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
The first issue with a narrow body will be the narrow front leg stance and foot shape. Without width or depth in the chest, the fore legs will be positioned close to each other. This produces “imbalance” in the cow’s front end, whether standing or walking. A “sturdy” cow will have legs far enough apart to stand “square” in front, with her feet pointing straight ahead and the distribution of weight to hooves will be even “side to side”. A “narrow” cow will spindle her foreleg, stand with feet toeing out, and you will see the front toes wear unevenly, representing the unequal distribution of weight at the toes.
The next issue with a narrow body is the slabby (vertically flat) rib shape, which starts from a narrow (more vertical than horizontal) chine structure behind the shoulder. As the rumen fills inside the body, it will quickly come in contact with the slabby rib, and this will constrict appetite. Production genes selected on high early-lactation peaks in the 1970s genetic preferences used a faster metabolism as the means to increase production from higher levels of grain concentrates, because the narrow body was a restriction to efficient use of bulky, high forage content rations. Such cows, however, lose more body condition as a result of persistent negative energy states, and this leads to more ketosis and displaced abomasums.
Having more “spring” and “openness” of rib (two different qualities, which linear confuses into one) creates an expansive body cavity that allows the rumen full room to “stretch and roll” and thus such a cow will have a more consistent appetite, less likely to fall into an unhealthy negative energy state.
Where is the abomasum?
The “abomasum” (fourth stomach, final nutrient absorption) sits underneath the rear of the rumen, thus in the flank and rear rib region of the cow. For a cow to be persistent in yield in later lactation, she is going to need both “depth” of rear rib and depth and spread of the “flank” region—because the fetus is developing into a calf in the same interior space of the cow. If the calf is competing for room with the abomasum, the calf will usually win—at the expense of the yield of milk.
While today the leading edge of Genomics is studying “feed efficiency”, the role of the rumen in feed digestion (and the cow physique that can optimize rumen function) has been overlooked by geneticists who focused only on milk volume (preferring bigger, taller cows), rather than on the efficiency of milk synthesis on a given volume of feed (preferring smaller, wider cows with traditional “dairy” character).
Wide rear ends—house the udder better, birth the calf easier
Any time you sense the hind leg is too close to the rear udder, you are milking a “narrow” rear end cow. This increases risk of leg or hoof injury to the udder or teats, and risks hiplock during any calving. As the udder matures, without proper pelvic dimensions, the udder can only grow “deeper” and thus even the life and health of the udder (seemingly unrelated to body in linear trait theory) is jeopardized.
Think about it. How many of your cows are you losing as a result of problems that can be linked to a lack of functional “width” in the heifers you are breeding? If in doubt of a solution, consider this:
The best fix to the solution you are seeking will be the concepts that explain the cause of the problem.
You just read an “aAa” method explanation of why so many cows die too young. Maybe using “aAa” instead of reductionist linear trait thinking could solve some problems that are costing you money.
Post a Comment