Feeding dairy cows in California can be a bit different than elsewhere. Alfalfa, generally in the form of hay rather than silage, and corn silage are almost universal, and cereal grain silages are also commonly available. In addition, it is fairly easy to obtain high quality fibrous byproducts, such as almond hulls, beet pulp, citrus pulp, fruit pomace and rice bran. It is not at all unusual for diets to contain a long list of ingredients!
While several sources of vegetable proteins may also be used in rations, canola meal is the protein of choice, providing economic advantages to ration formulation. But what happens if soybean meal becomes less costly? Can soybean meal be a viable replacement for canola meal in diets for dairy cows in California? That very question was posed to Dr. Peter Robinson, University of California. Having previously shown that up to 1/3 of the ration canola meal can be substituted with high protein distillers’ grains before performance is lost (Table 1) Dr. Robinson was the logical choice to run the study.
Table 1. Results of the canola vs high protein distiller’ grain study
|Distillers, % of ration dry matter||20||13.4||6.6||0|
|Canola, % of ration dry matter||0||6.6||13.4||20|
|Milk yield, lbs./cow/day||99.1||104.5||105.5||104.4|
|Milk fat yield, lbs.||3.45||3.63||3.60||3.52|
|Milk true protein yield, lbs.||2.88||3.07||3.10||3.06|
|Dry matter intake, lbs./cow/day||53.0||53.5||54.6||53.5|
|Increase in body condition score/ 28 days||0.01||0.03||0.06||0.03|
In the new study, Dr. Robinson and his team replaced canola meal on an equivalent protein basis with 0, 3.5 or 7.0% of the diet dry matter as soybean meal
Table 2. Results of the canola vs soybean meal study
|Distillers, % of ration dry matter||7.0||7.0||7.0|
|Canola, % of ration dry matter||13||8.2||3.5|
|Soybean meal, % of ration dry matter||0||3.5||7|
|Milk yield, lbs./cow/day||97.9||98.6||93.1|
|Milk fat yield, lbs.||3.54||3.51||3.32|
|Milk true protein yield, lbs.||2.91||2.91||2.75|
|Dry matter intake, lbs./cow/day||64.0||62.5||61.9|
|Increase in Body condition score/ 21 days||0.05||-0.02||-0.02|
As Table 2 shows, milk yield, fat yields and protein yields were similar between the all canola meal diet and the diet containing 3.5% soybean meal. However, while the canola meal permitted body condition score to increase, the soybean meal diet resulted in a decline in body condition score. The researchers determined that this difference would be equivalent, in terms of energy to 2.02 lbs. of milk lost.
Inclusion of 7% soybean meal in the diet resulted in a decline in milk and components. Again, there was a loss in body condition score. The researchers concluded that ration soybean meal should be limited to 2-3% of the ration dry matter to insure adequate health and performance.