Several years back I went to see the late Larry Leonhart at Shoshone Angus in Wyoming and satisfy my curiosity about his unorthodox breeding program.

Leonhart was one of the purebred breeders who sold a lot of high-priced cattle in the 1980s during the upsizing of cattle in this country. Then he dropped out of the mainstream and began linebreeding cattle and refusing to keep EPDs.

While I was at the ranch with him one beautiful fall day, Leonhart told me two things that seem permanently burned in my memory.

First, he said the turning point for him came when he realized his "best" cows were producing the worst calves.

Second, he explained that he decided he was selecting for the wrong things and needed nature to help him sort things out. Therefore he was using fewer inputs to prop up the cattle and multi-sire pastures to let the most fertile bulls do most of the breeding.

As a result, he said, his cows were getting more feminine and his bulls were getting more masculine.

It made sense to me.

Now we have Johann Zietsman visiting the US and writing a book to help us understand why this happens. It's worth knowing that Zietsman was at one time a star student of South African livestock guru Jan Bonsma. It was Bonsma who wrote the now hard-to-find book Man Must Measure, and who defined the feminine characteristics of a fertile cow and the masculine characteristics of a fertile bull.

I had the pleasure of spending time with Zietsman last week in a workshop setting and on Hopping Brothers livestock operation near Coweta, Oklahoma.

Zietsman outlined these concepts in the classroom setting and on the ranch last week. These excerpts from his book are good.

He writes, "It is well worth noting the sexual dimorphism that occurs in hormonally balanced herds. This refers to the large difference between bulls and cows in terms of weight, muscling and other secondary sex characteristics.

"High testosterone levels in a bull are indicated by muscling and muscle definition, high length-to-height ratio (relatively short legs), wide thighs as viewed from behind, deep chest, thick neck, large hump/crest, coarse hair on the sheath and tail switch and often on the neck, darkening of the forequarter and lower hip area and an 'aggressive' attitude but not necessarily bad temper.

"This aggressive attitude is also manifested in bulls herding cows, pawing the ground, fighting anthills and trees (creating a bald forehead) and giving a sideways look at potential adversaries.

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"With bulls it is much easier to assess testosterone levels at an early age and there is merit in doing this, particularly when looking at the opposite ends of the spectrum. Some bulls develop much earlier, sexually, than other bulls. Apart from the visual indicators of masculinity -- testis, hump/crest, defined muscling, darkening in color -- some bull calves will follow cows in heat and try to mount them. Those that do this at an earlier age are sexually earlier maturing. They will sire heifers that are sexually earlier maturing and who only require a genetic predisposition for good body condition, which is to say early physiological maturity, in order to be able to calve at two years of age on [pasture]. In the absence of appropriate performance figures it is advisable to evaluate a bull solely in terms of testosterone level and physiological maturity (8-in-5 package vs. 9-in-10 package).

"Cows with a good hormonal balance and a history of early and regular calving have a wedge-shaped appearance viewed from the side – deep hindquarter and shallow forequarter, often recognized as dairy type. They have the appearance of walking downhill with a prominent and loose shoulder blade that is level with, or higher than, the spinal processes. In zebu breeds the hump of a fertile cow is much smaller than that of less fertile cows. A fertile beef cow may be well fleshed but will show no sign of muscling, although she will pass muscling on to her male progeny."

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One of the brilliant things Zietsman says about fertility, and something which runs counter to conventional wisdom is this: "Reproduction is a survival trait. It must be highly heritable."

Of course it is.

I've always said the reason the heritability of reproductive traits is ranked so low is that scientists are trying to record increases in heritability among very infertile cattle. Without a change in body type to a shorter, stockier animal, along with the inherent improvements in such things as metabolic rate, hormonal balance, and early maturity, those reproductive traits cannot improve.

Here's how Zietsman explains it.

He reminds us the most important denominator to achieve reproduction is good body condition.

"If we say fertility is lowly heritable then we say body condition (frame size, climatic adaptation, resistance to parasites/diseases and appetite) is also lowly heritable since it is the major determinant of fertility," he says.

"If body condition was lowly heritable then 'survival of the fittest' would not apply and selection for adaptation would be impossible."