Sunday, February 15, 2015

The most consistent breeding program for increased cow longevity

I have provided a variety of ideas in our newsletter series to prod your thinking about the power of genetic selection and mating guides to improve longevity.    Today we put it all together.

Why is selecting for “longevity” so important?

The short herdlife cow costs your more money to raise than she makes in income over all costs.
During her life, her breeding expenses (due to her slower fertility response) were likely greater.
At the end of her life, she may have cost you a lot of extra expense—vet bills, and dumped milk.

Most of us raise our own heifers so we do not always add up all the costs.   But heifer growers will tell you it costs $1500 to take a $300 weaned calf to freshening at 24 months of age.     According to MSU telfarm data, the first two lactations just pay back raising.    It is only third and later lactation cows that are making you a profit.      Cow longevity is what pays off mortgages— not higher herd averages.

How do we select for longevity?        (1)   Is the bull’s type evaluation important ?

Traditional breeding assumes bulls need to be “plus” type to avoid the early age culling of cows whose udders fail, who are subject to chronic lameness, or cannot have calves unassisted.    When linear type scoring was developed, all sorts of data supported the importance of traits such as udder (ligament) support, teat placement, fore udder (elasticity), udder depth, foot angle, leg set, and rump slope.     In Holsteins, we developed Udder Composite and Foot/Leg Composite as a shortcut to identifying “better functional type” sires.     (Jerseys recently introduced Jersey Udder Index for the same reason.)

Type is important, primarily to avoid “early age culling” due to lack of functional adaptation.    But the selection for longevity requires more than linear trait type selection.    The rest of the cow is involved.

How do we select for longevity?       (2)   Is the bull’s genetic evaluation important ?

As soon as AI proved itself, most people had enough heifers.   The problem was not all heifers were ready to milk at competitive levels.    So emphasis in genetic selection was focused on sires that were “plus” for milk production.    Over time, the attitude developed: unless the bull has “milk” nothing else about him matters that much.     After awhile, the udder failures on many high production young cows returned attention to type, and we developed this attitude: unless the bull has “milk” with good udders, nothing else matters that much.    With the conversion to larger herds in free stalls, the proviso …and good feet & legs…  got added.       Indexes like “TPI” were developed as a shrotcut to find those bulls.

But something else did matter—cow fertility.     AI data showed a steady 1% loss in conception rate averages every year from 1960 to 1990 [insemination reports from the ABS national AI network].    It was not a “semen quality” problem—it was a loss of genetic cow fertility qualities.     But the industry, focused on young sire sampling and genetic ranking competition by that time, did not pay much attention.
How do we select for fertility ?                         (1)  is there a genetic measure ?            

The feed industry was telling us the higher production cow needed more grain energy to set a higher peak milk so her coasting down after being rebred in later lactation would stay above total feed costs.     
Unnoticed was that some cows got bred quicker than others [a genetic difference] no matter how high we pushed the energy density.     The feed companies developed body condition scoring to tell us the cows that still needed more grain (those thin cows did not cycle and breed back).  

Eventually, as the linear type selection made more angular cows, the drug companies developed ov synch drugs so we could “induce” fertility in thin, high production cows.     Nobody connected the dots on the genetic relationship between body conditioning ability, appetite, and fertility for a bit too long time.    But the way a cow rations her nutrient energy intake is genetically determined.

Who finally “connected the dots” between production and reproduction ?

aAa” breeding guide actually had it figured out in the 1970s, when it evolved to identify six essential qualities of function.     When you mate for a balanced physique, you not only improve udders and legs, you will avoid extreme cows that lose too much body condition, or lack stamina to remain persistent.   You also have easier calving, better recovery after calving, and thus faster rebreeding.    Thus it began to develop—the herds using “aAa” maintained better fertility, and had more longevity, than herds that just stuck with evaluation data alone for mating selection, or bred randomly to high indexed sires.

How did we get on track to measure fertility genetically ?

 In fact, the bigger 305d lactations made from higher and extended peaks (that gave their sires higher PD Milk ratings) were not the best way to go, if you also wanted to maintain economical cow fertility.    We    needed selection data for flatter lactation curves—cows that will breed on time but stay persistent in the later lactation milk yield.    Such cows are higher in pounds per day of lactation than the others—but as the sire evaluation system stuck with 305d ME measures, they were hard to identify.

The partial solution to this was somatic cell scoring.     Lower SCC rated sires will more often sire good health cows, cows that gain in yield volume each additional calving [Canadian Dairy Network research].    It is an industry error to equate SCC with only mastitis.    It actually indicates immune system function.  

The better solution to this was daughter pregnancy rate.     Sires whose daughters breed back on time are plus for DPR; sires whose daughters take more time are minus.    This was, like type, a great way to start avoiding sires whose daughters are inefficient at reproduction or worse, naturally infertile.

Added to SCC and DPR ratings, an additional piece of genetic data – Productive Life – had already been developed.    Scientists’ focus on “stayability” (avoiding early age culling) led to the PL measure, which is estimated total months of lactating per cow lifetime.   [full credit first 305 days, partial credit beyond]    

PL became an essential part of the USDA’s “Net Merit” ranking index.   Emphasis on PTA Milk was reduced in favor of PTA Fat and PTA Protein (the bulk of milk check value) over the full cow life.    It was an elegant improvement—and it can help you see that for better milk checks the size of PTA Milk (or the obsolete attitude that “it has to be plus”) in a high production era is virtually meaningless.

How do I sort the “longevity” sires from the “avoided early age culling” sires ?

Select among sires from the longer productive lifetime cow families.    These are “survivor” cows that stayed competitive against newer heifers entering their herd.    Without fertility, stamina, sound type and adaptability cows do not make twelve, eight, even five lactations.     A “sire stack” pedigree does not give you this information— you need to work with someone who is looking at the multiple generation official breed association pedigrees that show realized cow performance.    You will quickly find that many AI studs are so wrapped in “index” that depth of cow line longevity was not a consideration.


The  genetic  path  to  cow  longevity

Having trouble keeping the barn full, in spite of being on top of daily management?
The obvious problem is you need a different kind of cow.
Even if you do not plan on extra income from sale of surplus cows, it still pays to do mating selection in favor of cow longevity.         Why?

(1)    Mature cows have matured production capacity—they milk more than heifers.
(2)    Do you really enjoy breaking so many new heifers?    Recalved cows know the ropes.
(3)    Do you make any money on $500 cull cows, if the vet bill prior to culling is also $500??
(4)    The cow that lives to a mature age is healthier and more fertile at her younger ages.
(5)    The cow that lives to a mature age avoided bad calvings, a high cell count, injury, lameness…
She is relatively trouble-free.    She does her job without extra help from you.
She stuck around because she got bred back on time. 

Mating selection in favor of longevity is a lower cost way to increase both production and profitability on a dairy farm.    No one who has tried it ever goes back to their old ways.

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