Livestock Breeding Systems Overview
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Questions and Answers

What is the main purpose of selection and breeding systems in livestock populations?

To improve genetic makeup for enhanced productivity, disease resistance, and overall quality.

Differentiate between individual selection and family selection.

Individual selection focuses on an animal's specific performance traits, while family selection considers the average performance of an entire family.

Explain the role of progeny testing in selection methods.

Progeny testing evaluates an individual's breeding value based on the performance of its offspring.

What is the potential downside of inbreeding in livestock populations?

<p>Inbreeding can lead to increased homozygosity and inbreeding depression.</p> Signup and view all the answers

How does outcrossing differ from crossbreeding?

<p>Outcrossing involves mating animals that are not closely related within the same breed, while crossbreeding involves mating animals from different breeds.</p> Signup and view all the answers

What is the significance of differentiating between qualitative and quantitative traits in genetic control?

<p>Qualitative traits are classical Mendelian traits under genetic control, while quantitative traits are measurable and economically important.</p> Signup and view all the answers

What role does environmental management play in the context of breeding animals?

<p>Environmental management is crucial for creating optimal conditions that influence the health and traits of the animals, impacting their genetic expression.</p> Signup and view all the answers

How can poor nutrition lead to the expression of dormant genetic disorders in animals?

<p>Poor nutrition can activate genetic disorders that remain dormant in well-nourished animals, causing health issues.</p> Signup and view all the answers

Explain the significance of housing conditions in poultry regarding their health outcomes.

<p>Housing conditions significantly impact poultry health outcomes by affecting respiratory systems, especially when overcrowding and poor ventilation are present.</p> Signup and view all the answers

What are some practical solutions to mitigate stress in pigs that might lead to inherited conditions?

<p>Practical solutions include providing adequate space, gentle handling during transportation, and gradual dietary changes.</p> Signup and view all the answers

What did Angus John Bateman's research on Drosophila melanogaster contribute to the field of phenotypic selection?

<p>Bateman's research provided insights into the relationship between genotypes and phenotypes, influencing methods of animal breeding.</p> Signup and view all the answers

Identify and describe the impact of management practices on influencing genetic predispositions in animals.

<p>Management practices can exacerbate genetic predispositions by increasing stress and lowering immune responses, leading to more severe symptoms of inherited conditions.</p> Signup and view all the answers

What is the significance of autosomal recessive inheritance in the context of inherited disorders in farm animals?

<p>It highlights that an individual must inherit two defective gene copies to express genetic disorders, making breeding decisions critical in management.</p> Signup and view all the answers

Explain how artificial insemination (AI) exacerbates the spread of undesirable genes in livestock.

<p>AI and international semen trading allow for rapid genetic dissemination, increasing the likelihood of undesirable genetic traits entering the population.</p> Signup and view all the answers

Describe the characteristics and outcomes associated with Bovine Brachyspina Syndrome (BBS).

<p>BBS is characterized by a shortened spine leading to developmental abnormalities, often resulting in stillbirth or death shortly after birth.</p> Signup and view all the answers

What role does genetic screening play in managing inherited diseases in farm animals?

<p>Genetic screening helps identify at-risk animals, allowing for selective breeding strategies to mitigate the spread of inherited disorders.</p> Signup and view all the answers

Identify key management strategies to prevent the dominance of autosomal recessive disorders in livestock populations.

<p>Key strategies include selective breeding of carrier animals, regular health checks, and maintaining detailed records of genetic traits.</p> Signup and view all the answers

What are the clinical signs of Bovine Leukocyte Adhesion Deficiency (BLAD) in affected cattle?

<p>Affected cattle show signs of recurrent bacterial infections, delayed wound healing, stunted growth, and persistent marked neutrophilia.</p> Signup and view all the answers

Discuss how vaccination and health monitoring contribute to the management of inherited diseases in farm animals.

<p>Vaccination helps prevent secondary infections while regular health monitoring enables the early detection of inherited disorders.</p> Signup and view all the answers

How can record keeping assist in the identification of at-risk animals in the context of inherited diseases?

<p>Record keeping allows for tracking genetic traits and health history, aiding in identifying at-risk animals for targeted management strategies.</p> Signup and view all the answers

What is the primary cause of Porcine Stress Syndrome (PSS)?

<p>A defective ryanodine receptor leads to an excess calcium influx.</p> Signup and view all the answers

Describe the inheritance pattern of autosomal recessive disorders.

<p>Both copies of the gene must be mutated for the disorder to manifest.</p> Signup and view all the answers

How do genetic testing and selection help prevent single gene disorders in breeding programs?

<p>Genetic testing identifies carriers and allows breeders to avoid affected individuals.</p> Signup and view all the answers

What distinguishes multifactorial disorders from single-gene disorders?

<p>Multifactorial disorders are influenced by multiple genes and environmental factors.</p> Signup and view all the answers

Give an example of a multifactorial disorder and mention its contributing factors.

<p>Diabetes is an example, influenced by genetic predisposition and factors such as diet and lifestyle.</p> Signup and view all the answers

What is the significance of the X chromosome in X-linked disorders?

<p>X-linked disorders affect males more severely due to their single X chromosome.</p> Signup and view all the answers

What role do environmental factors play in multifactorial disorders?

<p>Environmental factors can exacerbate or mitigate genetic predispositions.</p> Signup and view all the answers

How do breeders aim to minimize the risk of multifactorial disorders?

<p>Breeders select individuals with fewer risk alleles for the disorder.</p> Signup and view all the answers

What is the inheritance pattern observed in Huntington's Disease?

<p>Huntington's Disease follows an autosomal dominant inheritance pattern.</p> Signup and view all the answers

In the context of breeding, why is the selection of carriers important?

<p>Identifying carriers allows for strategic mating to prevent the expression of genetic disorders.</p> Signup and view all the answers

Study Notes

Selection and Breeding Systems

  • Animal breeding aims to improve livestock genetic makeup, enhancing productivity, disease resistance, and overall quality.
  • This process heavily relies on selection and breeding systems.

Animal Breeding

  • The goal is to improve the genetic makeup of livestock populations.
  • This process is vital for enhancing various traits, including productivity, disease resistance, and overall quality.

Selection

  • Selection is the act of choosing individuals to become parents for the next generation.
  • It ensures desirable genes are passed on.

Selection Methods

  • Individual Selection: Focuses on the individual animal's performance, most effective for traits with high heritability.
  • Family Selection: Considers the average performance of a family, useful for traits with low heritability.
  • Pedigree Selection: Choosing breeding animals based on their ancestors' performance.
  • Progeny Testing: Evaluates an individual's breeding value based on its offspring's performance; especially helpful for traits observed after breeding or those restricted by sex.

Breeding Systems

  • Breeding systems involve mating animals to achieve specific genetic outcomes.
  • Example breeding systems include: outbreeding (outcrossing and crossbreeding), inbreeding, and species hybridization.

Outbreeding

  • Animals that are not closely related are bred.
  • Outcrossing: Mating animals that aren't closely related within the same breed.
  • Crossbreeding: Mating animals from different breeds; can exploit heterosis (hybrid vigor).

Inbreeding

  • Involves mating closely related animals.
  • Increases homozygosity (having identical alleles) of the population.
  • Often leads to inbreeding depression (reduced fitness).

Species Hybridization

  • Different species interbreed.
  • Results in hybrid offspring.
  • Can lead to new traits, adaptations, and in some cases, new species.

Genetic Control of Farm Animal Traits and Inherited Disorders

Phenotypic Traits

  • Qualitative: Classical Mendelian traits under strong genetic control, little environmental influence. Examples include form, structures, antigens, and antibodies.
  • Quantitative: Measurable traits strongly affected by both genetic and environmental factors. Examples include milk production, meat yield, height, and weight.

Management and Control of Inherited Diseases

  • Genetic Screening and Breeding Management:
    • Screening
    • Selective Breeding
  • Early Diagnosis and Identification of At-Risk Animals:
    • Health Monitoring
    • Management of Carrier Animals
  • Medical Management and Disease Control:
    • Vaccination
    • Medication
  • Regular Monitoring and Health Tracking:
    • Routine Health Checks
    • Record Keeping

Inherited Disorders in Farm Animals

  • Widespread use of artificial insemination and international semen trading spreads undesirable genes.
  • Most common inheritance pattern for genetic diseases is autosomal recessive.

Autosomal Recessive Inheritance

  • An individual must inherit two copies of a defective gene (one from each parent) to express the disorder.
  • Specific examples like Bovine Brachyspina Syndrome (BBS), Bovine Leukocyte Adhesion Deficiency (BLAD), and Porcine Stress Syndrome (PSS) are highlighted.

Control of Single Gene and Multifactorial Disorders by Selection and Breeding

Single Gene (Mendelian) Disorders

  • Mutations in a single gene create these disorders, with diverse inheritance patterns:
    • Autosomal Dominant: Mutation in one gene copy causes the disorder.
    • Autosomal Recessive: Both gene copies must be mutated for the disorder to appear.
    • X-Linked: Disorders linked to mutations on the X chromosome.

Breeding and Selection for Single-Gene Disorders

  • Effective breeding programs are facilitated by genetic testing allowing breeders to:
    • Identify carriers
    • Avoid affected individuals
    • Use genetic testing as a preventative tool

Multifactorial Disorders

  • Disorders influenced by multiple genes and environmental factors.
  • Specific example disorders mentioned include diabetes, heart disease, and cleft palate.

Breeding and Selection for Multifactorial Disorders

  • Breeders aim to reduce the risk by:
    • Selecting individuals with fewer risk alleles.
    • In the absence of precise genetic markers, selecting based on observable traits or health outcomes, and
    • Managing environmental factors affecting animals.

Non-genetic (Environmental) Control of Inherited Disorders

Environmental Factors

  • Environmental factors influence whether a genetically predisposed condition is expressed, including factors like nutrition, housing, and management practices.

1. Nutrition

  • Balanced diets are essential for optimal growth and health.
  • Poor nutrition can induce previously dormant genetic disorders.
  • Examples include nutritional disorders in livestock.

2. Management Practices

  • Stress can exacerbate genetic predispositions.
  • Stress lowers the animal's immune response.
  • Management practices (e.g., housing conditions, handling techniques) should minimize stress.

Types of Mating Systems In Sexual Animals

  • Monogamy: Single male with a single female; both contribute to defense and offspring care.
  • Polygamy: One male breeds with multiple females.
    • Resource defense
    • Male dominance
    • Harems
    • Lek
  • Promiscuity: Both males and females have multiple mates.
  • Polyandry: One female breeds with multiple males; multiple males often contribute to care and provisioning.
  • Polygynandry: Multiple females and males mate with each other; males may care for several females' offspring.

Selection of Phenotypes

  • Phenotypes are observable traits resulting from gene-environment interactions.
  • Physical characteristics and other observable traits are included in this process.

Phenotypic Selection

  • Individuals with different traits differ in survival/reproduction.
  • Phenotypic selection is nonrandom differential survival/reproduction of individuals.

Types of Selection

  • Stabilizing selection: Favors an average phenotype. Selection against extreme phenotypes.
  • Directional selection: Phenotypes at one end of the spectrum are favored. Selection caused by environment changes.
  • Diversifying selection: Phenotypes at opposite extremes are favored. Intermediate forms have lower fitness.

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Description

This quiz explores key concepts in livestock breeding systems, including individual and family selection, the significance of environmental management, and the effects of nutrition on genetic disorders. It also discusses the role of progeny testing and the impact of housing conditions on animal health. Ideal for those studying animal genetics and breeding practices.

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