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Does Size Matter?

“Warning: Some Material May Be Inappropriate for Children Under 13.  Article intended for readers ages 14 and older.  May contain strong violence and strong profanity, and depictions of sexual activity as long as they are within the context of the story.”

Were you one of those guys who wouldn’t shower after gym class because of embarrassment?  Pretty much since birth, most men are engrained  with an infatuation with size.  For many their very manhood is measured by size.  Most men live in constant fear that their manhood is not big enough.  Well I have great news for you Women don’t care.

The same is true for your dairy cattle breeding program.  For years, many dairy breeders put excessive emphasis on size.  Maybe it was because of the show ring and it is the easiest comparison  to judge.  Fortunately, the show ring now places less emphasis on size (although not totally gone).  More importantly, I have had many conversations with forward thinking breeders who are actually starting to put a negative emphasis on size.

Quality over Quantity

Having a bigger organ doesn’t hurt. Having a bigger cow can actually cause you and your cow pain.  Many cows are getting too big for their environments.  Cows are not fitting comfortably into their stalls and this is causing  both free stall and tie stall breeders to have to modify their environments.  The old theory that a bigger cow  produces more milk is actually incorrect.  When looking at the top 10 gTPI sires in the world, we see that their average estimated breeding value for stature is 1.80 and 1580 lbs. of milk.   The top 10 proven production sires average 1.45 for stature and 2757 for lbs. of milk.  Yet the top 10 proven PTAT sires  have an average  stature score of 3.78 and 112 lbs. of milk.  This clearly demonstrates  that bigger is not always better when it comes to milk production.

With that in mind, the Bullvine decided to look at the top overall production sires in the world and put an actual negative weight on size.  We developed the Bullvine Efficiency Index (BEI).  (Read more: 30 Sires that will produce Feed Efficient Cows) The formula is as follows:

  • BEI = Production (45%) + Durability (35%) + Health & Fertility (25%)
  • Production = 30 Fat Yield + 50 Protein Yield + 10 Fat% + 10 Protein%
  • Durability = 17 Herd Life + 42 Mammary System + 25 Feet & Legs  – 8 Body Depth – 8 Stature
  • Health & Fertility = 46 Somatic Cell + 23 Daughter Fertility + 23 Udder Depth + 8 Milking Speed


  1. Milk Yield is not included, as it contributes to more udder strain and added milk haulage or on-farm water removal costs.
  2. The negative weightings on Body Depth and Stature reflect that larger cows require extra feed to grow to that size and to maintain that larger size each day compared to cows of more moderate size.
  3. Also for the purpose of this article the sires could not be higher than a 5 for combined Stature and Body Depth.

The following is what we found.

Proven Sires:

NameMilkFatProtSCSConfStatureBody Depth
DE-SU OBSERVER-ET233691832.7112-2-4
DE-SU CIMARRON-ET289599882.691000
LONG-LANGS OMAN OMAN149083823.11126-2
DE-SU HISTORY-ET2083101812.72802
MORNINGVIEW LEVI132186742.5730-3
DE-SU ALTAGOALMAN-ET2856107892.773-2-3
CO-OP BOSSIDE MASSEY-ET115175662.52600
WELCOME BOL LATHAM-ET179778812.94722
KINGS-RANSOM B RUBLE307887922.987-2-2

Genomic Sires:

NameMilkFatProtSCSConfStatureBody Depth
DE-SU MUCHO 11209-ET1319102852.63920
MR CHARTROI ELOQUENT-ET1740106862.791231
PARILE LOCARNO177486842.67122-3
SANDY-VALLEY PANAMA-ET1841108742.4911-1-2
BUTZ-HILL LETTERS-ET199986852.7110-2-1
DE-SU THUNDER-ET1339100602.63164-2
DE-SU PHOENIX 588-ET2659113952.768-1-3
DE-SU SKYMONT 11195-ET163194742.7412-1-3
CHAMPION ALTABOOKEL196394792.8115-1-1

The Bullvine Bottom Line

In a world of supersize cars, jobs, meals, and just about everything else, it’s hard to stop thinking that bigger is actually better for everything.  Unfortunately, after years of locker-room comparisons, the go-to source of pride or shame seems to put the emphasis on size.  The same has been true in many breeding programs.  It’s time to stop thinking about size and start thinking about efficiency.  As they say, “It’s not the size that matters, it’s how you use it”.


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