Friday, January 30, 2015

What the “genetic base change” really means

From the January-February 2015 Dairy Route letter.

What the “genetic base change” really means

Every five years, AIPL recalculates the “genetic base” by the simple expedient of calculating testing averages off the most recent five years of cow birth dates and completed lactations.    Thus for this current cycle, the base period is 2010 (cows born 2010 or after with completed lactations) which is five years since the last base period (2005 through 2009 birth dates with completed lactations).

The concept of a “rolling” (annual, as Canada uses) or “stepwise” (five years, as USA uses) genetic base is that we need to compare “current” performance against “contemporaneous” standards.    Thus as long as herd averages in DHIA tested herds generally increase, the genetic “base” (average of recent yields) increases to keep pace with it.     If this were not done the argument is we would be printing evaluations with sires as high as +14,000 PTA Milk (ie, the first base period from the early 1960s found the average cow producing 12,000 pounds ME; today’s base average is more like 26,000 pounds ME).

The amount of change to “average” between 2005 and 2010

This latest base change produced an average gain in milk yield of:
Holstein = 382 pounds        Jersey = 327 pounds        Brown Swiss = 157 pounds
Equivalent gains in butterfat and protein yields of:
Holstein = 17 + 12              Jersey = 19 + 12               Brown Swiss = 6 + 6 pounds
Productive Life gains in months of lactation
Holstein = 1.0 months        Jersey = 0.8 months          Brown Swiss = 0.3 months.
Somatic Cell Score (logarithmic base)
Holstein = - 0.07                Jersey = 0.04                     Brown Swiss = - 0.02
Daughter Pregnancy rate
Holstein =  0.2                   Jersey =  0.0                      Brown Swiss =  0.0
Basically, if a given Holstein sire was + 382m +17bf +12pr and +1.0 PL 2.93 SCS +0.2 DPR “before” the base change, and he had no new daughters (born in the 2010 base period) his PTA values on the new base would now be +0 m +0 bf +0 pr  +0.0 PL 3.00 SCS +0.0 DPR.     If he had new daughters in the latest base period, they are part of the “current” base and his evaluation will basically be daughters vs contemporaries adjusted somewhat for whether these animals are in herds above or below the “base” average (ie, are the contemporaries providing the same level of competition as the base average?).

On the type side…

The Holstein Association is postulating the following base changes for type data:
0.99 Final Score    0.92 Udder Composite    0.78 Feet and Legs Composite
The Jersey and Brown Swiss Associations postulated 0.53 and 0.28 gains in final score.

Did all the classifiers in these breeds actually see type scores going up by a third (BS) to half (JE) to a full point?    I am guessing that in actuality there is an imputation based upon changes in linear scores for the “objective” measured traits, as the actual scoring procedures followed by type classifiers bases final scores in part on a standardized ratio of scores so that the population results conform to the “bell shape” distribution curve.     Ultimately, this just means “new” bulls have higher type ratings than “old” bulls (no matter how good in their era, Ivanhoe, Citation R, Chief, Bootmaker, Elevation, Astronaut, Valiant, Starbuck, Blackstar are all listed now as “minus” for type).

Are  we  really  making  genetic progress  ?

Of course we are—that is what the data says, and figures never lie.

We have to remind ourselves constantly in the business of breeding that “genetic” means “population” NOT  biological function or relative transmitting ability or even realized performance.    Genetics only measures the “current” measured generation, it does not compare the “new” against the “old” on either an individual animal basis or a philosophy of selection basis.

What do I mean?     Geneticists cannot tell you if “Mogul” today is superior to “Elevation” in his day.     You actually need a supply of Elevation semen to use at the same time on the same mates as Mogul to answer that question.     They prefer to assume that, because today’s herd averages are higher than in the 1970s, at least for yield traits, Mogul must be superior to Elevation.    

And as much as “breeders” will generally object to the idea that these newer, genomically identified “supersires” are “genetically” better (Genomic definition: possess a higher percentage of the desired “marker”genes associated with measured traits) –  geneticists, not breeders, control the agenda of selection for future AI sires, and are not concerned with prior industry definitions of “greatness”.

Thus, a sire like Rosafe Citation R *RC whose entire list of classified daughters averages an actual 84.0 points, but virtually all scored between 1962 and 1990, can be imputed as “minus” for type against the current type “headliners” whose actual score average may be less than 80.0 points.     The physical type considered superior in that era, while having transmitting influence behind today’s cattle, is different in many traits and can produce a different resulting score under current linear assumptions.

Likewise, while a higher percentage of tested “Citation R” daughters exceeded 100,000# and 200,000# lifetime production (before rBST or TMR) than any leading sire of the modern era, their annual lactation averages followed the classical pattern to maturity, doing their best efforts at ages cows no longer reach.
The relevant question is not being asked       

What is the goal of your breeding program?     If it is simply to have the highest indexing herd (without necessarily producing competitive animals in the high pressure Genomic market) just use the newest of the new, and buy them off the top of the list—the same way most AI salesmen tell you.     If you have a constantly updated physical and nutritional environment for your dairy, you will gain production.

My only question for you then, is “can you afford to constantly update your facilities, equipment and feeding to harvest all this accelerated genetic potential” if the only payback is a 382 pound gain over a five year period??      [How much equipment can you buy on the marginal profit from 76 pounds of milk per cow per year?]    

This is the ultimate fact of the numbers—55% of all semen sold is selected on the above premise, with data promising up to 2500 pound gains on individual sires—yet we are not harvesting a fraction of that.
Even if you argue but we were focusing Net Merit on health traits and longevity, not milk yield, why did Holsteins only gain one month (on an already short 29 month herdlife) over the same five years?

Genetic potential is only half of what it takes.   The other half is matings to produce sound physiques.

Most dairymen are going to use facilities already built for the remainder of their dairy career.    Each facility design was in part based on a given target production and requires a certain margin over feed and all other costs to generate the profitability needed to maintain desired household incomes.   If we try to push production above the level expected from the design, cows will die at earlier ages.    Margins fall on the incremental milk produced.   Profitability declines over time no matter how high the production.

Cows differ in their cost of production.    One of the long held assumptions of geneticists is that the cow who milks more has lower feed costs—as if every cow eats the same feed volume.    However, this idea never made sense even when we did stick cows in stanchions and give them all one coffee can of grain.  
As soon as we started “challenge feeding” cows, some of them went up in yield.    Because we did not measure anything else, we based evaluation on the assumption this was the core of “genetic value”.

Dairy profitability is based on controlling costs of production, not total yield.    This is because profit per unit in commodity production goes to the “least cost” producer, not the “biggest volume” producer.   
There are few economies in scale in animal housing, care and milking—only on the equipment side.   As a result, the best breeding program combines multi trait gene selection with physique-based mating to produce cows capable of competitive, high value per unit production at a minimal involuntary cost to sustain production.      This is the goal of our sire selection and mating guide.

No comments:

Post a Comment