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.

BABY CALF PROGRAM (2009) AT DUTCH HOLLOW JERSEYS

Paul & Melanie Chittenden—Alan (dairy mgr), Nathan (heifer mgr), Brian (farm mgr)

101 Running Creek Rd  --  Schodack Landing,  NY  12078  [near Albany, SE New York]

Interview with Melanie—she feeds calves with son Nathan.    As they milk 360 cows, they are dealing with large numbers of calves born year around.    Herd is expanding to 600 cows, from natural increase – ie, successful breeding program and competent calf/heifer rearing program.

Calving is in a pack barn addition on W side of a free stall barn set up for dry cows and close-up bred heifers.    Cows receive usual vaccinations in head locks of dry cow barn.    In specific case of J-5 [mastitis] vaccine, only give one shot dry, second shot after calving—to avoid experience they were having with aborted calves (born early,  backwards and not surviving).

They experience calf sizes from 40 pounds to 70 pounds.    The selection trend in the herd has been in favor of a larger, stronger Jersey, thus the increasing calf sizes.    Melanie noted range of size has to be factored into calf care—the little ones need concentrated nutrition, the big ones do better with an extra mid-day feeding to keep them growing.

Colostrum from momma is given at birth, with a target volume of two-three quarts depending on size at birth.     In the past year they started adding a package of an immunoglobulin product , “Alta-Gold”  [ footnote 1]  to insure the level of antibodies received by the calf is adequate to the need.     They use a “colostrometer” to check density of colostrum, as one maternal line had been discovered that seems to be routinely deficient—those calves receive stored colostrums.

Melanie notes the significance of the wide range of bf% and pr% tests modern Jerseys produce can have an effect on the “value” of momma’s milk—a cow testing 6%bf is going to have 50% more digestible fat in her milk than a cow testing 4%.     She strongly recommends, in the case of feeding whole milk, that Holstein and/or lower test Jersey momma’s milk be supplemented with the addition of a high fat milk replacer to insure the calf is getting “Jersey” nutrient density.

Calf pens are individual 4 x 8  inside a cold high roofline pole barn that is directly E side of the dry cow/calving barn, solid dividers so calves cannot kiss each other.    In extreme cold weather “Woolover” calf jackets are used (prefers “Woolover” type jacket due to ability to wick moisture away from calf’s hide).    Special needs calves may get a heat lamp for a bit.     [footnote 2]

These pens get shavings for bedding, to absorb urine.    In cold weather, straw is added on top.   Melanie believes the straw should be used year round, as young calves (not receiving hay) may want to chew on something with fiber, the straw would be safe, but the shavings are not.

They were losing calves when feeding conventional milk replacers (Cargill was mentioned).   So currently use “Renaissance 22/20 milk replacer” medicated with Oxytetracycline and Neomycin (medication is used due to prior pneumonia experiences).     There is no vegetable-based protein (ie, soy powder) in this replacer—it is all milk.    There is also a yeast ingredient to stimulate the early rumen development.       She mentioned they have also had good luck with IBA’s “Winter Care” milk replacer, the “Renaissance” is a regional (PA) brand they obtain at favorable prices.

50 degrees F  is seen as the benchmark temp for supplemental mid-day feeding, in which they use an electrolyte product with microflora, diluted in warm water.    Only one quart is given at the mid-day feeding, but two quarts is normal for the am and pm milk feedings.    The idea is to avoid loss of body heat that will lead to other problems.    As calves get bigger, say a month old, the mid-day electrolytes are replaced with a third milk feeding.     [footnote 2]

She does not force a newborn to eat her full feed each feeding.    She says that if they got a full load of colostrum day one, then take their full bottle day two am, by next feeding, they may not be hungry enough to eat a full bottle.    Feed them to appetite, then stop—next feeding they will be hungrier.    Force feeding just seems to lead to scours, and then you fight a battle you might lose.    If calf is normal, they will be up to full intake within a week.   

Calf starter  is provided from birth in a “Braden” feeding bottle.    Melanie believes this feeder has these advantages:  (1)   Jersey calves like to suck something—the Braden feeder uses nipple shaped ends that attract the calf;   (2)   Sucking the Braden nipple releases grain into the calf’s mouth, thus they will be introduced to grain without hand-forcing;   (3)   The design minimizes grain loss, as the calf cannot contaminate the grain in the feeder [as happens with buckets they can climb in, slobber over, or back up to].     The grain stays dry and thus fresher.

Fresh water is offered the calves while still on milk, as they need to learn to drink it prior to weaning.    Hay is first introduced after weaning.     [footnote 3]     

It seemed to be Melanie’s opinion  (she grew up with Guernseys, married into Jerseys)  that we lose more Jersey calves from damp environments and inadequate nutrition, than we ever lose from missing a vaccination.     The Jersey calf is born without fat reserves in her body, which makes her different from a Holstein or Brown Swiss calf—thus from day one and until weaned,  high fat, high protein, high digestibility milk  is the feed of choice.    [footnote 4]

She saw the use of pasteurized whole milk as fully equivalent to using a premium milk replacer, but she cautioned we recognize that “whole milk” from high production Holsteins might only be 3.3% butterfat and 2.8% protein – thus starts out at almost half the expectation of Jersey genes that momma is going to feed her baby 6.0% butterfat and 4.0% protein milk.    Thus, in a whole milk feeding system, she suggests we buy some good milk replacer, and add half a cup to the milk as fed, and see if you keep calves alive that way.     [footnote 5]   

She also suggests we avoid “cow grain” going into calves until past weaning, when they are also eating some hay.    Calf grain needs to not have fine particles in it that aggravate the calf lungs as a dust inhaled from eating the grain.    [footnote 6]

[end of interview]     Thank you to Melanie for her willingness to share her experiences.

This interview was conducted at Dutch Hollow Jerseys by Greg Palen on Feb 18, 2009.

[footnote 1]    Another successful brand widely available in Michigan is “Colostrix”.

[footnote 2]    Jersey calves in outdoor hutches in cold winter also benefit from bedding to trap body heat, due to thinner muscle/fat cover, and in our opinion, the calf jackets are a must when using hutches for similar reasons.     I saw bedding packs in all the hutches at Den-Kel Jerseys (Kip and Robin Keller, Byron NY) the day before visiting Dutch Hollow.

In hot summer a Jersey calf in an outdoor hutch that traps sun heat might also benefit from a mid-day feed of electrolytes and water, just to avoid dehydration??

[footnote 3]     The feed company prohibition against feeding calves “hay” is based on a blanket assumption that a “dairyman” would only raise “alfalfa”.     The rumen needs about four months’ development before it can process alfalfa, thus feeding it earlier tends to scour calves.   BUT if you have access to nice soft “grass” hay, a calf can eat that from day one, and it will dramatically improve the growth rate and shorten the weaning period for a Jersey calf, but requires water be available at the same time (chewing on the hay will make them thirsty).

[footnote 4]     John P Reber DVM, who both breeds Jerseys and practices as a veterinarian in a large number of Jersey herds around Wooster OH, says that in his experience, when called out to treat a sick Jersey calf, if they still die, the cause is frequently “starvation”.    In his experience you can feed a Jersey calf as much as a Holstein calf, after a few days of working them up to it.

[footnote 5]     Until the renaissance in Jerseys in the 1980s, Jersey bloodlines were regionalized and the type of Jersey preferred in the deep south and arid west tended to be a smaller, fine bone cow that milked heavier but tested lower (southern milk marketing still avoids paying for solids values—high milk, low test% bulls remain more popular there than in Midwest and Northeast).  

My question is—as those cattle never experience winter, do they have a reduced ability to make colostrums with the density of immunoglobulins to get a cold climate calf to live and grow??

[footnote 6]     We went through a winter where we were losing calves closely after weaning, and our veterinarian eventually said they were dying of Mycoplasmic Pneumonia.   The source of the mycotoxins was the ground corn in our weaning transition grain mix—the fine particles and mold particles would be inhaled by the calf while eating, and they basically foamed up in their lungs.     We went back to the calf starter for two more months, and the problem went away.

GENOMIC SIRE OPTIONS

So far, Genomic testing is being pursued in all breeds, but for assumptions of statistical reliability, are only being published in the Holstein and Jersey breeds.    The larger data set for Holsteins is assigning “G” tested bulls 60% to 70% Rel on individual traits;  for Jerseys a smaller data set is assigning “G” tested bulls 40% to 45% Rel on various traits.

We observe some dairymen (who trust data crunchers implicitly) buying individual “G” tested sires at premium prices, just as if they were truly “proven”.    NOTE that scientist consensus at this point is to “sample” a group of “G” tested sires like you would have a group of young sires selected strictly on pedigree merit.    This will be a safer approach, at least until we see progeny data on bulls being marketed from “G” estimates.

Taurus Service [Affiliated Sires] has published a directory of “G” tested young sires, and those are available to you upon request.    We have selected a group of these sires to offer at package discount prices—you will find them quite sensibly priced, relative to the heavy promotional pricing we have observed from other sire development systems.

“CORRELATION”  DOES  NOT  EQUAL  “CAUSATION”

Genomic tested sires (the highest ranked of whom all appear related) have raised the question of the advantages of “linebreeding”.    Here are some relevant thoughts:

Linebreeding possesses the same “risk to benefit” ratio it has always carried.   When you have found or bred the animal you want, the most economical way to replicate it is to linebreed it--  except that, in the process, without careful mating balancing, you will at some point produce more extreme phenotypes.

It is the “extreme” phenotype—when “dairy” turns “frail”, when “tall” turns “narrow”, when “refined” turns “small”—where we see the negative results in fertility, health, longevity, and limits on production.

In Holsteins, as a result of older classifier resistance to accept more recent direction that a wider front end has longevity value, we seem to be reverting to “the narrower the better” view of what makes a Holstein “dairy” and ‘stylish”.    (This was very evident in Holstein judging at Madison last fall.)    We can expect to see continued problems with functional longevity from this “narrow” view of the “dairy” phenotype.

Extreme phenotypes are created when both the  trait selection  and  mating processes  shift from being an “additive” approach to a “subtractive” approach.

When we are additive, we develop matings in which we compensate;  ie, width is added when we have reached our ideal stature; depth is added when we have our ideal length; substance is added when we have reached our ideal angularity; mobility is added when we have reached our ideal scale;  and an elongation of skeletal extremities reaches functional limits dictated by the housing environment.

We shift to subtractive when we get enthralled by a visual representation of the current “ideal” fads and begin to make “likes to likes” matings—thus instead of having a “balanced” (level with topline) front end, we get enthralled with cows walking “uphill” [to show] or “downhill” [to milk];  instead of “level” rumps (which maintain a level udder floor) we seek more “slope;  instead of “arched” pelvises (which provide the greatest calving ease) we seek “boxcar flat” rumps with tailsets sunk between the pins.

Focus on “stature” with “angularity” and you will  subtract  width, depth and spring of rib—leading to twisted abomasums.

Focus on high “peak” production with “angularity” and you will  subtract  body condition maintenance and cow fertility.

Focus on refined “bone quality” and you will  subtract  substance and stamina, thus overall adaptive ability.

Focus on narrow “dairy” front ends and you will  subtract  front leg mobility, replacing it with brittle bones and stiffness.

Focus on narrow “dairy” body and rear ends, and you will  subtract  forage feed efficiency and persistency in lactation.

The mating process that leads to our “ideal” is not a process of “like to like” --  it is a “what do I need to add next to get more improvement” process.     It requires us to address the individual weakness that inhibits full performance from each animal, identify its causation, and match her to a bull possessing an ability to provide causative improvement.     Thus, we gain function from an additive analyzation of the individual.

Statistical ranking indexes trap us in the fear that “I can only use the top sires across my herd, or I will go backwards”.     This frame of mind lacks objectivity about the relative imperfections of  animals we rank as “closest to perfection”.     There is no “perfect” cow or bull, which is why none of them produce “perfect” offspring in reality– the “like to like” effect always results in an element of subtractive realization starting within all the traits and qualities not considered important within the index “ranking” formula.

Think additively when designing matings on your cows.    Potential genetic improvement is only realized when we allow the better traits of the cow a chance to pass through to her offspring.    The bull only does 50% of it.

                                                   ENERGY RATIONING

When we look at PTA values for milk, bf%, pr%, DPR and SCS, we are seeing the effect of how that bull’s daughters are genetically programmed to ration nutrient energy.

It is a triangular                                          PRODUCTION                          

Interrelationship:                                              Volume                                (higher bf% and pr% yields

                                                                      Components                              require more calories)

                                                                          (all are

                         REPRODUCTION            energy driven                        HEALTH  

                            Calving vigor                      functions)                          Immunity

                             Fertility rate                                                             Body Condtion                               

In years past, most dairyman emphasized PD Milk (volume) as their primary selection criteria, followed by PTA Type (score) as their secondary selection criteria.   “Milk” was emphasized for income gain and “Type” was emphasized for longer productive life.     We only made one mistake—we defined a lack of body conditioning ability as “dairy”.    Since then, we have suffered loss of timely fertility.

The advent of health and fitness traits (including DPR, a fertility measure) reminded us of the genetics of fertility.    Trouble is, we are still milking cows whose genetics reflect the earlier, simplistic thinking.   How do we breed back in the milk value, fertility, and health qualities lost from earlier sire selections ??

Understand the cow’s energy metabolism

High PTA Milk volume bulls, possess genetics that will short either “health” or “reproduction” to make the higher peak test days leading to the bigger ME lactation values on which the PTAs are based.

(example— one of the current leading Holstein “sires of sons”)

“Shottle”    PTA +2165m   (+.08% bf) (+.00% pr)     99% Rel      ME daughter average 30245 pounds!                      

                   Health linked traits:  2.66 Somatic Cell Score        Productive Life  +4.0 months

                   Reproduction linked traits:   -2.0 DPR          8.0% Dtr C/E       5.8% Dtr Stillbirths

“Shottle” while negative for DPR (cow fertility rate) is so positive otherwise on health and repro linked traits (SCS below 3.00) (Stillbirths below 8.0%) (Productive Life high plus), that he is more likely an example of “delayed” fertility (ie, breed back once gaining body condition*) than “slow” fertility, that requires lots of hormone therapy to get back in calf.     This is consistent with his 2-4-3-6-1-5* aAa.

How “aAa” helps with energy rationing

Most sires who are more “sharp” (2-3-1) than “round” (5-4-6) in their mating qualities, will tend to be slower at gaining back body condition after reaching peak milk.     You will find that if you keep the “sharp” (performance) and “round” (substance) qualities in your herd in balance, that reproduction and health qualities will improve—allowing them to express their genetic yield capability more profitably.

But if you wish to be sure, also consider the cow line evidence—for example, “Shottle’s” dam set a UK milk record in her fourth lactation (the average commercial cow peaks in her second lactation and leaves in the middle of her third).    Thus she gives evidence of mature health, fertility and productivity. 

COLD vs WARM SEASON FORAGES

The persistent cooler, wet spring across most of Michigan has delayed intended plantings and raises questions about whether it is “too late” for spring seedings.

It might seem logical to ignore the calendar, and assume all the ground moisture is going to guarantee germination.     That may be a safe assumption prior to June 1^st—but as the soil warms, it will be less safe.    Seeds seem to germinate “in their season” which is why we name them “cold” or “warm” season forages, whether annuals or perennials.

If you had intended to do some alfalfa or alfalfa/grass spring seedings, the wiser course is starting to look like seeding a “warm season” summer annual, to make feed in this season and then put in your “cold season” forage seedings this fall.

What makes a hoof resistant to heel warts?

The dam of 179HO63  Needle Lane Ohlman *RC  is now over six years old, and has crossed the 100,000 pounds actual lifetime production mark with her fifth annual calving.   This cow has never had a heel wart and also has never needed her feet trimmed.    She lives in a 300 cow freestall barn year-round, and lots of her stablemates have chronic heel wart infections.    

Why is she different?      Luck, you might say.    But according to her breeder, Lorne Ruesink, you can make your own luck—through careful genetic selection and compensating mating.    Lorne is a longtime user of the “aAa” breeding guide, which places significant emphasis on mobility and foot/leg structure.   He is also a student of genetics and pedigrees, with a long memory for trait patterns.

Lorne’s 50 cows live within his neighbor’s 300 cow operation, where Lorne acts as herdsman.   Since he moved them there, he has been able to compare the results of his “aAa” use against the linear mating his boss contracts from a major AI stud.    Heel warts and slow fertility are a major problem for the owner’s cows, but increasingly Lorne feels he has avoided those problems.

The key difference between “aAa” and linear mating is that the analyzed cows get stronger, while the linearized cows get frailer.    Lorne has concluded that analyzed cows have stronger feet – deeper hoofs with harder horn walls to protect the soft inner sole—and they distribute their weight more properly on the entire hoof, instead of landing on heels or toes, which leads to abrasions that give warts a start.

But still—a cow who has made five calvings and never had a hoof problem?    Sound genetics is also at work here.     This quality in the dam makes us hopeful for a similarly strong foot on the daughters of her son, “Ohlman RC”  [still available for sampling].     Just to calve annually five times and average 3885 pounds above high-indexing herdmates (which she has done so far) is an exceptional cow today, given the average Holstein “Productive Life” is only 29 months.     When you examine the details of her pedigree, you find that her sire and closer maternal grandsires were all bulls whose dams made above- average lifetime productions and had pretty consistent reproductive histories.    

When some cows avoid what afflicts most others, their difference could be genetic

There are a lot more “genetic” traits in cows than we have the consensus to measure so far.    The kind of hoof that resists heel warts can be identified, and the sires of cows with above average resistance to foot infections could be summarized (just as is now done for Somatic Cell scores).     Thinking that the only “genetic” traits are “milk” and “type” has led the industry to some costly situations.     When you wish to look deeper into the causes of some chronic and costly herd problems, it is always important to ask the question, “Could this problem we face be caused by ignoring something genetic?”

Taking  a  second  look  at  foot and leg traits  and  mobility qualities

For three decades, the debate has been “straight” or “set” hocks, then it became “side view” or “rear view”.    Meanwhile, dairymen continue to keep hoof trimmers busy, and spend millions on treatments for heel warts and lameness—still culling cows for being unable to walk.     Mobility of high production cows remains a big issue.

Do we really evaluate foot and leg traits correctly?

Increasingly, when buying semen, Holstein dairymen just look at the Foot and Leg Composite (FLC) and skip the linear detail.    No one can decide if a straight leg is better than a set leg, and everyone is assuming that a steep foot angle measurement equates to a deeper heel (which it does not).   The front two legs are ignored totally (as well as the front end that positions them and requires their support).

Linear measurement obscures the controlling traits to functional mobility

In the research and design of foot and leg traits, many of the structural elements that affect mobility did not prove to be linearly measurable—so were left out of the equations for “genetic value”.   Of the noted structural elements, thurl position and loin strength, plus the weight-carrying front legs, are observed to be key elements in a cow’s ability to properly support her weight under motion, and get up and down in stalls with relative ease.     Just because you cannot “measure” them is no excuse for ignoring them.

The impact of the thurl joint

The “thurl” is the fusing point of the pelvic base, and acts as the joint/socket for the hind leg attachment. 

When the thurl has a “central” position in the side pelvic view, you will see the hind leg stays under the cow (regardless of degree of set) and helps to support the weight of the rear end.    When the thurl has a “square” (rearward) position in the pelvis, you will see hind legs angled behind the cow, which puts an increasing level of stress on the loin/spinal column and produces tension in the stifle muscles.   This can lead to the cow losing her ability to get up and down in free stalls.

Beyond this, the thurl can look “high” in flat rumped, and “low” in peaked-rumped cows.    That cow with a high thurl and flat rump often has a low hip, a weak loin, and will stand on her heels.   That cow with a peaked rump and low thurl, will stand stiffly, on her toes, with hind legs too close to the udder.   In each case, what would be more desirable is a relaxed stance, with the weight distributed evenly on the entire horn of the hoof—thus neither “flat/wide” nor “peaked/narrow” proves to be desirable.

  

Hock angle is a “two way” trait  (so is foot angle)

A hind leg needs a “shock absorber”.    The material used is cartilage and tendon—which cushion bones in movement and control the extent of movement.   The three leg joints—thurl, hock, and pastern—work best if they each carry part of the “shock” load—otherwise you will see swelling in the afflicted joint, or injuries that require veterinary or hoof trimming intervention.    “Too set” or “too straight” are both bad.

Some cows lift their hoof as they walk—others drag their toes as they shuffle.   No matter the foot angle, if the cow can control her hoof movement, she will maintain functional mobility and avoid the abraided heel that makes it so easy for the heel wart virus to invade the soft tissue of the heel and sole.

     Why do we totally ignore the front end legs and feet?   (They are carrying half the weight)

The rear skeleton of the cow (pelvis and hind legs) and the front skeleton of the cow (head, chest and ribcage) are not connected by the spinal column.     What holds the cow’s body together is muscle and the cartilage structures between bones, plus the tendon structures in all joints.    The animation of their body depends on oxygenation of the muscles by the heart and lung action, and neural signals sent by the brain across the nerves that radiate from the spinal column to contract or retract muscle movement.

If front legs are poorly positioned or too fine/small to carry the load, there will be an impact on overall mobility of the cow.     Thus a narrow focus on hind leg traits is not adequate to total function.

     Why do we totally ignore the back line (chine, loin, pelvic ridge) ?

   

A critical part of cow mobility is a continuously level spine to avoid abrasion or pinching of nerves by the movement of cervical bones.    Roached loins, sloped rumps, low/flat loins, square thurls under high pins, all of these imbalances bend the spine—lead to pinched nerves and loss of back muscle strength.

Do we really grasp what “calving ease” data is telling us?

Dairymen are split somewhat equally on what “calving ease” data means to them.    Some will only use “calving ease” sires, in hopes of avoiding heifer or cow paralysis from oversize bull calves.   Others will avoid using sires with really low “calving ease” %s in a belief that such bulls make small, harder calving cows, perpetuating the problems into the future.

Countries do not agree on how to collect or present the existing data.   In Canada, calving ease is called “percent of unassisted births”—an easy-calving bull is above 87% unassisted births, a hard calving bull is below 84% unassisted.      In the USA, calving ease is called “percent of difficult births”—an easier calving bull is 8% or below, average is 9%, a harder calving bull is 10% or above.     Researchers have found that length of gestation affects calving difficulty, with bulls that sire a shorter gestation length (eg, 6H999 Cole RC, whose c/e is 5% currently) being considered more desirable.

Should you be concerned with “calving ease”?

First—this is more of a Holstein/Brown Swiss issue than a concern of Jersey, Guernsey, Ayrshire, or Shorthorn breeders, where calving ability is a noted breed advantage.    Brown Swiss have the longest gestation length of the major dairy breeds, with Holstein next—so when a calf runs over term in those breeds, calving assistance is expected.      But the Holstein cow tends to produce larger calves than any other cow, regardless of breed of service sire—roughly 7% of mature body weight (Jerseys run about 5% of mature body weight).      So breed differences are a genetic influence on calving ease.

But within breeds, more recent research notes that “percentage of stillborn calves” has also been found to be heritable—a situation where cow fertility genetics overlaps with calving ability genetics.   So the calving ease figures you now read for bulls are 70% “calving difficulty” (a subjective measure) and 30% “stillbirth frequency” (an objective measure) rather than a pure “percent of difficulty”.    Geneticists are assuming that the goal of calving is not just a surviving cow but also a live calf—a better assumption.

Heifers being fed “hot” (high energy) rations in the last trimester of gestation will produce bigger calves given the nutrient diversion to the calf to complete its development.    Much calving difficulty is induced by feeding heifers like steers, prompting weight gain rather than frame development— so what sires you breed them to will have less success in avoiding difficult calvings under “steer feed” nutrition (that pack fat deposits into the pelvic cavity, the udder, and around internal body organs).

Sometimes type selection preferences interfere with calving ease.    The wide, flat “boxcar rump” that is a traditional Holstein standard, finds less favor in most other breeds, who recognize their calving ability comes in part from a “diamond shape” to the birthing channel.    You need thurl and pin width to get the hips out, but first you need pelvic height to get the head and shoulders started.    Both dimensions need to remain in proportion for minimal pelvic interference in birthing.     [This is one of the key areas of the cow physique improved by using the “aAa” breeding guide, instead of linear mating systems.]

Management pressure to breed heifers at earlier ages (to compete with the faster maturity of smaller frame breeds like Jerseys) has produced more heifer calving difficulty.   Heifers are not ready to breed until they are 55% of their expected mature weight.   Thus, if you like 1600 pound cows, do not breed heifers until they weigh 880 pounds—the blanket Holstein recommendation of 700 pounds is assuming you still milk the 1350 pound short-legged smoothies University dairies had in the 1960s.

Genetic   tradeoffs  in  calving ease

Most sire proof lists only show direct “calving ease”—the bull’s ranking as a service sire for birthing.

But in fact, two levels of data are calculated—“direct” and “maternal” calving ease.    The “maternal” rating is an indication of how his daughters are doing for birthing ability.

Exceptions to the assumed rules may prove the rule is defective

What you see across the broad data is a pattern—the lower the “calving ease” direct rating, the higher the “calving ease” maternal rating.    The old saw, “calving ease bulls produce small hard calving cows” is questionable, on the average of the data.    But who wants to milk “average” cows??    The secret is to find “calving ease” bulls whose daughters also calve easily, and produce live calves, for a full lifetime.        

The scoop on calving ease

Calving difficulties have led people to various strategies (breed heifers to Jersey bulls, breed heifers to sexed semen, use only calving ease rated sires) that seem to either raise our AI costs or lower our herd equity value.     Why did this happen?      It relates to the delayed recognition that calving ease was as “genetic” a trait as production or type, and is linked to broader health and fertility issues—such as the rate of still born calves—currently averaging 8% of all Holstein births-- as well as to structural mating issues in the width, length, and proportions of the pelvic rump shape.

One thing for sure—the data does not support some old-timer attitudes like “select for calving ease and you end up with small, narrow, frail cows”.     Increasingly there is recognition that “frailty” is a result of broader selection issues, such as the importance of balancing “sharp” and “round” body qualities in the overall [bull x cow] mating design.     [Programs like aAa breeding guide produce heifers that are more capable of calving unassisted with a living calf—selecting sires to avoid the genetic sources of a lack of vigor in calving, such as using maternal stillbirth rates, add to success in this area.]