Adjusted Birth weight??

What is this? How do they determine it and what does it mean? does it have actual significance?

In my oppinion it is a marketing tool used to make higher birth weight animals more marketable. I saw a bull once with an actual BW of 109lbs but his ADJ BW was 89lbs. I thought that was a pretty big adjustment. RW

To answer your questions in order:
What is it? A ploy
How do they determine it? A formula to make the big numbers smaller
What does it mean? Nothing. Just like most reported BW's, WW's and YW's.
Does it have any significance? Nope.

Now my opinion: It seems since the push for growth the birth weights have gotten larger. So, to market those animals, "adjusted bw's" have become popular. Just like those that do not pay attention to bw's of calves born of recep cows. I know of cattle that have had HUGE birth weights that were not "reported" to the associations because they were ET calves and born of recep cows. Now, don't get me wrong, it is not required to report these bw's in some breeds, but I still think it is crap.

It all boils down to dealing with people you can trust with a BREEDING PROGRAM that is reliable. Simple as that.

Show Heifer said:

I know of cattle that have had HUGE birth weights that were not "reported" to the associations because they were ET calves and born of recep cows. Now, don't get me wrong, it is not required to report these bw's in some breeds, but I still think it is crap.

It all boils down to dealing with people you can trust with a BREEDING PROGRAM that is reliable. Simple as that.

Click to expand...

to me, birth weights are validated in one's own herd.  they are only a guide.  what i would like to see is a histogram or a distribution curve of birth weights with ET calves a different color and included in the same sample.  trust has something to do with it, and verifying has nothing to do with not trusting.

I was at a sale a long time ago. I rememberthe auctioner joking that it didn't matter about the bulls bwt cause the hired men took care of the calving. It just isn't important.

Thanks for the replies everyone....I was curious because we had a ET meyer 734 calf born 2 weeks late...Ive heard that a calf gaines 2 pounds for each day it was late...so I was wondering if adjusted bwt was the actual weight minus the number of days late...and the number of days late times 2...idk if that makes sense lol

There can be something to adjustments. I think that a 13 year cow may have smaller calves just because of her age and condition. I know I had a cow that never had a calf under 100# but at age 13 she had a 90 pounder. She was in pretty frail condition.

So.... with so many people inducing cows and heifers that are going over.... what should their actual BW be reported as? As exactly what is their gestation length?

I agree aj, that is one of the things I was referring to, in a previous post, about looking at more than actual BW when selecting a calving ease sire especially for heifers. Age of dam, induced or not induced, actual or adjusted, natural birth or ET, etc etc etc are all things that can affect BW. Some of these things are very hard to find the answers to, but you have to find the answers that you can.  I have owned several bulls in partnerships and I have found varying BWs of a sires calves from different herds, probably due to the nutrition and amount of exercise each herd provides to their cow herds. Birth Weight is a tool,but it is not the only tool we need to consider.

I could never understand why a bull that was bred to a cow would have an influence on the cows gestation length. Maybe we need a bulls ave gestation length of their calves epd. It would essentially be a birth weight epd. But alot of people don't know the exact date of a service under natural breeding so this probably wouldn't work.

I have wondered the same thing, as to how a bull can influence the gestation length, but I also think a bull can actually do this. We brought two Irish bulls from Ireland in the 70s. There was 12 days difference in the gestation length of these two bulls( and it was almost always exactly 12 days). I kept pretty accurate breeding dates and I tried to track this and I was surprised at how close this was. The shorter gestation length was Highfield Irish Mist. The longer gestation was IDS Duke of Dublin.  I have used an Irish Mist son on my heifers for the past 4 years, and he has an even shorter gestation length than his sire did. He is one of the easiest calving bulls we have ever used. From that experience, I was fairly certain that the sire has a major influence on gestation length.



.....  then along came ET, and many of my theories about gestation length have not proven to be exact. I am seeing major differences in gestation length between full sibs implanted into recips on the same day. On two occasions, I have had 18 days between the first full sib, and the last one to be born. One of these 18 day calving intervals resulted in 5 full sib heifers, so the sex of the calf was not an issue in this case. All 5 heifers were DNA parentage tested  and all were proven to be ET calves. I also have one commercial cow that has now had 5 ET calves, and she seems to consistently have a longer gestation length. It now appears to me that the dam  can have an influence on the gestation length as well, but why is there so much difference between ET and naturally born calves?

Looks to me that there are no easy answers to some of these questions.... but then, there isn't much else in this business that is super easy either.

There has been tests proving that putting Charolais eggs in a Brahma receipt they were smaller than out of the charolais recipts, also put Brahma eggs in charolais an calves were bigger than the calves out of Brahma .  I wouldn't pay much attention to ET birth weights , WE PUT SOME ET eggs in  similar cows  in different years , the calves were full sibs an there was over 10 ibs different in them . The one year they were heavy an next quite a bit smaller .  Also some one answer why do some bulls work great calving out heifer with  no problem, early gestation , did this a couple years, started using on cows an their birth weights jump up to 100 some of them an this is in Angus . Have a Angus bull that is up to 3.5 bw EPD an the first two years clved out 1200 head , no problems, lot of them out of commercial heifers .

First of all season and age of dam effect birth weights. 
Second, ET birthweights are unreliable because the uterine environment of the recip dam is not an indication to that animals breeding value of the calf.  The calf is not usually related to the recip.
Third, the ECONOMICALLY RELAVANT TRAIT is calving ease.  That is the trait that influences whether you are pulling calves, loosing cows and calves, or sleeping through the night.
Animal breeding and EPDs are not hocus pocus, they are based on millions of observations and sound science.   

Here is what the Beef Improve Federation Guidelines say:

"For traits for which they are available, EPDs most efficiently combine phenotypic
performance data, records from all related animals, and information from genetically
correlated traits to predict the relative performance of future progeny of candidates for
selection. Information from these sources is optimally combined into a single predictor
of genetic merit. Therefore, there is no advantage in using information from sources
that contribute to the EPD when the EPD itself is available. For example, if the EPDs for
________________ BIF Guidelines 68 ________________
birth weight are available on two candidates for selection, then these statistics provide a
more accurate indication of the difference in birth weights of future progeny than the
actual or adjusted birth weight records of the candidates themselves. Likewise, if the
selection criterion is calving ease and calving ease EPDs are available, then
consideration of birth weight EPDs is unwarranted."

"Birth weight. Calf birth weight in relation to dam weight is a good indicator of calving
difficulty. If calving difficulty is a problem in the herd, selection of breeding animals for
lighter birth weight may be an effective strategy to improve direct calving ease.
However, single trait selection for lighter birth weight or shorter gestation intervals may
reduce calf viability and growth rate from birth to weaning.
Both sex of calf and age-of-dam influence birth weight of the calf. The factors for
adjusting birth weights for differences caused by age-of-dam are given in Appendix 3.1.
BIF recommends the use of additive rather than multiplicative age-of-dam adjustment
factors for weaning weight, because research indicates that they are more appropriate.
Birth and weaning weight adjustments for age-of-dam can differ from one breed to
another. Some breed associations have developed adjustments using their own data.
These should be substituted for the BIF standard whenever possible. All breed
associations are encouraged to develop their own age-of-dam adjustment factors for
birth and weaning weight.
Adj. Birth Wt. = Birth Wt. + Age-of-Dam Adj.
BIF age-of-dam categories are listed below:
Classification of Age-of-Dam
Age-of-Dam Range (days) Age-of-Dam (years)
Less than 1,004
1,004 to 1,338
1,339 to 1,703
1,704 to 3,561
3,562 to 3,926
3,927 to 4,292
4,293 to 4,657
More than 4,657
2
3
4
5 to 9
10
11
12
13
Season of birth also has an important influence on birth weight. Research indicates that
summer- and fall-born calves have lighter birth weights than spring-born calves.
Adjusted birth weight ratios calculated within season/sex contemporary group can be
________________ BIF Guidelines 18 ________________
used to compare calves from the same herd born in different seasons. It is
recommended that adjusted birth weight ratio be computed as follows:
Adj. Birth Wt. Ratio = Individual Adj. Birth Wt. _ X 100
Group Average Adj. Birth Wt."

http://www.beefimprovement.org/library/06guidelines.pdf

I would agree that ET birth weights are unreliable, if you are using cross bred recips.But the AAA allows the birthweight data to be recorded if the recip is a registered angus female,which imo the bws would tend to be more reliable,because of the data base.EPDS are just a tool .And remember the data is only as honest as the person turning it in.The good thing is though if enough people use the sires the truth will come out.Rusty

i would say that a sire's actual birth weight is poor measure of what his calves will weight at birth

simtal its kind of like if your grandparents and parents have heart problems,more than likely you will too. i think it can help somewhat.rusty

Would it be cool if Moormans or someone sold supplement blocks that was gaurented to reduce the gestation length of cows by 10 days. Or would that make the calves premies? How far can we go in trying to change the enviroment?