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 Confusing statement

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Grassfarmer



Posts : 850
Join date : 2010-09-27
Location : Belmont, Manitoba, Canada

PostSubject: Confusing statement   Fri Nov 04, 2011 6:26 pm

I was puzzled to read the statement I have highlighted in orange in the following article about the value of heterosis. Doesn't this contradict the results we are always talking about with the Shoshone pool of cattle - the number of exceptionally long lived cows and the good fertility in a population of cattle where the heterosis has been reduced through close breeding?

This brings me to one of the most interesting topics discussed at the RBCS that
could not be any more timely. “Crossbreeding: The Forgotten Tool”,
presented by soon-to-retire Dr. Jim Gosey, University of Nebraska Beef
Extension Specialist, that has emerged as the “voice of common sense” in
today’s beef production era characterized by commercial straight-bred Angus
production. Jim has devoted his professional career to helping beef cattle
producers make money largely through a clearer understanding of genetic
application principles. You can access his entire presentation at
http://www.rangebeefcow.com/speakers/Gosey.htlm.

Quotes from his presentation follow:
"Many commercial cowherds have drifted towards straight bred Angus in an
attempt to achieve management simplicity, greater uniformity and to pursue a
premium, non-commodity product."
"The result is the loss of most of the heterosis that once existed in many of our
commercial cowherds."
“Heterosis and breed complementarity are powerful forces that combine to
produce the total advantage of beef cattle crossbreeding systems.”
“Heterosis, or hybrid vigor, is measured as the performance advantage of
crossbreds over the average of their straight bred parents. Maximum heterosis is
realized in the first cross of distinctly different parents.”
"Most ranchers know crossbreeding can increase output, but perhaps don't
appreciate the potential advantage in lifetime productivity of crossbred cows."
“This crossbred advantage can amount to as much as 25% greater lifetime
productivity (pounds of calf weaned per cow exposed) for crossbred cows as
compared to straight bred cows.
Lost maternal heterosis shows up in the same lowly heritable traits that would be
associated with the inbreeding depression, namely reproductive, fitness and
longevity traits.

"Thus, the price paid for loss of heterosis occurs as a number of very small
losses that when added up can amount to a substantial sacrifice in lifetime
productivity."
"Ranchers would be wise to crossbreed even if heterosis were zero, due to the
complementary effects of matching strengths of one breed to offset the
weaknesses of another breed.”
“Heterosis can impact many traits, but is especially useful in improving
performance in lowly heritable traits, such as reproduction, early growth and
fitness or lifetime productivity as shown in Table 1. On the other hand, highly
heritable traits (above 40% heritability) like carcass traits respond to direct
selection within breed.”
Table 1 Average Heterosis in Beef cattle Traits
Trait % Heterosis
Calf Crop Weaned 8
Weaning Weight 13
Yearling Weight 4
Carcass Traits 3
Lifetime Productivity 25
“This huge increase in lifetime productivity of the crossbred cow is driven by the
reproductive performance through earlier puberty, higher conception rate, faster
breed back, greater longevity and the maternal impact on calf performance.”
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PatB



Posts : 455
Join date : 2010-09-25
Age : 53
Location : Turner, Maine

PostSubject: Re: Confusing statement   Sat Nov 05, 2011 8:34 am

How much does selection of parent stock affect the benefit of crossbreeding? If you have lines that produce into their teens how much more longevity will you gain from crossbreeding? If you have excellent fertility in your herd how much of a boost can you get from crossbreeding?
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Bob H



Posts : 371
Join date : 2011-02-17
Location : SW Idaho

PostSubject: Re: Confusing statement   Sat Nov 05, 2011 9:53 am

This is mainstream thinking that was brought about by not starting with lines of cattle to crossbreed. They used breed average cattle for their crosses which for the most part were already crossbred cattle. By doing that they just crossed a little different (breed) or type to get a hybrid with not allot of predictability . If they would stop and use pure lines of cattle they would find the theory that Larry talks about being fruit and seedless fruit is allot simpler and way more predictable. But most folks who write and preach this do not own enough cows to make a living so the write and preach to make money. Bob H
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chocolate cow



Posts : 103
Join date : 2010-09-24
Location : Kansas

PostSubject: Re: Confusing statement   Sat Nov 05, 2011 10:43 am

The bible (no disrespect implied) from Larry has a statement in it that says it all: The black baldie cow cannot reproduce herself consistently. I can't find the entire statement right now, but that slapped me upside the head. Livestock extension has promoted the BB cow forever. If you think it through, it's so obvious. She's terminal. That's the part extension leaves out. Yeah, cross 'em up all you want, but sell the whole works. No replacements kept. I believe you've got to forget, ignore,walk away from extension articles, Beef Magazine, the comments inside bull sale catalogs, and all the other crap that constantly bombards us. BobH is right. How many of these jokers own cattle? I'd bet they did and went broke, so now they've got a job teaching us. That makes 'em an ex-purt.

chocolatecow thinking i've got to highlight this stuff in larrys book
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Hilly



Posts : 406
Join date : 2010-09-24
Location : Sylvan Lake, Alberta

PostSubject: Re: Confusing statement   Sat Nov 05, 2011 10:53 am

I am probably off base but I think the comment is a general rule of thumb.

Many believe they are selecting for longevity and fertility when choosing their breeding stock but still try to force an ideal form or in some cases try to hold a minimum level on antagonistic traits, which is understandable as they are in most case trying to do all things well.

Any breeder that puts a specific function first would only do so with the understanding of intent in a crossbred purpose, to get more from less... just not for free.

Within a closed population the longest living most productive cows will not be the most depressed by nature, even if the mean of that population is well above industry standards, perceptiveness not being necessarily standard in the industry.
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