Higher grain prices in recent years have encouraged dairy producers to consider increasing the amount of forage and byproduct ingredients in rations for lactating dairy cows. Because this differs from past traditional diets, a feeding study led by Dr. Kenneth Kalscheur at South Dakota State University was conducted to evaluate milk production with diets with elevated levels of forage and byproducts.
The diets tested in the study contained 42, 50, 58 and 66 percent forage on a dry matter basis and were provided to Holstein cows in mid-lactation. The forage source was a 70-30 mix of corn silage-to-alfalfa haylage ratio for all of the forage level comparisons.
All of the diets had approximately the same amounts of fiber and starch, with fiber in the low-forage diets supplied by soybean hulls and beet pulp. All of the diets contained 11 percent canola meal, which allowed the protein requirements to be met with only 15.7 percent protein in the diets.
The investigators were delighted with their findings, summarized in Table 1 . Milk fat percentage and yield increased with the amount of forage in the diet.
Energy-corrected milk yields were similar for all diets. Because dry matter intakes decreased with the amount of forage in the diet, feed efficiency actually improved with the higher levels of forage.
Interestingly, protein yields were maintained, even though the diets contained less than 16 percent crude protein. Furthermore this resulted in milk urea nitrogen (MUN) levels to be below 10 milligrams per deciliter for all of the diets.
The South Dakota State team concluded that Holstein dairy cows fed increasing forage-to-concentrate ratio in conjunction with canola meal as the primary protein source did not result in loss in milk and actually resulted in improved feed efficiency. Canola meal supported milk production and milk protein yield over a wide range in dietary forage level.
Attacking the same issue of high feed prices, researchers Dr. Antonio Faciola from the University of Nevada and Dr. Glen Broderick from the Dairy Forage Research Center in Wisconsin conducted a study to determine if canola meal was more effective as a protein source than soybean meal when the mixture of alfalfa to corn silage was altered.
The study was conducted at the Dairy Forage Research Station and again involved mid-lactation Holstein cows. Six experiment diets were compared. The 60 percent forage diets contained a five-to-one, one-to-one or one-to-five ratio of alfalfa silage to processed corn silage.
All diets were balanced at 17 percent crude protein, with the supplemental protein derived from either soybean meal or canola meal at each forage ratio.
As Table 2 shows, milk and energy-corrected milk yield increased as more corn silage replaced alfalfa silage in the diets.
Keep in mind that there were six test diets. Within each diet testing the ratio of alfalfa silage to corn silage, there were two diets â one with soybean meal and the other with canola meal. Which protein source was the most effective?
The study showed that, no matter the ratio of alfalfa to corn silage, canola meal was more effective than soybean meal in supporting milk production ( Table 3 ). Milk yield, protein yield and fat yield were all higher with the canola meal than with soybean meal in this study. Moreover, MUN levels were lower when the diets contained canola meal.
These two studies show that milk production and feed efficiency can be maintained at a high level in diets with higher-than-average levels of forage. These results further demonstrate that canola meal makes an important contribution to achieving results when formulating diets with high percentages of forage in the dry matter. PD
The scientific abstracts from both studies are available on the Canolamazing website .
Essi Evans
Technical Advisory Services Inc.
