Massey135":7jcq1268 said:
The logic that brahman over hereford will throw larger bws than hereford x hereford regardless of the sires bw is the dumbest crap I've ever heard. No cattleman really believes that.
Even if bull B had an 80lb bw, you should still select the brahman bull A as the brahman sire should only increase bw by 7%. 72 + 7%<80.
The scenario you source is only applicable when youre comparing like birthweight groups.
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Reciprocal birth weight differences in Brahman-Bos taurus crosses
Articles, Brahman News | | June 28, 2010 at 12:00 pm
Brahman F1 cows continue to be very popular; their performance in cow-calf production is exceptional and well-known. There is a phenomenon associated with the production of F1 animals that should be understood by cattlemen who use Brahman in order to minimize difficult situations, both for themselves and for their customers. It may have been noticed by researchers earlier, but Dr. Tom Cartwright and his colleagues at Texas A&M prominently reported the reciprocal differences in birth weight for Brahman-Hereford crosses in 1964. Although not always recognized similarly, it appears that every major Brahman crossbreeding study with any Bos taurus breed since that time had this same reciprocal effect in the birth weight of their calves. Many producers are already familiar with this; probably it is still worthwhile to consider it.
The birth weight averages in the accompanying tables are from recent work in Florida and Texas and illustrate this effect quite well. This effect has two solid parts. First, Brahman-sired F1 calves have much heavier average birth weights than the reciprocal crosses. From these data, Brahman-sired calves were over 11 (Brahman-Angus in Florida) and 20 lb (Brahman-Hereford in Texas) heavier than the reciprocal crosses. Second, among Brahman-sired calves, bulls are much heavier than heifers, in these data 12 and 14 lb in Florida and Texas, respectively. Among the reciprocal cross calves, there was no statistically significant difference between bull and heifer birth weights (although heifers had numerically higher birth weights than bulls in the Florida data). Another characteristic of this effect may be that there is greater variability in birth weight among Brahman-sired calves than in reciprocal cross calves; we have documented this in two studies. Results from other projects have been consistent when bulls of other Bos indicus breeds were crossed with Bos taurus cows instead of Brahman. Results have been consistent when the other breeds crossed with Brahman in the crossbreeding program were Bos taurus breeds, including British, Continental, and even Criollo. Dr. Mark Thallman and his colleagues have demonstrated this effect using reciprocal cross Brahman-Simmental embryos transferred into Holstein recipients. Birth weight may not be the only trait influenced; females from the Florida crossbreeding project in Florida continue to be assessed for reciprocal differences in reproduction and maternal traits.
This information is practical and relevant, particularly as birth weight relates to calving difficulty and the associated economic losses. In the Florida animals, there was a birth weight standard deviation of just over 11 lb across all breed types of calves. The average birth weight for Brahman-sired bull calves was high but not particularly alarming (86 lb), but the average does not represent the potential problem well. Statistically we know that about 2.5% of bull calves will have birth weights greater than 119 lb (the mean of 86 lb + 2 standard deviations). This is a conservative estimate, because it is likely that the standard deviation is greater (as noted above) for Brahman-sired bull calves (which in fact was 13 lb in the Florida study). Clearly, the situation would be even more extreme using the Texas data.
Based on the above, a good policy is to never breed Bos taurus first calf heifers to Brahman bulls, regardless of individual bulls' birth weight EPD. The across-breed EPD adjustment factor for Brahman birth weight that is predicted by Dr. Larry Kuehn and his colleagues at the Meat Animal Research Center in Nebraska (
http://www.ars.usda.gov/sp2UserFiles/Pl ... 09News.pdf) is startlingly large (+ 11lb) but reflects only the sire breed side of this birth weight effect.
We are actively trying to determine the cause of these birth weight effects, as they do not behave according to typical genetic inheritance rules. There may be genes from a parent that are preferentially expressed; there are known biological mechanisms responsible for imprinting (preferential expression of the gene from one parent) traits in other species, such as mice. There may be aspects of the uterine environment or maternal interactions with the gestating fetus that influence such trait behavior. There likely are breed differences in the many layers of gene regulation that occur in the developing embryo. There may be other epigenetic effects that influence these reciprocal differences in birth weight. Epigenetic effects are those effects that are inherited but are apparently not caused by changes in DNA sequence. Texas researchers are developing a crossbred herd using Nelore and Angus as a resource for epigenetic investigation, and are collaborating with Australian scientists to study this effect in birth weight and in other traits.
Birth weight in Brahman-Angus crosses in Florida
Sire breed Dam breed Bulls Heifers
Brahman Angus 86 74
Angus Brahman 67 70
Brahman Brahman 70 65
Angus Angus 67 63
Birth weight in Brahman-Hereford crosses in Texas
Sire breed Dam breed Bulls Heifers
Brahman Hereford 101 87
Hereford Brahman 75 73
Brahman Brahman 74 71
Hereford Hereford 80
Massey, I think you need to read the next to last paragraph a few times....... You have some nice looking animals up there in North Texas and I think you have your heart in the right place, BUT sometimes its best to keep your trap shut when you are not sure of your facts. Some of us ol coots would give you the shirt of our backs if we thought it would help you in the cattle business. Having said that, we were taught to shut up and listen to the older cattlemen. Share your ideas with an open mind. Doesnt mean us old coots aint wrong from time to time, but some of the older cattlemen on this board have forgot more about cattle than you currently know!