By Vicky Carson
Yes, soybean meal is a great dairy cattle dietary source of ruminally degradable protein. It's consistent in quality from feed mill to feed mill, and from load to load.
But whoa! Check the bottom line of your feed bill! No wonder you and your dairy nutritionist are looking for alternative sources of RDP to soy meal.
A cheaper alternative is . . .
I've long been a fan of canola. But many nutritionists and producers consider canola a second-class protein supplement compared to soybean meal.
Soybean meal has been valued over canola because soybean meal is higher in crude protein (49.9 vs. 37.8%). However, a recent study report in the Journal of Dairy Science found that canola may be an equal or better RDP source.
They found that increasing RDP in the diet increased dry matter intake. Comparing dry matter intake of soybean meal diets vs. canola diets, dry matter intake was greater for canola diets. Milk yield response was also greater for canola diets vs. soybean meal diets. And milk protein yield followed the same pattern.
In my experience, when I add canola to lactating cow diets, the Cornell Penn Miner diet evaluation program predicts greater microbial yield. That means the RDP from canola grows more rumen microbes and increases microbial protein reaching the small intestine.
More microbial protein means greater amino acids for the cow to use. It's likely responsible for the increased milk and milk protein yield reported in the study and seen on the farm.
There's another advantage: Feeding canola reduces total dietary nitrogen and nitrogen in dairy emissions and manure.
Yes, I still add soybean meal to my diets. The best diets are corn silage based diets that contain both soybean and canola. Generally, I include up to two pounds of dry matter from soybean meal and make up the rest of the RDP needs with canola, up to eight pounds of dry matter.
Take a look at adding canola to your cow diets. There's about $100 per ton difference between the two sources.Carson and husband Steve partner in Harkdale Farms of Newbury, Vt. She's also a professor at Vermont Technical College.