Canola meal exceeds expectations in dairy rations
In the case of canola meal, an extensive body of research has demonstrated its ability to enhance milk yield, compared to other protein sources. But what makes canola meal such a standout ingredient?
By Essi Evans, Ph.D., E+E Technical Advisory Services
When used in dairy rations, canola meal often exceeds performance and value expectations. To understand why, nutritionists can use feed trials and meta-analyses to evaluate impacts.
In the case of canola meal, an extensive body of research has demonstrated its ability to enhance milk yield, compared to other protein sources. But what makes canola meal such a standout ingredient? Research points to its role in energy metabolism, protein utilization and overall efficiency in dairy diets.
Feed trials
In most feeding trials, the test diets are formulated with similar levels of all nutrients to focus the results only on the test ingredient. If one of the diets results in better performance than another, then the next step is for the researchers to determine why these differences occurred. Did the cows give more milk because they lost body condition score? Did the cows eat more of one diet, and therefore have more nutrients?
Similarly, a meta-analysis examines data from multiple independent studies on the same topic. A question is proposed, and trial results are combined to determine trends and uncover new information. Were there differences related to production or blood nutrient levels? Combining results from many trials, were there differences in production that could be related to the protein level in the diet? Were the differences associated with protein digestibility?
Canola meal meta-analyses reveal increased milk yield
An exceptionally large number of canola meal feeding trials have been conducted over the last 20 years. Furthermore, there have been five meta-analyses conducted to compare the results obtained with canola meal to other vegetable proteins. All conclude that canola meal provides greater milk yield than other plant proteins. The Canola Meal Dairy Feeding Guide provides details of how each of the five meta-analyses was conducted.
The analyses showed that factors such as how much canola meal is included in the diet, protein concentrations and amount of milk production are all important factors in predicting response to canola meal. With an average inclusion of 5 pounds of canola meal/cow/day, milk yield was 3 pounds/cow/day greater than when other supplemental proteins provided the same amount of protein to the rations.
Energy values are greater than predicted (from feed analysis)
When diets are formulated to the same specifications and performance consistently improves, it must be concluded that there is one or more factors not being considered with normal formulation techniques. Differences in body condition score and breeding ability have been ruled out.
There have been some clues as to what’s driving this performance improvement, and these seem to be related to energy metabolism. In feed libraries, the energy value of canola meal is shown to be lower than the energy value of soybean meal. That is expected, as canola meal provides more fiber than soybean meal. However, this energy value may be too low.
Some of the reasons for the low energy value can be attributed to how canola meal is digested in the rumen. Researchers found a reduction in enteric methane production when canola meal was substituted for soybean meal.[1] When methane is expelled into the atmosphere, it represents a loss in energy. When less methane is lost to the atmosphere, more is available to produce milk.
The trial also showed that milk yields were greater with canola meal, and the differences became greater as more canola was used in the diets.1 Such effects cannot be determined from digestibility studies or laboratory analysis.
Protein is used efficiently, lowering MUN
Another factor in canola meal’s performance in the diet is related to how the protein from canola meal is used after it is absorbed. When canola meal is compared to other protein meals, milk urea nitrogen (MUN) levels are lower for the canola meal diets than for the soybean meal diets.
The liver converts ammonia to urea, which is much less toxic to the body. Ammonia is produced by rumen microbes and absorbed into the bloodstream. Ammonia is also produced during the breakdown of feed protein and body tissue protein, which normally occurs so cows can produce milk protein. When the amino acid balance of feed proteins is inadequate, more tissue protein may be mobilized, or less milk protein may be produced. In either case, the synthesis of urea increases, and MUN levels increase.
A California study[2] demonstrated this effect. The synthesis of urea uses energy. In theory, this could result in changes in energy use for body tissue or milk. However, the research showed that the cost of producing urea had the greatest effect on milk energy and milk production.
This was confirmed by a Wisconsin evaluation[3] that demonstrated unused protein will result in reduced milk yield. Thus, what appear to be minor changes in the efficiency of energy use through less methane output, and the efficiency of protein use through an improved amino acid profile, can potentially be factors that result in greater milk yield with canola meal relative to other common proteins.
Decades of research and multiple meta-analyses consistently highlight the advantages of canola meal as a superior protein source for dairy cows. By using feed trial and meta-analysis data, nutritionists can better understand how nutrients are used within the cow’s metabolism, and make informed decisions that optimize performance and sustainability.
References
[1] Benchaar, C., Hassanat, F., Beauchemin, K.A., Gislon, G. and Ouellet, D.R., 2021. Diet supplementation with canola meal improves milk production, reduces enteric methane emissions, and shifts nitrogen excretion from urine to feces in dairy cows. Journal of Dairy Science, 104(9), pp.9645-9663.
[2] Reed, K.F., Bonfá, H.C., Dijkstra, J., Casper, D.P. and Kebreab, E., 2017. Estimating the energetic cost of feeding excess dietary nitrogen to dairy cows. Journal of Dairy Science, 100(9), pp.7116-7126.
[3] Letelier, P., Zanton, G.I. and Wattiaux, M.A., 2022. Production performance of Holstein cows at 4 stages of lactation fed 4 dietary crude protein concentrations. Journal of Dairy Science, 105(12), pp.9581-9596.
