Reproductive technologies. Lecture 15 Introduction to Breeding and Genetics GENE 251/351 School of Environment and Rural Science (Genetics)

Transcription

1 Reproductive technologies Lecture 15 Introduction to Breeding and Genetics GENE 251/351 School of Environment and Rural Science (Genetics)

2 Animal Breeding in a nutshell Breeding objectives Trait measurement Estimation of breeding value Reproductive technology - Artificial Insemination - MOET - JIVET - Cloning Selection, culling & Mating

3 Making genetic progress is about Selecting only the very best Selecting accurately R i m r L m m i f L r f f A Keeping generation intervals short Reproductive rates affect all of the above!

4 Reproductive technologies Reproductive boosting Artificial insemination, AI Multiple Ovulation and Embryo Transfer, MOET Oocyte Pickup Juvenile In Vitro Embryo Transfer, JIVET Sexing of semen and embryos Cloning Whizzy Genetics - breeding in a test-tube

5 Reproductive technologies Increases selection intensities Increases accuracy of EBVs Decreases generation intervals Increases inbreeding

6 Artificial Insemination More intensive use of best sires Use of overseas bulls Establish links between herds Progeny testing More rapid dissemination of superior genes

7 Multiple Ovulation and Embryo Transfer - MOET More intensive use of best cows turns a cow into a sow Use of overseas cows

8 AI and MOET Increased selection intensity Reduced generation interval Increased accuracy of EBV s

9 AI and MOET Increased selection intensity Reduced generation interval Increased accuracy of EBV s

10 AI and MOET Increased selection intensity Reduced generation interval Increased accuracy of EBV s

11 Increased intensity and accuracy... Increased response due to AI in rams. Rams Rams Ewes Ewes Parental Superiority Parental Superiority Response Response

12 Increased intensity and accuracy... Increased response due to MOET in ewes with AI in rams. Rams Rams Ewes Ewes Parental Superiority Parental Superiority Response Response

13 Adult dairy MOET scheme Cow: MOET progeny: Normal progeny: Months: not selected Birth Mate Birth Get record Select & MOET MOET Birth Generation interval 44 months More offspring of top cow after testing it

14 Juvenile dairy MOET scheme Cow: MOET progeny: Normal progeny: Months: not selected Birth Mate Select & MOET Birth MOET Birth Mate Select & MOET Birth MOET Birth Generation interval 22 months Generation interval 22 months More offspring of top cow before testing it Select base on parent average

15 Oocyte pickup and In Vitro Fertilization Juvenile In Vitro Fertilization and Embryo Transfer - JIVET Obtain oocytes before sexual maturity Selection based on parent average Less accuracy but much lower generation interval Australia 1999: 32 lambs born from a 6 mo old ewe

16 Juvenile beef MOET/JIVET Cow: MOET progeny: Normal progeny: Months: Birth Select & MOET Get records MOET Birth Select & MOET Get records MOET Birth Generation interval 15 months Generation interval 15 months

17 Even more juvenile beef MOET/JIVET Cow: MOET progeny: Normal progeny: Months: Birth Get records MOET Birth Select & MOET MOET Birth Select & MOET Get records Generation interval 12 months Generation interval 12 months

18 Juvenile sheep MOET/JIVET Sheep: MOET progeny: Months: 0 1½ 6½ ½ Birth Get records MOET Birth Select & MOET MOET Birth Select & MOET Get records Generation interval 6½ months Generation interval 6½ months

19 Genetic gain versus genetic diversity Sustainable breeding programs require optimal selection balancing genetic gain and genetic diversity Potential short term benefits from reproductive technologies are inhibited by the need to maintain diversity

20 The balance between increased merit and inbreeding 60 Mean merit Difference between scenarios much smaller if we have to keep inbreeding low mean merit Unrestr. IVEP MOET AI Different scenarios with use of repro technol Co-ancestry co-ancestry or inbreeding

21 Sexing semen or embryos Ability to sex semen makes little difference to rates of genetic gain: usually less than 5% extra genetic gains About 10% in dairy (sex limited, progeny testing) However, effect on commercial production efficiency can be dramatic: eg. Using male semen from terminal sires

22 The value of semen sexing in a breeding program Male candidates 50:50 sex ratio 50:50 sex ratio Female candidates Parental Superiority Progeny Progeny Superiority 20:80 sex ratio 20:80 sex ratio Small difference in response Response See also Genup / Ages

23 Cloning in animals Cloning from embryos, adults and cell lines. Cell lines easy genetic manipulation. Evaluate individuals via their clones... evaluations can be biased fewer genetic individuals as candidates. Clone elite individuals for use in industry eg. beef bulls for natural mating. Impact on rate of genetic improvement is minimal!

24 Salvage eggs from abattoir cows Get embryo from elite parents Grow embryo in the lab Embryo cleavage Remove genes Break embryo into identical cells. Electric pulse merges the two parts Some embryos start to develop + - Monash IRD / Genetics Australia EMT System from Sandy McClintock Transfer to recipients when enough have been made. Some can be frozen for later use. 5 to 10 times more embryos each 4 days.

25 Salvage eggs from abattoir cows Get tissue sample from an elite animal. Eg skin Grow cells in the lab Remove genes From cell lines Tissue culture Take a cell from a culture with a million identical cells. Direct Injection merges the two parts Some embryos start to develop Alternative Monash / Genetics Australia EMT System from Sandy McClintock Some embryos ready for freezing Transfer to recipients

26 Summary Reproductive Technologies Usage in breeding industry Benefit to rate of genetic improvem. Dairy Beef Sheep Pigs AI MOET JIVET Sexing Cloning -

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