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Definition
| the application of genetic principles in the selection of animals that will be the parents of the next generation |
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| What's the driving force of livestock production |
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| a loss of reduction of vigor, viability, or production that usually accompanies inbreeding |
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| Why do livestock breeders inbreed? |
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Definition
| To concentrate the good genes |
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Term
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Definition
| mating closely related animals for many generations |
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Definition
| mild form where inbreeding is kept low. Keep high genetic relationship |
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| Several Significantly Inbred Species |
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Definition
| mice, polled Herefords, Holstein cows, Quarter Horses |
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Term
| Phenotypic Effects of Inbreeding |
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Definition
Increases phenotypic uniformity if accompanied by selection:
o Superior Genetics: High homozygous & likely to pass on |
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Term
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Definition
- Usually detrimental to reproductive performance, preweaning, and postweaning growth.
- More susceptible to environmental stress
o 60-70% of inbreeds show bad effects
o 30-40% of inbreeds show no effect & posses improved productivity
- Sheep
o Low fertility, survival, and weaning weight
- Goats
o Low productivity due to stress |
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Term
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Definition
- Genetic effects of outbreeding (crossbreeding) are the opposite of inbreeding.
- The primary phenotype effect is an improvement in traits related to igor and physical fitness
- The increased vigor, often referred to as “hybrid vigor” or heterosis, is due to non additive gene action |
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Definition
- Unrelated animals within the same breed are mated (purebred)
- Gene pairs are primarily heterozygous
- Most popular system |
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Term
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Definition
- mating to opposite breeds
- Hybrid Vigor is defined as “the superiority of the crossbred offspring over the average of the pure breeds (parents) used to make the cross.
- The two primary reasons to crossbreed are: heterosis and complimentarity of traits
- Ex. 500lb weaning Angus x 600lb weaning Charolais
• A x C
• = 660 lbs
• ^ Hybrid vigor effect b/c avg. would only be 600lb |
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Term
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Definition
| indicates the proportion of the differences between individuals that is genetic. (is not constant; abbreviated as h2) |
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| Very rarely are successful breeding programs based on single-trait selection; so we must understand the genetic relationship between traits of interest |
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| refers to a situation in which the same or many of the same genes control two traits |
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| Breeding Value or Genetic Merit |
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Definition
| used as an estimate of the transmitting ability of an animal, and is calculated from information on an individual’s performance and the performance of progeny, sibs, parents, grandparents, and so on. |
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Term
| Expected Progeny Differences (EPD) |
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Definition
- Is equal to half of the breeding value
- Use of estimate how future progeny of the subject animal will compare to progeny of other animals within the breed.
- EPD’s account for
o Genetic value of cow the bull was bred to
o Environmental differences affecting contemporary groups
o Quality of other sires in the contemporary group
o Genetic trend |
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Term
| What are EPDs reported in forbirth weight, weaning weight, yearling weight, maternal weight, and maternal milk |
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| What is scrotal circumference is reported in? |
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| the genotypic advantage of those chosen to be parents; and the difference in the mean of those chosen to be parents and the mean of the population. (Ex. On pg. 232) |
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Definition
| used as an indicator of calving ease; larger birth weights generally indicated more calving difficulty |
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Definition
| reflects preweaning growth (as influenced by the dam’s milk production) |
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Definition
| reflects differences in 365 days adjusted weights. The best estimate of growth because less maternal influence in this weight. Would most closely predict feedlot performance. (is the best estimate of growth because mother influence is not involved) |
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Definition
| : the best estimate of fertility. Related to the bull’s semen quantity and quality as well as age of puberty in daughters |
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