Balance, Proportion, and Growth Spurts

There is a good reason why dogs are described as “ genetically plastic”. No other species exhibits such extreme variations of growth and proportion. It’s theorized that many distinctive canine features, like long floppy ears, emerged accidentally as the domestication process disrupted inherent growth patterns and genetic sequences. The same complex gene interaction responsible for reinventing ancestral behavior patterns also created gene linkages for physical traits unknown in wolves. This is where dogs and wolves really part company.

All newborn puppies begin life deceptively similar in appearance. Within the first three months, the blueprint of their genetic heritage directs drastic inconsistencies of growth responsible for creating recognizable traits of breed type. For every breed, the most intensive period of disproportionate development occurs during the first four weeks. After that, growth patterns become more stabilized, known as isometric growth, although these are interspersed with periods of disproportionate development. Needless to say, breed specific traits are highly varied. Most of them are controlled by complex interactions of polygenes in addition to being influenced by a range of factors. Some of which we are just beginning to understand. In other words, a good portion of puppy growth and development is predictable, and a great deal of it is not.

Varying hormonal and metabolic changes, nutrition and environment factors will all have a powerful effect on an individual puppy’s growth patterns.

Regulatory DNA controls the appearance and ultimate progress of every physical and behavioral trait during each stage of development. Although growth patterns may appear to be random, they are precisely controlled by epigenetic coding. Various phases are started, stopped, intensified or slowed by regulatory DNA. It directs the growth of specific body parts creating longer or shorter legs, or disproportionately long muzzles by triggering an abbreviated or prolonged growth period for that particular anatomical feature.

These exaggerations are responsible for creating breed type and intensifying functionality of specialized hunting, herding, and coursing breeds. It’s also the cause of exaggerations that have modified proportions beyond the bounds of functional efficiency. For instance, longer legs make a faster runner. However, there is a natural limit to the advantage resulting from this exaggeration. The maximum potential for speed is reached when legs are approximately 1.3 times longer than body depth. Beyond that, long legs cannot attain sufficient muscle power to maintain speed and the trait become a liability.

In addition to coordinating the growth rates of different body structures, it determines when overall growth will cease. Many toy breeds are proportionate dwarfs- the genes controlling ultimate size simply switch off earlier than this occurs in larger breeds. Piece for piece, the resulting dog becomes a perfect miniature version of the original model. Each developing part had conformed to normal isometric growth rates- except for the critical genes that turned off the process a bit too early.

It also explains why small dogs typically have a much longer lifespan than large dogs. The regulatory genes that slow growth early in life are also responsible for delaying the ageing process. Hormonal signals, triggered by regulatory DNA provide prolonged protection from the internal and external toxins responsible for age related disorders. In other words, individual cells have prolonged protection from the harmful effects of free radicals, ultraviolet sunlight, and environmental toxins for a proportionally longer time.

Breed specific genetic coding is additionally customized on a very individual basis by every puppy’s unique, inherited genotype. To a great extent, these family traits are predictable but not entirely. Individual gene pairings always include an element of chance. Long buried random recessives can pair up unexpectedly, and dominant pairs can tip that balance of a polygenic trait from desirable to disastrous.

To add to the confusion, research has revealed that the overriding effects of one parent’s genes are not simply a matter of dominance, luck or imagination. In some cases, the parent responsible for contributing a particular gene makes a tremendous difference in how the gene is expressed.

A number of genes are imprinted with molecular silencer tags. (So far 600 of these imprinted genes have been identified in the mouse.) The imprinted copy of a gene is rendered inactive regardless of whether it is dominant, healthy, or desirable. The other parent’s copy of that gene will always be responsible for determining that trait. The presences of imprinted genes can help to explain quite a few dog-breeding mysteries, such as why certain traits and conditions are invariably inherited from certain lines and pedigrees. It might also explain why faulty and defective puppies can and do pop up in lines with no history of such problems.

The effects of imprinting are determined long before birth but environment as well as inheritance can play a role. Research has also revealed that exposure to certain toxins, such as some pesticides, can eliminate silencer tags causing potentially harmful genetic changes in utero. This is not an environmentally induced mutation, which typically exerts less influence in each succeeding generation. Although the exact mechanism is not yet understood, it has been demonstrated that environmentally induced imprinting changes are transmitted unchanged, to succeeding generations.

As you can see, the most carefully planned breeding programs remain susceptible to quite a few unpredictable elements. Considering all these factors, accurately evaluating puppies seems impossible. However, for centuries dog breeders have demonstrated their unfailing ability to make astoundingly accurate predictions. Obviously, puppies do conform to some reliable rules.

Almost every puppy experiences at least one awkward growth phase during maturation. It is difficult to generalize about this. It not only varies between breeds, different families and individuals within a breed may experience completely different growth patterns.

Maturity, nutrition and condition will all have a drastic effect on various anatomical features- and only time and patience can reveal the final result. . For instance, brisket and ribspring are dependant on a combination of muscle mass and bone development. It’s possible to speed up bone development nutritionally. But muscle mass is a dependant on time and maturity. A narrow chest may fill out, thus correcting many immature “toed out” fronts. On the other hand, a perfectly filled out front is something you don’t want to see in a young puppy. Maturity can enhance them right out of proportion.

Despite these contradictions, a few general rules can be reliably applied to the evaluation of puppies.