Wednesday, March 22, 2017

Why narrow cows have more D/As early lactation and lose persistency late lactation

From the Sept - Oct 2014 Conceptions Dairy Newsletter

Looking at “type” in relationship to a cow’s productive functions

Both AI stud mating evaluators and Holstein USA type classifiers use the linear trait methodology to categorize the functional structure of the modern cow.    Often times, they do not agree on what that “perfect” cow should be physically, with the AI stud view (joined by Genomic scientists) being that our modern Holstein cow is “too tall” for commercial environments, while the Holstein classifier and farmer breeder view is that they see too many fine-boned, deep-uddered young cows they would not expect to live a full productive lifetime.  

Scientists, who first developed the linear type methodology in the 1970s and joined with AI studs to coerce the purebred breed associations to adopt it for official breed type classification, now tend to blame type classifiers for the cow faults in execution of the linear concept.     Meanwhile, breeders are sticking with the idea that the higher scored “Very Good” and “Excellent” cows will be the longer life producers, and object to the Genomic assumption that “Good Plus” is the best type for commercial use.

Then there is the “aAa” view

The Weeks’ “aAa” Breeding Guide is used in both commercial and purebred settings, but has never been officially endorsed by either side of the argument—thus tends to function “under the radar” to help its users avoid being trapped in the fads and fancies from theoretical science and traditional breeders that periodically disrupt functional cow structure in popularly mated herds (using computer mating systems or personal AI consultant mating).     

In the Weeks method, the qualities of the cow physique are assembled in an additive way, rather than in a preference for linear extremes in a handful of target traits.    Over my now twenty years as an approved    
“aAa” analyzer I would say that our current type issue is the prevalence for “narrow” physiques, which comes in part from the linear evaluation (by AI stud or breed classifer) preference for “angular” cows.

How a lack of “width” translates into a lack of “functional cow”

You can start right with the fore part of the cow, that linear concepts of the 1970s decided had no value:
the head.       100% of the air she breathes, the water she drinks, and the feed she eats has to enter the cow through the dimensions of her head.     If the head has a wide muzzle, big round nostrils, and a wide sinus structure, she has a chance of high performance.    If she has a wide forehead, there is room for the eyes to swivel in the skull and the brain to work inside the skull.     If the head is proportionate in size to the body behind it, you will find that all the body parts have more substance and function cohesively.

By contrast, too many linearly-selected heifers today have narrow heads, small muzzles, weak jaws, slits for nostrils, and spend too much time panting around the water tank any time heat or humidity rises.   In any stress situation, the narrow skull squeezes the brain and limits the range of her eyesight, producing a nervous cow.     Cows with narrow heads have less inherent balance when on the move.

Correlations between narrow heads and narrow chests, slabby ribs, stiff legged stances

Stand in front of any narrow headed heifer.   Do you see any front end capacity behind that?    Keep in mind that the heart sits in the center of the chest with the lungs aligned on either side.    The lifeblood in the cow is circulated out to muscles by the heart, and the oxygenating of the returned blood is performed by the lungs.    Both need chest room to fully function, the extension and contraction of both takes room.

Why narrow cows have more D/As early lactation and lose persistency late lactation

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