Low Birth Weight Bulls

[Bonsman]

I have a relatively new bull that I wanted to get some very accurate birth weight numbers from his calves. I put him on ten cows. Out of the ten calves he sired; eight weighted between 64 and 72 lbs. One bull calf weighed 76. Two bull calves weighed 98 and 104 respectively. I had to pull the two big bull calves both survived.

I have heard numbers thrown around that the bull's genetics contribute 40% to the birthweight of the calves, with other factors including genetics of the female, and amount of feed provided late in the calving process.

Any thoughts on the why two of the ten decided to be half-grown when they were born? Would you put him on a set of heifers?

 

[dun]

I wouldn;t use him on heifers until I had more data or knew everything there is to know about the heifers.
I don;t know how this whole bell curve deal works but even at .99 accuracy for any given EPD it only means that 66% will fall within the bell.

 

[redcowsrule33]

What were the respective ages/breed makeup on each of the cows? Were they all managed in the same group? What kind of birthweights have they produced in the past? This all factors in.

 

[Bonsman]

What were the respective ages/breed makeup on each of the cows? Were they all managed in the same group? What kind of birthweights have they produced in the past? This all factors in.

The Cows were all born in 2006; these were there second calves. They are full blood Bonsmara. The were all managed in the same group. During the winter they were fed alfalfa (all they could eat) and 4lbs per day of 20% breeders cubes.

The bull measures out really nice using the lineal measurement system developed by professor Bonsma. The two big bull calves came out of two cows heavily influenced by J8 genetics. The J8 Bonsmara genetics are well known in that third world country of South Africa.

The ten cows were heifers last year. I used a different bull on them, which led to birthweights in the 70's for heifer calves; and 80's for bull calves. Last year they did not receive as much groceries as they did this year.

Maybe it is partly genetics on the cow side; and partly too much to eat towards calving season.

 

[KNERSIE]

I wouldn;t use him on heifers until I had more data or knew everything there is to know about the heifers.
I don;t know how this whole bell curve deal works but even at .99 accuracy for any given EPD it only means that 66% will fall within the bell.

100% will fall under the bell curve, the catch is that the bell curve goes to infinity at either end.

66% will fall within one standard deviation from the mean under the bell curve.

95% will fall within 2 standard deviations from the mean under the bell curve.

The higher the accuracy the narrower the "body" of the bell will become, or in other words because the bell curve is narrower the standard deviation becomes smaller so the EPDs will better predict the outcome.

All in theory off course.

 

[bigag03]

An EPD is an estimate of breeding value. The higher the accuracy the smaller the standard error associated with that estimate. There is a 68% probability that the actual EPD of the animal is within one standard error of the estimate. 84% probability that it is within two standard errors and a 95% probability that it is within three standard errors.

Now that we have the statistics out of the way...an EPD, no matter what the accuracy, has absolutely ZERO predictive value of actual performance. There will be natural variation of any actual data. What matters is the average, and how that average compares to the other sire groups in the contemporary group. If this was the only sire used in the contemporary group then the data is useless and therefore cannot be used to make recomendations about the bulls breeding value or how he should be used in the future.

 

[SRBeef]

I have a relatively new bull that I wanted to get some very accurate birth weight numbers from his calves. I put him on ten cows. Out of the ten calves he sired; eight weighted between 64 and 72 lbs. One bull calf weighed 76. Two bull calves weighed 98 and 104 respectively. I had to pull the two big bull calves both survived.

I have heard numbers thrown around that the bull's genetics contribute 40% to the birthweight of the calves, with other factors including genetics of the female, and amount of feed provided late in the calving process.

Any thoughts on the why two of the ten decided to be half-grown when they were born? Would you put him on a set of heifers?

I am not at all familiar with the Bonsmara breed but in my limited Hereford experience 98 and 104 lb bull calves from a 3 yr old cow are not really "huge" calves. A range of 64 to 104 lb over 10 calves may just be the statistics of the bell curve as discussed by others.

Are these unusually small cows that would need a 104 lb normal presentation calf to always be pulled?

It's hard to see how you could pick any bull that would absolutely guarantee 100% lower BW's than you have. Does this one cow tend to have larger calves? Maybe these two cows tend to have larger calves? This is where good data may come in. Good luck.

Jim

 

[KNERSIE]

Are these unusually small cows that would need a 104 lb normal presentation calf to always be pulled?

Pulling a Bonsmara calf out of a Bonsmara cow is something unheard of here, I think the very limited genepool in the USA is probably the biggest culprit.

 

[edrsimms]

I have a relatively new bull that I wanted to get some very accurate birth weight numbers from his calves. I put him on ten cows. Out of the ten calves he sired; eight weighted between 64 and 72 lbs. One bull calf weighed 76. Two bull calves weighed 98 and 104 respectively. I had to pull the two big bull calves both survived.

I have heard numbers thrown around that the bull's genetics contribute 40% to the birthweight of the calves, with other factors including genetics of the female, and amount of feed provided late in the calving process.

Any thoughts on the why two of the ten decided to be half-grown when they were born? Would you put him on a set of heifers?

Other factors to include on those calves born heavy are their Dams CE (calving ease)and MCE (maternal calving ease) and of course the Sires' CE,MCE and birth weight
I bet that those 2 heavy calves are from cows with below average CE and MCE (I say below because you want the calving ease and maternal calving ease to reflect a higher number or better calving ease)

 

[xbred]

Dr.s' fred and robert thrift of Univ. of Kentucky and Univ of Fla. published a review of EPDs and actual progeny measurements. the epds were very in line with actual progeny measurements...(Source: thrift and thrift 2006. Professional animal scientist. 22:413-423) the only major difference, as i understand it, were that actual yearling weights were heavier when selection of the sire was for yearling weight...