes of traits by influencing gene expression through transcriptional regulation, post-transcriptional regulation, and epigenetic modification. In modern animal husbandry production, besides increasing growth and yield traits, investigations on the regulation mechanisms of immune factors, cytokines and other disease resistance-related indicators and traits are particularly important for improving the health and welfare of domesticated animals as well as public health. In recent years, researchers have made significant progress in understanding the regulatory mechanisms of lncRNA on the disease resistance traits of chickens (Gallus gallus), pigs (Sus scrofa), cattle (Bos taurus) and other important domesticated animals, thereby laying the basic foundation for the translational application of epigenetic markers in breeding of animals with disease resistance. In this review, we briefly introduce the biological functions and the origins of lncRNAs, then focus on the research progress on the regulatory effects of lncRNAs on disease resistance traits of domesticated animals, and thus providing the scientific basis for the research of lncRNA and its application in the breeding of disease-resistant animals.

Interferon-α-A (IFN-α-A) Diversity in Domestic Yak (Bos grunniens) of Pakistan

Among the various species of livestock, the domestic yak (Bos grunniens) belongs to the class Bovidae and is specially adapted for survival at high altitudes under extreme climatic conditions. Yak is a very useful species due to the multiple products it provides, such as meat, hide, milk and other dairy products. Like other livestock species, domestic yak is also in danger of infection by microbial infections. However, multiple immunity genes encode special protein products to fight infection. One of these immunity genes is interferon-α-A (IFN-α-A), which encodes proteins that belongs to cytokines and fights viral infections. The current study analysed the genetic variation and phylogenetic analysis of the IFN-α-A gene in domestic yak, with comparisons to other mammalian species to investigate immune diversity level, with the aim of designing molecular selection strategies for better disease resistant animals.

Livestock Breeding for Disease Resistance: A Perspective Review

Livestock plays a momentous role in a country’s economy especially in a developing nation like India, where livelihoods of about 20.5 million people depend upon livestock and its allied sectors, suggesting that about two-third of the rural community is involved (Annual Report, 2018). The small ruminants like sheep and goat provide main source of income for many economically poor people, especially marginal and landless farmers. Similarly the role of these livestock to various pastoral communities cannot be ignored. So whenever there is a disease outbreak, the burden of huge economic loss falls on these poor livestock keepers. The traditional methods of disease management involve either treatment with antibiotics or vaccination for prevention of diseases. However, the indiscriminate use of these antibiotics has lead to antibiotic-resistant pathogens and likewise it is extremely difficult to develop vaccines against a wide range of pathogens that are frequently mutating and are caused by multi etiological factors. Hence, considering all these factors breeding of disease resistant animals becomes a top priority in this changing world. The literature is filled with references of indigenous animals and poultry being resistant to many diseases. Keeping this in view, the current review has been written to highlight sustainable and feasible methods for breeding them for disease resistance.

Basic principles of nuclear techniques and applications in livestock production

It is known. that many of the advances which have been made in improving the feeding, fertility and health of livestock in developed countries would not have been possible without nuclear tech-niques. Nuclear techniques have been used by scientists to study and understand those biological processes which are responsible for growth, reproduction and disease resistance in animals. Tracer tech-niques based on isotopes have been used for tagging feed constituents, amino acids and other metabolites, whereby their fate .can be fol-lowed within the digestive system and other parts of the body. This forms an integral part of the armoury used by animal nutritionists to establish the nutri-tional value of all the materials potentially available to feed animals. The development and use of highly sensi­tive immunoassay methods, to measure the minute quantities. of reproductive hormones in the blood enables us to determine when. animals are ready- for breeding, check whether animals have been inseminated at the correct time, diagnose pregnancy early enough, and devise corrective measures for reproductive disorders and improve the efficiency of artificial insemination and embryo transfer programmes. Radioisotopic methods have been used to study the immune system. to examine infec­tious agents and how they Stimulate this system, and to develop specific and sensitive methods for development of veterinary vaccines and diagnostic tests.