Here is a next bit of my notes from Woody Lane’s lecture on grass and nutrition. First, I should offer the caveat that he gave, which was that he felt he had to oversimplify some technical terms, due to the time constraints of the 2-hour class (which he normally teaches over several weeks). And, a second caveat that if something seems wonky in the information, surely it is my note-taking, and not Woody’s information, which is incorrect. 😉 Comments are welcome if I’ve gotten something wrong.
Woody introduced two terms which are important in considering what grazing animals need to eat in order to grow.
The first is “TDN” or “total digestible nutrients,” expressed in a percentage. That is basically the “energy content” of the feed in question. Here is a chart of common edible things (for ruminants), and their average TDNs:
The second term is “crude protein” or “CP.” What we’re really interested in is the “true” protein content of food, but protein tests are not practical to administer. So instead the nitrogen content is measured, which has a linear relationship to protein content and gives a reasonable estimate of true protein. The nitrogen value is multiplied by 6.25 to factor-up to 100% protein. I.e. 1% nitrogen content means there is 6.25% “crude protein”. When people talk about “x% hay” they are referring to the CP content of the hay.
Below is a chart of typical CP values of feeds people use for ruminants. Lambs need at least 16% CP for good growth.
Woody qualified that good quality green grass is generally above 20%, and can sometimes be above 30%. So, this sets the stage for the financial viability of grass-fed lamb: yes, it is possible to grow lambs (and other ruminants) rapidly on grass alone! Green grass is a solid competitor against any feed, and you don’t have to do much work-the sheep harvest it for you!
So why do we feedlot meat animals in this country so much? The answer isn’t because grain-feeding is better, or faster, at growing meat. It’s purely because it’s cheap, given our ability to grow row crops at rock-bottom prices in the U.S. When you ponder the chart above, figure on blending a lot of corn with some soybean or cottonseed meal, you’ve got an inexpensive, high-CP feed for fattening meat animals.
But, that fact could be about to change, possibly radically altering the way we grow food in this country. As grain-based fuels catch on here, the price of grain could rise significantly, putting feedlots out of business and pushing us back to grass-fed operations. This would also make pork a very expensive meat.
Cattle are slow growers and typically only produce one calf a year, so they are not very profitable when you can’t feed them cheap grain. Sheep (and goats), on the other hand, not only have great feed conversion rate and the willingness to eat a lot of stuff, but offer the potential for a 200-300% annual crop, if they are well managed.
It turns out, sheep are one heck of a ranch animal, and can convert even a weedy pasture into meat on the table and money in the bank. Most of the rest of the world has never forgotten this, and eats a lot of lamb. So, though the sheep industry has been on an eighty-year decline in this country, it’s possible we are about to see that turn around.
So, now we know grass feeding is practical, feasible and definitely the wave of the future (if not because of ethanol, there is just an increasing customer demand for “natural” in our culture). Next, I’ll get to the actual “how-to” of pasture grass management; because “good grass” is the holy grail of lamb growth.