A recent issue of Holstein International had an article discussing the industry trend toward an ever- straighter hind legs and the decline in quality of mobility leading to higher young cow culling rates.
The trend in Holsteins has alarmed Holstein USA to announce an entirely new formula for “Foot and Leg Composite” (FLC), removing linear scores for “rear legs side view” and adding linear scores for stature in its place.
Linear scoring has very little to say about legs and feet, basically ignoring front legs and feet, putting emphasis on foot angle, then measuring the degree of “set” to the hock from side and rear views. We are now looking at the fourth version of “FLC” since linear scoring was introduced in 1972. Across four decades, the expert recommendation on set of hind leg has failed to reduce foot and leg problems.
So what does “stature” have to do with Foot and Leg structure? It appears that the young cows that leave our herds with stiff, straight hind legs also are quite tall. Ironically, “stature” not only has been highly correlated with positive type values, it is increasingly associated with superior milk yields. The current sources of the straightest legs are also among the elite Genomic levels forGTPI and GNM$.
(Of course, a couple generations of “sires of sons” have yet to show progeny production data.) On the data graphed by Holstein International the generational trend for “straight” was unmistakable.
Will this latest FLC solve everyone’s problems? I have watched the trends in “indexing” for forty years and expect nothing will change, especially as a majority of sires already selected for AI show in their own physiques the potential for siring legs too straight, joints too stiff, feet not standing sturdy.
Not including “leg set side view” in FLC means straighter-legged examples can persist in the mating population due to selection for udder, milk yield, fat and protein and somatic cell levels in the indexes.
Solving the mobility problem
Which cows exhibit the best mobility? Cows who stand comfortably on four feet. “Sturdy” cows with “central” thurls have proper weight bearing on their feet both front and rear. They have supple, flexible hock joints and springy pasterns (demonstrating an equal distribution of shock absorption from walking). They do not stand on toes nor shuffle their heels—their weight bearing is at the center of the hoof. They are not pigeon toed—their weight bearing is even from inner to outer toe.
Have you ever tried to stand up on your toes for any period of time? How about walking with extended toes? It is painful, from your ankles up into your calves. Yet in preferring “steep” foot angle we have asked our cows to walk like ballerinas, in spite of slippery concrete. This foolishness continues in the latest FLC. If you look up the greatest progenitors of Productive Life (eg,Rudolph and Ramos) you are likely to find sires criticized for “low” foot angle (based on herdmate deviation).
Our fixation on extreme linears (reinforced by typical linear mating system formulas) keeps us breeding extreme physical character in our young cows. We never stop with “good enough”, we keep seeking a “gooder than good” mating combination that produces more extreme frame expressions. Feet and legs are the extremities furthest from the body core and thus tend to show the results of extreme mating first.
Linear theories of the physique were focused on defining the traits that correlated with a faster maturity of production volume. For 45 years we have followed these, and have culled millions of failures
Consider the “aAa” solution
The “aAa” Breeding Guide (Weeks Analysis) preceded linear type traits by 20 years. Scientists who developed linear measurement thought their new program would make “aAa” obsolete. Instead we find “aAa” still going strong around the dairy world, after 45 years of linear confusion. How does a program that thrives without breed association (classification) or AI stud (Genomic) support or subsidy persist? Because it understands physical heritability and it solves problems of physical function.
Specific to Legs and Feet: Quality of mobility in “aAa” methods is analyzed as an integrated whole rather than the average of a few individual parts. The entire skeletal structure is considered; muscling activating the skeleton is considered; cartilage and tendon structures in all joints are considered. Both front and rear legs and feet are analyzed, as a functional unit and as they are attached to the body core.
A crucial defect in modern high-genetic cows is the “square” thurl position. When the thurl is back from center in the pelvic structure, angling hind legs out towards the rear, you find it thrusting pins up and shifting rear end weight onto the loin (a structure which is not designed to carry added weight).
In an attempt to be sturdy, feet are thrust forward (on legs with “set” hocks) or posty backwards (on legs with tight hocks) and cows then walk “flat footed” and ‘spread toed”—all in an attempt to redistribute weight. As cows age, loins flatten out and stiffness in the back impedes mobility.
Another defect in modern high-genetic cows is the confusion of “dairyness” with angularity leading to narrowing of the chest. This narrowing brings the forelegs closer together. Again, with all the front end weight to support, on a narrowing pedestal, cows learn to turn their feet out in an attempt for more stability. Weight is then carried on the inside toe, leaving the outer toe to grow and curl. Again, the quality of mobility is impeded. Chronic lameness can result, no hoof trimming can fix this.
“Narrowing” of the frame is a side effect of the selection in favor of more stature (such heifers show more angularity from longer bones and stretched muscling across the skeletal extension). If the loin is narrow, the entire body will be narrow (ribs will lose the ability to “spring” as rumen and abomasums try to fill with feed). The difficulty classifiers have with cows lacking stature is “they just don’t look dairy enough to score higher”. Showring judges have the same visualization problems. Yet loss of body capacity will result in loss of productive ability – a “loss of dairy function”.
Think about the combination of square thurls and narrow front ends. Take it a generation further and lose the depth and spring of rib. Put that narrow, anorexic heifer up on her toes by stiffening all her joints. In each generation you have a highly-ranked sire, but you are losing function and producing young-age culls. You have to adopt a breeding guide that protects you from going too far so that all this genetic “potential” on which you have been selecting mating sires can still be harvested in fully functioning physiques. This is why “aAa” Breeding Guide (Weeks Analysis) thrives.
Conclusion: selecting on index rank and mating on linear traits is doubling your emphasis on data that leads to limitations of the physique. Loss of mobility is just one of the many limitations that are causing too many promising young cows to have short herd life. Consider adding a mating method that understands transmission of physical qualities and experience the freedom from agonizing over genetic theories that promise much but deliver little sustainable improvement.
Linear traits help you sort which bulls to use, but have proven ineffective in telling you which cow fits which bull. “aAa” matches cows to bulls for improved function. It can fix your mobility problems.
Fixing problems with feet and legs by mating selection
If a problem persists long enough, with all efforts to fix it basically unsuccessful, it is easy to assume (as some geneticists feel) that foot and leg problems are “normal” to the high production dairy herd—at least for Holsteins, which is 90% of all milk cows.
Why then do a handful of cows remain highly productive into teen ages, while more seem to fail at younger ages? Nothing seems to have more impact on early culling today than “failure of mobility”. These are definably genetic differences, NOT the fault of facility or herd management. Our methods of genetic selection are not consistently producing cows that are adaptable to the physical environment where they must walk every day.
There is a mating system that is focused on quality of mobility as part of overall physical adaptability to the cow environment you have. This program does not require you to change AI studs or give up on your genetic goals. It just answers the question that your current breeding approach does not address.
Source: Michigan Livestock Services