In the last newsletter, we questioned why somebody at a major Agronomy Journal (back near the turn of the century!) thought Italian Ryegrass was a weed. And in that article, we documented research that established some exceptionally good reasons why this particular weed—Italian ryegrass—is a good weed to grow from an agronomic standpoint. This work was done by Dr. Dan Undersander, UW-Madison Professor of Agronomy, Emeritus.
Now we want to address the nutritional part of this study which was done by a graduate student under the auspices of Dr. David Combs, UW-Madison Professor of Dairy Science, Emeritus. In personal communication with Dr. Combs, I discovered from his reaching back into his archives, the MS degree was never completed, although most of the work including the feeding trial was. The trial was an attempt to show the viability of feeding high-quality grass (weeds, according to the reviewer at the agronomy journal) to high-producing dairy cows.
With this start to rediscovering the value (digestibility and energy) of grass on high-producing dairy farms, Dr. Combs began a research project which resulted in a forage quality measurement tool that would enable accurate comparisons of the whole range of dairy forage types. This tool is termed TTNDFD or total tract neutral detergent fiber digestibility. Obviously, it was not used on any of this data since it was not yet developed! Remember this was near the turn of the century! (I was born closer to the turn of the previous one!)
Why was this research important?
Remember, in Wisconsin, forage grasses were almost a ghost of the past. Earlier researchers and Extension influencers in Wisconsin had promoted alfalfa as a sole forage for dairy farms. (Blue Tubes dotted the landscape!) After the 1988 drought, corn silage made inroads to the point, it has become today, the dominant forage in the Upper Midwest and in many other areas. At that time dairy folks were afraid their cows might die when they were forced to feed more corn silage as it was nearly all they had. Guess what? The cows did not die!
Table 1 above shows the production and quality represented from the trial by Dr. Undersander. The IRG raised as a monoculture had higher quality (NDFD, yes, digestibility is important!) than the corn silage or the alfalfa. The corn silage had slightly more milk per acre, however, one of the big advantages of the Forage Innovations system is rotation and not just rotation, but rotation of crops which help each other! By raising about half of the forage crop acres as corn silage rather than 75%, every corn crop can be planted as first-year corn. This is an advantage in both yield and the cost to produce the corn silage as shown by the yields from the Feeding Weeds, Chapter One.
Grasses began their entrance into the game with this UW research and a push by Byron Seeds (back after the turn of the century!) We (Forage Innovations) now have many diets on large dairies without any alfalfa haylage (or at least transitioning away from it). Oh my, the world has changed (no, not that transitioning!)
The student’s thesis, titled, Partial Replacement of Corn Silage and Alfalfa Silage with Italian Ryegrass Silage in Diets of High-Producing Dairy Cows. I am quoting the thesis, “Two experiments were conducted to evaluate milk yield and milk composition when high-quality Italian ryegrass silage was used as a source of digestible fiber and digestible energy in rations of high-producing dairy cows. In experiment I, 6 pens of 8 animals were randomly assigned to a control diet (n = 3) or a treatment diet (n = 3) in a 6-week crossover design (3 weeks/treatment). In experiment II, 10 pens of 8 animals were assigned to the same control diet (n = 5) or the same treatment diet (n =5) in a randomized complete block design. See the diets in Table 2.
In both experiments, the control diet consisted of alfalfa silage (25% of diet DM), corn silage (25% of diet DM), high-moisture corn (30% of diet DM), and concentrate.
Besides checking milk production and especially fat-corrected milk or FCM, the study was also looking at lameness prevention due to the fact that the IRG diet contained less NFC and more NDF. Unfortunately, even though the diets were equal in energy and protein. The trial did not last long enough to notice any apparent differences in foot health. As we now know lower NFC diets over time will maintain healthier feet. Fat test increased significantly (p<0.05).
Milk production was as much as four pounds higher, and the butterfat test was as much as 0.5 higher as shown in the graphs.
Many in Wisconsin, at the time, would have expected the partially grass-fed cows would fall off the cliff. Obviously, they did pretty well. When doing feeding trials and when all grain and concentrate are kept the same, the ration may not be balanced the way it might be if one was just feeding the grass and not worrying about the control cows.
Here is what we find when cows are fed high-quality grasses (cool and warm season grasses) approaching or exceeding half of the forage in the diet.
First, ration protein levels may not be as high as a CS/Alf diet due to the quality of the grass protein. Second, starch levels can be reduced even though there is less corn from the corn silage, however, there is more sugar in the diet (both 5- and 6-carbon). 6-carbon sugars are indicated on your feed test under the description of water-soluble carbohydrate or WSC. 5- carbon sugars are less identifiable on the forage test sheet but are contained in the difference between the ADF and NDF.
For example, if an alfalfa NDF is 38% and its ADF is 30%, the difference is 8% of the DM. In high-quality grass, the ADF may still be 30%, but the NDF will be 45 – 50% or roughly twice as much. (this is called hemicellulose, but in fact, is mostly a very highly digestible 5-carbon sugar termed a polysaccharide complex). 5-carbon sugars play an important role in increasing milk solids.
The third characteristic of a diet with warm- and cool-season grasses is the most impactful. You will see an increase in dairy efficiency (EC milk produced/actual feed eaten). This is the biggest factor dollar-wise. We never try to get an extra pound of feed into a high-producing cow, we just want more of her feed to be digested. If she can get her needed energy from a few pounds less feed (without losing body weight) it can make huge margin opportunities! See the article on Efficiency!