birth weights (+/- 2.5 lbs per day)

commercialfarmer said:

DL said:

Using the birth weight of the bull as a criteria for calving ease is pretty crazy - not only does it totally ignore the contribution of the dam (as well as all the ancestors on both sides)  to the calf's weight and calving  ease it implies that it is a meaningful number

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I understand your points regarding both sides of the linage, but I don't see it being crazy.  What are you going to do to change your cows EPD's?  It is far easier to make adjustments in what bull you use and have a large impact (50% of all genetics tied up in 1 animal) vs having to sell your entire herd and start over.  In two generations you can change 75% of your genetics with 2 animals. 

After considering conformation, size should be considered.  Two long lanky bulls that sire similar calves and all else equal, but 1 avg 115 lbs and the other 85- which is more likely to result in a dystocia? 

DL said:

I agree that there must be some relationship btwn gestation length and BW but I don't think itis linear - I would be interested in the relationship btwn gestation length and CE

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If you increase the length of gestation, you will have increased time for growth in the period of exponential growth. You aren't going to see a downtrend. 

Since the birth canal isn't getting any larger with increased gestation, and the calf isn't getting any smaller.  My hypothesis has been made about CE.   

Click to expand...

Okotoks said:

commercialfarmer said:

DL said:

Using the birth weight of the bull as a criteria for calving ease is pretty crazy - not only does it totally ignore the contribution of the dam (as well as all the ancestors on both sides)  to the calf's weight and calving  ease it implies that it is a meaningful number

Click to expand...

I understand your points regarding both sides of the linage, but I don't see it being crazy.  What are you going to do to change your cows EPD's?  It is far easier to make adjustments in what bull you use and have a large impact (50% of all genetics tied up in 1 animal) vs having to sell your entire herd and start over.  In two generations you can change 75% of your genetics with 2 animals. 

After considering conformation, size should be considered.  Two long lanky bulls that sire similar calves and all else equal, but 1 avg 115 lbs and the other 85- which is more likely to result in a dystocia? 

DL said:

I agree that there must be some relationship btwn gestation length and BW but I don't think itis linear - I would be interested in the relationship btwn gestation length and CE

Click to expand...

If you increase the length of gestation, you will have increased time for growth in the period of exponential growth. You aren't going to see a downtrend. 

Since the birth canal isn't getting any larger with increased gestation, and the calf isn't getting any smaller.  My hypothesis has been made about CE.   

Click to expand...

I agree with Commercialfarmer on this. I think it's really important to report the actual birth weights. I would be pretty annoyed to find out the BW was the adjusted weight based on length of gestation. The calf will probably sire longer gestations thus bigger BW's. If the calf is induced it's not really a relevant BW. Also if it's a twin that should be reported as again when it sires a single calf it's BW won't mean much.

Click to expand...

DL said:

Okotoks said:

commercialfarmer said:

DL said:

Using the birth weight of the bull as a criteria for calving ease is pretty crazy - not only does it totally ignore the contribution of the dam (as well as all the ancestors on both sides)  to the calf's weight and calving  ease it implies that it is a meaningful number

Click to expand...

I understand your points regarding both sides of the linage, but I don't see it being crazy.  What are you going to do to change your cows EPD's?  It is far easier to make adjustments in what bull you use and have a large impact (50% of all genetics tied up in 1 animal) vs having to sell your entire herd and start over.  In two generations you can change 75% of your genetics with 2 animals. 

After considering conformation, size should be considered.  Two long lanky bulls that sire similar calves and all else equal, but 1 avg 115 lbs and the other 85- which is more likely to result in a dystocia? 

DL said:

I agree that there must be some relationship btwn gestation length and BW but I don't think itis linear - I would be interested in the relationship btwn gestation length and CE

Click to expand...

If you increase the length of gestation, you will have increased time for growth in the period of exponential growth. You aren't going to see a downtrend. 

Since the birth canal isn't getting any larger with increased gestation, and the calf isn't getting any smaller.  My hypothesis has been made about CE.   

Click to expand...

I agree with Commercialfarmer on this. I think it's really important to report the actual birth weights. I would be pretty annoyed to find out the BW was the adjusted weight based on length of gestation. The calf will probably sire longer gestations thus bigger BW's. If the calf is induced it's not really a relevant BW. Also if it's a twin that should be reported as again when it sires a single calf it's BW won't mean much.

Click to expand...

You guys have completely misinterpreted what I said - using the BW of the bull as a way to determine if you will have calving issues totally ignores the contribution of the dam - ie if the dam is big boned and weighed 110 at birth using a bull with an 80 pound birth weight does not guarantee that the calf will be small - the point is to understand and know your cows (not to sell half your herd) when picking a bull

Re gestation length and BW - I didn't say anything about a downward trend - I was asking what the relationshop was - I do not believe it is totally linear

okotoks - I didn't say anything about not reporting the actual BW

Click to expand...