Post by Damon on Apr 20, 2010 19:16:14 GMT -5
I contacted a professional bovine geneticist who is a good friend of a friend. I provided him basic information stated by Ann B above asking his opinion on the matter and the following is his reply:
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Your friend is mistaken. Bulls have udders (as men have breasts), they just never receive the level of hormone stimulation to develop them. If you look under any bull you will see teats-- and they are even useful as a first predictor of some of the udder characteristics.
Both "quantitative" linear trait heritabilities (which are relatively high for udder traits)and the success of aAa in predicting broader "qualitative" characteristics proves you can have a big impact on udders through sire selection.
Genomics research to date confirms that while there are both the mitochondrial DNA (that a cow passes only to female offspring, in the nucleus of the ovum) and some x-y chromosome details, the vast majority of genetic effects are based on the pairing of genes, one from the sire and one from the dam, as occurs at time of conception.
Much of what the many unscientifically trained observational consultants believe they see is likely the effect of homozygous vs heterozygous trait pairings-- producing a tight range of result in one case, a wide range of variation in the other.
The weakness of dairy evaluaiton systems is its lack of distinction between maternal and performance traits (you see most beef breeders distinguish both sire lines and cow lines to focus gene selection in that way, and then they act as linebred animals to make a "hybrid vigor" result in crosses between them.)
Just as a point of discussion I thought it would be interesting to read his "take" on such things.
***************************************************
Your friend is mistaken. Bulls have udders (as men have breasts), they just never receive the level of hormone stimulation to develop them. If you look under any bull you will see teats-- and they are even useful as a first predictor of some of the udder characteristics.
Both "quantitative" linear trait heritabilities (which are relatively high for udder traits)and the success of aAa in predicting broader "qualitative" characteristics proves you can have a big impact on udders through sire selection.
Genomics research to date confirms that while there are both the mitochondrial DNA (that a cow passes only to female offspring, in the nucleus of the ovum) and some x-y chromosome details, the vast majority of genetic effects are based on the pairing of genes, one from the sire and one from the dam, as occurs at time of conception.
Much of what the many unscientifically trained observational consultants believe they see is likely the effect of homozygous vs heterozygous trait pairings-- producing a tight range of result in one case, a wide range of variation in the other.
The weakness of dairy evaluaiton systems is its lack of distinction between maternal and performance traits (you see most beef breeders distinguish both sire lines and cow lines to focus gene selection in that way, and then they act as linebred animals to make a "hybrid vigor" result in crosses between them.)
Just as a point of discussion I thought it would be interesting to read his "take" on such things.