Simple Inheritance in Beef Cattle
Darrh Bullock
University of Kentucky
dbullock@uky.edu
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Summary:Managing traits that are controlled by simple inheritance has economic importance to many beef operations. Understanding simple inheritance can assist producers in breeding cattle that are the phenotype desired, such as polled, or avoid undesirable traits, such as lethal defects. This information sheet explains how simple inheritance works and how it can be managed.
For production traits the best tools for making selection decisions are Expected Progeny Differences (EPD). Expected Progeny Differences are computed for many quantitative traits, traits controlled by many genes (polygenic) and affected by the environment, that have economic importance to beef producers. There are also simply inherited traits which are traits that are controlled by a single gene and often with one allele being dominant to the other. Some examples of traits that are simply inherited with complete dominance are red/black coat color, horned/polled and lethal defects. This fact sheet will discuss simple inheritance and how to effectively manage traits controlled by one gene.
For simply inherited traits one allele completely masks the expression of the other allele when the alleles are heterozygous for the gene. This results in heterozygote animals having the exact same phenotype as hom*ozygote dominant animals. This is the type of dominance we see in red/black coat color, where black is dominant to red. Cattle that have two black alleles are black (hom*ozygous dominant), cattle that have one black and one red allele are also black (heterozygous), and red animals are the result of having two red alleles (hom*ozygous recessive). When dealing with traits with complete dominance, heterozygous animals are often called carriers because they are carrying the recessive allele and can pass it to their offspring even though they do not express the recessive phenotype themselves. That is why it is possible to breed two black animals and get a red calf; each parent was a red allele carrier.
Coat color is a good trait to demonstrate how alleles interact in a trait with complete dominance. For this example, we will mate an Angus bull to Hereford cows. The Angus bull is hom*ozygous dominant, which means he has two black alleles (BB). The Hereford cows are hom*ozygous recessive, which means they have two red alleles (bb). When mated, all offspring will be heterozygotes (Bb). The Punnett Square in Figure 1 illustrates this mating.
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Figure 1. Punnett Square for coat color when mating a hom*ozygous black bull to hom*ozygous red cows. The joining of the gametes shows the potential genotypes of offspring and their phenotype (color). |
If we were to breed these heterozygous heifers back to a Hereford bull, we would get fifty percent heterozygous black (Bb) calves and fifty percent hom*ozygous red (bb) calves (Figure 2.). If we were to mate the Hereford x Angus heifers to Hereford x Angus bulls then we would get all three possibilities: hom*ozygous black (BB), heterozygous black (Bb) and hom*ozygous red (bb) (Figure 3). The ratio would be 25%:50%:25%,respectively. The phenotypic ratio would be 75%:25% black to red.
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Figure 2. Punnett Square for coat color when mating a hom*ozygous red bull to heterozygous black cows. The joining of the gametes shows the potential offspring and their color. |
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Figure 3. Punnett Square for coat color when mating a heterozygous black bull to heterozygous black cows. The joining of the gametes shows the potential offspring and their color. |
Traits controlled by one gene, with complete dominance, are easy to understand, but can cause problems because of the possibility of carriers. For some traits, the only way to detect carriers is through progeny testing, which is costly and time consuming.However, with advancements in molecular technologies, carriers can be identified for many traits by conducting a DNA test on a tissue sample. The simplest way to avoid having hom*ozygous recessive calves is to always breed to a hom*ozygous dominant bull. With this breeding strategy, even if you have the undesirable allele in your herd it will never be expressed because onlyhom*ozygous dominant or carrier calves will be produced. This strategy can improve markets in the case of the red and horn allele, and increase reproductive rates when lethal alleles are involved. The eBEEF fact sheet “Genetic Defects” (2014-9) and “Managing Genetic Defects” (2014-10) may provide useful supplemental reading on the inheritance of genetic defects.
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FAQs
Simply inherited traits are usu- ally affected by only one gene. The classic example of a simply inherited trait in beef cattle is red/black coat color. Some genetic disorders are also simply inherited. Simply inherited traits are typically observed as either/or: either the animal is black, or they are red.
What is the heritability of beef cattle? ›
Both have heritability of 25% in American Angus. Slightly lower heritability have been reported in pilot studies of Red Angus and Simmental cattle. This means that making genetic progress on structural soundness, particularly when using an EPD, is possible for both seedstock and commercial producers.
What are the dominant and recessive genes in cattle? ›
Red and black are probably the two most common coat colors in cattle. The black gene is dominant over the red gene and causes the hair to be black. The red gene is recessive and causes the production of red pigment only.
What is the most economically important trait in beef cattle? ›
All traits of economic value should be considered when selecting beef cattle. The major traits influencing productive efficiency of desirable beef are: Reproductive Performance or Fertility. Maternal Ability.
What are 3 examples of inherited animal traits? ›
Fur color, pattern, and eye color all are inherited from the parents of an animal. These are not things he has learned or likes to do; these are traits that he was born with.
What traits are present in a beef cow? ›
Some examples of these traits are temperament, polledness, structural and udder soundness, disease and pest resistance, heat tolerance, doing or “fleshing” ability, mothering ability, and calving ease. Many are not highly heritable but contribute to the ease of participating in and enjoying the beef cattle industry.
How are beef cattle genetically modified? ›
Genetically engineered livestock were produced using gene editing technology, mainly somatic cell nuclear transfer (SCNT) or microinjection (MI).
Why are genetics important in beef cattle? ›
Important beef enterprise profit drivers related to animal performance – including weaning rate, cow survival rate, cow weight, calving ease, sale weight, retail beef yield, P8 fat depth and marbling score – are influenced by the genetic make-up of the herd.
How heritable is fertility in cattle? ›
While fertility traits are important, we need to recognize they are low heritable traits, around 1-2% for heifer and cow conception rates, and around 4% for daughter pregnancy rate.
What are the dominant and recessive patterns of inheritance? ›
These are called inheritance patterns. Examples of inheritance patterns include: autosomal dominant – where the gene for a trait or condition is dominant, and is on a non-sex chromosome. autosomal recessive – where the gene for a trait or condition is recessive, and is on a non-sex chromosome.
The simplest form of inheritance is known as single-gene inheritance, or the Mendelian pattern of inheritance. This type of inheritance occurs when a single gene codes for a trait. Common single-gene traits include eye color, widow's peak hairline, freckles, dimples, and type of earlobe.
What are five recessive traits? ›
Recessive Trait Examples
- Straight hairline (widow's peak is dominant)
- Attached Earlobes (unattached are dominant)
- Smooth Chin (cleft chin is dominant)
- Lack of Dimples (dimples are dominant)
- Left Handedness (right-handed is dominant)
- Straight Hair (curly hair is dominant)
- No Freckles (freckles are dominant)
Final answer: Weaning weight generally has the highest heritability estimate in cattle, indicating a strong genetic influence. High heritability allows breeders to select effectively for genetic improvements in traits, making it possible to achieve greater gains from selective breeding.
What traits in beef cattle have the highest heritability? ›
Carcass traits are moderately heritable. While traits such as hip height, frame score (age adjusted hip height) and mature weight are highly heritable. This can be seen by looking at how rapidly the frame size of past na- tional shows changed over time.
What genetic traits lead to high quality beef for consumers? ›
Marbling – This EPD focuses on marbling score. The higher the score, the higher the quality of the beef. Ribeye area – Looking at genetic history, this EPD predicts the size of calves' ribeye areas. Fat thickness – This EPD predicts a calf's fatness when measured at the 12th rib.
What are the genetic traits of a cow? ›
Traits include milk, protein, fat, somatic cell score, calving ease and many more. For PTA's, the average for every trait is zero. An animal with a positive number is better than average for that trait and an animal with a negative number is worse than average for that trait.
What are common traits of cattle? ›
common trait
in the personality theory of Gordon W. Allport, any of a number of enduring characteristics that describe or determine an individual's behavior across a variety of situations and that are common to many people and similarly expressed.
What are the different traits of cattle? ›
The major functional traits important in beef production include body size, milking potential, age at puberty, hot climate adaptability, fleshing ability, muscle expression, cutability, and marbling. Body size is best evaluated as weight at a stated level of condition or body fatness.
Which of the following traits have high heritability for beef cattle? ›
Final answer: Weaning weight generally has the highest heritability estimate in cattle, indicating a strong genetic influence. High heritability allows breeders to select effectively for genetic improvements in traits, making it possible to achieve greater gains from selective breeding.
