Sunday, November 9, 2014

The pelvic region of the cow’s physique—a multi use structure

Ever consider how much goes on in the pelvic region of the cow?
(1)   It houses the mammary gland, thus impacts upon milk production
(2)   It positions the hind legs, thus impacts upon mobility
(3)   It houses the birth canal, thus impacts upon calving ease

75% of most dairy breed type classification systems involve the measurements of traits within the pelvic region--  rump angle, pin set, thurl width, pin width, leg set, foot angle, and all the udder traits.    In the Holstein breed, both Udder Composite and Foot and Leg Composite are calculated from views of traits developed in the pelvic region.    The other two type composites are mostly ignored in sire ranking lists.

Is that all that matters in structural selection?

Compare the above “pelvic region” traits to the “frame” traits we measure:
Stature, “Strength”, Body Depth, Dairy Form.     The volume of the cow ahead of the hips is 75% of the total cow as a physiological and physical being, yet 75% of our selection attention is from hips to tail.
A large percentage of AI semen is sold strictly on the level of UDC and FLC that bulls’ data expresses.

But it is a biological mistake to assume that the only genes that “matter” are in the rear end.    Nowhere is this more evident, than in the frequency with which bulls who are plus UDC and FLC still end up as a “minus” for Productive Life—ie, their offspring leave dairy herds earlier than the average cow herdlife.

What connects the “front end” to the “rear end” of a cow?

If you study a bovine skeleton, you realize that the head, neck, foreleg, chine, and rib cage are one set of interconnected bones.   The pelvis, loin, hind legs and tail are a separate set of bones.    Connecting one to the other is the spinal (vertebral) column.     But the actual connective tissue of all skeletal structures is cartilage, tendons, muscling, nerves, and hide—what a biologist calls “soft tissue structures”.

The functioning interaction of muscles and bones is dependent on five internal organic systems, that are functioning in parallel— respiratory, circulatory, glandular, digestive, and nervous systems.    Glands produce hormones that regulate growth, digestion, metabolism, and reproduction.    Respiration is the method of oxygenating the blood, which circulation moves through the musculature and transports the nutrients.    Digestion takes raw food elements and breaks them down into blood-soluble proteins and nutrient energy forms, which the body organs either use now or store for later.    Respiration, circulation and water intake team up to cool the body that is heated by the ruminant digestive processes.     Through all this, the nervous system both sends signals for muscular movement (both external and internal) and regulates the disposition of the animal to its environment.    All of this must be efficiently “housed”. 

Production – in biology, a subset of reproduction

Our selection focus in dairy breeding has been both the direct (lactation yield) and indirect (visual type) measurement of “productive ability”.      Along the way, we standardized lactation measurement lengths so we could “rank” production, and we focused on linearly measurable traits we could “rank” based on their perceived contribution to productive behavior and ease of milking and handling.    We only added new measures (butterfat %) (protein %) (somatic cell score) as the milk market offered differential pay- ments for milk relative to the presence or absence of these substances in milk harvested.
Production—in biology, a subset of reproduction        (page two)

But as our focus on measurement increased, we lost sight of the factors affecting the efficiency of the production harvested.    We ignored fertility, assuming what was OK now would stay OK generations later.    And as we lost ground, we developed new technologies to replace the genes lost for fertility.   These replacement technologies included rBST (persistency in a needle) and OvSynch (fertility in same).

How should we look at the pelvis, separate or connected to the overall frame??

Now that genetic focus is shifting toward “longevity” as lower-cost production than “fast maturity”, we have a chance to return to a more comprehensive view of the physique as a connected totality.   Because the key differences between the fast maturity and the functional longevity cow are structurally related.

If you draw a cow, you realize that linearly measured traits to not describe the entire cow physique.   We chose traits, based on two criteria:  (1) consistent measurability on a linear scale,  (2) relationship to the faster maturing production ability.      The resiliency of the total organic system was not considered, as the primal assumption was that low milk yield was the primary genetic reason cows were culled young.

Today, we see mostly structural reasons for cows leaving herds early:  (1)  leg or hoof troubles, (2) udder troubles, including mastitis, (3) failure to conceive, (4) injury during calving, (5) death after metabolic disease, (6) injury in stalls or group stables.      Many cows marked “cull= low production” actually drifted into culling as a result of primary reasons (1) thru (6).     So common sense tell us the benefit of good type is to resist early death loss from structural reasons, or 2/3 of the reasons noted.

In this, there is an “ideal” physical expression, and it may not match type selection fads in some breeds.

How much emphasis in sire selection and mating should be given to “frame”?

This is an important question in an era where “longevity” is again considered of value, primarily to reduce the replacement costs of maintaining higher production (mature cows that remain healthy and mobile give the most milk, exceeding heifers by 20% annually even after “genetic selection trend” has its impact).

“Frame” matters – primarily as we remember the ruminant function of the dairy cow. 
Forage capacity of the cow is dictated by a frame proportion equally tall and wide, with depth and openness of rib to allow full expansion of the rumen and abomasums

The functional traits enclosed by the pelvis (calving, hind leg mobility, udder position) require support from the front end and body of the cow for optimal lifetime production.

The mating system we use has a comprehensive focus on the interrelationships above.

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