1. Livestock Breeding Systems
Principles of Agricultural Science - Animal
Unit 6 Lesson 6.2 Generating Generations
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2. Livestock Breeding Systems
Principles of Agricultural Science - Animal
Unit 6 Lesson 6.2 Generating Generations
Principles of Agricultural Science – Animal
Livestock Breeding Systems
Unit 6 – Lesson 6.2 Generating Generations
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3. Livestock Breeding Systems
Principles of Agricultural Science - Animal
Unit 6 Lesson 6.2 Generating Generations
Breeding Systems
Straight breeding
Mating animals of the same breed
Purebreds, inbreeding, out crossing, and grading up
Crossbreeding
Mating animals of different breeds
Two-breed crosses, three-breed crosses, and rotational breeding
Animal producers commonly use two types of mating systems. Those whose goal is the production of purebred breeding stock use straight breeding. With straight breeding animals of the same breed are mated and the genetics of that breed persist.
The other mating system is crossbreeding where animals of different breeds are mated. These offspring tend to perform well due to hybrid vigor. One common crossbreed in the cattle industry is the Hereford-Angus cross, which produces commercial black-baldy cattle.
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4. Livestock Breeding Systems
Principles of Agricultural Science - Animal
Unit 6 Lesson 6.2 Generating Generations
Straight Breeding
Animals maintain qualities of ancestors.
It is used mostly in the production of breeding stock.
Purebreds are eligible for registration.
Straight breeding is mostly used by purebred producers. Animals maintain the qualities and characteristics of their ancestors and those that are purebred are eligible for registration.
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5. Types of Straight Breeding
Livestock Breeding Systems
Principles of Agricultural Science - Animal
Unit 6 Lesson 6.2 Generating Generations
Types of Straight Breeding
Inbreeding and line-breeding involve the crossing of related individuals.
Desirable traits more visible, undesirable traits more visible.
Out-crossing is the mating of animals of different lineage within the same breed. It is the most popular system of pairing animals.
Animals are not closely related, but are within the same breed.
Inbreeding and line-breeding are two methods that are commonly misunderstood. Inbreeding can be a useful tool if used carefully. Inbreeding involves the mating of very closely related animals, such as father and daughter. It increases the visibility of desirable traits. The downside is that it also increases the visibility of undesirable traits. Line-breeding is the mating of more distantly related animals. The frequency of genetics defects is lower than with inbreeding.
Out-crossing is the mating of animals of different lineage within the same breed. It is the most popular system of pairing animals. The animals are not closely related, but are within the same breed. The chances of genetic defects are low.
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6. Livestock Breeding Systems
Principles of Agricultural Science - Animal
Unit 6 Lesson 6.2 Generating Generations
Crossbreeding
Combine qualities of two or more breeds
Tends to result in offspring that are superior to the contribution of each parent
Heterosis, or hybrid vigor, is the increase in productivity of offspring above the average of the parents
Used mostly in the production of market animals
Crossbreeding is used to increase the performance of offspring. The qualities of two or more breeds are combined, generating animals with hybrid vigor. While the first generation of crossbred animals tend to be very high performing, subsequent crossings of crossbred animals may not exhibit the increased performance. This system is used mainly in the production of market animals.
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7. Livestock Breeding Methods
Livestock Breeding Systems
Principles of Agricultural Science - Animal
Unit 6 Lesson 6.2 Generating Generations
Livestock Breeding Methods
Natural Breeding (a.k.a. Live Cover)
Pasture Breeding
Hand Breeding
Artificial Insemination
Embryo Transfer
Cloning
The four basic livestock breeding methods that will be discussed are natural breeding (also known as live cover), which we divide into pasture breeding and hand breeding. Hand breeding is further divided into artificial insemination, embryo transfer, and cloning.
This powerpoint will spend more time on artificial insemination and embryo transfer, as students usually have a quick understanding of natural breeding, but struggle with the variety of concepts associated with artificial insemination and embryo transfer.
Cloning will only be touched upon, as it is possible, but at this point in the industry, not practical.
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8. Livestock Breeding Systems
Principles of Agricultural Science - Animal
Unit 6 Lesson 6.2 Generating Generations
Natural Breeding
Two methods:
Pasture breeding – Females are kept in pasture with the male. The male physically mounts female and deposits semen on his own.
Hand breeding – Females are kept separately from males. The males are brought to females in heat and allowed to mount by the breeder. The breeder controls both animals at all times.
Pasture breeding is the all-encompassing method of livestock reproduction. This is considered to be true natural breeding because the breeding is controlled by the animals themselves. Pasture breeding is the easiest breeding system for a producer, but depending upon the species, pasture breeding may have a lower conception rate and result in harm to animals.
For these reasons, the horse industry, specifically, chose to utilize hand breeding. In hand breeding, the breeder detects heat in the female and brings the male to her when she is in heat. Hand breeding generally results in higher conception rates than pasture breeding.
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9. Artificial Insemination (A. I.)
Livestock Breeding Systems
Principles of Agricultural Science - Animal
Unit 6 Lesson 6.2 Generating Generations
Artificial Insemination (A. I.)
Advantages
Use superior male genetics
Faster genetic improvement
Frozen semen may be stored and transported around the world
Can be less expensive – no need to own a sire
Safety – aggressive males
Disadvantages
Labor intensive – have to monitor heat cycles of females carefully
Requires training
Decreases genetic diversity
Conception rates
There are many advantages and disadvantages with artificial insemination. The issues vary among species as well. Currently, the use of artificial insemination is very widespread in dairy cattle, common in beef cattle, swine, and horses.
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10. Livestock Breeding Systems
Principles of Agricultural Science - Animal
Unit 6 Lesson 6.2 Generating Generations
Embryo Transfer
Advantages
Takes advantage of superior female and male genetics
Females can have more offspring per year
Disadvantages
Requires skill – vet may be required
Expensive and may only yield a few viable embryos
Used primarily in cattle and horses.
The process of embryo transfer:
Superovulation of superior female
Artificial insemination using sperm of superior male
Embryos flushed from uterus of donor
Embryos implanted in uterus of recipient
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11. Livestock Breeding Systems
Principles of Agricultural Science - Animal
Unit 6 Lesson 6.2 Generating Generations
Cloning
First vertebrate cloned – Dolly the sheep 1996
Cattle successfully cloned in 1998
May be done using cells that haven’t yet specialized or adult cells
Very costly process
Many potential benefits
Dolly the sheep was our first successful vertebrate clone.
Since this is such new technology, it is very costly, making it less than economically feasible for most livestock producers. However, there is great potential for cloning of livestock in the research arena, in areas such as disease treatment testing, organ production for organ transplant, pharmaceutical production, or cloning endangered species to prevent extinction.
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12. Estrus (Heat) Detection
Livestock Breeding Systems
Principles of Agricultural Science - Animal
Unit 6 Lesson 6.2 Generating Generations
Estrus (Heat) Detection
Done prior to artificial insemination to ensure semen is delivered at the right time
Methods vary by species
Visual observation
Teaser (i.e., sterilized or intact male)
Heat mount detectors
Computer chip based systems
Estrus must be detected in females prior to delivery of semen to the reproductive tract in order for fertilization to be possible. There are a variety of methods that can be used to detect heat.
Signs of estrus in cattle include restlessness, attempting to mount other cows, and clear mucous discharge from the vulva.
In sheep and goats, a teaser, or sterile male, is equipped with a marking harness that attaches to the brisket much like the chin marker in cattle. The rumps of ewes and does are marked as they are mounted.
In swine, the vulva is normally red and swollen. When this sign is observed, the breeder can place their hand on the sow or gilt’s back and apply pressure. If the female is in estrus, she will take on a very rigid stance.
In horses, the mare will elevate her tail, spread her legs and frequently urinate when placed near a stallion. In addition, she will contract the vulva in a manner that is referred to as “winking” the vulva.
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13. Estrus Synchronization
Livestock Breeding Systems
Principles of Agricultural Science - Animal
Unit 6 Lesson 6.2 Generating Generations
Estrus Synchronization
The use of synthetic hormones to make a group of females come into heat at the same time.
Benefits
Large number of calves in the same time frame
Essential for successful embryo transfer programs.
Detecting estrus (heat) can be a very labor consuming task. Producers may utilize hormones to ensure that all or large groups of females are in estrus at the same time. Instead of the task of calving being spread throughout the year, cows and heifers can be synchronized so that calving happens in a short time period, which allows the producer a greater economic advantage when selling calves as they will have many calves at the same size that they can group for sales.
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14. Semen Collection and Freezing
Livestock Breeding Systems
Principles of Agricultural Science - Animal
Unit 6 Lesson 6.2 Generating Generations
Semen Collection and Freezing
Collection methods
Artificial vagina
Electroejaculator
Fresh semen only usable for 1-2 days, more practical in most cases to freeze it using liquid nitrogen
Semen tanks kept at -112 degrees
Semen is commonly collected for artificial insemination by use of either the artificial vagina or electroejaculator.
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15. Livestock Breeding Systems
Principles of Agricultural Science - Animal
Unit 6 Lesson 6.2 Generating Generations
Semen Handling
Semen must be kept free of:
Chemical threats
Cleaners, disinfectants, spermicidal lubricants
Thermal threats
Temperature can’t be increased above body temperature of animal
Temperature can’t be lowered quickly
Breeders must be very conscious of the cleanliness and temperature of all equipment used during the handling of semen. Many common disinfectants are fatal to sperm. It is recommended that deionized water be used to clean any equipment.
Semen cannot be heated higher than the normal body temperature of the animal it has been collected from. In addition, the breeder must be careful how quickly semen is cooled. If it is cooled too quickly, this results in shock and can cause abnormalities in motility and morphology as well as death of the sperm cells.
Semen can be shipped cooled as well as frozen, however, for long-term storage, it must be frozen.
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16. Semen Freezing and Thawing
Livestock Breeding Systems
Principles of Agricultural Science - Animal
Unit 6 Lesson 6.2 Generating Generations
Semen Freezing and Thawing
Thawing
Done in warm (i.e., degree) water for a minimum of 40 seconds
Must be kept warm until use
Once semen has been cooled, it is extended and placed into straws for insemination. It can then either be used fresh or frozen in liquid nitrogen. In either case it must be warm when utilized for insemination.
Breeders that use frozen semen maintain a liquid nitrogen filled semen tank that has a canister in the center that holds canes of semen straws. The breeder must be careful to not remove too many straws from the tank, as they may not be re-frozen. Semen straws are thawed in warm water and must be kept warm until use to minimize risk of cold shock. The most difficult period to maintain temperature is during the time when the thawed semen is being transported to the female.
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17. Livestock Breeding Systems
Principles of Agricultural Science - Animal
Unit 6 Lesson 6.2 Generating Generations
Semen Evaluation
Evaluated to determine potential fertility of a sample
Based on:
Sperm concentration
Sperm motility
Sperm morphology
Sperm is evaluated based upon many different criteria. Four common criteria are:
Sperm concentration-(sperm per milliliter) is evaluated either by physically counting the sperm in a given area on a microscope slide or by using a hemocytometer, which is a specialized type of slide with a grid that allows easy counting.
Sperm motility involves viewing live sperm and watching their movement on a slide.
Sperm morphology includes looking for abnormal structure in sperm.
It is important to remember that a male can have an outstanding semen evaluation, but still be sterile!
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18. Livestock Breeding Systems
Principles of Agricultural Science - Animal
Unit 6 Lesson 6.2 Generating Generations
References
Bowen, R. (2003). Collection and evaluation of semen. Retrieved December 31, 2008, from Pathophysiology of the reproductive system Web site:
Gillespie, J.R., & Flanders, F.B. (2010). Modern livestock and poultry production (8th ed.). Clifton Park, NY: Delmar.
Herren, R. V., & Donahue, R. L. (2000). Delmar’s agriscience dictionary with searchable CD-ROM. Albany, NY: Delmar. 
Selk, G. Artificial insemination for beef cattle. Oklahoma cooperative extension service fact sheet. Retrieved December 31, 2008, from
Taylor, R.E. (1992). Scientific farm animal production: An introduction to animal science. New York, NY: Macmillan Publishing Company.
The National Council for Agricultural Education CASE – Copyright 2010