Sunday, September 3, 2017

CDCB introduces PTA “Cow Livability” to the mix of dairy evaluation traits

From the September October 2016 Dairy Newsletter

In July, just before the August release of the latest Genetic progeny evaluations (Genomic imputations are calculated monthly) AIPL announced the addition of “Cow Livability” to the list of PTAs they are calculating for Dairy sire genetic evaluations (this is not as yet calculated for cows, just their sires).

“Cow Livability” [PTA- LIV]  is defined as the ability of a cow to stay alive.    It seems that on average 7% of all dairy cows in DHIA herds die annually (including cows euthanized as “downers”).    Over the average of three calvings per cow, this leads to 20% of all cows leaving our herds will not produce any “salvage” value (cull cow income).    Death loss therefore currently averages $200+ per cow milked.

Prior to calculation of “Livability” we have had 21 years of “Productive Life” PTA measurements, that tell us the relative number of months cows lactate in our herds compared to herdmate averages.    Data shows that the inclusion of PL in genetic reports reversed a five-decade trend in which average herdlife lost 16% (canceling much of the gain in production levels from genetic selection).    As a related trait, Somatic Cell Score (PTA- SCS) also quit rising, and is now part of the estimation formula for PL for Genomic and newly progeny-proven sires.

When a cow must leave, culling generates income whereas death generates expense.   The salvage value for culled cows that walk on a truck over a year’s time is significant to all dairymen.    LIV is an attempt to sort this out, and will eventually be incorporated into $NM (Lifetime Net Merit).

Our perspective is that LIV might be more pertinent to the prediction of “longevity” than was ever true of Productive Life (PL).    All PL tells you is the sires mostly likely to produce short herdlife cows, and (because there is a link between high SCS and shorter herdlife) this has its own value—but for those of us seeking to generate increased herd production (from mature cow capability) and a second cash flow from surplus cows (beyond culls), longevity involves making physically balanced matings and seeking bulls from cows lines of proven lifetime capability.    Such cattle are more likely to look good on LIV.

I recently enjoyed a presentation by Don Bennink, the owner of North Florida Dairies (4000+ purebred Holsteins milking) who documented from his herd records that healthy mature (3rd and later) cows are producing 30% percent more pounds of milk than first calf heifers.    He is one of the leading breeders in favor of selection on fertility and health measures with balanced matings—his herd is now closing in on a 30,000 pound herd average (note- we’re talking Florida, heat, humidity and lignified forages!!)
Many of the No-Fla prefix sires found in AI systems descend from a 375,000-pound lifetime “Rudolph” (found as a young cow in Pennsylvania) that has generated a cow family from her female descendants.
LIV is among the measures Don is now using to screen future mating sires.

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